Phase I study of stereotactic ablative radiotherapy (SABR) in inoperable breast cancer
Abstract
Purpose: A significant percentage of elderly patients with early-stage breast cancer are not surgical candidates or refuse surgery, and exclusive hormone therapy offers poor local control. SABR, by delivering biologically ablative doses in a few fractions, could be a non-invasive and effective alternative. This phase I clinical trial's primary objective was to determine the safety, tolerability, and maximum tolerated dose (MTD) of SABR as a definitive treatment in this population.
Material and methods: A single-center, single-arm, phase I study was designed. Eligible patients were ≥70 years old with unifocal, T1-2N0 M0-1 breast cancer, considered inoperable or who refused surgery. A Fibonacci (3 + 3) dose-escalation design was used to deliver SABR to the primary tumor in 5 fractions. Dose levels were 36 Gy (Level 1), 38 Gy (Level 2), and 40 Gy (Level 3). The primary endpoint was dose-limiting adverse effects, defined as any ≥ Grade 3 events (per RTOG/Harris scales) within the first 6 months. Secondary endpoints included local control (LC), progression-free survival (PFS), and overall survival (OS).
Results: Between March 2021 and March 2024, 10 patients (11 tumors) with a median age of 91 years (range: 83-96) were enrolled. Three patients received 36 Gy, three received 38 Gy, and four received 40 Gy. With a median follow-up of 27 months (range: 4-40), no dose-limiting adverse events were observed in any cohort, and thus the MTD was not reached. No acute adverse events were…
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Evidence Hub reads this as a clinical trial, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence.
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