ESTRO 2023 - Abstract Book

S960

Digital Posters

ESTRO 2023

PO-1199 Challenges of delineation of hypopharyngeal tumors

E. Rylander 1 , G. Alexandersson von Döbeln 2 , E. Onjukka 3 , S. Jonmarker Jaraj 4 , M. Hedman 5

1 Karolinska University Hospital, Karolinska Comprehensive Cancer Center, Stockholm, Sweden; 2 Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Stockholm, Sweden; 3 Karolinska University Hospital, Department of Medical Radiation Physics and Nuclear Medicine, Stockholm, Sweden; 4 Karolinska University Hospital, Department of Neuroradiology, Stockholm, Sweden; 5 Karolinska University Hospital, Department of Radiation Oncology, Stockholm, Sweden Purpose or Objective Delineation of hypopharyngeal tumors has traditionally been carried out by a radiation oncologist at our institution. We hypothesized that radiologist consultation can improve the accuracy of delineation. Materials and Methods 54 patients were included in a retrospective single-center study of all patients with hypopharyngeal cancer treated with definitive radiotherapy with or without concomitant and/or induction chemotherapy between 2009 and 2015. Blinded for the original delineation of the gross tumor volume (GTV) and the clinical target volume (CTV) a radiation oncologist and a head and neck radiologist defined new GTVs with guidance from diagnostic radiology. New CTVs were defined by the oncologist and peer reviewed by a second radiation oncologist using current guidelines. Qualitative and quantitative analyses comparing the original and new target delineations were performed. The qualitative measure consisted of a four grade scale while the quantitative measures considered were sensitivity and positive predictive value, using the updated volumes as reference. The agreement between the quantitative- and qualitative measures, respectively, was assessed in a Spearman correlation analysis. Results The median volume of all new targets decreased after re-delineation (primary GTV (GTVp) from 17.4 to 9.2 cc, lymph node GTV (GTVn) from 11.0 to 9.8 cc and CTV from 203.7 to 93.8 cc). In the overlap analyses the mean positive predictive values +/-SD were 0.53 +/-0.24 (GTVp) and 0.61 +/-0.30 (GTVn) meaning that 53% and 61% of the GTVs in the original delineation consisted of the updated GTVs. This indicates a large overestimation of the original GTV. The mean sensitivity values +/- SD were 0.73 +/-0.19 (GTVp) and 0.63 +/-0.24 (GTVn) which means that 73% and 63% of the updated GTVs were included in the original delineation. Qualitatively, 21 (39%) and 10 (19%) of the original GTVp and GTVn, respectively, were considered acceptable. The sensitivity score for GTVp correlated with the qualitative measure, but the other quantitative measures did not correlate with the qualitative. Conclusion Incorporating radiological expertise in the delineation of hypopharyngeal tumors may reduce the risk of overestimating the GTV and the CTV and thereby irradiation of healthy tissues. Furthermore, it might reduce the risk of missing the target. 1 Osaka Heavy Ion Therapy Center, Radiation therapy, Osaka, Japan; 2 Osaka International Cancer Institute, Head and Neck Surgery, Osaka, Japan Purpose or Objective This report aims to evaluate preliminary results of carbon ion radiotherapy (CIRT) in patients (pts) with mucosal melanoma of the head and neck (MMHN). Materials and Methods Between October 2018 and April 2022, a total of 41 pts with MMHN were treated with CIRT. None of these patients had either regional lymph node or distant metastasis before CIRT and had previous history of radiotherapy for same lesion. The prescribed tumor doses were 57.6 or 64.0 Gy (RBE) in 16 fractions over 4 weeks. Twenty-seven of 41 pts (66%) received immune checkpoint inhibitors (ICIs) to prevent metastases after CIRT. Local response within 6 months and toxicity were respectively evaluated using RECIST and CTCAE v.4.0 criteria. Local control (LC), overall survival (OS), and progression-free survival (PFS) rates were determined using the Kaplan-Meier method. All survival times were calculated from the first day of CIRT. Results The patients consisted of 15 males and 26 females aged from 37 to 92 years with a median age of 76 years. Tumor site was nasal and/or paranasal sinus in 40 cases and oral cavity in one. Thirty-five pts (85%) were irradiated with 64.0 Gy (RBE) and 6 pts (15%) were with 57.6 Gy (RBE). Median follow-up period was 15.3 months (range, 2.0-42.6 months). Tumor response using RECIST was complete response (CR) for 16 pts (39%), partial response (PR) for 18 pts (44%) and stable disease (SD) for 7 pts (17%), with the effective rate (CR + PR) being 83%. The 1-year and 2-year LC rates were 92.3% (95% confidence interval [CI] 72.5%-98.0%), respectively. In-field recurrence was observed in 3 pts. LC period from the start of CIRT to recurrence in these pts was 10.6, 11.5, and 32.1 months, respectively. None of these pts received ICIs after CIRT. The 1- and 2-year PFS rates were 59.5% (95% CI 42.4%-73.0%) and 20.8% (95% CI 4.5%-45.1%), respectively. Of 23 pts (56%) who developed recurrence, the initial recurrence pattern was distant metastasis in 12 pts, regional recurrence in 7, regional plus distant PO-1200 Preliminary evaluation of mucosal melanoma of the head and neck with carbon ion radiotherapy A. Hasegawa 1 , T. Teshima 1 , O. Suzuki 1 , M. Anzai 1 , H. Uchida 1 , J. Fujimoto 1 , T. Fujii 2