Purpose: To evaluate long-term outcomes of adjuvant breast intensity-modulated radiation therapy (IMRT), with a comparison cohort receiving conventional radiation (cRT) during the same period.
Methods and materials: Retrospective review identified patients with Stages 0-III breast cancer who underwent irradiation after conservative surgery from January 1999 to December 2003. Computed tomography simulation was used to design standard tangential breast fields with enhanced dynamic wedges for cRT and both enhanced dynamic wedges and dynamic multileaf collimators for IMRT. Patients received 1.8-2-Gy fractions to 44-50.4 Gy to the whole breast, followed by an electron boost of 10-20 Gy.
Results: A total of 245 breasts were treated in 240 patients: 121 with IMRT and 124 with cRT. Median breast dose was 50 Gy, and median total dose was 60 Gy in both groups. Patient characteristics were well balanced between groups. Median follow-ups were 6.3 years (range, 3.7-104 months) for patients treated with IMRT and 7.5 years (range, 4.9-112 months) for those treated with cRT. Treatment with IMRT decreased acute skin toxicity of Radiation Therapy Oncology Group Grade 2 or 3 compared with cRT (39% vs. 52%; p = 0.047). For patients with Stages I-III (n = 199), 7-year Kaplan-Meier freedom from ipsilateral breast tumor recurrence (IBTR) rates were 95% for IMRT and 90% for cRT (p = 0.36). For patients with Stage 0 (ductal carcinoma in situ, n = 46), 7-year freedom from IBTR rates were 92% for IMRT and 81% for cRT (p = 0.29). Comparing IMRT with cRT, there were no statistically significant differences in overall survival, disease-specific survival, or freedom from IBTR, contralateral breast tumor recurrence, distant metastasis, late toxicity, or second malignancies.
Conclusions: Patients treated with breast IMRT had decreased acute skin toxicity, and long-term follow-up shows excellent local control similar to a contemporaneous cohort treated with cRT.