Adjuvant breast inversely planned intensity-modulated radiotherapy with simultaneous integrated boost for early stage breast cancer : Results from a phase II trial

Abstract

Purpose: To report early toxicity and 5‑year clinical outcomes of adjuvant breast inversely planned intensity-modulated radiotherapy with simultaneously integrated boost (IMRT-SIB) after breast-conserving surgery for early stage breast cancer patients.

Patients and methods: In all, 467 patients including 406 invasive breast cancer and 61 ductal carcinoma in situ (DCIS) were enrolled in a single institutional phase II trial. All patients underwent IMRT-SIB treatment to irradiate the whole breast and the tumor bed. Doses to whole breast and surgical bed were 45 and 60 Gy, respectively, delivered in 25 fractions over 5 weeks. The grade of maximum acute skin toxicity during treatment was recorded. Lung toxicity was noted within 6 months and patient-reported cosmetic outcomes were recorded at the 12 month follow-up after the end of radiotherapy. Clinical outcomes were assessed during follow-up.

Results: Median follow-up time was 5.46 years. Median age was 46 years old (range 22-70 years old). No patient with DCIS had a local recurrence or distant metastasis. Among 406 patients with invasive breast cancer, the unadjusted 5‑year actuarial rate of locoregional control was 98.7% (95% confidence interval [CI] 97.5-100), and distant metastasis-free survival 98.7% (95% CI 97.4-100), respectively. Acute skin toxicity was recorded at grade 0-1 in 76.5% of patients, and grade 2 in 23.5% of patients. None of these patients had grade 3 or more than grade 3 skin toxicity. Grade 1 pneumonitis was found in 25.3% of patients. Assessment of patient reported cosmetic outcomes at the 12 month follow-up showed good or excellent outcome in 86.5% of cases.

Conclusions: The use of inversely planned IMRT-SIB as part of breast-conserving therapy results in optimal 5‑year tumor control and minor early toxicities.

Keywords: Adjuvant radiotherapy; Breast cancer; Breast-conserving surgery (BCS); Intensity-modulated radiotherapy (IMRT); Simultaneously integrated boost (SIB).