Whole-breast Radiotherapy With Boost for Node-negative Breast Cancer: Conventionalvs. Hypo-fractionation

Abstract

Background/Aim: Many breast cancer patients receive adjuvant radiotherapy. Tumor bed boost may reduce risk of local failure in high risk patients. We compared hypofractionated whole-breast irradiation (WBI) plus boost (HF+boost) and conventionally fractionated WBI plus boost (CF+boost). Patients and Methods: One-hundred-andtwenty-eight patients receiving HF-WBI (40 Gy in 15 fractions) plus boost (group A) were matched to 127 patients receiving Gy in 28 fractions) plus boost (group B), utilizing 10 characteristics. Results: Grade ≥2 dermatitis rates were 16.4% in group A vs. 44.1% in group B (p<0.0001), and grade ≥2 pneumonitis rates were 1.6% vs. 2. 4% (p=0.68). Four-year rates of local control, metastases-free survival, and overall survival were 100% vs. 99% (p=0.81), 98% vs. 100% (p=0.29), and 98% vs. 100% (p=0.17), respectively. Conclusion: HF+boost was associated with significantly less grade ≥2 dermatitis with similar disease control and survival.Breast cancer patients generally receive adjuvant radiotherapy (RT) if treated with breast-conserving surgery (1). In the majority of these patients, RT is administered as whole-breast irradiation (WBI) with those at high risk of developing a local failure receiving an additional boost to the tumor bed (2). The tumor bed boost can be given following (sequential boost) or concurrently with WBI (simultaneous integrated boost, SIB). In the German IMRT-MC2 trial, both techniques of tumor bed boost were associated with similar late toxicity and similar 5-year outcomes in terms of local control (LC), metastases-free survival (MFS), and overall survival (OS) (3, 4). However, using a SIB leads to a reduction of the overall treatment time.Another option to shorten the overall treatment time is the use of hypo-fractionation (HF) with doses per fraction of >2.0 Gy. Common regimens of HF include 42.5 Gy in 16 fractions and 40 Gy in 15 fractions. Four large randomized trials, each with more than 1,000 patients, demonstrated that these regimens were not inferior to 50 Gy of CF with respect to LC and cosmetic outcomes (5-9). However, in these four trials, only 0.0%, 23.2%, 42.6%, and 51.5% of the patients, respectively, had received a radiation boost to the primary tumor bed (5-9). This likely reflects the pattern-of-practice that radiation oncologists tended to use a boost significantly more often after CF than after HF (10-12).Few studies have compared HF and CF in which all patients received a boost in addition to WBI (13-16). Thus, additional studies are required comparing HF+boost and CF+boost for adjuvant RT of breast cancer. Our study compares both RT regimens with respect to dermatitis, pneumonitis, LC, MFS, and OS in patients with early breast cancer.2628