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High-dose radiation therapy showed superior long-term cancer control in prostate cancer
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Men with early-stage prostate cancer were more likely to be free from an increasing PSA 10 years after therapy and less likely to require additional cancer therapy when treated with high-dose radiation compared with men treated with conventional-dose radiation.
Researchers enrolled men with T1b-T2b prostate cancer to a conventional dose of 70.2 Gy (n=197) or a high dose of 79.2 Gy (n=197) to update the results of the Proton Radiation Oncology Group /American College of Radiology 95-09 trial and provide long-term follow-up data.
Men in the high-dose group were less likely to have local failure than men in the low-dose group (HR=0.57; 95% CI, 0.43-0.74). When adjusted for other covariates, this result remained. There was also a statistical difference in local failure for patients with low-risk disease (P=.01) and intermediate-risk disease (P=.002).
Based on the American Society for Therapeutic Radiology and Oncology consensus definition, the 10-year biochemical failure rates were higher in the conventional-dose group vs. the high-dose group (32.3% vs. 16.7%; P=.0001).
No difference in OS was observed between groups with survival rates of 78.4% for those treated with the conventional dose and 83.4% for those treated with the high dose (P=.41).
Three percent of patients in the conventional-dose group and 2% of patients in the high-dose group had acute genitourinary toxicity grade 3 or worse, according to RTOG criteria. In both groups, 2% of patients experienced late genitourinary toxicity of grade 3 or worse, and 1% had late gastrointestinal toxicity of grade 3 or worse, according to the researchers.
In an accompanying editorial, W. Robert Lee, MD, professor in the department of radiation oncology at Duke University Medical Center, in Durham, N.C., said questions about topics, including the benefits of routine use of doses more than 80 Gy, delivery of high dose, optimal conventional fraction schedule and the overall benefits of high-dose radiation, still remain unanswered.
“Although each of the dose escalation studies demonstrate a reduction in biochemical recurrence with increased dose, none of the studies have observed an improvement in overall (or prostate cancer-specific) survival,” Lee wrote. “The accumulating evidence that active surveillance is a safe alternative highlights the notion that 78 to 79 Gy may not be the best dose for all men. In fact, for the 73-year-old man with low-risk prostate cancer, the best dose may be 0 Gy.”
Zietman AL. J Clin Oncol. 2010;doi:10.1200/JCO.2009.25.8475.