Single pre-operative radiation therapy (SPORT-CK) trial for low-risk breast cancer: Early results of a phase 2 study

Preoperative partial breast irradiation (PBI) is a novel technique that can be used in patients with early-stage breast cancer with the goal of limiting the irradiated breast volume, toxicity and number of fractions. The aim of this trial is to assess the toxicity, surgical, oncologic and cosmetic outcomes of preoperative PBI.

In this single-arm phase II trial, we enrolled women ≥ 60 years, with unifocal low-risk breast invasive ductal carcinoma (cT1N0, grade 1-2, ER+, Her2-). Patients were treated with a single fraction of 20 Gy of preoperative PBI using volumetric modulated arc therapy (VMAT). Patients then underwent breast-conserving surgery (BCS) +/- sentinel lymph node biopsy within 72 h of radiation. Primary outcomes were rate of surgical complications and early toxicity. Secondary outcomes were cosmesis at 12 months, chronic toxicity and ipsilateral breast tumor recurrence.

Twenty-five patients were recruited with a median age of 67 years, and a median follow-up of 60 months. Sentinel biopsy was positive in 1 out of 24 patients (4 %). Two patients received adjuvant RT for close margins or positive lymph nodes. Within the first 90 days, none of the patients had surgical complications; almost all had grade 0 to 1 acute and late RTOG skin toxicity. The cosmetic outcome was rated between good and excellent in all cases by physicians and patients, except for one patient who self-rated her cosmesis as fair as of the third year. There were no recurrences.

Preoperative single-fraction PBI is a safe and feasible treatment for elderly patients with low-risk early-stage breast cancer, with no surgical complications, very low rates of acute and late radiation toxicity, and excellent cosmetic outcomes. Randomized controlled trials are needed to compare preoperative to adjuvant PBI in this patient population.