Intensity modulated radiation therapy with simultaneous integrated boost in early breast cancer irradiation. Report of feasibility and preliminary toxicity.

PURPOSE: To investigate the feasibility and tolerance in the use of adjuvant intensity modulated radiation therapy (IMRT) and simultaneous integrated boost in patients with a diagnosis of breast cancer after breast-conserving surgery.

PATIENTS AND METHODS: Between September 2011 to February 2013, 112 women with a diagnosis of early breast cancer (T1-2, N0-1, M0) were treated with IMRT and simultaneous integrated boost after breast-conserving surgery in our institution. A dose of 50Gy in 25 fractions was prescribed to the whole breast and an additional dose of radiation was prescribed on the tumour bed. A dose prescription of 60Gy in 25 fractions to the tumour bed was used in patients with negative margins after surgery, whereas if the margins were close (<1mm) or positive (without a new surgical resection) a dose of 64Gy was prescribed. All patients were followed with periodic clinical evaluation. Acute and late toxicity were scored using the EORTC/RTOG radiation morbidity score system. Both patient and physician recorded cosmetic outcome evaluation with a subjective judgment scale at the time of scheduled follow-up.

RESULTS: The median follow-up was 28 months (range 24-40 months). The acute skin grade toxicity during the treatment was grade 0 in 8 patients (7%), grade 1 in 80 (72%), grade 2 in 24 cases (21%). No grade 3 or higher acute skin toxicity was observed. At 12 months, skin toxicity was grade 0 in 78 patients (70%), grade 1 in 34 patients (30%). No toxicity grade 2 or higher was registered. At 24 months, skin toxicity was grade 0 in 79 patients (71%), grade 1 in 33 patients (29%). No case of grade 2 toxicity or higher was registered. The pretreatment variables correlated with skin grade 2 acute toxicity were adjuvant chemotherapy (P=0.01) and breast volume ≥700cm(3) (P=0.001). Patients with an acute skin toxicity grade 2 had a higher probability to develop late skin toxicity (P<0.0001). In the 98% of cases, patients were judged to have a good or excellent cosmetic outcome. The 2-year-overall survival and 2-year-local control were 100%.

CONCLUSION: These data support the feasibility and safety of IMRT with simultaneous integrated boost in patients with a diagnosis of early breast cancer following breast-conserving surgery with acceptable acute and late treatment-related toxicity. A longer follow-up is needed to define the efficacy on outcomes.