Prognostic Factors of Oligometastasis After Stereotactic Body Radiotherapy: The Real-World Utility of the European Society for Radiotherapy and Oncology/European Organisation for Research and Treatment of Cancer Classification.

AIM: The efficacy of local therapy for oligometastatic disease (OMD) remains unclear. This study aimed to evaluate the prognostic utility of the classification system for OMD and explore which groups may benefit from stereotactic body radiation therapy (SBRT). METHODS: This single-center retrospective study included 45 patients (52 sites) with solid tumors and 1-3 extracranial oligometastases who underwent SBRT for all metastases at our institution between January 2018 and December 2021. OMD states were classified based on the European Society for Radiotherapy and Oncology (ESTRO) and the European Organisation for Research and Treatment of Cancer (EORTC) classification system. Local control (LC), overall survival (OS), and progression-free survival (PFS) for each group were analyzed using the Kaplan-Meier method. Acute and late adverse events (AEs) were evaluated according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. RESULTS: The median follow-up period was 14 months (range: 0-48 months). The numbers of patients in the de novo (first diagnosis of OMD), repeat (previous history of OMD), and induced (previous history of polymetastatic disease) OMD groups were 15, 17, and 13, respectively. The LC rates at one year for the entire, de novo, repeat, and induced cohorts were 87.2%, 87.5%, 90.2%, and 83.9%, respectively (p=0.80). The one-year PFS rates for each group were 35.0%, 56.7%, and 29.9%, respectively (p=0.58). The one-year OS rates for each group were 80.0%, 86.2%, and 80.8%, respectively (p=0.50). Grade 2 or 3 AEs occurred in five patients (10.4%). No grade 4 or 5 AEs were observed. CONCLUSIONS: SBRT is safe and highly effective for local control. Patients with repeat OMD demonstrated a trend of longer PFS, suggesting that this subgroup may benefit from local therapy at metastatic sites.

CT-based image-guided brachytherapy in uterine cervical cancer: Effect of tumor dose and volume on local control.

BACKGROUND AND PURPOSE: To determine the optimal primary tumor dose for cervical cancer treatment using computed tomography (CT)-based image-guided brachytherapy (IGBT). MATERIALS AND METHODS: We retrospectively reviewed 171 patients with cervical cancer who underwent both external beam radiation therapy (EBRT) and IGBT between May 2015 and December 2019. Majority of EBRT plan included central shielding technique. CT-based IGBT was performed weekly a median of three times. Magnetic resonance imaging preceded the first and third session of IGBT for target delineation. RESULTS: The median age of the patients was 64 years (range: 30-91 years). The median follow-up time for living patients was 43 months (range: 6-76 months). The 3-year local control rates according to the International Federation of Gynecology and Obstetrics (FIGO, 2008) stages were 89%, 100%, 92%, 89%, 78%, and 100% for stages IB, IIA, IIB, IIIA, IIIB, and IVA, respectively. The median EBRT dose to the central pelvis and parametrium/pelvic wall was 41.4 Gy and 50.4 Gy, respectively. Patients who received a cumulative 2 Gy equivalent dose (EQD2) (α/ß = 10 Gy) of high-risk clinical target volume (HR CTV) D90% ≥ 75 Gy achieved a long-term local control rate of 93%, compared with 80% in those who received <75 Gy (p = 0.02). CONCLUSION: This is one of the largest CT-based IGBT series examining the treatment of cervical cancer based on the tumor dose-volume relationship. An HR CTV D90% ≥75 Gy was significantly associated with favorable local control in this study.