S992
Clinical - Oligometastatic cancer
ESTRO 2026
6 Nuclear Medicine, The University of Texas, MD Anderson Cancer Center, Houston, USA
had extrahepatic disease (controlled/treated concurrently). All treated liver metastases were progressing at SABR. Median treated liver metastases per patient was 2; gross tumor volume (GTV) was 34.4 cc (IQR 13.9–179.6) and diameter was 4 cm (IQR 2.5– 7.3). The most common dose was 35 Gy in 5 fractions to PTV (median BED 157.5 Gy ₂ , IQR 120–229.4). SABR was delivered as upfront treatment in 5 patients. At the time of liver SABR, 7 patients were on 1st line IO, 5 were on 1st line targeted therapy and 2 were on 2nd line IO. In patients on IO, the median time from systemic initiation to SABR was 7.7 months (IQR 3.9- 14.6). At 1 and 5 years, LC was 86.7% (73.6–100%) and 76% (59–97%); PFS was 28.1% (15.14–52.1%) and 15% (6–39%); OS was 74.3% (59.5–92.7%) and 30.7% (17– 55.4%). Median PFS was 5 months (95% CI 3–13). UVA showed non-uveal primaries correlated with worse PFS (HR 6.07, 95% CI 1.87–19.7, p=0.0027) and Stage III/IV at diagnosis correlated with worse OS (HR 4.91, 95% CI 1.47–16.48, p=0.0099). Two patients had toxicities (acute grade 2 nausea/vomiting, grade 3 esophagitis). Eighteen developed extrahepatic metastases post-SABR. Eight received IO following SABR and 18 had additional local therapies (surgery, ablation, Y90 or SABR). Four remained with liver only metastases that were controlled at last follow-up. Conclusion: SABR for melanoma liver metastases yields durable local control, though most patients progress outside of the irradiated volume. 5-year OS and PFS of 30.7% and 15% respectively suggest an oligometastatic state in a minority of patients, controllable by local therapy. Keywords: oligometastases, oligoprogression, melanoma Radiotherapy for Hormone-Sensitive Prostate Cancer with Synchronous Non-Regional Node (M1a) Metastases Kayeong Shin 1 , Gregory Chronowski 1 , Marc E Delclos 1 , Comron J Hassanzadeh 1 , Sean E McGuire 1 , Henry Mok 1 , Chad Tang 1 , Steven J Frank 1 , Quynh-Nhu Nguyen 2 , Karen Hoffman 3 , Phuoc T Tran 1 , Paul Corn 4 , Brian F Chapin 5 , Devaki S Surasi 6 , Seungtaek Choi 1 1 GU Radiation Oncology, The University of Texas, MD Anderson Cancer Center, Houston, USA. 2 Thoracic Radiation Oncology, The University of Texas, MD Anderson Cancer Center, Houston, USA. 3 Breast Radiation Oncology, The University of Texas, MD Anderson Cancer Center, Houston, USA. 4 GU Medical Oncology, The University of Texas, MD Anderson Cancer Center, Houston, USA. 5 Urology, The University of Texas, MD Anderson Cancer Center, Houston, USA. Digital Poster 4877 Survival Outcomes After Consolidative
Purpose/Objective: Clinical outcomes are rarely reported for patients with synchronous non-regional nodal (M1a) hormone- sensitive prostate cancer (HSPC) treated with radiotherapy (RT). Additionally, the optimal extent of RT, including the use of whole pelvic radiotherapy (WPRT) and elective nodal irradiation (ENI), has not been clearly defined. This study reports survival outcomes and treatment-related toxicities in synchronous M1a HSPC treated with consolidative RT along with systemic therapy. Material/Methods: Patients with synchronous M1a HSPC treated with consolidative RT and systemic therapy between 2016 and 2024 were retrospectively reviewed. Those with <18 months of follow-up were excluded. RT was delivered using intensity-modulated photon or proton therapy (IMRT/IMPT) to the prostate, with or without WPRT and ENI. In patients with retroperitoneal lymph node (LN) involvement, the RT field could be extended superiorly to at least one vertebral body above the highest LN, and any grossly involved nodes within the field could receive a boost. All patients received androgen deprivation therapy, and androgen receptor pathway inhibitors or chemotherapy could be added. Outcomes included overall survival (OS), biochemical recurrence-free survival (bRFS), nodal recurrence-free survival (NRFS), and distant metastasis-free survival (DMFS), and genitourinary/gastrointestinal (GU/GI) toxicities graded per CTCAE v5.0.. Kaplan-Meier method and log-rank test were used for analyses. Results: Fifty-five patients met inclusion criteria (median follow- up, 47 months; IQR 27–64). WPRT was delivered in 50 (90.9%) patients and ENI in 42 (76.4%) patients. Three- and five-year OS were 93.7% (95%CI, 86.9–100) and 87.9% (95%CI, 78.2–98.7); bRFS, 78.8% (95%CI, 67.7– 91.7) and 62.5% (95%CI, 47.3–82.4); NRFS, 85.7% (95%CI, 76.2–96.3) and 76.3% (95%CI, 64.0–91.0); DMFS, 93.5% (95%CI, 86.5–100) and 75.6% (95%CI, 61.3–93.2), respectively. In subgroup analyses, use of PET-CT at diagnosis was not associated with significant differences in OS (p=0.3), NRFS (p=0.3), or DMFS (p=0.2), and showed a borderline association with bRFS (p=0.06). Early grade ≥ 3 GU and GI toxicities occurred in 0% and 1.8%, with grade 2 in 25.5% and 5.5%. Late grade ≥ 3 GU and GI toxicities were 2.3% and 0%, and grade 2 in 15.9% and 9.1%, respectively. Among 12 nodal recurrences, 8 occurred out-of-field and 4 both in- and out-of-field.
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