Cosmetic Results and Acute Toxicity using Breast Intensity Modulated Radiation Therapy with Simultaneous integrated Boost in Patients with Early-stage Breast Cancer

Abstract

Materials/Methods: Sixty-two consecutive patients with TNM Staging (Tis, T2 and N0) were treated with the previously reported IMRT + SIB mono - isocenteric setup technique.* The planning target volumes were ipsilateral breast tissue and the boost (CT-defined resection cavity and surgical clips) with a 2-cm margin. A campsite inverse-planned IMRT plan for the boost with an irregular surface compensator planned IMRT for the breast with dynamic multileaf collimators was developed using Eclipse software (Varian Medical Systems). A total of 52.5 Gy in 30 fractions was prescribed to the breast and 60 Gy to the boost concomitantly. Toxicity scoring was based on the NCI CTC version 2.0. Early cosmetic results were evaluated in all patients using criteria established by the Harvard Group. Results: Thirty-eight patients treated had infiltrating breast cancer (IBC); stage I 45%, IIA 16%, while 24 had ductal carcinoma in situ (DCIS). The median breast volume was 855 cc and median cavity volume 198 cc. The average volume of the PTV-breast and PTV-boost receiving more than 95% of the prescribed dose was 97%. The volume of PTV-breast, excluding PTV- boost, receiving a dose higher than 95% of the boost dose was 58 cc (range, 35-109 cc). Median follow-up was 24 months. Acute Grade 2 dermatitis, edema, and hyperpigmentation were seen in 14% and two patients (3%) had Grade 3 dermatitis. Chronic Grade 2 breast edema was reduced by 75% in the patients who underwent IMRT compared to the conventional radiation therapy. Assessment of breast cosmesis at a minimum of twenty-four month follow-up was available in 70% of the cases of which 95% were judged good or excellent, while 5% had fair cosmesis. Conclusion: IMRT + SIB mono - isocenteric setup technique to the breast allows the radiobiologic advantage of higher dose per fraction to the tumor cavity - the site of highest risk of recurrence - while using conventional fractionation for the remaining breast tissue. This technique is extremely well tolerated and easily implemented with relatively low incidence of acute skin toxicity. *Coen et al., Int J Radiat Oncol Biol Phys 2006;66:923.