One cancer expert said he couldn't explain why external beam radiation would increase the risk of these cancers, especially lung cancer.
"I'm not sure how external beam radiation to the pelvis for prostate cancer would increase the risk for lung cancer," said Dr. Bruce Roth, professor of medicine and urologic surgery at Vanderbilt University.
The radiation therapy would be more likely to increase the risk for bladder cancer and colorectal cancer, which are nearer the prostate, he noted.
Roth said it's important to give prostate cancer patients several treatment choices. "I will give them a number of options and let them pick based on the side effect profile. There are many patients who may not be good surgical candidates, therefore you might lean toward external beam radiotherapy," he said.
In another study presented Monday, researchers found that survivors of childhood cancers treated with the chemotherapy drug cyclophosphamide were five times likelier to develop bladder cancer later in life, compared with the general population.
Children up to 4 years old treated with the drug for retinoblastoma, leukemia and non-Hodgkin lymphoma had a particular risk for developing bladder cancer, the researchers found.
Cyclophosphamide is an immunosuppressive drug used to treat several types of cancers and is known to cause bladder damage that can lead to bladder cancer.
In patients followed for up to 50 years, the researchers found that the chances of developing bladder cancer increased over time. The percentage of patients diagnosed with bladder cancer at 20, 30, 40 and 50 years of age was 0.02 percent, 0.08 percent, 0.37 percent and 0.71 percent, respectively, the researchers reported.
More information
For more about prostate cancer, visit the National Cancer Institute.
