Defining the appropriate radiation dose for pretreatment PSA ≤ 10 ng/mL prostate cancer

Abstract

Purpose: To investigate whether a dose response exists for biochemical no evidence of disease (bNED) control in prostate cancer patients with pretreatment prostate-specific antigen (PSA) ≤ 10 ng/mL and to identify the patient subgroups affected. Methods and Materials: Between 5/89 and 10/97, 488 T1–T3 NX-0 M0 prostate cancer patients with PSA ≤ 10 ng/mL were treated with three-dimensional conformal radiation therapy (3D-CRT) alone. Median and mean pretreatment PSA values were 6.3 and 6.2, respectively. Gleason scores of 2–6 and 7–10 were noted in 386 and 102 men, respectively. AJCC 1992 palpation T1–T2AB tumors were noted in 415 patients. Perineural invasion (PNI) was noted in 60 men. Mean and median age was 67 and 68 years, respectively. Dose to the center of the prostate ranged from 6260 cGy to 8409 cGy with a mean and median of 7423 cGy and 7278 cGy, respectively. Patients were stratified into three groups according to dose: <7250 cGy, 7250–7599 cGy, and ≥7600 cGy. Median dose in these three groups was 7067 cGy, 7278 cGy, and 7734 cGy, respectively. Univariate analysis was performed to determine differences in bNED control (American Society for Therapeutic Radiology and Oncology [ASTRO] Consensus Guidelines definition of failure) by dose group for the entire cohort, for 310 good prognosis patients (T1–T2A, Gleason score 2–6, absence of PNI), and for 178 poor prognosis patients (T2B–T3 or Gleason score 7–10 or presence of PNI) (1). Multivariate analysis (MVA) was performed to determine if dose was an independent predictor of bNED control. Median follow-up was 36 months. Results: A dose response was not demonstrated for the entire group of patients with pretreatment PSA ≤10 ng/mL. Doses of <7250 cGy, 7250–7599 cGy, and ≥7600 cGy were associated with 5-year bNED control rates of 73%, 86%, and 89%, respectively ( p = 0.12). MVA demonstrated prognosis group ( p = 0.038) to be the only independent predictor of bNED control. Good prognosis patients had a 5-year bNED of 85% and no dose response was seen. The subgroup of poor prognosis patients demonstrated a 5–year bNED control rate of 81% and a dose response was seen for those receiving ≥7600 cGy, compared to the two lower dose groups (94% vs. 75% vs. 70%; p = 0.0062). MVA for the poor prognosis subset demonstrated dose ( p = 0.01) to be the only independent predictor for improved bNED control. Conclusions: The poor prognosis subset of PSA ≤10 ng/mL prostate cancer patients benefit from dose escalation. A dose response is not demonstrated for prostate cancer patients with pretreatment PSA ≤10 ng/mL and other favorable features.