cause of suspected X-linked disorders; in most centres only the sex of the fetus was determined. Of the 46% of fetuses found to be male, most were aborted, although approximately 50% were normal a serious reproach to medical expertise. However, recently a number of X-linked diseases, including hemophilia,0'7 have been diagnosed antenatally.8 In addition to ultramicro and ultrasensitive techniques, other approaches open up new possibilities; for example, the prenatal detection of congenital adrenal hyperplasia9 and Fanconi's syndrome10 by HLAtyping and cytogenetic analysis of chromosome breaks respectively. With regard to postnatal followup, a corollary to general screening programs and antenatal diagnosis, probably the most spectacular advance has been neonatal thyroid screening.11 Already in Quebec and the northeastern and northwestern United States some 750 000 newborn infants have been tested, 163 of whom were found to have congenital hypothyroidism. The prevention or amelioration of mental retardation by early therapy, as well as the cost-effectiveness of the program have been considerable. RALPH E. BERNSTEIN, MB, DCP[E], FRC PATH[E]

56 Avonwold Dr. 2196 Saxonwold Johannesburg, South Africa

References 1. SMITH AD, WALD NJ, CUCKLE HS,

et al: Amniotic-fluid acetyicholinesterase as a possible diagnostic test for neural-tube defects in early pregnancy. Lancet 1: 685, 1979 2. CHUBB 1W, PILowSKY PM, SPRIN-

GELL HJ, et al: Acetylcholinesterase in human amniotic fluid: an index of fetal neural development. Ibid, p 688 3. DALE G, BONHAM JR, LOWDON P, et at: Amniotic-fluid acetyicholin-

esterase and neural-tube defects (C). Ibid, p 880 4. BERNSTEIN RE: Diagnosis of open neural tube defects. Lancet (in press) 5. SiM.'soN NE, DALLAIRE L, MILLER

JR, et al: Prenatal diagnosis of genetic disease in Canada: report of a collaborative study. Can Med Assoc J 115: 739, 1976 6. BERNSTEIN RE: Prenatal diagnosis of X-linked disorders. N Engi J Med (in press) 7. MAHONEY MJ, HOYER L, FIRSHEIN 5, et al: Prenatal diagnosis of hemo-

philia A (abstr). Am J Hum Genet 30: 59A, 1978 8. MIBASHAN RS, RODECK CH, THUMP-

STON JK, et al: Prenatal plasma assay of fetal factors VIII and IX.

Br J Haematol 41: 611, 1979 9. POLLACK MS, MAURER D, LEVINE LS, et al: Prenatal diagnosis of congenital adrenal hyperplasia (21hydroxylase deficiency) by HLA

typing. Lance 1: 1107, 1979 10. AUERBACH

AD,

WARBURTON

D,

BLOOM AD, et al: Prenatal detection of the Fanconi anemia gene by cytogenetic methods. Am I Hum Genet 31: 77, 1979

11. FISHER DA: Neonatal thyroid screening. Pediatr Clin North Am 25: 423, 1978

Mammography

To the editor: The controversy about the use of mammography between Drs. J.E. Devitt and A.B. Miller (Can Med Assoc 1 120: 1370, 1372, 1374; 1979) and many other investigators may be due to the fact that they are seeing and feeling different parts of the same elephant. Let us consider the possible value of mammography in two separate situations: in the screening of asymptomatic women and in the management of women with breast complaints. Data can be used from both situations to help resolve each aspect. What information is available on the possible value of screening asymptomatic women? The American Cancer Society/National Cancer Institute breast cancer detection demonstration projects,1 in which 270 000 women were studied, were unfortunately not designed to answer anything but logistic questions - and there are no answers, nor will there be. In the randomized trial conducted by the Health Insurance Plan of Greater New York 31 000 women were screened and there was a supposedly suitable control group of 31 000.2 At the end of 10 years 97 of the women who were screened and 137 of the control group had died of breast cancer. It is discouraging that more deaths due to breast cancer have not been delayed or prevented, because the cost (i.e., additional surgical procedures to define the nature of radiologic shadows, risk from radiation, time and money) has been great. The difference of 40 in the number of deaths in this group of 62 000 is a

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maximum potential gain - potential because there are several unanswered questions about the study that I won't consider here. If Canada is going to sponsor a clinical trial it must be truly randomized, the potential benefit should be maximized and the cost should be minimized. The dollar cost of mammography is very significant, and with computed tomographic mammography in the wings "we ain't seen nothin' yet". One obvious way to reduce health care costs is to determine whether expensive methods of investigation and treatment are indeed of value. During the planning of the proposed Canadian multicentre screening trial some interesting questions were raised regarding the reproducibility of mammographic interpretation, which has an important bearing on the clinical management of breast problems. Each centre identified their expert on mammographic interpretation, who was then sent the xeromammograms of 50 patients for whom the diagnosis was known. Across the country there was a very significant falsenegative and false-positive rate.3 A further study of this very important problem will soon be published (personal communication, 1979). When mammography was first being performed in British Columbia the treatment of cancer was often delayed if mammography gave false-negative results, because it was thought that mammography was more reliable than it actually is. As a result of physician education this seldom occurs now. Of course, one should proceed with biopsy if it is clinically indicated and ignore the mammogram. The situation is analogous to an endoscopic suspicion of gastric malignant disease in the face of a negative result of a barium study. The main problem with all breast cancer screening methods is the falsepositive results. Patients with breast cancer frequently require sophisticated techniques of finding and excising the cause of the radiologic shadow, which usually indicates admission to hospital and administration of a general anesthetic - and, of course, results in disability, cost and worry. Occasionally death will occur. However, when one is dealing with a symptomatic patient the

significant false-negative and false- cannot be excluded" for purely tinent to this problem and arrive at positive results can be accepted be- medicolegal reasons and may not an appropriate solution. Fortunatecause the potential benefit is greater wish to imply that biopsy is neces- ly no reports of adverse effects on than when one is dealing with an sary. Communication with the pa- health have been received to date. asymptomatic patient. The cost! thologist is also required. One Carbon monoxide is generated by benefit ratio is particularly favour- should try to determine the risk for fossil-fuelled ice-resurfacing vehiable in the management of sympto- subsequent breast cancer inherent cles, which are widely used in matic patients and individuals at in the lesion removed and treat skating arenas that were not inihigh risk. Factors indicating that the patient appropriately. No one tially constructed with ventilation a person is at high risk of breast knows the natural history of breast adequate to keep emission levels cancer (in their approximate order carcinoma in situ. It is possible, as within acceptable standards. of importance) are as follows: There are few reports in the in the cervix, that some lesions may * Dominant or discrete (three- regress or progress, as Dr. Devitt literature of carbon monoxide poidimensional) mass or lump.4 has stated. There is a wide spec- soning attributed to the ice-resurfa* Postmenopausal with sponta- trum, from premalignant to border- cing vehicles. In fact, reports of neous nipple discharge.5 line to minimal to frank cancer; episodes in Seattle1 and Michigan2 * Any age with bloody sponta- physicians and pathologists may not appear to be the only ones pubneous nipple discharge.5 even be using the same nomencla- lished. Occasionally the popular * Previous cancer in one breast ture. press carries an item pertaining to (five times the risk). this problem (Winnipeg Tribune, R. CAMERON HARRISON, MD * Family history of breast canMar. 5, 1979, p 2), but almost cer700 West 10th Ave. cer, especially bilateral or of preVancouver, BC tainly if symptoms are mild and menopausal onset (two to eight only a few individuals are affected times the risk). the episodes are not reported; an * Previous history of a breast References accurate diagnosis is rarely made. operation, particularly if multiple 1. BYRD BF: Progress report on AmerOur correspondence with numerintraductal papillomas, a gross cyst ican Cancer Society/National Cancer ous municipal and provincial agenInstitute breast cancer detection dem- cies across Canada has revealed or lobular neoplasia was found6 onstration projects, in Breast Cancer. that incidents of carbon monoxide (two to four times the risk). Proceedings, International Symposium * Late age at first pregnancy or on Breast Cancer, Lucerne, Switzer- poisoning in skating arenas have nulliparity (one and a half times land, July 13-Aug. 4, 1976, MONTA- occurred in various parts of the GUE AC, STONE GL JR, LEwIsoN EF country, but, although the incidents the risk). (eds), Liss, New York, 1977, p 177 were perhaps publicized locally, * Early menarche or late meno2. SHAPIRO 5: Efficacy of breast cancer they were not more widely known. pause or both. screening, in Screening ill Cancer. A * Exposure to radiation (due to Report of a UICC international No deaths have been recorded. repeated fluoroscopy or mammoA recent paper by Spengler, Workshop, UICC tech rep ser, vol 40, Geneva, 1978, p 133 graphy). Stone and Lilley,3 however, indi* Family history of benign 3. BOYD NF: A preliminary appraisal of cates that the incidence of toxic the effects of length biased sampling effects may well be very high. A breast disease. and observer variability on screening. study of hockey players before and * Upper-middle-class or higher Ibid, p 40 socioeconomic status. 4. HARRISON RC: When to biopsy lumps after a practice in an arena with in the breast. CA 13: 214, 1963 an average ambient carbon mon* Above-average height and 5. Idem: The management of breast oxide concentration of 22.5 parts weight. problems in practice. Can Med Assoc per million (ppm) showed a marked * Estrogen use during the meJ 83: 849, 1960 nopause. 6. HAAGENSEN CD: The relationship of increase in the players' carboxyI believe almost all patients gross cystic disease of the breast and hemoglobin levels, from a mean of carcinoma (E). A an Surg 185: 375, 1.1% to 3.2%. Though the conshould undergo bilateral mammo1977 centrations are low in comparison graphy prior to breast operations with those usually observed in acute - an opinion with no hard data to support it. Because the first three Carbon monoxide in indoor skating toxic events, suggestions have been made that some performance paraindications are absolute rather than arenas meters (i.e., discrimination between relative indications for breast operations the potential benefit of mam- To the editor: During the winter time intervals, adaptation to the mography is worth the cost. In my of 1978 the Manitoba Department dark and coordination4) may be afopinion mammography is not worth of Mines, Natural Resources and fected at low concentrations; therewhile as part of a general check-up, the Environment conducted surveys fore, even low concentrations of and it may cause unwarranted con- to determine the concentrations of carbon monoxide can present a pofusion. However, mammography carbon monoxide in skating arenas tential danger, particularly for can prove beneficial when one is in Winnipeg, and found that the hockey players. Further, individuals dealing with women at high risk of concentrations were elevated. Fol- with circulatory compromise in breast cancer. lowing the surveys several meetings whom the concentrations are slightOne must communicate with the were held with health, environment ly higher may experience difficulradiologist. He or she may be rou- and recreation officials in an at- ties because of lowered oxygen tentinely using a term such as "cancer tempt to gather information per- sion.3 Though spectators and even CMA JOURNAL/OCTOBER 20, 1979/VOL. 121

.-For prescribing information see page 1104

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