Although radiation is an effective form of treatment for prostate cancer, a new study found that too much radiation will not improve survival rates.
For this study, the researchers headed by Dr. Robert Den, a researcher at the Sidney Kimmel Cancer Center at Thomas Jefferson University, examined 12 trials that involved using radiation treatment for patients with non-metastatic prostate cancer, which meant that the cancer had not spread out. A total of 6,884 men were enrolled in the trials.
To assess health outcomes from the treatment, the researchers focused on long-term variables, which included whether or not the men developed metastatic cancer or had died from the cancer. The researchers also factored in the prostate cancer antigen (PSA) test, which is the standard tool that doctors use to assess improvement.
The researchers found that overall, PSA levels fell more in patients who received higher levels of radiation. However, despite the drop, overall survival rates were not affected by the amount of radiation a patient had received. Radiation also did not affect the incidence rate of metastases.
"In the field of radiation oncology, we often assume that the highest dose that the body can tolerate will be most effective at killing cancer," said Den, the senior author of the study. "Our results argue that this may not be the case, at least not with lower-risk prostate cancer patients."
Den also found that treating patients with higher doses of radiation did not lead to an increase in toxicity, which means that even though increasing radiation might not affect overall survival and metastases rate, it at least does not harm the patient.
The Chair of Radiation Oncology at the Sidney Kimmel Medical College at Thomas Jefferson University, Adam Dicker, said this study's findings suggest that monitoring PSA levels alone might not be enough.
"It's important to check our assumptions," Dicker said. "This study suggests that our reliance on the PSA test as a proxy for patient outcomes may not as useful as many researchers thought, which has broad implications for the design of future clinical trials and the interpretation of current and previous studies."
Prostate cancer is the second most common cancer in American men after skin cancer. According to the American Cancer Society's estimates, there will be about 180,890 new cases of prostate cancer and about 26,120 deaths in 2016.
The study was published in the American Journal of Clinical Oncology.
