Automatic Radiobiological Comparison of Radiation Therapy Plans: An Application to Gastric Cancer

SIMPLE SUMMARY: The radiotherapy plans are usually judged using physical quantities, including dose and dose-volume values. Biological indices may also be applied for plan evaluation. A new software was developed for the quick and automatic calculation of tumor control probability (TCP) and normal tissue control probability (NTCP) from any radiation therapy plan and any fractionation scheme. Limited information has been published about the radiobiological metrics associated with gastric cancer irradiation. The new software was applied to radiobiologically compare photon plans for gastric malignancies generated with three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). The IMRT and VMAT plans provided higher TCPs than 3D-CRT. They also reduced the NTCPs and the risk of late adverse effects in most of the surrounding healthy organs compared to 3D-CRT. The presented results are useful for the plan optimization and choice of the appropriate radiotherapy technique for gastric cancer. ABSTRACT: (1) Aim: This study was conducted to radiobiologically compare radiotherapy plans for gastric cancer with a newly developed software tool. (2) Methods: Treatment planning was performed on two computational phantoms simulating adult male and female patients. Three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans for gastric cancer were generated with three-photon beam energies. The equivalent uniform dose (EUD), tumor control probability (TCP) of the target and normal tissue control probability (NTCP) of eight different critical organs were calculated. A new software was employed for these calculations using the EUD-based model and dose-volume-histogram data. (3) Results: The IMRT and VMAT plan led to TCPs of 51.3–51.5%, whereas 3D-CRT gave values up to 50.2%. The intensity-modulated techniques resulted in NTCPs of (5.3 × 10(−6)–3.3 × 10(−1))%. The corresponding NTCPs from 3D-CRT were (3.4 × 10(−7)–7.4 × 10(−1))%. The above biological indices were automatically calculated in less than 40 s with the software. (4) Conclusions: The direct and quick radiobiological evaluation of radiotherapy plans is feasible using the new software tool. The IMRT and VMAT reduced the probability of the appearance of late effects in most of the surrounding critical organs and slightly increased the TCP compared to 3D-CRT.