Background: The epidemiological and clinical characteristics of multiple cancers in prostate cancer men remain unclear.
Aim: To characterize the difference in men with prostate cancer only and multiple cancers.
Methods: Patients with prostate adenocarcinoma diagnosed between 1973 and 2010 in SEER were divided into two groups: 1). by the number of cancers: one cancer (prostate cancer only), two cancers, three cancers and four or more cancers, and 2) by the order of prostate cancer occurrence: prostate cancer is the first cancer, last cancer, and neither the first nor the last cancer. These patients' age at prostate cancer diagnosis, race, marital status at diagnosis, cause of the death and survival were evaluated.
Results: Among 955,031 men with prostate cancer, 1,139,227 cancers were reported with a rate of 1.2 cancers/man. The ratios of men with one, two, three and four or more cancers were 83.5, 14.2, 2.0 and 0.3%, respectively. Older age, married and white men were more likely to have multiple cancers (p < 0.001). Patients with multiple cancers showed a longer survival compared with patients with prostate cancer only. Prostate cancer death was the first cause of death for men with prostate cancer only. Lung cancer and heart diseases were the most common causes of death among men with multiple cancers.
Conclusions: A large portion of prostate cancer patients has multiple cancers, which shows different epidemiological and clinical characteristics from the men with prostate cancer only. These findings indicate the challenges in clinical management of these men and the need to study the cause-effect between prostate cancer and other cancers in cancer development, detection, and treatment modality. Further evaluation on the risk factors such as race, age, marital status, histology, staging, treatment, and interrelations of these cancers is warranted.