Advantages to a Compressed Radiation Schedule for Prostate Cancer Patients

Newswise — There are many advantages to a compressed or hypofractionated prostate radiotherapy, setting the stage for further studies, according to a study presented on October 20, 2003, at the American Society for Therapeutic Radiology and Oncology's Annual Meeting in Salt Lake City.

The optimal radiation dose-fractionation schedule for localized prostate cancer is unclear. The purpose of this study was to determine if a shorter 4-week radiation schedule was as effective as a longer 6.5-week schedule.

Patients with T1 and T2 prostate cancers were randomized to 66 Gy in 33 fractions over 6.5 weeks or 52.5 Gy in 20 fractions over 4 weeks. The choice of the dose for the short arm (hypofractionated) was based on the available literature and the experience at two of the participating institutions. The primary outcome was the cluster defined by biochemical failure, clinical local failure, distant failure, hormonal intervention prostate cancer death. The treatment arms were compared in a time-to-event analysis. Secondary outcomes included presence of tumor on prostate biopsy at 2 years, survival and toxicity. The trial was a joint project of the Ontario Clinical Oncology Group and the National Cancer Institute of Canada Clinical Trials Group.

Between 1994 and 1998, 936 patients were randomized at 16 Canadian centers, 470 to the long arm and 466 to the short arm. The median follow-up was 59 months. At baseline, the treatment groups were well balanced with regard to stage, Gleason score and pre-treatment PSA level. To September 2002, there have been 460 failures: 216 in the long arm and 244 in the short arm. At 2 years, 73 percent of patients had a planned post-radiotherapy biopsy. In the long arm, 53.2 percent of the patients who underwent biopsy were positive while in the short arm, 50.7 percent were positive. The overall survival at five years was 85.7 percent and 88.3 percent in the long and short arms respectively.

"This is the first reported randomized study evaluating the use of hypofractionated radiotherapy in the management of localized prostate cancer," said Himu Lukka, lead author of the study. The PSA failure rate is 7 percent higher in the shorter arm and statistically investigators cannot exclude the possibility that the short arm is inferior to the long arm. "Although the acute toxicity was higher in the short arm, it is reassuring that the late toxicity was comparable between the two treatment arms. This trial provides useful clinical data to design future studies to help the choice of appropriate hypofractionated dose and fractionation using dose escalation protocols in the settings of conformal and IMRT radiotherapy techniques."

The American Society for Therapeutic Radiology and Oncology is the largest radiation oncology society in the world, with more than 7,000 members who specialize in treating patients with radiation therapies. As a leading organization in radiation oncology, biology and physics, the Society's mission is to advance the practice of radiation oncology by promoting excellence in patient care, providing opportunities for educational and professional development, promoting research and disseminating research results and representing radiation oncology in a rapidly evolving socioeconomic healthcare environment.