Background: The study of cancer in spouses may play an important role in the assessment of cancer etiology.
Methods: Patterns of occurrence of cancer in 195 couples related by marriage only and treated in a regional hospital are reported. The distribution of tumors by site was compared with national data.
Results: Seven sites of cancer were found to be more frequent in married couples than in the general population, in particular carcinoma of the colon (37 observed vs. 19.5 expected in husbands [relative risk (RR) = 1.89 (95% confidence intervals [CI], 1.5-2.4); P < 0.001] and 32 vs. 16.7 in wives [RR = 1.92 (95% CI, 1.4-2.5); P < 0.001]), carcinoma of the prostate (32 vs. 20 in husbands [RR = 1.6 (95% CI, 1.19-2.09); P < 0.01]), and carcinoma of the female breast (84 vs. 55 in wives [RR = 1.53 (95% CI, 1.3-1.8); P < 0.001]). Same site tumors were observed in 13 couples versus 6.21 expected in the general population (RR = 2.09 [95% CI, 1.25-3.26]; P < 0.01). A combination of carcinoma of the prostate and female breast sites was found in 18 couples versus 5.4 expected in the general population (RR = 3.34 [95% CI, 2.19-4.84]; P < 0.001).
Conclusions: The distribution of cancer sites among spouses in those families in which both spouses have developed a cancer differs from that of the general population. These differences may be caused by shared risk factors. Increased awareness can explain only part of the excess.