Radiobiological evaluation of hypo-fractionated breast cancer radiotherapy regimens in comparison with conventional approaches

Purpose: This study compares tumor control probability (TCP) and normal tissue complication probability (NTCP) across different hypo-fractionated (HypoRT) and conventional breast radiotherapy regimens using radiobiological models. Materials and methods: Computed tomography data from 30 patients with left breast- conserving surgery were used to evaluate three HypoRT regimens (39 Gy and 41<middle dot>6 Gy in 13 fractions, and 40 Gy in 15 fractions) and a conventional regimen (50 Gy in 25 fractions). Dose- volume histograms (DVHs) were extracted for radiobiological calculations using Equivalent Uniform Dose (EUD) and Poisson models for TCP, and EUD and LKB (Lyman-KutcherBurman) models for NTCP. Results: Conventional treatment achieved significantly higher TCP (95%) than all HypoRT regimens (p < 0<middle dot>001), with no significant differences between HypoRT regimens (p> 0<middle dot>05. The 39 Gy/13 fraction regimen showed the lowest lung NTCP (p < 0<middle dot>05). HypoRT regimens had significantly lower NTCP for the lungs and heart compared to the conventional regimen (p < 0<middle dot>01). TCP and NTCP values from Poisson and LKB models were higher than those from the EUD model (p < 0<middle dot>01). Conclusion: HypoRT regimens reduced NTCP, with the lowest values in the regime of 39 Gy/13 fractions regimen, though the conventional regimen had higher TCP.