Superior prognostic utility of gross and metabolic tumor volume compared to standardized uptake value using PET/CT in head and neck squamous cell carcinoma patients treated with intensity-modulated radiotherapy

Objective To compare the prognostic utility of the 2-[¹⁸F] fluoro-2-deoxy-D-glucose (FDG) maximum standardized uptake value (SUV _max), primary gross tumor volume (GTV), and FDG metabolic tumor volume (MTV) for disease control and survival in patients with head and neck squamous cell carcinoma (HNSCC) undergoing intensitymodulated radiotherapy (IMRT). Methods Between 2007 and 2011, 41 HNSCC patients who underwent a staging positron emission tomography with computed tomography and definitive IMRT were identified. Local (LC), nodal (NC), distant (DC), and overall (OC) control, overall survival (OS), and diseasefree survival (DFS) were assessed using the Kaplan-Meier product-limit method. Results With a median follow-up of 24.2 months (range 2.7-56.3 months) local, nodal, and distant recurrences were recorded in 10, 5, and 7 patients, respectively. The median SUV_max, GTV, and MTV were 15.8, 22.2 cc, and 7.2 cc, respectively. SUV_max did not correlate with LC (p = 0.229) and OS (p = 0.661) when analyzed by median threshold. Patients with smaller GTVs (<22.2 cc) demonstrated improved 2-year actuarial LC rates of 100 versus 56.4 % (p = 0.001) and OS rates of 94.4 versus 65.9 % (p = 0.045). Similarly, a smaller MTV (<7.2 cc) correlated with improved 2-year actuarial LC rates of 100 versus 54.2 % (p<0.001) and OS rates of 94.7 versus 64.2 % (p = 0.04). Smaller GTV and MTV correlated with improved NC, DC, OC, and DFS, as well. Conclusion GTV and MTV demonstrate superior prognostic utility as compared to SUV_max, with larger tumor volumes correlating with inferior local control and overall survival in HNSCC patients treated with definitive IMRT.