Part 1. The Years 1920-1960, and Beyond
Chronic human exposure to ionizing radiation, from natural sources, has been occurring since the beginning of our species. Then along came Dr. Wilhelm Roentgen with his discovery of x-rays in 1895. Just a few years later, human exposure to ionizing radiation began to grow rapidly. Some segments of the population began receiving extra radiation exposures far greater than natural radiation exposures. Soon thereafter, radium and radon also became widely available as radiation sources in medical practice.
We could start our study at the very beginning of such medical irradiation, but it is not essential to go back quite that far. Instead, we go back to 1920. We pick the forty-year period of 1920 to 1960 as the period for which we will determine the annual production-rate of radiation-induced breast-cancers, because we are interested in the much later set of years when the annual incidence-rate of radiation-induced breast-cancers is equal to the annual production-rate (Chapter 4).
To build up to that point of equality can take decades of steady cancer-production, and to decline from that point of equality can also require decades --- as depicted, for example, by Figure-A of the preceding chapter. Even if every bit of medical irradiation of breasts had suddenly stopped in 1960, decades would still be required for the delivery of all the radiation-induced breast-cancers produced before 1960.
Moreover, irradiation of breasts most certainly did not cease in 1960. Even if we assume that the average annual dose-level to female breasts after 1960 fell appreciably below the average level of 1920-1960, we can not ignore the large increase in the average population of women receiving the average annual dose. The two changes would balance each other out and would maintain the earlier annual production-rate of radiation-induced breast-cancer, to a good "first approximation."
For these reasons, the study of the annual production-rate of radiation-induced breast-cancers during the 1920-1960 period will be adequate for our "first cut" at estimating the annual incidence-rate of radiation-induced breast-cancer for approximately the years 1960 to 2000.Part 2. What about Constancy of Population and Dose-Rate?
The "Law of Equality" (Chapter 4) requires both a constant number of persons irradiated per year, and a constant level of exposure, year after year.
We know that the female population of the USA grew during the 1920-1960 period (Table 2, located after the final chapter). So we have calculated an average annual population for 1920-1960, which makes the total size the same in every year. Although the age-distribution of the female population may have changed somewhat during the 40-year period, we consider that this is a secondary phenomenon which we ignore in our "first cut" estimate. In Chapter 8, readers will see exactly how we obtained our constant number of females in each age-year (age 0 means from birth to the first birthday, age 1 means from the first birthday to the second birthday, etc.).
We will often use the term "age-year," in order to prevent a mix-up with "calendar-year."
With respect to radiation-induced cases of breast-cancer, the annual exposure-level of breasts per age-year determines the annual production-rate of breast-cancers in people irradiated at a particular age. And the annual production-rate is what we need, to obtain the annual incidence-rate in later years from the "Law of Equality." Because radiation-sensitivity changes with age at exposure, we must keep the annual production-rate for all 65 age-years distinct in our work, until we are ready to add up the separate production-rates from all ages, for a single calendar-year of exposure.
Not even for a single age-year can we expect the annual medical breast-dose to remain constant over a 40-year period. But, as readers will first see in Chapter 8, we can develop an average annual breast-dose per age-year which typifies each calendar-year of our 1920-1960 period. Not everyone, of course, received the medical procedures evaluated in our study. When we speak here of the average annual breast-dose per age-year, we mean the breast-dose received by those who were irradiated, adjusted downward by distributing their dose (mathematically) over the whole female population of the same age-year.
We consider irradiation of females only below the 65th age-year --- an approximation which introduces a slight underestimate into our findings.
Starting in Chapter 8, we will demonstrate all these abstractions with real-world numbers, and we will show the reasonable approximations forced upon us by the real world, rather than the ideal world described in Chapter 4. Readers who go through this entire book will, we believe, be convinced that the method we use is sound.Part 3. The Worst Possible Outcome on This Subject
As the method used in this book is also used in the future by ourselves and by others --- to study other cancers, and additional aspects of breast-cancer --- we expect that we and others will be able to sharpen the method appreciably. However, expected refinements of the method would be a horrible excuse for delaying appropriate action to start the prevention of breast-cancer, now, in the United States and in other countries too.
We have seen comments, from some physicians who should know better, that "There is speculation about a possible relationship of ionizing radiation with breast-cancer."
There is no basis for such comments. Breast-cancer induction by ionizing radiation is a settled issue. There are a few aspects of the issue which can not yet be settled, such as the full duration of the effect for females exposed below age 10, as already noted in Chapter 2, Part 2. But to suggest that the relationship of ionizing radiation with breast-cancer is "speculative" suggests some defect in a physician's medical training, at this stage of history. There is a reason for emphasizing the point:
The worst possible outcome on this subject would be just to hold hearings, or to appoint some new Presidential Commission, or to say that "Future research may show radiation to be a cause of breast cancer." These are the usual substitutes for action on such matters. But there is already more than enough knowledge to say, with certainty, that there will be a reduction in future breast-cancer incidence if people take all the steps needed to reduce medical and other radiation exposures as much as possible.
Ionizing radiation is not just "a cause" of breast-cancer. The evidence summarized in this book indicates that radiation is the major cause of breast-cancer in the United States. We ought to start doing something very constructive on this issue, and not be satisfied with procrastination and substitutes for action.Part 4. Main Sources of Raw Information for This Study
By careful detective work and by studying literature in the x-ray field for 1920 to 1960 (and some later and earlier documents), we have tried to reconstruct the probable radiation dose to breasts for females in each of the age-years, for one average year of the 1920-1960 period. Without the dosage, nothing is possible in any effort to figure out how much of the recent, current, and future breast-cancer problem is due to past radiation.
It has been an illuminating tour through medicine.
We wish to express our gratitude for the existence of collections of the American Journal of Roentgenology and Radium Therapy for that entire period. What an excellent journal! The extensive discussions, following presentation of papers at meetings, are all there --- not only the papers. Thus, one can get a flavor of the times and the debates, not just the data themselves. And the sections covering journals throughout the world were an invaluable source of references needing attention. Timely editorials were very useful in highlighting problems of the period. We are particularly impressed with the series of scholarly papers by Dr. Arthur Desjardins of the Mayo Clinic, on mechanisms of radiation action. In the 1930s, he set out the rationale of x-ray therapy for disorders of various physiological systems, in papers which are fascinating and most useful. Other journals were helpful too, of course. It is quite refreshing to have such a fine window on a past era.
Starting with such literature, we have evaluated as many types of radiation procedures as possible with respect to breast-dose. We wish to state with emphasis that we are trying to evaluate the dosage, but we are not evaluating the rationale, success, or failure of the usage. We are not in judgment of the procedures themselves. We are just trying to learn the magnitude of an unintended consequence: Breast-cancer.
During each year of the 40-year period (1920-1960), breast-cancers were being produced (committed) by medical x-rays and radium gamma rays. Some of the radiation was used to treat non-cancerous disorders of the breast-tissues. Most often, the radiation was not planned for reaching the breasts, but reached the breasts unavoidably during the planned irradiation of other tissues and organs.
Potential Surprises for Young Physicians Today
There will undoubtedly be some readers of the stories in this book who will be critical of the radiation-uses which occurred in the early period. Of course, 20/20 hindsight is a powerful instrument. But there is little room for latter-day experts to be judgmental, in our opinion. Monday-morning quarterbacking is of no value. What has value is to gain some wisdom for the future, about the too-rapid introduction of certain technologies, and the too-little appreciation for the long incubation period for certain important diseases.
It would be "poetic license" to say that, in the early period of roentgenology, ionizing radiation from radium or from x-ray machines was tried for virtually any disorder or disease one could name --- but it is no exaggeration to say that it was tried out to seek relief for a great variety of afflictions. It was tried, too, for an affliction of uncertain existence, called "enlarged thymus gland." (The thymus gland, part of the immune-response system, is located in mid-chest, under the sternum, or "breast bone.")
We doubt that many young physicians in practice today would know, for example, that leading institutions would refuse to do a tonsillectomy and adenoidectomy without first ascertaining (with diagnostic x-rays) whether enlargement of the thymus existed. And if it did exist, therapy (with x-rays) was required before surgery would be contemplated.
Many, today, may be surprised to read that bronchial asthma was treated with x-rays, that whooping cough (pertussis) was treated with x-rays, that bacterial pneumonia was considered to be highly effectively treated with x-rays, and that many articles cited x-rays as the treatment of choice for serious inflammatory problems such as carbuncles.
A Regrettable Exclusion from Our Evaluation
There are many types of medical exposure reported in the literature which did not permit us to make quantitative estimates of breast-dose. For this reason, we are confident that the annual average breast-dose per age-year must have been appreciably higher than our estimates. In turn, this is a source of underestimation in our annual production-rate per age-year of radiation-induced breast-cancer, and necessarily in our estimated annual incidence-rate (delivery-rate), occurring decades later. Section 3 of this book discusses the sources of radiation exposure which we know to have existed, but which were not quantified in this investigation.
A Deliberate Exclusion from Our Evaluation
In our search of the literature, we deliberately excluded from our analysis the use of radiation in the treatment of existing malignancies, or in treatment of any other disease known to cause appreciable life-shortening. Our interest is in estimating the annual production-rate of radiation-induced breast-cancer in people who had a reasonable chance of living long enough to develop the disease. We exclude radiation therapy for existing malignancies because we want to avoid blaming radiation for more consequences than would be correct.Part 5. Conversion-Factors from Dose to Cancer-Production
When we have achieved an evaluation of annual breast-dose in the 1920-1960 period for each age-year, the next step is to convert dose into an annual production-rate of breast-cancer.
There is rather good agreement today about the percentage increase in breast-cancer per rad of breast-irradiation, as illustrated in Chapter 3, Part 3. There is still some disagreement about the exact shape of the dose-response curve, but the disagreement does not make a big difference in this particular study --- partly because many of the breast-doses from medical procedures occurred at relatively high dose-levels, where we and others have always been in rather good agreement about the magnitude of the radiation effect.
The term "conversion-factor" can be used for any formula which says how many radiation-induced cancers result from exposure to each rad of dose.
The number of cases produced per rad of dose is always the same, at any total dose, if the dose-response is linear. However, if the dose-response is non-linear, the number of cases produced per rad varies with the size of the dose. Our 1990 analysis of the A-Bomb Study shows a supra-linear dose-response, with the most cases induced per rad at the lowest doses. As total doses increase, each additional rad produces fewer cancers (Gofman 1990, Chapters 14 and 15).
Readers will see in this book, starting in Chapter 8, exactly how we adjust the actual breast-doses downward, whenever appropriate, so that our low-dose conversion-factors will not overestimate the consequences from higher doses. In other words, we adjust the dose rather than the conversion-factors.
The Issue of a "Threshold" or "Safe Dose"
A "threshold" for radiation effect is the hypothesis that no health-risk occurs from radiation if a dose is below a certain level (the threshold-level). A risk-free dose is a safe dose. A dose which creates a risk is not a safe dose.
Back in 1970, it was still possible to speculate that a threshold-dose might be found with respect to radiation-induced cancer, although human evidence was already trending strongly against the speculation (Gofman 1969, p.6; Gofman 1971, p.262). In the 1990s, the hope for a safe dose must yield to real-world evidence. By any reasonable standard of biomedical proof, that issue was settled in our 1990 book (Chapters 18 through 21).
Existing human evidence, combined with analysis of the number of ionization tracks created per cell-nucleus from various doses, invalidates older claims that proof of cancer-induction is limited to doses which are greater than 10 or 20 rads. In reality, there is human evidence in the mainstream medical journals of cancer-induction from radiation doses which are close to the lowest possible dose and dose-rate --- and some of that evidence happens to come from studies of radiation-induced human breast-cancer.
There is no safe dose (risk-free dose) with respect to radiation-induced cancer. Every dose counts in the total exposure. The doses received early in life count more in the risk of subsequent cancer-occurrence, but all doses count.Part 6. The "Master Table" of This Book
Near the end of this book, in Chapter 39, is the "Master Table." This table assembles all the findings about annual average breast-dose per age-year, from the chapters of Section 2. So the Master Table applies to a single calendar-year, and to 65 different age-years. The final columns of the Master Table (Columns U, V, and W) apply the conversion-factors which yield the annual production-rate of radiation-induced breast-cancers for each age-year.
The sum of the annual production-rates for all 65 age-years is, of course, the annual production-rate for all females (USA) during each year of the 1920-1960 period. From Chapter 4 and from Part 1 of this chapter, readers already know how the 1920-1960 annual production-rate of radiation-induced breast-cancer relates to the recent, current, and future annual incidence-rate of breast-cancer.
The sum in Column W is a remarkable number. Nonetheless, the number is unrealistically low with respect to past exposure-levels, for reasons which will become clear to the readers of Sections 2 and 3.
Overview of the Exposures Evaluated in the Master Table
Below is an overview of the various types of breast-exposure which are evaluated in the columns of the Master Table. The sequence of the columns is arbitrary, and is not related to the size of the consequences.
- Column C, Enlarged Thymus Gland: X-ray breast-dose, during first year of life (usually during first few months), in diagnosis and therapy of "enlarged thymus" and "status lymphaticus." Chapter 8.
- Column D, Enlarged Thymus Gland: X-ray breast-dose, mainly during age-years 2 through 15, in screening and therapy for "enlarged thymus," prior to tonsillectomy, adenoidectomy, and other childhood surgeries. Chapter 10.
- Column E, Acute Mastitis: X-ray breast-dose in therapy of acute mastitis (inflammation of the mammary gland). Chapter 13.
- Column F, Chronic Mastitis: X-ray breast-dose in therapy of chronic mastitis, a disorder which has many names (including fibroadenosis, chronic cystic mastitis, benign fibroadenoma, or adenofibrosis), and is characterized by lumpy, tender breasts. Chapter 14.
- Column G, Management of Tuberculosis: X-ray breast-dose in the fluoroscopic monitoring of artificial pneumothorax therapy, for patients having tuberculosis (the Detroit experience). Chapter 15.
- Column H, Management of Adolescent Scoliosis: X-ray breast-dose from spinal x-rays in the monitoring of adolescent scoliosis (curvature of the spine). Chapter 21.
- Column I, Mass Screening for Tuberculosis: X-ray breast-dose in mass screening-programs to detect tuberculosis (unlike Column G). Chapter 16.
- Column J, Bronchial Asthma: X-ray breast-dose in the therapy of bronchial asthma (the Mayo Clinic experiences). Chapter 17.
- Column K, Pre-Birth Breast-Irradiation: X-ray breast-dose to the fetus as a result of the mother's pelvic and abdominal x-ray examination while pregnant. Chapter 12.
- Column L, Hyper-Thyroidism: X-ray and gamma-ray (from radium and iodine-131) breast-dose in the radiation therapy of hyper-thyroidism, whether exophthalmic or not. Chapter 20.
- Column M, Enlarged Thymus Gland: X-ray breast-dose, mainly during age-years 1 through 9, in prophylactic therapy of "enlarged thymus" (the experience of the Massachusetts Eye and Ear Infirmary). Chapter 9.
- Column N, Whooping Cough: X-ray breast-dose in the therapeutic management of pertussis (whooping cough). Chapter 19.
- Column O, Fission-Product Fallout: Equivalent medical rads to breasts from radioactive fallout in the 1945-1960 period of weapons-testing. Chapter 25.
- Column P, General Diagnostic X-ray Exams: X-ray breast-dose from general diagnostic exams, roentgenograms plus fluoroscopic examination. Chapter 23.
- Column Q, Occupational Exposures: X-ray breast-dose, occupationally incurred. Chapter 24.
- Column R, Chiropractic Exams: X-ray breast-dose in chiropractic applications, largely from full-spine x-rays used in diagnosis and follow-up. Chapter 22.
- Column S, Pneumonia: X-ray breast-dose in the roentgen therapy of pneumococcal pneumonia. Chapter 18.
We now begin the stories of the various radiation exposures, which left their "mark" within the breast-cells of so many women.
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About Dr. George Pfahler
In our travels back through the literature of roentgenology in its early years, we met Dr. George Pfahler many times. He was regarded as "the dean of American radiologists" (see below), and readers of this book will find him quoted on several topics.
In 1955, when Dr. Pfahler reached his 80th birthday, there were tributes. One was written by Dr. James T. Case, a past president of the American College of Radiology. Entitled "Dr. George E. Pfahler, An Appreciation," it appeared in the journal CA: A Bulletin Of Cancer Progress, Vol.5, No.1: 11-13, January 1955. Dr. Case said:
"Fifty-five of Dr. Pfahler's eighty years have been devoted to the science of radiology. An account of his activities and contributions in this field constitutes a veritable history of radiology in America. He is held in respect and affectionate regard by his colleagues throughout the world as the dean of American radiologists. He belongs to the group of pioneers in radiology."
Dr. Case recounted that the Board of Managers of the Philadelphia General Hospital decided to buy a roentgen-ray machine and asked the young resident, Dr. Pfahler, to take charge of it. Dr. Pfahler at first "doubted the propriety of getting into a thing like radiological practice, which he thought had been already pretty much worked over, for the bones had been studied and foreign bodies had been demonstrated." But he did take the responsibility. This eminent physician, who had suggested it was essentially all over for new developments in radiology, finally published about 350 medical articles!
In this book, we "hear" from Dr. Pfahler on thymus disorders, chronic mastitis, and liver measurements. And also:
- Dr. Pfahler's story about the surgeon and the dentist (p.203).
- Dr. Pfahler's impassioned warning (in 1925) about mis-users of the roentgen ray (p.206).
- And Dr. Pfahler's own reflections in 1955 on what had followed from the discoveries of the x-ray and radioactivity (p.260).