VMAT partial-breast irradiation: acute toxicity of hypofractionated schedules of 30 Gy in five daily fractions.

PURPOSE: To report acute toxicities in breast cancer (BC) patients (pts) recruited in a prospective trial and treated with accelerated partial-breast irradiation (APBI) using Volumetric Modulated Arc Therapy (VMAT) delivered with a hypofractionated schedule. METHODS: From March 2014 to June 2019, pts with early-stage BC (Stage I), who underwent breast conservative surgery (BCS), were recruited in a prospective study started at the National Cancer Institute of Milan. Pts received APBI with a hypofractionated schedule of 30 Gy in five daily fractions. Radiotherapy treatment (RT) was delivered using VMAT. Acute toxicity was assessed according to RTOG/EORTC criteria at the end of RT. RESULTS: Between March 2014 and June 2019, 151 pts were enrolled in this study. 79 Pts had right-side and 72 had left-side breast cancer. Median age was 69 (range 43-92). All pts presented with pathological stage IA BC, molecular classification was Luminal A in 128/151 (85%) and Luminal B in 23/151 (15%) cases. Acute toxicity, assessed at the end of RT, consisted of G1 erythema in 37/151 (24. 5%) pts and skin toxicities higher than G1, did not occur. Fibrosis G1 and G2 were reported in 41/151 (27. 1%) pts and in 2/151 pts (1. 3%), respectively. Edema G1 occurred in 8/151 (5. 3%) pts and asthenia G1 occurred in 1/151 (0. 6%) pts. CONCLUSIONS: APBI with VMAT proved to be feasible and can be a valid alternative treatment option after BCS in selected early breast cancer pts according to ASTRO guidelines. A longer follow-up is needed to assess late toxicity.

Axillary nodal involvement by primary tumor features in early breast cancer: an analysis of 2600 patients.

BACKGROUND: Primary tumor characteristics, which are readily available to all clinicians, may aid in selecting the optimal adjuvant therapy for patients with breast cancer (BC). Herein, we investigated the relationship between tumor size, hormone receptor and HER2 status, Ki67 and age with axillary lymph node metastases (ALNM) in early-BC patients. METHODS: We analyzed data on consecutive 2600 early-BC cases collected in the registry of Fondazione IRCC Istituto Nazionale dei Tumori, Milano, Italy. Correlation between Ki67 and primary tumor size (T-size) was calculated by Spearman's rank correlation coefficient. Association of ALNM with Ki67 and other tumor characteristics was investigated by logistic regression. Adjusted odds ratios (ORs) with 95% confidence intervals (95% CIs) were estimated in all cases, and separately analyzed according to age, T-size and BC subtype. RESULTS: Large tumor size strongly associated to ALNM, with an adjusted odds ratio (OR) for each 5-mm increase of 1.32 (95% CI 1.24-1.41), except for triple-negative BC (TNBC) cases. In tumors =10 mm, without lymphovascular invasion, representing the strongest predictor of ALNM (OR 6.09, 95% CI 4.93-7.53), Ki67 resulted particularly informative, with a fourfold increased odds of ALNM for values > 30%. CONCLUSIONS: These results raise the question whether axillary node status is redundant in cases with exceptionally good features, i.e., small tumors with low Ki67, or in those candidate to adjuvant systemic treatment/radiotherapy anyway including TNBC, and support the incorporation of primary BC tumor characteristics as stratification factors in ongoing trials aiming at de-escalating axillary surgical procedures.