Increased cumulative incidence of prostate malignancies in colorectal cancer patients.

Background: Identifying subjects at an increased risk of colorectal cancer (CRC) is of considerable importance in designing effective screening strategies. Malignancies that cosegregate with CRC provide important markers for higher-risk patients. CRC and prostate cancer share many similarities with regard to etiological factors. However, the previous reports on associations between these common malignancies are contradictory and confounded by a lack of rigorous controls.

Aim Of The Study: The aim of this study was to further elucidate the relationship between CRC and prostate cancer.

Methods: We performed a retrospective case-control study of subjects receiving medical care at the Omaha Veteran's Administration Medical Center between 1992 and 2002. Cases (patients with CRC) were obtained through the pathology records, whereas controls (patients with a negative colonoscopy during the same time period) were found through assessment of the endoscopy database. All subjects had the pathology database queried for other malignancies. The medical record also was assessed for confounding factors such as prostate cancer screening, radiation therapy status, and so on.

Results: We identified 149 male patients with CRC cases and 186 controls (age-matched male patients with a negative colonoscopy). The 10-yr cumulative incidence of prostate cancer was 10.7% of the cases but only 3.8% of the controls (p = 0.016). There were no significant differences between cases and controls among 11 other primary malignancies evaluated. The association between CRC and prostate cancer was unrelated to characteristics such as location in the colon and differentiation. Furthermore, confounding factors including frequency of prostate cancer screening and radiation therapy status did not explain the cosegregation between CRC and prostate.

Conclusion: This preliminary report suggests that there is an association between CRC and prostate cancer. If replicated in other populations, this may have important implications for cancer screening strategies.