A study looking at the genetic information of more than 1500 patients with prostate cancer has identified two variants linked to increased risk of radiotherapy side effects.
Used in nearly 50% of patients with prostate cancer, radiotherapy can be an effective treatment option, but it has also been associated with significant adverse events. Between 10% and 50% of men who receive radiotherapy experience long-term problems with urinating or rectal bleeding.
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To better understand why some men are more susceptible to these side effects than others, researchers led by Catherine West, PhD, University of Manchester (Manchester, United Kingdom), analyzed individual-level data from four genome-wide association studies of prostate cancer radiotherapy cohorts to see if any genetic markers of toxicity could be identified. They published their results in the journal EBioMedicine.
Genetic profiling was carried out in 1564 patients with prostate cancer from four centers based in Europe and North America. Researchers examined genetic variants described as single nucleotide polymorphisms (SNPs), which form part of the subunits of DNA.
Overall, researchers observed that, two years after radiotherapy, 17.8% of patients included in the study experienced rectal bleeding, 15% had an increase in urinary frequency, and 8.1% reported a decrease in urine stream.
A fixed-effects meta-analysis identified two SNPs as those most associated with frequency of urinating and decreased flow (rs17599026 on 5q31.2; and rs7720298 on 5p15.2, respectively). However, researchers are still unsure as to why the associations exist.
The results show that radiotherapy cohorts can be combined to identify new moderate-penetrance genetic variants associated with treatment toxicity. The researchers concluded that more research is needed in order to develop a test capable of predicting a patient’s risk of radiotherapy side effects.
“There are currently more than 32 million people alive five years after having cancer, so the side-effects of their treatment are an important issue for them,” said Dr West. “If we can develop a test that means people can reduce the risk of these problems that will be of huge benefit to this group.”
