Predictive value of 3′-deoxy-3′-[18F]fluorothymidine positron emission tomography/computed tomography for outcome of carbon ion radiotherapy in patients with head and neck mucosal malignant melanoma

Objective The purpose of this prospective study was to assess the prognostic value of 3′-deoxy-3′-[ 18 F]fluorothymidine (FLT) positron emission tomography/computed tomography (PET/CT) for the outcome of carbon ion radiotherapy (CIRT) in patients with mucosal malignant melanoma (MMM) of the head and neck. Methods Thirteen patients (69 ± 13 years) with histologically proven MMM tumor were enrolled. CIRT was performed with a total dose of 57.6–64.0 gray equivalents per 16 fractions over a period of 4 weeks. FLT-PET/CT was performed before and again 1 month after CIRT. Tumor FLT uptake was quantitatively assessed using the maximum standardized uptake value (SUV max ). FLT-PET parameters [pre-CIRT SUV max , post-CIRT SUV max , and the reduction rate (RR)] and clinical parameters [age, gender, tumor site, tumor status, gross tumor volume (GTV), and regional lymph node involvement] were evaluated in relation to survival estimates. The follow-up period was 16.1 ± 5.9 months for 9 deceased patients, and 36.7 ± 7.9 months for 4 survivors. Results Pre-CIRT SUV max of ≥4.3, age of ≥80 years old, sinonasal cavity tumor site, and GTV of ≥39 mL were found to be statistically significant prognostic factors for better overall survival. Pre-CIRT SUV max of ≥5.0, age of ≥80 years old, sinonasal cavity tumor site, and the absence of regional lymph node involvement were statistically significant prognostic factors for better metastasis-free survival. RR of ≥35 % and GTV of