Normalization of prostate specific antigen (PSA) in patients treated with intensity modulated radiotherapy (IMRT) for clinically localized prostate cancer

Abstract

4771 Background: In this study, we determined the expected time to Prostate Specific Antigen (PSA) normalization with or without neoadjuvant androgen deprivation therapy (NAAD) after treatment with Intensity Modulated Radiotherapy (IMRT) for patients with clinically localized prostate cancer. Methods: Fifty-five patients with clinical stage T1c to T2b prostate cancer (1997 AJCC staging) treated in a community setting with IMRT between January 2002 and February 2003 were retrospectively reviewed for time to PSA normalization (using PSA<2 ng/mL and PSA<1 ng/mL as criteria). Of these 55 patients, 22 (40%) received NAAD, whereas 33 (60%) did not. In 24 patients (47%), radiotherapy was delivered to a limited pelvic field followed by an IMRT boost; 31 patients (53%) received IMRT alone. Median pretreatment PSA was 7.6 (r=1.95–34). Median radiotherapy dose was 75.6 Gy. Median follow-up was 7.4 months (r=0.5–16). Actuarial times to PSA normalization were calculated using the Kaplan-Meier method. Univariate analyses were performed on hypothesized predictors of PSA normalization using the Cox Proportional Hazards Model. Results: Serum PSA values normalized to <2 in 46 of 54 (85%) patients and <1 in 37 of 55 (67%) patients analyzed. The actuarial mean time to normalization was 4.5 months for PSA<2 and 5.9 months for PSA<1. The mean time to normalization of PSA<2 was 2.1 months for patients receiving NAAD versus 6.1 months for patients not receiving NAAD (p=0.002). Mean time to normalization of PSA<1 was 2.5 months for patients receiving NAAD versus 8.3 months months for those not receiving NAAD (p=0.002). PSAs of patients receiving NAAD were 2.9 times more likely than those not receiving NAAD to become <2 (95% CI: 1.54–5.58), and 3.5 times more likely to become <1 (95% CI: 1.68–7.13). Conclusions: In this study with limited followup, the expected time to normalization of serum PSA after IMRT may be measured in months. Using PSA<1 ng/mL as the criterion for normalization, PSA may take an extensive period of time to achieve normalization after IMRT. NAAD given with IMRT predicts for shortened time to PSA normalization. No significant financial relationships to disclose.