Clinical audit of breast cancer patients treated with helical tomotherapy for irradiation of the internal mammary chain

Aim: To evaluate efficacy of helical tomotherapy (HT) for treatment of breast cancer with internal mammary lymph node involvement. Methods: This is a retrospective clinical audit of planning, dosimetry, toxicity and short-term survival of a cohort of 65 patients. Patients were treated between November 2014 and May 2019. The primary and nodal region was prescribed a dose of 50 Gray (Gy) in 25 fractions, while all cases of breast conserving surgery received a simultaneous integrated boost to a dose of 61 Gy in 25 fractions. Results: The 95% coverage for the primary, supraclavicular, internal mammary node and tumour bed was 93.4%, 96.8%, 90.7% and 98.3%, respectively. Mean dose to total lung, heart and contra-lateral breast was 10.6 Gy, 6.92 Gy and 4.32 Gy, respectively. None developed grade III skin or oesophageal toxicity. Twenty-one patients had progression; of which eighteen developed only distant failure while three also had loco-regional recurrence. At a median follow-up of 36 months, the 3-year loco-regional control, disease-free survival and overall survival were 93.5, 73.9 and 85.9%, respectively. Conclusion: We report encouraging clinical outcome for patients treated uniformly with HT. The predominant pattern of failure was distant metastases which suggests the need for systemic control intensification.