Human Cancer in Relation to Heredity

Abstract

IN previous lectures you have had an exposition of the present knowledge of heredity and genetics, the present understanding of the way in which characters are transmitted from one generation to another, and from Miss Slye you have had a statement of her particular piece of work on the relation of heredity to cancer. As I understand, my particular task is to bring together these two lines of work and other related facts, and try to explain, as best I may, by such light as I have been able to obtain myself, just how modern genetics applies to the problems of human cancer, and perhaps we may be able to furnish a surmise concerning the influence of our inheritance upon our prospects of getting cancer or of getting away from it. The medical literature contains and has contained for many years a long series of most discordant statements as to the influence of heredity upon cancer, and the reason they are discordant is that they are not based upon a sound foundation. They are based upon a theory of heredity that is not correct and based upon cancer material totally valueless for the purpose under investigation. The old idea of heredity was, you know, that each of us had half of each of his parents, a quarter of each of his grandparents, etc., and that tradition is prevalent in the minds of most of us. A physician does not ordinarily look upon a condition as inherited unless the parents of the patient have shown it or it has appeared in his immediate relatives, whereas the geneticist knows that a character exhibited by an individual may not be present in ten or fifteen generations and yet be perfectly well inherited from some ancestor of long ago. Before the days of genetics, we called those things “sports.” Our cancer heredity material was also entirely worthless, for it consisted ordinarily of hospital statistics, and all of us know how valueless those are in respect to family histories. How many in this room can tell me what your great-grandparents died of? And even at the best you have merely a family tradition or what some physician of the old days thought was the matter. Then, of course, the statistics we have are always biased and always tend to show that more relatives of cancer patients have cancer than relatives of the non-cancerous patient, and so the assumption is easy enough that cancer is hereditary; but when you consider the material you see that that conclusion is not warranted. For example, take our hospital material from which this is obtained: Each patient on coming in is asked as to the occurrence of cancer in his family. A woman comes in with cancer of the breast. Before she comes in for operation, she has talked with all the relatives about it and has found that Uncle Jim's first wife had a cancer of the breast, and there was a cousin of Fanny Brown who had a cancer of the stomach, etc., etc.