ASCO PROSTATE: More Radiation Improves PSA Control but Increases Toxicities

KISSISSIMEE, FLA., Feb. 26 -- Escalated-dose conformal radiotherapy for localized prostate cancer was associated with a 34% reduction in the relative risk of biochemical failure in a randomized trial of 843 men also treated with androgen deprivation.

But the improvement in PSA control was associated with increased late bowel and bladder toxicity, said David P. Dearnaley, M.D., of the Institute of Cancer Research in Sutton, England, reporting the first results from the Medical Research Council RTO1 trial.

Dr. Dearnaley said this was the only randomized trial to assess radiation conformal dose escalation along with a routine policy of neoadjuvant androgen deprivation therapy.

Men with localized prostate cancer were randomized to standard therapy (64 Gray delivered in 32 fractions) or to escalated dose (74 Gray in 37 fractions) plus three to six months of androgen deprivation therapy given "before, during, and after radiation."

All men were followed at six month intervals for two years and then annually. The data he reported at a prostate cancer symposium here reflected five years of follow-up.

Among the findings:

• Treatment with escalated dose was associated with a hazard ratio for biochemical failure of 0.66 (95% CI, 0.52-0.84, P=0.0007).
• At five years, 72% of the men who received escalated dose radiation showed no biochemical failure versus 60% of men who received standard dose therapy-a 12% improvement in PSA control.
• Dose escalation was associated with a 51% increase in RTOG grade 2 or higher bowel toxicity and a 33% increase in late bladder toxicity.
• At five years, 10% of men in the escalated dose arm reported bowel toxicities of grade 3 or higher.

"Overall, these first results are positive, but a meta-analysis of conformal radiation therapy trials will probably be needed to confirm survival advantage," Dr. Dearnaley said.

Dr. Dearnaley reported receiving honoraria from AstraZeneca Oncology.