ESTRO 2024 - Abstract Book

S1353

Clinical - Head & neck

ESTRO 2024

Carbon-Ion Radiotherapy for Head and Neck Malignant Mucosal Melanoma

Ankita Nachankar 1,2 , Maciej Pelak 1 , Mansure Schafasand 3,4,5 , Slavisa Tubin 1 , Petra Mozes 1 , Eugen Hug 1 , Joanna Gora 3 , Giovanna Martino 3 , Antonio Carlino 3 , Markus Stock 3,5 , Piero Fossati 1,6 1 MedAustron Ion therapy Center, Radiation Oncology, Wiener Neustadt, Austria. 2 ACMIT Gmbh, Medical Research and development, Wiener Neustadt, Austria. 3 MedAustron Ion therapy Center, Medical Physics, Wiener Neustadt, Austria. 4 Medical University of Vienna, Department of Radiation Oncology, Vienna, Austria. 5 Karl Landsteiner University of Health Sciences, Division Medical Physics, Krems an der Donau, Austria. 6 Karl Landsteiner University of Health Sciences, Radiation Oncology, Krems an der Donau, Austria

Purpose/Objective:

Purpose/Objective: Malignant mucosal melanomas (MMM) are very rare aggressive malignancies with very poor prognosis [1]. Surgery is the mainstay of treatment for most MMM of the head and neck. Adjuvant photon-based radiotherapy improves local control but not survival. Improved local control rates were observed in Japanese series using carbon ion radiotherapy (CIRT) as a sole local therapy in inoperable MMM [2]. In this study we discuss early clinical outcomes of MMM treated with CIRT.

Material/Methods:

Material/Methods: Seventeen non-metastatic MMM were treated with CIRT. Six patients underwent surgical resection prior to CIRT and then were treated with CIRT in view of gross residual disease and the others had only biopsy. Nine patients received immunotherapy in neoadjuvant (2), adjuvant (7), concurrent (2) setting. Five patients received combination of Nivolumab and Ipilimumab (1-4 cycles) followed by either Nivolumab or Pembrolizumab (upto 20 cycles) and rest received single agent Nivolumab. Patients were treated with CIRT to a RBE weighted-dose of D RBE|LEM-I|50% = 68.8 (60.2-68.8) Gy (RBE)/15-16 fraction (4 fractions/week) optimized using the European biological model for CIRT dose calculations-local effect model-I (LEM-I). We subsequently recomputed doses based on the Japanese biological model for CIRT dose calculations-modified microdosimetric kinetic model (mMKM). The LEM-I prescription doses and dose constraints were adapted with respect to corresponding mMKM prescription doses as per translation schema given by Fossati et al. [3]. Low dose-CTV (LD-CTV) encompassed areas at risk of microscopic infiltration through local and submucosal infiltration. There is no general consensus on elective node irradiation of the cN0 neck in mucosal melanoma. Oral cavity cases with nodular growth pattern or macular growth pattern and maximum diameter > 4 cm or subsite in the tongue or lower jaw., pharyngeal MMM or laryngeal MMM were treated with ENI. One patient received 8 Gy/1 fraction with photons at an external institution for hemostatic purposes prior to referral for CIRT.

Results: Patient / Tumor Characteristics

MMM (n = 17)

Age

Median (years)

65.3

Range (years)

55.5 - 88.5

Gender

Male

6 (36%)