HYPORT adjuvant acute toxicity and patient dosimetry quality assurance results - Interim analysis.

BACKGROUND: HYPORT adjuvant trial is a randomised phase III open-label noninferiority trial comparing standard moderately hypofractionated 3 week adjuvant radiation therapy in breast cancer with a novel 1-week schedule. The trial was initiated in March 2019 and is open to recruitment with a total sample size of 2100. We report the results of dosimetric quality assurance, acute toxicity and pre planned first interim safety analysis in the first 271 patients. METHODS: Stage I-III breast cancer planned for adjuvant radiation therapy to the breast/chest-wall (along with regional nodes as indicated) were randomised to receive 40 Gy/15 fractions/3 weeks or 26 Gy/5 fractions/1 week. For simultaneous integrated boost, the patients in the control arm received 8 Gy/15 fractions/3 weeks, while those in the experimental arm received 6 Gy/5 fractions/1 week (to the tumour bed). For sequential boost, the prescribed dose was 12 Gy/4 fractions/4 days in both arms. Compliance to pre specified dosimetric parameters and acute toxicities were evaluated. RESULT: Data of the first 271 patients was analysed of whom 104 patients received tumour bed boost using SIB. All mandatory dosimetric criteria were met apart from one patient with a higher contralateral breast dose due to optimal internal mammary nodal coverage. Overall three patients (1.1%) experienced grade 3 radiation dermatitis (none received SIB), no other Grade 3 or higher toxicities reported. CONCLUSION: This acute toxicity interim analysis demonstrates that hypofractionated adjuvant radiotherapy with SIB for patients with breast cancer is feasible, and associated with minimal severe acute toxicities.