Risk factors for penile cancer: results of a population-based case-controlstudy in Los Angeles County (United States)

The etiology of penile cancer is poorly understood, with neonatal circumcis ion being one of the few recognized nondemographic risk factors. Multiple l ogistic regression was used to analyze interview data from 100 matched case -control pairs; cases of carcinoma in situ (CIS) and invasive carcinoma of the penis were analyzed separately as well as together. Phimosis was strong ly associated with invasive carcinoma (adjusted odds ratio [OR] = 16; 95% c onfidence interval [CI] = 4.5-57) but not CIS (OR = 1.7; 95% CI = 0.32-7.8) , and these associations persisted when the analyses were restricted to unc ircumcised subjects. Neonatal circumcision was inversely associated with in vasive carcinoma (OR = 0.41; 95% CI = 0.13-1.1) but not CIS, and the observ ed association with invasive carcinoma was weakened appreciably when the an alysis was restricted to subjects with no history of phimosis (OR = 0.79; 9 5% CI = 0.29-2.6). Other factors positively associated with invasive carcin oma or CIS or both were injury to the penis, cigarette smoking, physical in activity and, to a lesser extent, genital warts and other infections or inf lammation of the penis. Conclusions: Although many effects were imprecisely estimated in this study, the protective effect of circumcision on invasive penile cancer appears to be mediated in large part by phimosis; furthermor e, the effects of certain factors such as phimosis and circumcision appear to differ for CIS and invasive carcinoma.