Postoperative Radiation Performed at the Same Surgical Facility Associated With Improved Overall Survival in T4 Major Salivary Gland Cancers.

PURPOSE/OBJECTIVE(S) T4 major salivary gland cancers often require postoperative radiation (PORT), and communication among the surgical and radiation oncology teams is essential to plan and provide optimal treatment, particularly given the complicated surgeries and associated radiation treatment volumes. To better understand the impact of this on patient outcomes, this study evaluated the impact of receiving PORT at the same facility (SF) as surgery versus at a different facility (DF) from surgery. MATERIALS/METHODS The National Cancer Database (NCDB) was queried for patients with T4 non-metastatic salivary gland cancers diagnosed from 2004-2016. All patients first underwent definitive surgery at the NCDB reporting facility followed by PORT with or without chemotherapy. PORT was coded as performed at either the SF or at a DF. Survival analysis was performed using Cox regression and plotted using Kaplan-Meier curves. Variables included in multivariate (MVA) and propensity score-matched (PSM) cohorts included age, Charlson-Deyo (CD) score, patient distance from surgical center, whether the patient underwent neck dissection, duration of radiation treatment course, receipt of concurrent chemotherapy, and facility case volume and geographical region. RESULTS A total of 1,230 patients met inclusion criteria, 813 (71.9%) of whom underwent PORT at the SF. The PSM cohort included 634 patients. Median follow-up was 3.4 yrs (range 0.2-14.5 yrs). Median and 4-year overall survival (OS) rates were higher in patients undergoing PORT at the SF compared to a DF: 6.3 yrs (95% confidence interval [CI] = 5.5-7.7) vs 5.4 yrs (CI = 4.0-7.1) and 64.0% vs 56.0% (P = 0.01), respectively. PORT performed at the SF was associated with lower overall mortality in all patients (hazard ratio [HR] = 0.73; CI = 0.61-0.88; P = 0.001) and in the PSM cohorts (HR = 0.76; CI = 0.61-0.95; P = 0.014). Receiving PORT at the DF was associated with older age (odds ratio [OR] = 1.12/decade; CI = 1.01-1.25; P = 0.04), CD score ≥1 (OR = 1.43; CI = 1.03-1.97; P = 0.03), and longer distance (> 100 miles) from surgical facility (OR = 2.33; CI = 1.52-3.57; P 2 case/year) (OR = 2.48; CI = 1.47-4.19; P = 0.001), higher rates of radiation treatment course < 7 wks (OR = 1.46; CI = 1.11-1.92; P = 0.01), and higher rates of concurrent chemotherapy (OR = 1.44; CI = 1.06-1.96; P = 0.02). CONCLUSION In patients with T4 major salivary gland cancers, receipt of PORT and surgery at the SF was associated with longer OS. Reasons for this may be related to improved communication between surgical and radiation oncologists or increased surgical involvement in radiation volume delineation. PORT provided at the same surgical facility appears to influence survival in T4 major salivary gland cancers and warrants further investigation.