Carbon-Ion Radiotherapy as Non-Surgical Treatment for Early-Stage Breast Cancer: Five-year Results from the Phase II Part of the First Prospective Clinical Trial
Mené sur 12 patientes atteintes d’un carcinome canalaire invasif ER+ HER2- de stade I et âgées d'au moins 60 ans (durée médiane de suivi : 73 mois), cet essai de phase I/II évalue l'efficacité, du point de vue du taux de contrôle local à 5 ans, et la sécurité d'une radiothérapie par ions carbone pour les patientes inopérables ou refusant la chirurgie
Purpose: To evaluate the long-term efficacy, safety, and cosmetic outcomes of carbon-ion radiotherapy (C-ion RT) as a non-surgical treatment option for patients with early-stage breast cancer (BC).
Materials and Methods: This single-center, prospective phase I/II trial enrolled women aged ≥60 years with stage I (cT1N0M0), ER-positive, HER2-negative invasive ductal carcinoma, ≤2 cm in diameter. Patients received C-ion RT at a total dose of 60 Gy (relative biological effectiveness) in four fractions, followed by adjuvant aromatase inhibitors. The primary endpoint was 5-year local control (LC). Secondary endpoints included complete response (CR) rate, adverse events (AEs), cosmetic outcomes, disease-free survival (DFS), and overall survival (OS). Imaging was used for evaluating tumor response, and follow-up was conducted for a median of 73 months.
Results: Twelve patients were treated in the phase II component of the trial. The CR rate was 100%, with a median time to CR of 12 months (range: 4–36 months). The 5-year LC and DFS rates were both 92%, and the OS rate was 100%. One case of in-field recurrence occurred in a patient with a high Ki-67 index. Acute Grade 1 dermatitis was observed in six patients. No Grade ≥2 acute AEs were reported. Regarding late AEs, Grade 1 rib fractures (n=2) and Grade 1 mastitis-related pain (n=3) were managed conservatively. Magnetic resonance imaging revealed subclinical pectoral muscle inflammation in seven cases. All patients except one (who underwent mastectomy due to recurrence) maintained excellent cosmetic outcomes.
Conclusion: C-ion RT demonstrated excellent long-term tumor control with minimal toxicity and favorable cosmetic outcomes in selected patients with early-stage BC. These findings support its potential as a non-surgical alternative for patients who are medically inoperable or decline surgery, warranting further investigation in larger, controlled trials.
International Journal of Radiation Oncology, Biology, Physics , résumé, 2025