Hypofractionated Helical 3DCRT and IMRT systems for the Post-Operative Treatment of Prostate Cancer: A Mono-Institutional Report

Abstract

The role of hypofractionation in prostate cancer is established for the definitive setting, while it is still investigational in the post-surgical treatment. The following study reports acute and late toxicities and biochemical control rates in a retrospective series of 102 patients with prostate cancer who were treated in the post-operative setting with moderate hypofractionation delivered by a 3DCRT and IMRT system. From April 2013 to April 2018, 102 patients, with median age 68 years (range, 54-84), received postoperative radiotherapy, delivering to prostate bed a total dose of 63.8 Gy (EQD2=67.4 Gy) using 2.2 Gy fractions. Adjuvant treatment (n=52) was administered within 6 months after surgery for patients with PSA ≤0.2 ng/ml in presence of adverse features like an extracapsular extension, seminal vesicles invasion, positive margins, or lymph nodal involvement. Salvage therapy (n=50) was delivered 6 months after prostatectomy with PSA≥0.2 ng/ml or for patients with persistent post-surgery PSA. Basing on the evidence of pathological adverse features (pN+, inadequate lymph nodal dissection (<10 nodes), and/or Gleason Score>8) pelvic irradiation was administered in 68% of cases with a median dose of 49.3 Gy (range, 48-55.1 Gy) using conventional fractionation. Concurrent hormonal therapy was prescribed in 50% of cases. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicity assessment were performed following Common Terminology Criteria for Adverse Events v4.0. Any PSA level rise of≥0.2 or more above the post-radiotherapy nadir was considered biochemical progression. Assuming p values ≤0.05 as significant, Chi-squared tests were applied for statistical analysis. Kaplan-Meier method and log-rank test were adopted for survival estimates. Acute GU toxicities were as follows: G1 in 44% and G2 in 4.9%, detecting no G≥3 events. For GI toxicity, we recorded G1 in 33% and G2 in 19.6%. With a median follow-up of 24 months (10-60), we detected as late toxicity G2 GI in 4.9%, and G≥2 GU in 3.9%, including 2 patients surgically treated for incontinence correction. At statistical analysis, pelvic irradiation was significantly associated with acute G2 GI adverse events (p=0032). Actuarial 2- and 3-years biochemical-free survival were respectively 88.9% and 74% for the entire population; in a subgroup evaluation no difference in terms of biochemical control was observed between adjuvant or salvage treatment (p=0.23). All patients are alive, except for one death by cerebrovascular disease, resulting in 2- and 3-years overall survival rates of both 97.7%. In our series, moderate hypofractionated post-operative RT with HT resulted in a low incidence of adverse events, also collecting excellent biochemical control rates.