Objectives: There is limited high-quality data that has compared treatment strategies for oral cavity cancer, and recent evidence has demonstrated the survival benefit of elective neck dissection for patients with cT1-2N0 tumors. Due to the high rate of regional positivity, numerous patients are up-staged to pT1-2N1 with limited neck disease and it is currently unknown how important adjuvant radiation is for these patients. Due to the lack of evidence, treatment trends vary between institutions. The primary purposes of this study were to use the Surveillance, Epidemiology, and End Results (SEER) database to evaluate current practice patterns in the use of adjuvant radiation for T1-2N1 oral cavity cancer patients and to investigate its efficacy in the population-based setting.
Methods: There were 835 adult patients treated surgically for T1-2N1 oral cavity cancers from 1988 to 2008 identified in the SEER database. Forty-three percent of patient had T1N1 tumors and 57% patients had T2N1 tumors. The breakdown of patients treated with adjuvant radiation is summarized in Table 1. 5-year disease-specific survival (DSS) and overall survival (OS) were the primary outcomes.
Results: Treatment with adjuvant radiation therapy was significantly associated with improved 5-year DSS (65% versus 51%; p<0.001) and OS (54% versus 44%; p=0.007) for patients with T1N1 tumors (Figures 1 and 2, respectively). Treatment with adjuvant radiation therapy was also significantly associated with improved 5-year DSS (58% versus 38%; p=0.009) and OS (48% versus 28%; p=0.004) for patients with T2N1 tumors (Figures 3 and 4, respectively). Improved DSS and OS were significant after controlling for other known covariates on multivariate analysis (HR 0.62, 95% CI 0.47 – 0.81, p=0.001; HR 0.63, 95% CI 0.50 – 0.80, p<0.001). The percent utilization of adjuvant radiation has significantly increased through the study time period from 63% to 74% (p<0.001).
Conclusion: Adjuvant radiation is associated with a significant survival benefit for patients with T1-2N1 oral cavity cancer, with an absolute DSS improvement of 16 percentage points and OS improvement of 14 percentage points in this population-based study. Utilization of adjuvant radiation is increasing over time for these patients.
Table 1. Utilization of adjuvant radiation therapy in patients with T1-2N1 oral cavity cancers.
||Adjuvant Radiation (%)
||No Radiation (%)
|# of Pts.
Figure 1. DSS comparing patients that received adjuvant radiation therapy and those that did not for T1N1 oral cavity cancer (p<0.001).
Figure 2. OS comparing patients that received adjuvant radiation therapy and those that did not for T1N1 oral cavity cancer (p=0.007).
Figure 3. DSS comparing patients that received adjuvant radiation therapy and those that did not for T2N1 oral cavity cancer (p=0.009).
Figure 4. OS comparing patients that received adjuvant radiation therapy and those that did not for T2N1 oral cavity cancer (p=0.004).