The purpose of this study was to evaluate the impact of breast size on acute and late side effects in breast cancer (BC) patients treated with hypofractionated radiotherapy (Hypo-RT). In this study we analyzed patients over 50 years with a diagnosis of early BC, candidate for Hypo-RT after conservative surgery. Acute and late skin toxicities were evaluated in accordance with the RTOG scale. Multivariable logistic analysis was performed using dosimetric/anatomical factors resulted associated with toxicity outcome in univariable analysis. Among patients treated between 2009 and 2015, 425 had at least 5 years of follow-up. At RT end, acute skin toxicity ≥ G2 and edema ≥ G2 occurred in 88 (20.7%) and 4 (0.9%) patients, respectively. The multivariable analysis showed association of skin toxicity with boost administration (p < 0.01), treated skin area (TSA) receiving more than 20 Gy (p = 0.027) and breast volume receiving 105% of the prescription dose (V105%) (p = 0.016), but not breast size. At 5 years after RT, fibrosis ≥ G1 occurred in 89 (20.9%) patients and edema ≥ G1 in 36 (8.5%) patients. Fibrosis resulted associated with breast volume ≥ 1000 cm3 (p = 0.04) and hypertension (p = 0.04). As for edema, multivariable logistic analysis showed a correlation with hypertension and logarithm of age, but not with boost administration. Breast volume had an unclear impact (p = 0.055). A recurrent association was found between acute and late toxicities and breast V105%, which is correlated with breast size. This may suggest that a more homogenous RT technique may be preferred for patients with larger breast size.
Keywords: 3D Conformal Radiotherapy; Breast cancer; Hypofractionated radiotherapy; Large breast size; Late toxicity.
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