End-of-radiation PSA as a novel prognostic factor in patients undergoing definitive radiation and androgen deprivation therapy for prostate cancer
In men undergoing definitive radiation for prostate cancer, it is unclear whether early biochemical response can provide additional prognostic value beyond pre-treatment risk stratification.METHODS:
Prostate cancer patients consecutively treated with definitive radiation at our institution by a single provider from 1993 to 2006 and who had an end-of-radiation (EOR) PSA (n = 688, median follow-up 11.2 years). We analyzed the association of an EOR PSA level, obtained during the last week of radiation, with survival outcomes. Multivariable-adjusted cox proportional hazards models were constructed to assess associations between a detectable EOR PSA (defined as ≥ 0.1 ng ml-1) and biochemical failure-free survival (BFFS), metastasis-free survival (MFS), prostate cancer-specific survival (PCSS) and overall survival (OS). Kaplan-Meier survival curves were constructed, with stratification by EOR PSA.RESULTS:
At the end of radiation, the PSA level was undetectable in 30% of patients. Men with a detectable EOR PSA experienced inferior 10-year BFFS (49.7% versus 64.4%, P < 0.001), 10-year MFS (84.8% versus 92.0%, P = 0.003), 10-year PCSS (94.3% versus 98.2%, P = 0.007) and 10-year OS (75.8% versus 82.5%, P = 0.01), as compared to men with an undetectable EOR PSA. Among National Comprehensive Care Network (NCCN) intermediate- and high-risk men who were treated with definitive radiation and androgen deprivation therapy (ADT), a detectable EOR PSA was more strongly associated with PCSS than initial NCCN risk level (EOR PSA: HR 5.89, 95% CI 2.37-14.65, P < 0.001; NCCN risk level: HR 2.01, 95% CI 0.74-5.42, P = 0.168). Main study limitations are retrospective study design and associated biases.CONCLUSIONS:
EOR PSA was significantly associated with survival endpoints in men who received treatment with definitive radiation and ADT. Whether the EOR PSA can be used to modulate treatment intensity merits further investigation.