Men with prostate cancer that underwent radiotherapy during their treatment were more likely to develop a second primary cancer compared with men who did not undergo radiotherapy, according to a study published in JAMA Network Open.
The study researchers noted that although the risk was low, it is important that this risk be discussed with patients during shared decision-making about treatment options.
“Although the long-term toxic effects of radiotherapy are important to discuss when counseling patients on the risk-benefit profile of prostate radiotherapy, they need not deter physicians from recommending radiotherapy if appropriate,” study researchers wrote. “Patient selection and shared decision-making remain important when considering prostate cancer treatment options.”
The retrospective study included more than 150,000 male veterans aged 18 or older who had localized prostate cancer diagnosed between January 2000 and December 2015.
About one-third (36.8%) of included patients had received primary radiotherapy; 63.2% did not. A second primary cancer more than 1 year after prostate cancer diagnosis was reported in 3.7% of men who underwent radiotherapy compared with 2.5% of those who did not.
The median time to development of any second primary cancer was 6 years after prostate cancer diagnosis. The most frequent types of second primary cancer were bladder cancer, leukemia, lymphoma, rectal cancer, hematoreticular cancer, soft tissue cancer, anal cancer, male genital cancer, and bone cancer.
The researchers conducted a multivariable analysis and found that patients who underwent radiotherapy had a higher risk of second primary cancer compared with those who did not at 1 to 5 years postdiagnosis (hazard ratio [HR]=1.24; 95% CI, 1.13-1.37; P<.001). The adjusted HRs increased with increasing time up to 15 years: 5-10 years (aHR=1.50; 95% CI, 1.36-1.65; P<.001), 10-15 years (aHR=1.59; 95% CI, 1.37-1.84; P<.001).
“Prostate cancer is common, occurring in approximately 1 in 8 men in the US, and even a low-risk event can have consequences for a large absolute number of patients,” the researchers noted. “Careful consideration of risks and benefits among accepted treatment modalities is therefore paramount.”