Abstract

Petr Burkon^1,2, Iveta Selingerova^3,4, Marek Slavik^1,5, Tomas Kazda^1,2, Miroslav Vrzal¹, Pavel Slampa^1,2

¹Masaryk Memorial Cancer Institute, Department of Radiation Oncology, Brno, Czech Republic; ²Faculty of Medicine, Masaryk University, Department of Radiation Oncology, Brno, Czech Republic; ³Masaryk Memorial Cancer Institute, Research Centre for Applied Molecular Oncology, Brno, Czech Republic; ⁴Faculty of Medicine, Masaryk University, Department of Pharmacology, Brno, Czech Republic; ⁵ Faculty of Medicine, Masaryk University, Department of Radiation Oncology, Brno, Czech Republic

The adjuvant radiotherapy (RT) of the early breast cancer as local treatment aims to eliminate the potential microscopic residual disease in the surgery bed. Based on published studies, accelerated partial breast irradiation (APBI) is recommended for strictly selected patients. Several techniques were shown to be appropriate, namely interstitial brachytherapy or external beam RT. Another possibility is stereotactic body radiotherapy (SBRT) which offers a more precise dose application associated with target volume reduction, which may lead to a reduction in toxicity and better cosmetic effect. The aim of this single-institution prospective randomized study was to compare the targeted APBI delivered by SBRT technique with the currently more commonly used accelerated whole breast irradiation in terms of feasibility, safety, tolerance, and cosmetic effects.

Early breast cancer patients after partial mastectomy were screened for eligibility. The inclusion criteria were age ˃ 50 years, no lobular histology, size ≤ 2 cm, margins ≥ 2 mm, L0, ER-positive, BRCA negative. Enrolled patients were equally randomized into two arms according to RT regiments – the SBRT surgery bed radiotherapy (5×6Gy) and accelerated whole breast irradiation with the boost (15×2,67Gy + 5×2Gy). These preliminary results of the ongoing study evaluated the first 57 from 84 planned patients. The follow-up evaluation was planned at the end of RT, one and three months after RT and then every three months. Quality of life was evaluated by the official Czech translation of EORTC QoL questionnaires. Cosmetics results and toxicity were evaluated using questionnaires, CTCAE criteria and photodocumentation of irradiated chest.

The median age was 65 years. The tumors were grade 1 in 60% of patients, the median size of 9 mm and 70% were classified as invasive ductal carcinoma. Significant differences between groups in baseline characteristics were not observed. A total of 29 patients were enrolled in the SBRT group. All patients were evaluated one month after RT. A total of 40 and 33 patients had examinations 3 and 6 months after RT, respectively. Toxicity evaluation showed statistically significantly fewer acute adverse events in the SBRT group in terms of skin erythema, desquamation, skin tenderness, dryness, edema, pigmentation, breast pain and fatigue. Late toxicities were significantly higher in the control arm. Cosmetic effect was more favorable to the SBRT group.

This single-institution prospective randomized study compared the feasibility, toxicity, the cosmetic and economic influence of two radiotherapeutic regiments. SBRT technique turned out to be a less toxic and easier feasible approach for adjuvant radiotherapy of early-stage breast cancer patients. Consequently, the presented study increases the level of evidence for RT-indicated patients to the establishment of SBRT into daily clinical practice of APBI. Supported by grant NV19-03-00354 of the Czech Ministry of Health.