Interim Cosmetic and Toxicity Evaluation Utilizing 3D Conformal External Beam Radiotherapy to Deliver Accelerated Partial Breast Irradiation In Patients With Early Stage Breast Cancer Treated With Breast Conserving Therapy

Abstract

Purpose/Objective: We present our ongoing clinical experience utilizing 3D-conformal radiation therapy (3D-CRT) to deliver accelerated partial breast irradiation (APBI) in patients with early-stage breast cancer treated with breast conserving therapy (BCT).Materials/Methods: 82 patients referred for post-operative radiation therapy after lumpectomy were treated with APBI using our previously reported 3D-CRT technique. The clinical target volume (CTV) consisted of the lumpectomy cavity plus a 10 mm margin. The planning target volume (PTV) consisted of the CTV plus a 10 mm margin for breathing motion and treatment set-up uncertainties. The prescribed dose (PD) was 34 or 38.5 Gy in 10 fractions b.i.d. (6 patients and 76 patients, respectively) separated by 6 hours and delivered in 5 consecutive days. Patients were treated in the supine position with 3–5 beams (mean-4) designed to irradiate the CTV with < 10% inhomogeneity. The median follow-up duration is 10.5 months (range 0–55 months). 3 patients have been followed for > 4 years, 6 for > 3.5 years, 11 for > 3.0 years, 15 for > 2.5 years, 22 for > 2.0 years, 34 for > 1.5 years and 40 for > one year. Late toxicity and cosmetic results were analyzed in the subset of patients (n=39) with greater than ≥ 6 months of follow-up.Results: No local recurrences have been observed to date. Cosmetic results were rated as good/excellent in 87% of all evaluable patients at ≥6 months follow-up (n=39), 90% at 1 year (n=35), 90% at 1.5 years (n=33), 86% at 2 years (n=22), 93% at 2.5 years (n=15), and in 91% of the patients followed ≥ 3 years (n=11).Conclusions: 3D-CRT to deliver APBI resulted in minimal chronic toxicity (≥ 6 months)to date with Good/Excellent cosmetic results. Additional follow-up will be needed to assess the long-term effects of these larger fraction sizes on normal tissue sequelae and the impact of this fractionation schedule on treatment efficacy.Tabled 1 Purpose/Objective: We present our ongoing clinical experience utilizing 3D-conformal radiation therapy (3D-CRT) to deliver accelerated partial breast irradiation (APBI) in patients with early-stage breast cancer treated with breast conserving therapy (BCT). Materials/Methods: 82 patients referred for post-operative radiation therapy after lumpectomy were treated with APBI using our previously reported 3D-CRT technique. The clinical target volume (CTV) consisted of the lumpectomy cavity plus a 10 mm margin. The planning target volume (PTV) consisted of the CTV plus a 10 mm margin for breathing motion and treatment set-up uncertainties. The prescribed dose (PD) was 34 or 38.5 Gy in 10 fractions b.i.d. (6 patients and 76 patients, respectively) separated by 6 hours and delivered in 5 consecutive days. Patients were treated in the supine position with 3–5 beams (mean-4) designed to irradiate the CTV with < 10% inhomogeneity. The median follow-up duration is 10.5 months (range 0–55 months). 3 patients have been followed for > 4 years, 6 for > 3.5 years, 11 for > 3.0 years, 15 for > 2.5 years, 22 for > 2.0 years, 34 for > 1.5 years and 40 for > one year. Late toxicity and cosmetic results were analyzed in the subset of patients (n=39) with greater than ≥ 6 months of follow-up. Results: No local recurrences have been observed to date. Cosmetic results were rated as good/excellent in 87% of all evaluable patients at ≥6 months follow-up (n=39), 90% at 1 year (n=35), 90% at 1.5 years (n=33), 86% at 2 years (n=22), 93% at 2.5 years (n=15), and in 91% of the patients followed ≥ 3 years (n=11). Conclusions: 3D-CRT to deliver APBI resulted in minimal chronic toxicity (≥ 6 months)to date with Good/Excellent cosmetic results. Additional follow-up will be needed to assess the long-term effects of these larger fraction sizes on normal tissue sequelae and the impact of this fractionation schedule on treatment efficacy.