Cancer in MZ and DZ Twins

Abstract

Important works on the question of hereditary influence on the occurrence of cancer with application of twin series are those by v. Verschuer and Kober (cf. Spranger and v. Verschuer, 1964), Jarvik and Falek (1961) and Harvald and Hauge (1963). Their findings are by and large consistent with most earlier reports (Schull et al, 1959) and indicate that hereditary factors do not seem to influence the development of cancer as such, but possibly play a role in the localization of the tumor. In view of the fact that (except for Harvald and Hauge's investigation) the twin series studied have been comparatively small and yielded statistically unreliable numbers of cancer of specific site, it seems to be of value to extend the data by reporting findings from the Swedish Twin Registry, comprising about 11000 unselected twin pairs.The present paper reports mortality and morbidity in cancer of different site as well as concordance rates for MZ and DZ twins. In addition, the influence of smoking habits on cancer development has been analyzed, as this environmental factor is known to be associated with certain forms of cancer, particularly lung cancer (Smoking and Health, 1964).Cancer data have been obtained from two sources, the Swedish Cancer Registry and the Registry of Causes of Death.The Swedish Twin Registry in the present report comprises 10 945 twin pairs, and covers, in principle, all same-sexed twins born in Sweden in 1886-1925, and still living in the country as unbroken pairs at the time of compilation (1961). A detailed report of the compilation procedures and demographic data is given by Cederlöf (1966).