Hypofractionation not superior to standard dose radiation for prostate cancer

2009 Genitourinary Cancers Symposium

Men with prostate cancer assigned to a five-week course of intensified radiotherapy had similar biochemical recurrence rates as men assigned to a standard seven-week course, according to recent trial results presented at the 2009 Genitourinary Cancers Symposium.

Alan Pollack, MD, PhD, chairman of radiation oncology at the University of Miami Miller School of Medicine and Sylvester Comprehensive Cancer Center, said he and his colleagues had expected patients assigned to the hypofractionation schedule to have a better response compared with patients assigned to standard-dose intensity-modulated radiation therapy.

“Even though the data did not show a difference in freedom from biological failure, the fact the results were similar in terms of toxicity and freedom from biological failure, and the hypofractionation treatment was 2.5 weeks shorter, is encouraging,” Pollack told HemOnc Today. “Although the trial was not designed to test for noninferiority, if the treatments are similar and you can deliver treatment in a shorter period of time, there’s a significant time-saving and financial gain for patients.”

Pollack and colleagues randomly assigned 152 men to 38 treatments of 2 Gy standard intensity modulated radiotherapy for 7.5 weeks and 151 men to 26 treatments of 2.7 Gy hypofractionated intensity modulated radiotherapy for 5.1 weeks.

After a median 39 months of follow-up, the researchers concluded there was “no significant difference” between the treatment arms. The patients were evenly distributed in terms of T-category, Gleason score, pretreatment initial PSA and use of short-term or long-term androgen deprivation. The five-year biochemical failure rate for the standard-dose group was 21% (95% CI, 12%-37%) compared with 17% for the hypofractionation group (95% CI, 10%-28%).

Pollack suspected that the low alpha/beta ratio for prostate cancer, which supports a rationale for use of hypofractionation, is inaccurate, which threw off the results. “The trial doesn’t prove that conclusively, but raises concern that the alpha/beta ratio is higher than previously believed, which would influence the design of future regimens,” he said. – by Jason Harris

This trial clearly supports our efforts to understand the possibility of reducing length of treatment and perhaps the cost of treatment. This was not a noninferiority design, and so couldn’t answer that question, but the results are encouraging nonetheless.

– Robert S. DiPaola, MD

Director, Cancer Institute of New Jersey, New Brunswick, N.J.

For more information:

Pollack A. #4. Presented at: the 2009 Genitourinary Cancers Symposium; Feb. 26-28, 2009; Orlando.