Risk of second primary tumors in men diagnosed with prostate cancer: a population-based cohort study

The survival of men diagnosed with prostate cancer has improved over time, and the current 10-year relative survival rate is 99.7%. The long survival of patients with this common cancer raises questions about the risk of a second primary cancer and the need for continued surveillance.

A population-based cohort of 441,504 men who were diagnosed with prostate cancer between 1992 and 2010 was identified from Surveillance, Epidemiology and End Results Program (SEER) data (SEER13). The standardized incidence ratio (SIR) was calculated as an estimate of the risk of a second primary malignancy based on the incidence in the general population.

Prostate cancer survivors had a lower risk of being diagnosed with another cancer overall compared with the US population (SIR = 0.60; 95% confidence interval, 0.60-0.61). The risks of leukemia and cancers of the oral cavity and pharynx, esophagus, stomach, colon and rectum, liver, gallbladder, pancreas, lung and bronchus, and larynx were significantly lower. Conversely, these patients had a greater risk of bladder, kidney, and endocrine and soft tissue cancers. Men who received treatment with radiation therapy (external-beam radiation therapy) had long-term increases in their risk of bladder cancer (SIR = 1.42) and rectal cancer (SIR = 1.70) risk compared with who did not receive radiation (SIRbladder  = 0.76; SIRrectal  = 0.74). There were significant racial differences in the risk of being diagnosed with a second primary cancer, and the magnitude and direction of these risks depended on tumor type.

Prostate cancer survivors remain at risk of subsequent malignancies, and race and treatment choice important determinants of long-term risk.