ESTRO 2024 - Abstract Book

S6005

RTT - Treatment planning, OAR and target definitions

ESTRO 2024

In the evaluation of the PTV, IMRT was significantly better than FiF for V 105% (p=0,043), while VMAT was significantly worse than FiF for CI (p=0,043) and V 95% (p=0,043). For D max , Hybrid-IMRT was significantly worse than FiF (p=0.043), with an average D max of 1.85 Gy above the average FiF D max . All the techniques complied with the optimal parameters described according to the FAST-FOWARD protocol, except for the VMAT, showing that good coverage was achieved by all other techniques. Regarding the ipsilateral lung, all techniques presented results below the mandatory parameter, except for VMAT, which in one case exceeded this value. The Hybrid-IMRT technique presented the best average result compared to the other techniques, however, the differences were small. In the heart for V 25% , all techniques presented values lower than the mandatory parameters. However, IMRT and Hybrid-IMRT being significantly better than FiF (p=0,043). The Hybrid-IMRT also showed a statistically lower V 5% compared to FiF (p=0,043). VMAT had the highest V 25% mean value and statistical difference (p=0,043) and exceeded the V 5% mandatory limit (two cases) and was significantly worse than FiF (p=0,043).

The planning time was slightly different between techniques, with Hybrid-IMRT being the fastest. All plans were significantly faster than FiF, except VMAT, with worse results.

Regarding beam-on-time, which was clearly influenced by the level of modulation of the various techniques, all plans demonstrate significantly longer treatment times compared to FiF.

The main limitation of this study was the small patient sample, which will not allow generalizing the results to the whole population. However, since this was a hypothesis generating study for a future study performed by the same research team, the sample was deemed sufficient. Furthermore, dose evaluation for other OARs (e.g. contralateral breast and lung) should be considered, although they are not considered in the FAST-FOWARD protocol.

Conclusion: