ESTRO 2022 - Abstract Book

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Abstract book

ESTRO 2022

and validation (2017-2020) cohorts using recently reported methods (R&O 148, p.151; R&O 157, p.147). NTCP models were used for model-based clinical validation and for estimating the clinical benefit of proton therapy in 135 patients receiving IMPT. Results The prevalence of TFD was 40.7%, 41.3% and 31.7% (last week of RT, W6/7) and 34.9%, 30.6% and 19.2% (week 12) during ParRT, SwRT and MoRT, respectively (Figure 1). The predictors for the final models were: Oral cavity Dmean; Superior PCM Dmean; Accelerated radiotherapy; Chemoradiation; and Bioradiation. With MoRT, TFD in the last week of RT was 31.7%, which was lower than predicted (34.5%, 95%CI: 30.6-38.3%). In week 12, the prevalence of TFD was 19.2%, also lower than predicted (24.9%, 95%CI: 20.7-29.1%). The NTCP of TFD with the clinical Mo-IMPT plans was reduced with 5.1 (46.9-41.8) and 6.6 (36.9-30.3) percent point in the last week of RT and in week 12 as compared with the backup Mo-VMAT plans. The observed prevalence with IMPT was 4.2 (46.9-42.7) and 13.7 (36.9-23.2) percent point lower than the NTCP predicted for the backup Mo-VMAT plans in the same weeks, respectively (Figure 1).

Conclusion A marked decline of TFD during treatment for head and neck cancer was observed during 13 years of continuous technological improvements and improved organ sparing capabilities. In a recent cohort of patients treated with multi- organ sparing VMAT or IMPT the prevalence of TFD was even lower than expected. IMPT further reduces the NTCP of TFD with 5-7 percent point compared with VMAT, and with IMPT recovery of TFD seems even better than expected in the weeks following RT.

OC-0089 Acute toxicities in proton therapy of head-neck cancer – a matched analysis of DAHANCA 35 pilot data

K. Nowicka-Matus 1,2 , J. Friborg 3,4 , C.R. Hansen 5,4 , E. Andersen 6 , M. Bernsdorf 3,4 , U. Elstrøm 4 , M. Farhadi 7 , C. Grau 4,8 , J.G. Eriksen 8,9 , J. Johansen 5,4 , M. Nielsen 10 , J.B.B. Petersen 8 , E. Samsøe 7 , P. Sibolt 6 , B. Smulders 4,3 , K. Jensen 4 1 Aarhus University Hospital , Danish Center for Particle Therapy , Aarhus , Denmark; 2 Aalborg University Hospital, Department of Oncology, Aalborg, Denmark; 3 Copenhagen University Hospital, Department of Oncology, Copenhagen, Denmark; 4 Aarhus University Hospital, Danish Center for Particle Therapy, Aarhus, Denmark; 5 Odense University Hospital, Department of Oncology, Odense, Denmark; 6 Herlev Hospital, Department of Oncology, Herlev, Denmark; 7 Zealand University Hospital, Department of Oncology, Naestved, Denmark; 8 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark; 9 Aarhus University Hospital, Departement of Experimental Clinical Oncology, Aarhus, Denmark; 10 Aalborg University Hospital, Departement of Oncology , Aalborg, Denmark Purpose or Objective DAHANCA 35 (DAH35) is the first Danish study of proton radiotherapy in squamous cell carcinoma (SCC) of the pharynx or larynx. In the pilot phase patients (pts) were offered proton therapy if the risk of late dysphagia or xerostomia could be potentially reduced with proton therapy using Normal Tissue Complication Probability (NTCP) models. The present study aimed to describe the severity of a range of acute toxicities for patients in the pilot phase compared to a matched group of patients treated with photon therapy. Materials and Methods Between April 2019 and October 2020, 62 pts with histologically verified SCC of the pharynx or larynx received proton therapy in the pilot phase of DAH35. A matched control group consisting of 124 pts, who completed standard photon therapy according to DAHANCA guidelines between 2012 and 2020 was selected. Patients in the control group were matched to proton-treated pts in ratio 1:2 on the treatment center, tumor site, TNM stage according to UICC version 7, p16 status for oropharynx cancers (OPC), concurrent chemotherapy, and radiation dose. Data on toxicity was registered at the treating facility during treatment. Data on follow up were all registered at the referring photon clinic.

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