Ongoing clinical experience utilizing 3D conformal external beam radiotherapy to deliver 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 partial breast irradiation (PBI) in patients with early-stage breast cancer treated with breast conserving therapy (BCT). Materials/Methods: Thirty-one patients referred for post-operative radiation therapy after lumpectomy were treated with PBI using our previously reported 3D-CRT technique. Ninety-four percent of patients had surgical clips outlining the lumpectomy cavity (mean 6). The clinical target volume (CTV) consisted of the lumpectomy cavity plus a 10-mm margin in 9 patients and 15 mm in 22 (median 15 mm). 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 was 34 or 38.5 Gy in 10 fractions b.i.d. (6 patients and 25 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 and a comparable or lower dose to the heart, lung and contralateral breast compared with standard whole breast tangents. The median follow-up duration is 8 months (range 1 – 30 months). Four patients have been followed for > 2 years, six for > 1.5 years and five for > one year. The remaining 16 patients have been followed < 12 months. Results: No skin changes greater than grade I erythema were noted during treatment. At the initial 4–8 week follow-up visit, 19 patients (61%) experienced grade I toxicity and 3 patients (10%) grade II toxicity. No grade III toxicities were observed. The remaining 9 patients (29%) had no observable radiation effects. Cosmetic results were rated as good/excellent in all evaluable patients at 6 months (n=3), 12 months (n=5), 18 months (n=6), and in the 4 evaluable patients at >2 years after treatment (Table Legend: CTV-Clinical Target Volume, PD-Prescribed Dose, PBI-Partial Breast Irradiation, V-30-Volume receiving 30% of PD). Conclusions: Utilizing 3D-CRT to deliver PBI is technically feasible and acute toxicity to date has been minimal. 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.