Purpose: Conformal radiation technology results in fewer late complications and allows testing of the value of higher doses in prostate cancer.
Methods and materials: We report the biochemical freedom from disease (bNED) rates (bNED failure is Prostate Specific Antigen (PSA) > or = 1.5 ng/ml and rising) at 2 and 3 years for 375 consecutive patients treated with conformal technique from 66 to 79 Gy. Median follow-up was 21 months. Biochemical freedom from disease was analyzed for patients treated above and below 71 Gy as well as above and below 73 Gy. Each dose group was subdivided by pretreatment PSA level (< 10, 10-19.9, and > or = 20 ng/ml). Dose was stated to be at the center of the prostate gland.
Results: There was significant improvement in bNED survival for all patients divided by a dose above or below 71 Gy (p = 0.007) and a marginal improvement above or below 73 Gy (p = 0.07). Subdividing by pretreatment PSA level showed no benefit to the PSA < 10 ng/ml group at the higher dose but there was a significant improvement at 71 and 73 Gy for pretreatment PSA 10-19.9 ng/ml (p = 0.03 and 0.05, respectively) and for pretreatment PSA > or = 20 ng/ml (p = 0.003 and 0.02, respectively).
Conclusions: Increasing dose above 71 or 73 Gy did not result in improved bNED survival for patients with pretreatment PSA < 10 ng/ml at 2 or 3 years. Further dose escalation studies may not be useful in these patients. A significant improvement in bNED survival was noted for patients with pretreatment PSA > or = 10 ng/ml treated above 71 or 73 Gy; further dose escalation studies are warranted.