Presenter(s)
H. Zhang, X. Qi, and H. Z. Li; Department of Radiation Oncology, Peking University First Hospital, Beijing, China
Purpose/Objective(s): Salvage Re-irradiation (re-RT) has been considered a high-risk treatment due to exceeding the tolerable dose for normal tissues. We investigated the safety and efficacy of re-RT for intra-field or peri-field oligoprogression after prior radiotherapy in prostate cancer.
Materials/Methods: We conducted a retrospective cohort study of patients with prostate cancer treated with re-RT between 2018 and 2025 at one institution. Eligible patients had biopsy-confirmed or imaging-defined (PSMA PET/CT or MRI) oligometastatic progression localized within the prior pelvic RT field or its immediate margin. All patients underwent image-guided RT with or without concurrent systemic therapy. Primary efficacy endpoints were PSA50 and PSA90 response rates—defined as =50% and =90% decline in serum PSA from baseline (pre-reRT) to one month post-treatment completion, respectively. Toxicity was assessed according to CTCAEs version 5.0.
Results: Seventeen patients were included. Median age at re-RT was 69.0 years (range, 48–84 years). Median interval from initial RT to recurrence was 38 months (range, 6–264 months). At recurrence, the median PSA was 0.677 ng/mL (range, 0.126–6.057 ng/mL). Initial RT was delivered as definitive (11.8%), postoperative (58.8%), or for metastatic disease (29.4%). Targets comprised whole-pelvic RT (prostate ± seminal vesicles region and elective nodal drainage areas) in 88.2% of patients, with concurrent pelvic/retroperitoneal nodal or bone metastases treated in 29.4% and 23.5%, respectively. Re-RT was delivered as SBRT (58.8%, 30–40 Gy/5 fx to the planning gross tumor volume (PGTV); 20% received elective nodal irradiation to the nodal drainage basin at the same level, 25 Gy/5 fx) or moderate-hypofractionated RT (41.2%, 65–70 Gy/25 fx to PGTV; 85.7% received concurrent elective nodal irradiation, 47.5 Gy/25 fx). The cumulative EQD2 dose (a/ß = 10 Gy) from initial and re-RT was: small intestine D???, 48.1–82.5 Gy; V50 (volume receiving =50 Gy), 0–127.5 mL; duodenum D???, 0–57.7 Gy; rectum D???, 62.8–75.0 Gy; and spinal cord D???, 0–45.9 Gy. Combination therapy: 15 patients (88.2%) received androgen deprivation therapy (ADT) plus androgen receptor pathway inhibitors (ARPI) concurrent with re-RT; 1 (5.9%) received ADT plus bicalutamide; 1 (5.9%) received ADT alone. Median follow-up was 7 months (interquartile range [IQR] 6–18 months). Acute grade 1 gastrointestinal (GI) toxicity occurred in 29.4% of patients, with no grade =2 adverse events observed. No genitourinary (GU) toxicity was reported. No neutropenia or thrombocytopenia occurred. At 1 month, PSA50 and PSA90 response rates were 94.1% and 41.2%, respectively.
Conclusion: This study shows that re-RT—whether delivered via SBRT or moderate hypofractionation—is feasible and has acceptable toxicity for oligoprogressive prostate cancer. Further prospective studies are necessary to confirm these preliminary results and to determine late toxicity.