To the Editor.—I regret that I was not aware of Lowry's 1970 letter to Lancet. It is clear that conceptually he and I are closely attuned. The evidence he has cited concerning enhanced survival in the yolk sac tumor of the infantile testis (mesoblastoma vitellinum) and Burkitt's lymphoma in infants less than 1 year of age adds significantly to the basic concept. The problem at the present time is to determine if a period of cancer repression in early life is a universal biological phenomenon. This we are attempting to demonstrate with a number of experimental cancers, with the aim of elucidating a mechanism.
That immune deficiency is involved in the pathogenesis of cancer, seems clear from both experimental and clinical studies. The extent and precise nature of this involvement is as yet unclear in human neoplasia. It is tempting to ascribe an early cancer