Journal of Surgical Oncology 44:201-204 (1990)
EDITORIAL COMMENTS
Cancer Education in Latin America KEY WORDS:oncology training, undergraduate, postgraduate, comprehensive cancer centers
INTRODUCTION Latin America represents a region of the world with a population of more than 350 million (including the Caribbean) distributed among 20 countries [ I ] . There is considerable variation in cancer incidence and mortality in the different Latin American countries, but, taken as a whole. more than 270,000 deaths from cancer occur every year. Cervical cancer is the most common and annually kills more than 40,000 women between the ages of 35 and 50 years. These numbers emphasize the importance of cancer as a massive health problem in most Latin American countries. Recognition of cancer as a group of diseases that require specific care is well established by the presence of cancer units, cancer hospitals, or comprehensive cancer centers in practically all Latin American countries. By the end of the 1970s, under the auspices of the office of International Affairs and the Division of Cancer Treatment of the National Cancer Institute of the United States initially, a program of collaborative cancer clinical research projects between Latin America and United States cancer institutes was fostered and developed with the coordination of the Pan Anierican Health Organization. A Collaborative Cancer Research Program was established in five Latin American countries and seven selected cancer institutions, and this was later extended to nine countries and 12 institutions. More than 3,000 patients were accrued to various protocols. Unfonunately, when the benefits of this implementation were just beginning to emerge, the program was discontinued after only 5 years of operation. In Latin America there are 17 centers that comply with the minimal requirements for a comprehensive cancer center; most are government dependent and usually belong to the National Health Service. In addition, we have been able to identify 59 hospitals, services, and departments of oncology. either in general or in university hospitals. At the beginning of the present century, there was a recognition of cancer as a disease that requires specialC 1990 Wiley-Liss, Inc.
ized knowledge and services for its medical management. The midcentury saw the organization of professional groups and institutions, with people trained in the United States and in Europe, who established in their own countries the basis for the interdisciplinary study and care of the patient with cancer. In 197 1 , by the passage of the National Cancer Act and its implementation by the U.S. Government, physicians and scientists have accelerated the fight against cancer. This has benefited and will continue to benefit not only patients, but also physicians, beyond the borders of the United States. This is especially true in the field of information.
UNDERGRADUATECANCEREDUCATION Throughout Latin America, there is a consensus that there exist major deficiencies in the cancer education of undergraduate medical students and a necessity to improve the overall teaching quality in basic science and clinical cancer education. It is recognized also that the curriculum time is becoming more limited in the majority of the medical schools. Therefore, the number of contact hours between faculty and students is actually decreasing. New courses are unlikely to be successfully introduced into the curriculum. It therefore seems that teaching such as cancer prevention and detection involving different groups of health care professionals should be integrated into general preventive medicine education. Cancer education in the medical school can be approached as a horizontal activity, through a coordinator who coordinates the different chairs such as biochemis-
Accepted lor publication February 16, 1990. Address reprint requesls to Eduardo Caceres. MD. Instiluto Nacional de Enfcrmedades Neoplasticas, A v . Angatnos Este 2520, [,inla 34, Peru.
Caceres try, pharmacology, internal medicine, surgery, radiology, preventive medicine, etc., for the teaching of cancer through the whole curriculum, thereby avoiding repetition of the same subject and keeping controversies to a minimum. Such a coordinator should have the rank of prinicpal professor. This system is the most accepted approach and is in practice in most medical schools in Latin America. From the practical point of view, it presupposes a uniform system rather than a wide variation of philosophical trends and inclinations. Unless the coordinator has good support from the faculty members, however, it is difficult for him or her to organize an interdisciplinary program of cancer education and for the program to acquire the “critical mass” that will truly make an impact on cancer education. It usually takes the wholehearted effort of the members of the different disciplines. Another way to impart cancer education in the medical school is through a vertical system, which supposes a special chair in oncology with a special curriculum in cancer. Such a program is independent of the other faculty curricula, and all such matters as etiology, cancer epidemiology, cancer prevention, early diagnosis, treatment, etc., are presented to the medical student in this oncology curriculum. This system is not followed by the majority of the medical schools in Latin America. To my knowledge, only one medical school, the El Salvador University in Buenos Aires, Argentina, has a full chair in oncology. Undergraduate cancer education in Latin America requires an urgent program reevaluation, with attention to the slight variations according to the conditions in each country. The areas of knowledge in cancer where data are meager and controversial need to be identified; where the existing evidence is substantial, such as the harmful effects of tobacco and excessive sunlight, as well as the benefits of screening for breast cancer and cervical cancer, these should be emphasized to avoid a preponderance of advanced disease in our population. The ideal would be that each country consider having a joint meeting of several diverse groups for the purpose of reviewing the overall cancer education needs of medical students. These should include representatives from the ministries of health and education, deans of medical schools, professors of oncology, directors of cancer institutes, and heads of cancer societies. There are few medical schools in Latin America or throughout the world that have attempted to develop an integrated and multidisciplinary set of objectives for cancer education. Also, in a large percentage of medicalschools, there is little or no teaching about epidemiology, cancer prevention, and early detection. The multidisciplinary group described above could address these needs. 202
POSTGRADUATECANCEREDUCATION The concept of additional clinical training after graduation from medical school began as a 1-year internship, late in the 19th century, in New York City. The more widespread acceptance of the importance of a year of internship for young physicians came along in the early part of this century and then became a routine in medical education. Residency training was a later development and is essentially a 20th century phenomenon. In Latin America, a 1-year rotating internship of surgery-medicine-pediatric-obstetric and in some countries an additional year of rural service is required before the medical degree and medical license are granted and before eligibility to enter a residency training program. The rotating internship has allowed close, hands-on care in the various medical disciplines, often providing students with time to make a thoughtful career decision. Without the rotating internship, medical students would be required to decide on a specialty during the junior year in medical school, after a brief clinical exposure to clerkship. Luckily, a rotating internship before starting a residency program in any speciality is still a predominant requisite in all Latin American countries. The residency system of postgraduate education was really an American invention developed in the 1940s and 1950s and has been widely admired and emulated in other countries, some where the old preceptor method is still common. The residency system in Peru was first introduced by us in 1952, as an oncology residency, and later by our university hospitals in 1964 in other specialities. The basic objectives in a residency training program in a speciality include the acquisition of appropriate education and experience, combined with supervision and teaching, proper working conditions, and the avoidance of inappropriate duties, as the primary purpose of a residency program is resident education, not service to the hospital. However, the basic objectives of residency training have not been uniformly attained in all residency programs, either because of lack of recognition of the essentials or lack of economic support. Education and training in oncology have been changing during the last decade. Therefore, postgraduate training in oncology, at the present time, involves several major clinical disciplines in a multidisciplinary fashion. The resident should have a wide view of all treatment modalities such as surgery, chemotherapy, immunotherapy, or a combination of these disciplines. The resident must work quite closely with the pathologist to stage the disease accurately and should be aware of the limitations of systemic therapy and radiation therapy, keeping in mind that both surgical treatment and radiation therapy are for local and regional control only.
Cancer Education in Latin America
203
The resident should have a wide view of all standard chemotherapeutic agents, their maximum effect, and their side effects. The resident should finish training with a broad view of cancer control problems, allowing him or her to support cancer programs in his community.
the university or directly to the hospital. Because the number of applicants for postgraduate training usually are several times more than the number of positions available, only the top candidates will be accepted.
CANCER EDUCATION SURVEY To obtain information regarding the facilities and capabilities in cancer education in Latin American cancer institutes, we circulated in 1984 a questionnaire to 23 cancer institutions in the area, 13 of which answered our first inquiry and six responded to our second request, making a total of 19 (82%) replies. Of these 19 institutions, 16 were the comprehensive cancer centers of the 17 existing in the region. We are limiting our analysis to these 16. Only one of the 16 comprehensive cancer centers did not offer cancer education. Three institutions offered it to all levels: undergraduate, postgraduate, and paramedical; I I institutions included cancer education for medical students: 13 had a program of residency; nine offered continuing education; and 1 1 institutions offered paramedical education. The questionnaire sought information on various aspects of cancer education: I ) the qualifications of candidates for admission to the training program; 2) affiliation of the training institution to a university; 3) length of the program for the different subspecialities; and 4) evaluation of the program during and at the end of the basic training in oncology.
Affiliation of the Training Institution Because the quality of graduate education invariably improves when the program comes under the direction of the medical school, our main interest was to know how many institutions were affiliated with the university and what percentage of the staff of the cancer center were faculty members of the medical school. Of the 16 cancer centers, ten (62.5%) are affiliated with universities. and only six are not affiliated with a medical school. As regards the relation of the medical staff of the center to the university, in three institutions 100% of the staff are faculty members; in six institutions 50% or more are members; and in another six, less than 50% are faculty members. In only one center did the medical staff have no affiliation to a medical school. These figures express very well that the majority of the Comprehensive cancer centers have the manpower necessary for an adequate training program.
Resident Selection The selection of high-quality house staff is of vital concern to any residency training program. However, the large number of applicants, the variability of available applicant data, and the limited opportunity for direct applicant contact make this process difficult. In most of the Latin American countries, the number of applicants exceed by far the number of positions. Usually the training is begun after a 1-year internship, which is obligatory in Latin America. However, the programs are willing to accept candidates with more training than this. Most programs use a combination of specific selection factors that hopefully correlate with future success as a resident staff member. The hospital administration and medical staff. through the appropriate committees, scrutinize the qualifications of each applicant: quality of the medical school of origin, preliminary education, medical school performance, published research, andin the majority of institutions-the results from an ultimate written examination of medical knowledge. Interpersonal skills are often reflected in personal letters of recommendation and certainly in the interview process. The candidate will apply for residency, either through
Length of Training Programs The length of the different training programs varies from one institution to another; but, according to the different specialities, the training in oncology by the cancer institutions in Latin America in each of the 16 institutions evaluated are as follows: 15 offer postgraduate training in surgical oncology, one for 4 years, ten for 3 years, and four for 2 years; eight offer Postgraduate training in medical oncology, three for 3 years, and five for 2 years; ten offer postgraduate training in radiation therapy, four for 3 years, five for 2 years, and one for 6 months; three offer postgraduate training in nuclear medicine, one for 3 years and two for 2 years; only one institution offers postgraduate training in epidemiology; ten institutions offer postgraduate training in tumor pathology, four for 3 years, four for 2 years, and two for l year. Program Evaluation In most centers there is close follow-up of pcrformance through several evaluations per year. In addition, annual examination that can be repeated only once is given. Those who fail for the second time are unable to continue their training. There is, however, no quality control at the end of surgical, medical, o r tumor pathology training. Nearly 50% of universities ask for the pre-
Caceres sentation of a thesis before the title of specialist is granted. Another important factor in cancer education is the presence of a director or a department of education. Of the 16 institutions analyzed, 14 (87%) have a department of education.
204
COMMENTS One of the problems in cancer education that immediately comes to light is the accurate definition of a trainee or resident and the definition of a fully trained and qualified oncologist. A trainee or resident is usually defined as a doctor who has finished medical school, 1 year of intership, and 1 year of rural service, as required in Argentina, Brazil, Chile, Mexico, and Peru, and who is enrolled in a training program in one of the subspecialities in oncology (surgery, medical oncology, pathology, radiation therapy, nuclear medicine, etc.). No special training in pediatric or gynecological oncology is yet established in most of Latin America. However, a tendency to offer additional training in these areas, once the resident has finished general training in oncology, has been observed. For example, in Peru after 4 years of surgical training or 3 years of medical training, some residents, depending on their qualifications, are offered an additional year in one of the subspecialities, such as head and neck, gynecology, thoracic surgery, etc. A qualified oncologist can be defined as a fully trained, independent practicing oncologist who is totally
responsible for patient care and is in active practice, usually with a hospital position. Although there is no surplus of oncologists in Latin America, there is an acute shortage in several subspecialities such as radiotherapy, pathology, and radiology. A decrease in the number of applicants for training in these disciplines is increasingly felt because of a lack of economic incentives under the present national health program in most Latin American countries and because of the rapid sophistication of required and difficultto-obtain equipment for private practice. After graduation and an appropriate clinical training period, most oncologists become full- or part-time private practitioners. Even those who are academically inclined and appointed to university posts continue their private practice because the salary from these institutions is insufficient to support a family. Unfortunately, this inhibits the academic growth of the centers and the growth of the cancer education programs.
Eduardo Caceres, MD, Instituto Nacional de Enfermedades Neoplasticas, Lima, Peru
REFERENCES 1. Parkin, DM, Laara, E Muir, CS: Estimates of the Worldwide Frequency of Sixteen Major Cancers in 1980. Int J Cancer 41:184-
197, 1988.
EDITORIAL COMMENTS
Cancer Education in Latin America KEY WORDS:oncology training, undergraduate, postgraduate, comprehensive cancer centers
INTRODUCTION Latin America represents a region of the world with a population of more than 350 million (including the Caribbean) distributed among 20 countries [ I ] . There is considerable variation in cancer incidence and mortality in the different Latin American countries, but, taken as a whole. more than 270,000 deaths from cancer occur every year. Cervical cancer is the most common and annually kills more than 40,000 women between the ages of 35 and 50 years. These numbers emphasize the importance of cancer as a massive health problem in most Latin American countries. Recognition of cancer as a group of diseases that require specific care is well established by the presence of cancer units, cancer hospitals, or comprehensive cancer centers in practically all Latin American countries. By the end of the 1970s, under the auspices of the office of International Affairs and the Division of Cancer Treatment of the National Cancer Institute of the United States initially, a program of collaborative cancer clinical research projects between Latin America and United States cancer institutes was fostered and developed with the coordination of the Pan Anierican Health Organization. A Collaborative Cancer Research Program was established in five Latin American countries and seven selected cancer institutions, and this was later extended to nine countries and 12 institutions. More than 3,000 patients were accrued to various protocols. Unfonunately, when the benefits of this implementation were just beginning to emerge, the program was discontinued after only 5 years of operation. In Latin America there are 17 centers that comply with the minimal requirements for a comprehensive cancer center; most are government dependent and usually belong to the National Health Service. In addition, we have been able to identify 59 hospitals, services, and departments of oncology. either in general or in university hospitals. At the beginning of the present century, there was a recognition of cancer as a disease that requires specialC 1990 Wiley-Liss, Inc.
ized knowledge and services for its medical management. The midcentury saw the organization of professional groups and institutions, with people trained in the United States and in Europe, who established in their own countries the basis for the interdisciplinary study and care of the patient with cancer. In 197 1 , by the passage of the National Cancer Act and its implementation by the U.S. Government, physicians and scientists have accelerated the fight against cancer. This has benefited and will continue to benefit not only patients, but also physicians, beyond the borders of the United States. This is especially true in the field of information.
UNDERGRADUATECANCEREDUCATION Throughout Latin America, there is a consensus that there exist major deficiencies in the cancer education of undergraduate medical students and a necessity to improve the overall teaching quality in basic science and clinical cancer education. It is recognized also that the curriculum time is becoming more limited in the majority of the medical schools. Therefore, the number of contact hours between faculty and students is actually decreasing. New courses are unlikely to be successfully introduced into the curriculum. It therefore seems that teaching such as cancer prevention and detection involving different groups of health care professionals should be integrated into general preventive medicine education. Cancer education in the medical school can be approached as a horizontal activity, through a coordinator who coordinates the different chairs such as biochemis-
Accepted lor publication February 16, 1990. Address reprint requesls to Eduardo Caceres. MD. Instiluto Nacional de Enfcrmedades Neoplasticas, A v . Angatnos Este 2520, [,inla 34, Peru.
Caceres try, pharmacology, internal medicine, surgery, radiology, preventive medicine, etc., for the teaching of cancer through the whole curriculum, thereby avoiding repetition of the same subject and keeping controversies to a minimum. Such a coordinator should have the rank of prinicpal professor. This system is the most accepted approach and is in practice in most medical schools in Latin America. From the practical point of view, it presupposes a uniform system rather than a wide variation of philosophical trends and inclinations. Unless the coordinator has good support from the faculty members, however, it is difficult for him or her to organize an interdisciplinary program of cancer education and for the program to acquire the “critical mass” that will truly make an impact on cancer education. It usually takes the wholehearted effort of the members of the different disciplines. Another way to impart cancer education in the medical school is through a vertical system, which supposes a special chair in oncology with a special curriculum in cancer. Such a program is independent of the other faculty curricula, and all such matters as etiology, cancer epidemiology, cancer prevention, early diagnosis, treatment, etc., are presented to the medical student in this oncology curriculum. This system is not followed by the majority of the medical schools in Latin America. To my knowledge, only one medical school, the El Salvador University in Buenos Aires, Argentina, has a full chair in oncology. Undergraduate cancer education in Latin America requires an urgent program reevaluation, with attention to the slight variations according to the conditions in each country. The areas of knowledge in cancer where data are meager and controversial need to be identified; where the existing evidence is substantial, such as the harmful effects of tobacco and excessive sunlight, as well as the benefits of screening for breast cancer and cervical cancer, these should be emphasized to avoid a preponderance of advanced disease in our population. The ideal would be that each country consider having a joint meeting of several diverse groups for the purpose of reviewing the overall cancer education needs of medical students. These should include representatives from the ministries of health and education, deans of medical schools, professors of oncology, directors of cancer institutes, and heads of cancer societies. There are few medical schools in Latin America or throughout the world that have attempted to develop an integrated and multidisciplinary set of objectives for cancer education. Also, in a large percentage of medicalschools, there is little or no teaching about epidemiology, cancer prevention, and early detection. The multidisciplinary group described above could address these needs. 202
POSTGRADUATECANCEREDUCATION The concept of additional clinical training after graduation from medical school began as a 1-year internship, late in the 19th century, in New York City. The more widespread acceptance of the importance of a year of internship for young physicians came along in the early part of this century and then became a routine in medical education. Residency training was a later development and is essentially a 20th century phenomenon. In Latin America, a 1-year rotating internship of surgery-medicine-pediatric-obstetric and in some countries an additional year of rural service is required before the medical degree and medical license are granted and before eligibility to enter a residency training program. The rotating internship has allowed close, hands-on care in the various medical disciplines, often providing students with time to make a thoughtful career decision. Without the rotating internship, medical students would be required to decide on a specialty during the junior year in medical school, after a brief clinical exposure to clerkship. Luckily, a rotating internship before starting a residency program in any speciality is still a predominant requisite in all Latin American countries. The residency system of postgraduate education was really an American invention developed in the 1940s and 1950s and has been widely admired and emulated in other countries, some where the old preceptor method is still common. The residency system in Peru was first introduced by us in 1952, as an oncology residency, and later by our university hospitals in 1964 in other specialities. The basic objectives in a residency training program in a speciality include the acquisition of appropriate education and experience, combined with supervision and teaching, proper working conditions, and the avoidance of inappropriate duties, as the primary purpose of a residency program is resident education, not service to the hospital. However, the basic objectives of residency training have not been uniformly attained in all residency programs, either because of lack of recognition of the essentials or lack of economic support. Education and training in oncology have been changing during the last decade. Therefore, postgraduate training in oncology, at the present time, involves several major clinical disciplines in a multidisciplinary fashion. The resident should have a wide view of all treatment modalities such as surgery, chemotherapy, immunotherapy, or a combination of these disciplines. The resident must work quite closely with the pathologist to stage the disease accurately and should be aware of the limitations of systemic therapy and radiation therapy, keeping in mind that both surgical treatment and radiation therapy are for local and regional control only.
Cancer Education in Latin America
203
The resident should have a wide view of all standard chemotherapeutic agents, their maximum effect, and their side effects. The resident should finish training with a broad view of cancer control problems, allowing him or her to support cancer programs in his community.
the university or directly to the hospital. Because the number of applicants for postgraduate training usually are several times more than the number of positions available, only the top candidates will be accepted.
CANCER EDUCATION SURVEY To obtain information regarding the facilities and capabilities in cancer education in Latin American cancer institutes, we circulated in 1984 a questionnaire to 23 cancer institutions in the area, 13 of which answered our first inquiry and six responded to our second request, making a total of 19 (82%) replies. Of these 19 institutions, 16 were the comprehensive cancer centers of the 17 existing in the region. We are limiting our analysis to these 16. Only one of the 16 comprehensive cancer centers did not offer cancer education. Three institutions offered it to all levels: undergraduate, postgraduate, and paramedical; I I institutions included cancer education for medical students: 13 had a program of residency; nine offered continuing education; and 1 1 institutions offered paramedical education. The questionnaire sought information on various aspects of cancer education: I ) the qualifications of candidates for admission to the training program; 2) affiliation of the training institution to a university; 3) length of the program for the different subspecialities; and 4) evaluation of the program during and at the end of the basic training in oncology.
Affiliation of the Training Institution Because the quality of graduate education invariably improves when the program comes under the direction of the medical school, our main interest was to know how many institutions were affiliated with the university and what percentage of the staff of the cancer center were faculty members of the medical school. Of the 16 cancer centers, ten (62.5%) are affiliated with universities. and only six are not affiliated with a medical school. As regards the relation of the medical staff of the center to the university, in three institutions 100% of the staff are faculty members; in six institutions 50% or more are members; and in another six, less than 50% are faculty members. In only one center did the medical staff have no affiliation to a medical school. These figures express very well that the majority of the Comprehensive cancer centers have the manpower necessary for an adequate training program.
Resident Selection The selection of high-quality house staff is of vital concern to any residency training program. However, the large number of applicants, the variability of available applicant data, and the limited opportunity for direct applicant contact make this process difficult. In most of the Latin American countries, the number of applicants exceed by far the number of positions. Usually the training is begun after a 1-year internship, which is obligatory in Latin America. However, the programs are willing to accept candidates with more training than this. Most programs use a combination of specific selection factors that hopefully correlate with future success as a resident staff member. The hospital administration and medical staff. through the appropriate committees, scrutinize the qualifications of each applicant: quality of the medical school of origin, preliminary education, medical school performance, published research, andin the majority of institutions-the results from an ultimate written examination of medical knowledge. Interpersonal skills are often reflected in personal letters of recommendation and certainly in the interview process. The candidate will apply for residency, either through
Length of Training Programs The length of the different training programs varies from one institution to another; but, according to the different specialities, the training in oncology by the cancer institutions in Latin America in each of the 16 institutions evaluated are as follows: 15 offer postgraduate training in surgical oncology, one for 4 years, ten for 3 years, and four for 2 years; eight offer Postgraduate training in medical oncology, three for 3 years, and five for 2 years; ten offer postgraduate training in radiation therapy, four for 3 years, five for 2 years, and one for 6 months; three offer postgraduate training in nuclear medicine, one for 3 years and two for 2 years; only one institution offers postgraduate training in epidemiology; ten institutions offer postgraduate training in tumor pathology, four for 3 years, four for 2 years, and two for l year. Program Evaluation In most centers there is close follow-up of pcrformance through several evaluations per year. In addition, annual examination that can be repeated only once is given. Those who fail for the second time are unable to continue their training. There is, however, no quality control at the end of surgical, medical, o r tumor pathology training. Nearly 50% of universities ask for the pre-
Caceres sentation of a thesis before the title of specialist is granted. Another important factor in cancer education is the presence of a director or a department of education. Of the 16 institutions analyzed, 14 (87%) have a department of education.
204
COMMENTS One of the problems in cancer education that immediately comes to light is the accurate definition of a trainee or resident and the definition of a fully trained and qualified oncologist. A trainee or resident is usually defined as a doctor who has finished medical school, 1 year of intership, and 1 year of rural service, as required in Argentina, Brazil, Chile, Mexico, and Peru, and who is enrolled in a training program in one of the subspecialities in oncology (surgery, medical oncology, pathology, radiation therapy, nuclear medicine, etc.). No special training in pediatric or gynecological oncology is yet established in most of Latin America. However, a tendency to offer additional training in these areas, once the resident has finished general training in oncology, has been observed. For example, in Peru after 4 years of surgical training or 3 years of medical training, some residents, depending on their qualifications, are offered an additional year in one of the subspecialities, such as head and neck, gynecology, thoracic surgery, etc. A qualified oncologist can be defined as a fully trained, independent practicing oncologist who is totally
responsible for patient care and is in active practice, usually with a hospital position. Although there is no surplus of oncologists in Latin America, there is an acute shortage in several subspecialities such as radiotherapy, pathology, and radiology. A decrease in the number of applicants for training in these disciplines is increasingly felt because of a lack of economic incentives under the present national health program in most Latin American countries and because of the rapid sophistication of required and difficultto-obtain equipment for private practice. After graduation and an appropriate clinical training period, most oncologists become full- or part-time private practitioners. Even those who are academically inclined and appointed to university posts continue their private practice because the salary from these institutions is insufficient to support a family. Unfortunately, this inhibits the academic growth of the centers and the growth of the cancer education programs.
Eduardo Caceres, MD, Instituto Nacional de Enfermedades Neoplasticas, Lima, Peru
REFERENCES 1. Parkin, DM, Laara, E Muir, CS: Estimates of the Worldwide Frequency of Sixteen Major Cancers in 1980. Int J Cancer 41:184-
197, 1988.
