Dosimetric impact of adaptive proton therapy in head and neck cancer – A review

CBCT-Based Dose Monitoring and Adaptive Planning Triggers in Head and Neck PBS Proton Therapy

“…Studies also reported wide ranges of tumor response for patients within the same study, showing 73-79.6% reductions in tumor volume to 13-18.8% increases in tumor volume [1]. Given this inconsistency between patients, which has been demonstrated for patients at similar points in the treatment course being treated at the same institution and with identical planning practices and modalities, it is unsurprising that the review by Huiskes et al [2] did not Despite the improved dosimetric accuracy of the virtCT compared to the corrCBCT that was found in this analysis, there remains a clinical utility that is unique to the corrCBCT. The corrCBCT displays the actual anatomy that was imaged in the CBCT, while the virtCT relies on the accuracy of the DIR and low-density masking corrections.…”

“…Experience at our institution has shown that a loss of target coverage is the primary reason for triggering adaptive therapy, and the experiences of other institutions support this. A review article by Huiskes et al [2] found that for all studies reviewed for adaptive proton therapy in head and neck cancer patients, adaptive therapy was indicated due to target coverage deterioration and was never indicated due to doses to OARs. This was not true for adaptive therapy with photons, and this difference is likely due to the improved initial OAR sparing seen in proton therapy [2].…”

“…A review article by Huiskes et al [2] found that for all studies reviewed for adaptive proton therapy in head and neck cancer patients, adaptive therapy was indicated due to target coverage deterioration and was never indicated due to doses to OARs. This was not true for adaptive therapy with photons, and this difference is likely due to the improved initial OAR sparing seen in proton therapy [2]. Based on the established thresholds for plan review (D99 decrease of >3% for high-risk CTVs and >5% for standard-risk CTVs), 19% of patients included in the study would trigger a physician and physicist review for adaptive proton therapy in our new workflow.…”

“…Head and neck cancer patients are strong candidates for adaptive therapy due to complex target volumes, multiple critical structures close to treated areas, and aggressive tumor response that results in significant changes to target and organ-at-risk (OAR) anatomy [1]. Previous studies have shown that adaptive radiation therapy can improve target coverage, OAR sparing, plan quality, and quality of life for head and neck cancer patients [2][3][4][5][6]. Adaptive radiation therapy has also demonstrated a significant correlation with the disease-free survival and overall survival of head and neck cancer patients [1,4].…”

A retrospective study on the investigation of potential dosimetric benefits of online adaptive proton therapy for head and neck cancer

“…Using a smaller setup margin for online adaptation was also suggested in multiple other studies on adaptive radiotherapy 37,38 A recent review paper by Huiskes et al on adaptive proton therapy in HN cancer noted that the majority of online adaption studies did not use any setup margin. 39 We would like to mention that our determina-tion of the 1.5 mm margin size was based on a study on intra-fractional motion of HN cancer patients 25 and a study on spot positioning uncertainty. 26 The optimal margin size for each individual patient needs further investigation in the future with the technology of online APT being in place.…”