While advances in technology have allowed physicians to administer higher doses of radiation to treat prostate cancer, results from a recent study have revealed that escalating dose may not help patients in the long term, at least not those with localized or locally advanced disease.
In radiation therapy, it has often been assumed that the highest possible dose the body can tolerate would also be the most effective at killing cancer cells. However, while some studies have shown improved results through the use of more precise, higher-dose techniques, some have also shown that increasing dosage can lead to greater toxicity.
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To better understand the relationship between higher doses of radiation therapy and improved outcomes at tolerable toxicity levels, researchers led by Robert Den, MD, Sidney Kimmel Cancer Center (Philadelphia, PA), conducted a meta-analysis to determine how increasing the biologic equivalent dose of external radiation therapy correlates with freedom from biochemical failure, as measured by the prostate cancer antigen test, and overall patient outcomes. They published their findings in the American Journal of Clinical Oncology.
Data for the study was taken from 12 randomized controlled trials of external beam radiotherapy (EBRT) published after 1990. Of the 6884 patients with non-metastatic prostate cancer, 5506 underwent conventionally fractionated EBRT dose escalation, and 1828 were in trials of conventionally fractionated EBRT versus hypofractionated EBRT.
Increasing biologically equivalent dose of EBRT correlated with improved freedom from biochemical failure, with 10-year absolute improvements of 9.6% for low-risk patients and 7.2% for intermediate-risk patients. However, no significant improvements in overall patient outcomes of distant metastasis, cancer-specific mortality, or overall survival were found, and increasing dose was not associated with worse treatment toxicity. Therefore, researchers concluded the freedom from biochemical failure as measured by the prostate cancer antigen test may not be as useful as previously believed.
The findings suggest that current treatment practices may be safe to continue.
