Quality Of Life And Toxicity Based Treatment Plan Optimization For Head And Neck Cancer

A comprehensive set of NTCP-models for common toxicities has recently been developed and validated for definitive radiotherapy for head and neck cancer (HNC). The relative impact of the various toxicities on Quality of Life (QoL) were modeled and combined with the NTCP-models to facilitate VMAT treatment plan optimization. The aim of this study was to compare OAR doses, NTCPs and QoL with regular OAR-based optimization and QoL-weighted NTCP-based optimization. This study included 31 HNC patients who were treated with definitive radiotherapy. The clinical VMAT plans of these patients were used as a reference. These plans were optimized by experienced dosimetrists by using OAR dose objectives and manually adjusted weights to reduce OAR dose as much as possible. QoL-weighted NTCP-based plans had identical target coverage but were optimized without the use of OAR dose objectives. Instead, optimization was performed directly on 44 NTCP models of 11 common toxicities on 4 different time points (6 – 24 months after RT) and each NTCP model was weighted relative to the impact of that toxicity on QoL (EORTC QLQ-C30). The impact on QoL differed per toxicity. E.g., the relative impact of dysphagia ≥ grade 2 was 18% while the relative impact of patient reported moderate-to-severe xerostomia and physician rated xerostomia grade ≥ 2 was 3% and 0%, respectively. As a result, QoL-weighted NTCP-based plans prioritized sparing of swallowing related structures over xerostomia related structures, increasing the average NTCP of moderate-to-severe xerostomia from 58% to 60% (p < 0.001) and from 31% to 38% (p < 0.001) for physician rated xerostomia grade ≥ 2, while at the same time reducing the average NTCP of dysphagia ≥ grade 2 from 51% to 44% (p < 0.001). In a similar fashion, additional sparing was obtained for the OARs related to hoarseness and aspiration. QoL-weighted NTCP-based plans were produced in less time, were less dependent on the dosimetrists experience and yielded more consistent results. The average calculated QoL increased with 1.3 points on a 0-100 scale (p < 0.001). QoL-weighted NTCP-based VMAT treatment plan optimization is feasible and resulted in significant reductions of NTCPs for dysphagia, aspiration and hoarseness at the cost of an increase of the NTCP for xerostomia. The method is a step towards automated planning based on patient outcome and is expected to result in a small but systematic increase in QoL.