Quantitating regrowth delay of prostate cancers after failure of radiation therapy

To evaluate the benefit of radiation therapy as determined by regrowth delay of prostate tumors and to identify tumor and patient characteristics associated with prolonged regrowth delay.

The records of 113 patients with prostate cancer were studied retrospectively after radiation therapy failed. Pretreatment prostate-specific antigen (PSA) levels and three or more post-failure PSA levels were obtained. The post-failure PSA doubling time was used to estimate the time until the pretreatment PSA level would be reached. The difference in time between the initiation of treatment and the return to pretreatment PSA levels is the regrowth delay.

Regrowth delay ranged from 1 to 584 months in the 133 patients: 0-12 months (14 patients); 13-24 months (22 patients); 24-59 months (39 patients); and 60 months or more (38 patients). Gleason score was significantly correlated with interval to failure, PSA doubling time, and regrowth delay (P = .01, .04, and .02 respectively). Pretreatment PSA and clinical T stage were not statistically significantly related to regrowth delay.

Regrowth delay is a clear quantitative benefit of radiation therapy to patients with incurable prostate cancer. Nearly 70% of patients realize a 2 year or greater delay in tumor progression, with 34% having a delay greater than 5 years. This observation supports continuing use of radiation therapy in prostate cancer.