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Pre-operative 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 and toxicity. The aim trial is to assess the toxicity, surgical complications, and oncologic and cosmetic outcomes of pre-operative PBI.

In this single-centre phase II, single-arm trial, we enrolled elderly women (age ≥ 60), with unifocal low-risk, early-stage breast invasive ductal carcinoma (cT1N0, grade 1 and 2, ER positive, Her2 negative, without LVI on biopsy). Patients were treated with 20 Gy in 1 fraction of pre-operative PBI using volumetric modulated arc therapy (VMAT). Patients then underwent breast-conserving surgery (BCS) +/- sentinel lymph node biopsy within 72h from radiation. Patients with positive surgical margins underwent margin re-excision. Adjuvant whole breast or locoregional irradiation was indicated for several unexpected pathologic findings such as tumour > 3cm, grade 3 disease, positive lymph nodes, pure lobular pathology or if final pathological margins were < 1mm and re-excision surgery was not performed. Patients were assessed for surgical complications, cosmetic outcome, and local recurrence on post-operative days 7, 14, and then at 3, 6, and 12 months for the first year and then annually for 10 years.

25 patients were recruited with a median age of 67, and a median follow-up of 3.5 years. Treatment was successfully completed as per protocol in all patients. Following initial BCS, 6 patients were found to have close or positive margins. 5 patients underwent surgical margin revision, one of which underwent a second completion mastectomy for persistent close margins. Another patient with margins <1mm received adjuvant breast RT without revision surgery. Only one patient had a positive sentinel lymph node, and received adjuvant locoregional RT. None of the patients had surgical complications, including wound infections or healing delays, and all had grade 0-1 skin toxicity at day 7 and 14 post-op. There were no local, regional or metastatic recurrences. The cosmetic outcome was assessed in 21 out of 25 patients: 95% of assessed patients had an excellent or good cosmetic outcome, while it was fair in one patient.

Pre-operative PBI is a safe and feasible treatment for elderly patients with low-risk early-breast cancer, providing excellent local control and cosmetic outcomes with minimal acute adverse effects. Randomized controlled trials are needed to compare pre-operative to adjuvant PBI in this patient population.