News News
Inferior Units About 98% of this country's mammography machines are dedicated units, usually free of radiation hazard. But almost a third are inexpensive units with low radiation output, often producing images of inferior quality, Hendrick said. Richard Gross, of the Food and Drug Administration's Center for Devices and Radiological Health, said there is no evidence that these machines are inferior, or to justify their removal from the marketplace. "A mammogram produced by a low-output machine is better than no mammogram at all," he added. Gross said the FDA requires manufacturers to guarantee that a machine has a certain beam quality and delivers the dose it is instructed to deliver. Hendrick said that "if safe means not dying from radiation exposure, then FDA is correct in saying that our mammography machines are safe. But a poor mammogram that can result in an incorrect diagnosis and death is not safe." He added that "image quality is more important than dose. The odds of radiation exposure from mammography causing cancer are a few per million, 396
but a woman's chances of dying because of a misdiagnosis may be 1 in 3,000." Nevertheless, progress is being made. FDA surveys of mammography faculties show that image quality in 1988 was significantly better than it was in 1985. According to the FDA's Nationwide Evaluation of X-ray Trends, or NEXT, 36% of the fadlities surveyed in 1985 did not meet ACR phantom image quality criteria (established after 1985), compared with 13% of facilities surveyed in 1988. "I am confident that we are making progress, but until we are further along, the best advice I have for women older than 35 is to follow the guidelines [of NCI and the American Cancer Society] for frequency of mammography screening and to contact NCI or ACS to locate the closest ACR-accredited facility," said Gerald D. Dodd, M.D., ACS president and professor at the University of Texas MX). Anderson Cancer Center. —By Florence S. Antoine
Dr. Gerald D. Dodd
Vitamin C: How It May Protect Against Cancer Is Unclear Foods rich in vitamin C may protect against stomach, colorectal, cervical, and possibly other cancers. But the mechanism of protection is still unclear. "There is a protective factor against cancer in fruits and vegetables, and vitamin C is the most consistent factor," said Geoffrey Howe, PhX>., director of epidemiology, National Cancer Institute of Canada. "The strongest evidence for vitamin C is with stomach cancer, then colon, breast, and cervical," he added.
Strong Association Thirty-three of 46 epidemiologjc studies reviewed by Gladys Block, Ph.D., of the U.S. National Cancer Institute's Division of Cancer Prevention and Control, showed statistically significant protective effects of vitamin C-rich foods for some cancers. She saw a notably strong association between low intake of vitamin C and a higher risk of oral, laryngeal, and esophageal cancers. Regina Ziegler, Ph.D., of NCI's Division of Cancer Etiology, is less certain. She is only convinced that there is a protective effect of vitamin C for stomach cancer. She added that most epidemiologjc studies have had to rely on indirect vitamin C measurements, and that serum measurement of vitamin C has been complicated by its rapid degradation. Ziegler and Sam Margolis at the National Institute of Standards and Technology have developed a way to keep vitamin C stable during blood collection and storage over extended periods of time. This method has been used in Journal of the National Cancer Institute
Downloaded from http://jnci.oxfordjournals.org/ at New York University on May 20, 2015
for about half of this country's 10,000 mammography units. Approximately 2,400 units are now accredited, with a lag time of 3 to 4 months between application for and receipt of accreditation. ACR also sponsors weekend seminars, self-study courses, and publications aimed at sharpening the skills of those performing and interpreting mammograms. The American Board of Radiology is also working to improve professional competence. As of June 1990, physicians applying for specialty boards in radiology are required to pass a 30minute oral mammography section.
News News
Vol. 83, No. 6, March 20, 1991
while supplementing the diet with ascorbic acid and beta-carotene. Investigations into the vitamin's role in cancer treatment are limited. A study combining radiation therapy with high doses of vitamin C showed "no modification in degree of treatment success, but tissues of the skin and bone marrow had a 25% improved radiation tolerance," said Paul Okunieff, M.D., Harvard Medical School.
Not Enthusiastic Okunieff is not enthusiastic about the findings Late-reacting tissues were not studied, and the large doses of vitamin C required may not be possible to achieve in the clinic. Zuckerkandl is one of the few researchers to make recommendations. "For use in treatment, high doses of vitamin C are recommended as a valuable adjuvant to conventional therapy and not as a replacement," he said. —By Amy Aubertin
Dr. Pelayo Correa
NEWS 397
Downloaded from http://jnci.oxfordjournals.org/ at New York University on May 20, 2015
International Conference on Cancer Prevention last month. "Ascorbic acid is picked up by the blood and secreted by stomach mucosa," Correa said. "This secretion protects us from dietary carcinogens. We don't know exactly why. The hypothesis is that the flow of blood with ascorbic acid into the lumen blocks formation of carcinogens." Vitamin C operates mainly as a free radical scavenger. "Our tissues seem to be exposed to a constant flow of carcinogens... we need a constant flow of ascorbic add, betacarotene, and other antioxidants to keep everything in check," Correa said. "Other probable mechanisms include vitamin C s effect on the imi m u n e system and its essential function in collagen synthesis. Both [mechanisms] aid in resisting cancer," said Emile Zuckerkandl, Phj)., director of the Linus Pauling Dr. Reglna Zlegler Institute, Palo Alto, Calif. Immune cells contain high concenstudies conducted by NCI and in an ontrations of vitamin C. The concentragoing prospective study conducted tion is 20 to 100 times higher than in the through the Johns Hopkins University. blood, according to Mark Levine, Despite the vitamin C associations MX)., director of intramural nutrition with reduced risk, there are other facresearch at the National Institute of tors to consider. "People who have Diabetes and Digestive and Kidney higher intakes of vitamin C also conDiseases. sume higher amounts of fiber, betacarotene, and other vitamin-rich foods. Role Unclear Therefore, it's hard to determine if it is vitamin C or a diet rich in fruits and "If immune cells use vitamin C and vegetables," Howe said. the immune cells are involved with the cancer process, then there is a relation "It's possible that vitamin C, carotto cancer, but it is all unknown. The enoids, and other factors in fruits and role with cancer is unclear," Levine vegetables act jointly," Block said. said. "Vitamin C is a good scavenger and Nitrosamines Blocked in theory, it makes sense that it eats up Vitamin C acts by blocking the free radicals... but we don't know for production of nitrosamines and other sure," he added. carcinogens in the stomach, according Correa plans to start a 4-year interto Pelayo Correa, M.D., of Louisiana vention study in Colombia this spring. State University, who presented at the The study will monitor cancer rates
Inferior Units About 98% of this country's mammography machines are dedicated units, usually free of radiation hazard. But almost a third are inexpensive units with low radiation output, often producing images of inferior quality, Hendrick said. Richard Gross, of the Food and Drug Administration's Center for Devices and Radiological Health, said there is no evidence that these machines are inferior, or to justify their removal from the marketplace. "A mammogram produced by a low-output machine is better than no mammogram at all," he added. Gross said the FDA requires manufacturers to guarantee that a machine has a certain beam quality and delivers the dose it is instructed to deliver. Hendrick said that "if safe means not dying from radiation exposure, then FDA is correct in saying that our mammography machines are safe. But a poor mammogram that can result in an incorrect diagnosis and death is not safe." He added that "image quality is more important than dose. The odds of radiation exposure from mammography causing cancer are a few per million, 396
but a woman's chances of dying because of a misdiagnosis may be 1 in 3,000." Nevertheless, progress is being made. FDA surveys of mammography faculties show that image quality in 1988 was significantly better than it was in 1985. According to the FDA's Nationwide Evaluation of X-ray Trends, or NEXT, 36% of the fadlities surveyed in 1985 did not meet ACR phantom image quality criteria (established after 1985), compared with 13% of facilities surveyed in 1988. "I am confident that we are making progress, but until we are further along, the best advice I have for women older than 35 is to follow the guidelines [of NCI and the American Cancer Society] for frequency of mammography screening and to contact NCI or ACS to locate the closest ACR-accredited facility," said Gerald D. Dodd, M.D., ACS president and professor at the University of Texas MX). Anderson Cancer Center. —By Florence S. Antoine
Dr. Gerald D. Dodd
Vitamin C: How It May Protect Against Cancer Is Unclear Foods rich in vitamin C may protect against stomach, colorectal, cervical, and possibly other cancers. But the mechanism of protection is still unclear. "There is a protective factor against cancer in fruits and vegetables, and vitamin C is the most consistent factor," said Geoffrey Howe, PhX>., director of epidemiology, National Cancer Institute of Canada. "The strongest evidence for vitamin C is with stomach cancer, then colon, breast, and cervical," he added.
Strong Association Thirty-three of 46 epidemiologjc studies reviewed by Gladys Block, Ph.D., of the U.S. National Cancer Institute's Division of Cancer Prevention and Control, showed statistically significant protective effects of vitamin C-rich foods for some cancers. She saw a notably strong association between low intake of vitamin C and a higher risk of oral, laryngeal, and esophageal cancers. Regina Ziegler, Ph.D., of NCI's Division of Cancer Etiology, is less certain. She is only convinced that there is a protective effect of vitamin C for stomach cancer. She added that most epidemiologjc studies have had to rely on indirect vitamin C measurements, and that serum measurement of vitamin C has been complicated by its rapid degradation. Ziegler and Sam Margolis at the National Institute of Standards and Technology have developed a way to keep vitamin C stable during blood collection and storage over extended periods of time. This method has been used in Journal of the National Cancer Institute
Downloaded from http://jnci.oxfordjournals.org/ at New York University on May 20, 2015
for about half of this country's 10,000 mammography units. Approximately 2,400 units are now accredited, with a lag time of 3 to 4 months between application for and receipt of accreditation. ACR also sponsors weekend seminars, self-study courses, and publications aimed at sharpening the skills of those performing and interpreting mammograms. The American Board of Radiology is also working to improve professional competence. As of June 1990, physicians applying for specialty boards in radiology are required to pass a 30minute oral mammography section.
News News
Vol. 83, No. 6, March 20, 1991
while supplementing the diet with ascorbic acid and beta-carotene. Investigations into the vitamin's role in cancer treatment are limited. A study combining radiation therapy with high doses of vitamin C showed "no modification in degree of treatment success, but tissues of the skin and bone marrow had a 25% improved radiation tolerance," said Paul Okunieff, M.D., Harvard Medical School.
Not Enthusiastic Okunieff is not enthusiastic about the findings Late-reacting tissues were not studied, and the large doses of vitamin C required may not be possible to achieve in the clinic. Zuckerkandl is one of the few researchers to make recommendations. "For use in treatment, high doses of vitamin C are recommended as a valuable adjuvant to conventional therapy and not as a replacement," he said. —By Amy Aubertin
Dr. Pelayo Correa
NEWS 397
Downloaded from http://jnci.oxfordjournals.org/ at New York University on May 20, 2015
International Conference on Cancer Prevention last month. "Ascorbic acid is picked up by the blood and secreted by stomach mucosa," Correa said. "This secretion protects us from dietary carcinogens. We don't know exactly why. The hypothesis is that the flow of blood with ascorbic acid into the lumen blocks formation of carcinogens." Vitamin C operates mainly as a free radical scavenger. "Our tissues seem to be exposed to a constant flow of carcinogens... we need a constant flow of ascorbic add, betacarotene, and other antioxidants to keep everything in check," Correa said. "Other probable mechanisms include vitamin C s effect on the imi m u n e system and its essential function in collagen synthesis. Both [mechanisms] aid in resisting cancer," said Emile Zuckerkandl, Phj)., director of the Linus Pauling Dr. Reglna Zlegler Institute, Palo Alto, Calif. Immune cells contain high concenstudies conducted by NCI and in an ontrations of vitamin C. The concentragoing prospective study conducted tion is 20 to 100 times higher than in the through the Johns Hopkins University. blood, according to Mark Levine, Despite the vitamin C associations MX)., director of intramural nutrition with reduced risk, there are other facresearch at the National Institute of tors to consider. "People who have Diabetes and Digestive and Kidney higher intakes of vitamin C also conDiseases. sume higher amounts of fiber, betacarotene, and other vitamin-rich foods. Role Unclear Therefore, it's hard to determine if it is vitamin C or a diet rich in fruits and "If immune cells use vitamin C and vegetables," Howe said. the immune cells are involved with the cancer process, then there is a relation "It's possible that vitamin C, carotto cancer, but it is all unknown. The enoids, and other factors in fruits and role with cancer is unclear," Levine vegetables act jointly," Block said. said. "Vitamin C is a good scavenger and Nitrosamines Blocked in theory, it makes sense that it eats up Vitamin C acts by blocking the free radicals... but we don't know for production of nitrosamines and other sure," he added. carcinogens in the stomach, according Correa plans to start a 4-year interto Pelayo Correa, M.D., of Louisiana vention study in Colombia this spring. State University, who presented at the The study will monitor cancer rates
