Stereotactic image-guided neoadjuvant ablative single-dose radiation, then lumpectomy, for early breast cancer: the SIGNAL prospective single-arm trial of single-dose radiation therapy

Abstract

Background and purpose: Adjuvant whole-breast irradiation after breast-conserving surgery, typically delivered over several weeks, is the traditional standard of care for low-risk breast cancer. More recently, hypofractionated, partial-breast irradiation has increasingly become established. Neoadjuvant single-fraction radiotherapy (rt) is an uncommon approach wherein the unresected lesion is irradiated preoperatively in a single fraction. We developed the signal (Stereotactic Image-Guided Neoadjuvant Ablative Radiation Then Lumpectomy) trial, a prospective single-arm trial to test our hypothesis that, for low-risk carcinoma of the breast, the preoperative single-fraction approach would be feasible and safe.

Methods: Patients presenting with early-stage (T < 3 cm), estrogen-positive, clinically node-negative invasive carcinoma of the breast with tumours at least 2 cm away from skin and chest wall were enrolled. All patients received prone breast magnetic resonance imaging (mri) and prone computed tomography simulation. Treatable patients received a single 21 Gy fraction of external-beam rt (as volumetric-modulated arc therapy) to the primary lesion in the breast, followed by definitive surgery 1 week later. The primary endpoints at 3 weeks, 6 months, and 1 year were toxicity and cosmesis (that is, safety) and feasibility (defined as the proportion of mri-appropriate patients receiving rt).

Results: Of 52 patients accrued, 27 were successfully treated. The initial dosimetric constraints resulted in a feasibility failure, because only 57% of eligible patients were successfully treated. Revised dosimetric constraints were developed, after which 100% of patients meeting mri criteria were treated according to protocol. At 3 weeks, 6 months, and 1 year after the operation, toxicity, patient- and physician-rated cosmesis, and quality of life were not significantly different from baseline.

Conclusions: The signal trial presents a feasible method of implementing single-dose preoperative rt in early-stage breast cancer. This pilot study did not identify any significant toxicity and demonstrated excellent cosmetic and quality-of-life outcomes. Future randomized multi-arm studies are required to corroborate these findings.

Keywords: Radiation oncology; sbrt; stereotactic body radiotherapy.

Conflict of interest statement

CONFLICT OF INTEREST DISCLOSURES We have read and understood Current Oncology’s policy on disclosing conflicts of interest, and we declare that we have none.

Figures

FIGURE 1

Study schema showing the entire course of the experimental protocol undergone by the patients. QOL = quality of life; MR = magnetic resonance; CT = computed tomography; RT = radiotherapy.

FIGURE 2

Patient flow diagram. MR = magnetic resonance; CT = computed tomography; RT = radiotherapy.