Objetivos de la radioterapia de objetivo para el cáncer de amígdala tratado con radioterapia unilateral: un estudio...

Unilateral radiotherapy (URT) is an effective treatment strategy in selected patients with lateralized tonsil cancer. However, there is a lack of established planning guidelines for URT treatment leading to suboptimal optimization of contralateral and midline organs at risk (OARs). This study aimed to re-optimize URT plans to maximize sparing of midline and contralateral OAR's while maintaining target coverage, providing dosimetric guidelines for URT planning.

Treatment plan data for patients treated with URT on XXXX were re-optimized using Eclipse V16.01. All relevant midline and OAR contours were contoured to align with international OAR consensus guidelines. Treatment plans were re-optimized, aiming for maximal midline and contralateral sparing while maintaining XXXX protocol-mandated target coverage (GTV: D100%>95%; PTV: D95%>95%). A second re-optimisation was performed to align with NRG acceptance criteria (PTV: D95%>100%).

All re-optimized plans achieved the XXXX and NRG protocol target volume coverage. Clinically meaningful reductions in dose to the pharyngeal constrictors (trial delivered plan vs XXXX re-optimized plan, median of mean dose, 48.5 Gy vs 37.4 Gy, estimated mean difference [ED] -9.5Gy, p<0.001), contralateral submandibular gland (14.9 vs 6.7 Gy, ED -11.0, p<0.001) and larynx (22.1 vs 12.1, ED -12.2, p<0.001). Improvements were also seen in contralateral parotid gland (9.2 vs 4.9, ED -5.0, p<0.001) and oral cavity (39.5 vs 35.9, ED -3.0, p<0.001), which were considered less likely to be clinically relevant. There was no increase in dose to the ipsilateral or contralateral mandible.

The results of this re-optimization study provide planning guidelines to guide dosimetrists and radiation oncologists on achievable OAR sparing when delivering URT.