June 9, 1995

Radiation and Breast Cancer

Those of you who have been in the field for a long time know that it was once the practice of pediatricians to fluoroscope babies and young children every month and when they had their annual checkup. When we questioned the practice, pediatricians would say, "Well, the parents expect it. They think if I don't fluoroscope the patients, they are not getting a complete examination."

Hanson Blatz, former director of the Office of Radiation Control, New York City Department of Health, 1970

I have just finished reading a remarkable new(1995) book by John W. Gofman, entitled Preventing Breast Cancer.

Gofman calculates that 75% of all cases of breast cancer found today were caused by the large amount of medical X-ray used from about 1910 on. He further believes that this is a conservative estimate.

If he had claimed that one case out of four was due to X-ray, it would have been enough to knock my socks off, but 3 out of 4 was almost unbelievable. If he is correct, that means that the incidence of breast cancer in the days before the use of medical X-ray would have been one quarter of what it is today. I didn't believe it, so I decided to check it out.

Gofman's theory is easy enough to check. Roentgen discovered X-ray in 1895. Add 10 years for its dissemination and add 10 years for the latent period between the time of the radiation and the appearance of the first cancers. That means that prior to 1915, the incidence of breast cancer should have been about one quarter of what it is today. The problem with working with incidence is that it is highly variable, depending on the techniques and care in examination, and reporting practices that were in effect at the time, particularly 80 years ago. Mortality rate would be a more reliable figure, when comparing today with 80 years ago. The cure rate, for the last 30 or so years, has been over 50%, so the incidence should be at least twice the mortality rate. If 3 out of 4 breast cancers were due to radiation, I would expect the mortality rate in 1910 to be about half of what it is today. When I looked it up, the death rate from breast cancer in 1980 was 28 deaths per 100,000 population. From 1906 to 1910, it was 13 per 100,000 (Since not many cancers were cured in 80 to 90 years ago, the mortality rate and the incidence rate would be similar). Gofman's numbers seem to be in the ball park. I believe that Gofman has made the best estimate, to date, of the effect of radiation as a cause of of breast cancer.

There are very few people who are able to make sense out of the hodgepodge of very incomplete information about human radiation and cancer, and Gofman is one of them. He received his Ph.D. in physics and worked on the development of the atomic bomb. He then went to medical school and, after obtaining his M.D., took an internship in internal medicine. After this, he joined the Department of Medical Physics at the University of California in Berkeley, where he remained until his retirement. He is now 76 years old. He has had a distinguished career as a research scientist, which apparently is not yet over.

Most of the book is devoted to the prevailing medical X-ray use practices in the past. Nothing that Gofman said surprised me; I grew up during that period. My family physician had a fluoroscope in his office, and he kept patients -including me- under it for long periods of time. My doctor, as did almost everyone, thought that X-rays were harmless. I worked in a children's hospital for 10 years and I know how often children were subjected to high-dose radiological procedures. I know about the frequent, high dose irradiation of the thymus gland, to shrink it because it seemed enlarged -a large thymus is normal in infants. The younger a person is, the more severe the cancer-producing effects of radiation are, so irradiating infants has a much greater cancer-causing affect than the same amount used in an adult.

In view of Gofman's findings, there is some bad news and some good news. The bad news is that a hellofalot of breast cancer, as well as other types of cancer, have been produced by medical X-ray. The good news is that, with better equipment, films and technique, radiation exposure, per procedure, is now much less than it was 50 years ago. In view of this, we might expect a substantial drop in breast cancer incidence in the next 50 years -unless a much much greater number of X-rays taken will make up for the improved techniques in use today.

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