Prostate Cancer and Other Primary Malignancies

Background

As the detection and treatment of cancer improve, the prevalence of multiple primary malignancies has increased and will undoubtedly continue to increase. One out of every two men will receive a cancer diagnosis in their lifetime, with prostate cancer comprising 44% of these diagnoses. According to the Surveillance, Epidemiology, and End Results (SEER) Program database, as of 2013, 16% of new cancer diagnoses represented a second- or higher-order malignancy. Prostate cancer is no exception. In a review of the Minneapolis Veterans Affairs tumor registry, Powell et al. concluded that one out of every nine cancer diagnoses represented second-order malignancies, and prostate cancer was the most common primary cancer diagnosis and the second most common secondary cancer diagnosis. Approximately 17% of all prostate cancer diagnoses occur in combination with another primary malignancy diagnosed before or after the time of diagnosis of prostate cancer. The overall incidence of multiple primary tumors in prostate cancer patients ranges from as low as 11.5% to as high as 20%. Evaluation of autopsy specimens by Hajdu and Hajdu reported an incidence of multiple malignancies in prostate cancer patients as high as 27% ; however, current data correlate with previously stated range.

When considering multiple malignancies of the same patient, it is important to consider the timing of diagnosis and distinguish between metachronous and synchronous malignancies. Metachronous malignancies are likely a result of the improvements in treatment modalities and the increased cancer-specific survivorship. As treatment strategies improve and patients are surviving longer with the diagnosis of prostate cancer, the probability of developing a second malignancy increases. Synchronous malignancies are likely the result of epidemiologic risk factors in a given population. Family history is one the greatest risk factors in the development of prostate cancer and many other malignancies. It can therefore be inferred that patients who develop one malignancy may have a genetic predisposition to developing malignancies at other anatomic locations. The advent of screening protocols for prostate cancer and other malignancies such as colon cancer has allowed for the diagnosis of lower-grade and lower-stage cancers that previously would have been clinically undiagnosed. The most common secondary cancer diagnoses made after a primary diagnosis of prostate cancer are colorectal, lung, and bladder. Renal cell cancer comprises approximately 5% of cancer diagnosis made in patients following a diagnosis of prostate cancer.