Pretreatment 18F-FDG Positron Emission Tomography Maximum Standardized Uptake Value as a Predictor of Radiation Therapy Response and Survival for Patients With Salivary Gland Carcinoma

Abstract

Purpose/Objective(s): Current NCCN guidelines for treatment of head and neck cancer recommend initiating radiation therapy within 6 weeks from surgery. We sought to determine the ideal package time (days from surgery to completion of radiation), and how pathologic risk factors impact ideal package time. Materials/Methods: Patients with squamous cell carcinoma of the oropharynx, oral cavity, hypopharynx, and larynx cancer were identified from the National Cancer Data Base between 2004 and 2012. Patients were excluded if they had distant metastases, received less than 45 Gy, or had a package time outside of 9-20 weeks. High risk factors were defined as an oral cavity tumor, T3-4 or N2-3 disease, positive surgical margins, extracapsular extension, and lymphovascular invasion. Overall survival was estimated with the Kaplan-Meier method, and hazard ratios (HR) with Cox regression models. Adjustments were made for socioeconomic variables, comorbidity, risk factors, type of facility for surgery and radiation therapy, distance travelled to facility, length of hospital stay after surgery, unplanned hospital readmission, chemotherapy, radiation dose, and use of IMRT. Results: 38,266 patients were identified, consisting of 30% oral cavity tumors, 27% larynx, 28% tonsil, 12% non-tonsil oropharynx, and 3% hypopharynx. The most commonly employed radiation doses were 60-66 Gy (37%), 66-72 Gy (28%), and 72-76 Gy (23%). 2-year survival was greatest with a 10-week package time (P < 0.0001), and compared to 10 weeks, hazard ratios were significantly worse for package times !12 weeks. 2-year survival was 87% for 9-11 week package times, 83% for 12-14 weeks, 77% for 15-17 weeks, 75% for 18-20 weeks (P < 0.0001). Compared to 9-11 week package time, multivariate analysis showed a HR of 1.03 (P Z 0.22) for 12-14 weeks, HR of 1.14 (P < 0.0001) for 15-17 weeks, and HR of 1.18 (P < 0.0001) for 18-20 weeks. For patients with !3 risk factors, a 9-11 week package time was associated with improved survival compared to 12-14 weeks (HR 1.69, P Z 0.01), 15-17 weeks (HR 2.11 P Z 0.0004), and 18-20 weeks (HR 2.11, P Z 0.0009). For patients with no risk factors, shorter package times were not associated with survival gains; for 1 risk factor, survival loss was associated with 18-20 week package times (P Z 0.01); for 2 risk factors, survival loss was associated with 15-17 and 18-20 week package times (P Z 0.02 and 0.04, respectively). A sensitivity analysis of patients treated to !60 Gy demonstrated similar findings, as did a model restricted to patients receiving IMRT. Conclusion: For patients with non-metastatic squamous cell carcinoma of the head and neck, improved survival after definitive treatment with surgery and adjuvant radiation is associated with a shorter interval from date of surgery to completion of radiation. We found the most effective package time depends on risk factors, and the ideal package time is 11 weeks for patients with !3 risk factors.