The relationship between biochemical failure and time to nadir in patients treated with external beam therapy for T1-T3 prostate carcinoma

Purpose and background: To determine a prostatic-specific antigen (PSA) nadir value and time to nadir that predict a high probability of freedom from biochemical failure in men treated with external beam therapy for prostate cancer. Materials and methods: Between January 1990 and March 1994, 228 men with T1-T3 adenocarcinoma of the prostate received a radical course of external beam irradiation with no prior or adjuvant hormonal therapy. All men had pre- and post-treatment serum PSA evaluations, and were followed up for at least 24 months, to ensure PSA nadir was reached. Biochemical failure was defined as three successive post-treatment rises in serum PSA, regardless of the magnitude of elevation. Results: Overall, 4-year biochemical disease-free survival (BDFS) was 42%. PSA nadir was predictive of subsequent BDFS. For those whose serum PSA nadir was less than or equal to 1 ng/ml, 4-year BDFS was 70%, versus 12% for those with serum PSA nadir >1 ng/ml (P = < 0.001). The 4-year BDFS for patients with time to nadir less than or equal to 1 year, was 28%, versus 58% for those with time to nadir >1 year (P < 0.001). For patients with PSA nadir less than or equal to 1 ng/ml, 4-year BDFS was 75% for those with time to nadir >1 year, versus 61% for those with time to nadir less than or equal to 1 year (P < 0.021). In multivariate analysis, PSA nadir (less than or equal to 1 ng/ml versus >1 ng/ml, and time to nadir (less than or equal to 1 year versus >1 year) were independent predictors of BDFS alone with pre-treatment PSA and Gleason score. Conclusion: Only those who achieved PSA nadir less than or equal to 1 ng/ml following external beam therapy have a favourable chance of lasting biochemical disease control, while those with nadir >1 ng/ml have a high subsequent failure rate. The prognosis is better in patients with late time to nadir. In addition to PSA nadir, time to nadir, pretreatment PSA, and Gleason score were of independent prognostic significance. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.