Utility of Stereotactic Body Radiation Therapy (SBRT) in Establishing Local Control for Invasive Breast Cancer Patients Not Undergoing Definitive Surgery
Menée sur la période 2015-2022 auprès de 21 patientes atteintes d'un cancer du sein et non éligibles au traitement chirurgical (âge médian : 78,4 ans ; durée médiane de suivi : 14,7 mois), cette étude analyse le contrôle local et la survie globale après une radiothérapie stéréotaxique
Introduction: Surgery is the backbone of breast cancer (BC) treatment. For patients who cannot undergo surgery, improving local control (LC) of the primary tumor is paramount. To that end, this study explored the role of SBRT. Methods: Between 2015-2022, 21 non-surgical candidates (10 metastatic, 11 stage IA-IIIC) received 23 SBRT courses to primary BC. Seven were analyzed retrospectively; 15 are currently enrolled in a prospective study. SBRT (40 Gy/5 fractions) was delivered every other day. Follow-up imaging was reviewed. Acute (≤3 months) and late toxicities were evaluated using CTCAE. LC and overall survival (OS) were estimated using Kaplan-Meier curves. Results: Median age was 78.4 (45.9-97.3) years. Median follow-up was 14.7 (3.3-70.3) months. Median pre-SBRT index lesion size was 3.1 (0.5-14.5) cm and PTV was 32.4 (11.5-522.4) cc. Initial post-treatment imaging performed at a median 4.0 (0.6-11.9) months post-SBRT demonstrated median decrease in index lesion size of 20.8 (0-100)%; SUV reduction of 65.2 (20.8-100)%. Second follow-up scans at a median 7.8 months post-SBRT showed 62 (0-100)% and 88 (33.3-100)% median reduction in tumor size and SUV, respectively, compared to pre-SBRT values. The estimated LC rate was 100% at 6 months and 93.3% at 12, 24, and 36 months. Local progression occurred in 1 case 9.5 months after SBRT, following an initial response. Regional progression occurred in 4 (17.4%) cases at a median 18.6 (5.2-22.7) months post-SBRT. Six (35.3%) patients developed distant progression at a median 2.7 (0.9-16.2) months. The estimated OS was 85.7% at 6 months, 69.6% at 12 months, and 63.8% at 24 and 36 months. The rates of acute toxicity were: G1: 47.8%, G2: 4.3%, G3: 8.7%, G4: 0%. Conclusions: Definitive SBRT for primary BC resulted in good LC in non-surgical patients and was well-tolerated. Considering the pattern of progression, additional approaches to improve regional/distant control should be investigated.
International Journal of Radiation Oncology, Biology, Physics 2023