Although there have been several breakthrough innovations in the treatment of oral cancer (e.g., target therapy or immune checkpoint inhibitors), patients with oral cancer with regional recurrence frequently incur grave outcomes [2,3,4, 6]. Besides radical resection of primary tumor with adequate margin, the next step was to perform an adequate neck dissection. Previous studies have reported a positive association between LN yield and survival rates [11, 18]. However, strategies to improve LN yield have not been identified. The current study was the first to explore the impact of non-compulsory multiple-step action among surgeons to improve the quality of neck dissection and several novel findings were noted. First, the difference in the difference was an increase of LN yield of 13.78. Second, a reduction of 11.6% in regional recurrence was noted in cN0 oral cancer patients (Table 5). These findings have relevance to long-term outcomes in head and neck cancers. Government agencies, like the health promotion administration in Taiwan, regularly announced the survival rates of major cancers. However, strategies to improve outcomes are not clearly outlined. Our results provide evidences about that multiple-step action was associated with increased LN yield and decreased regional recurrence in patients with oral cancer. This observed activity may promote surgeons to improve the quality of neck dissections, is simple for clinical use.
Several mechanisms might explain the effect of the multiple-step action plan. First, landmark identification during neck dissection was not emphasized purposely in department A. Our previous publication and related literature outlined the importance of maximization of LN yield, and the best and simplest strategy was to perform an en-bloc neck dissection with landmark identifications in order to preserve function and maximize the LN yield simultaneously [11, 13]. Second, the positive association between LN yield and survival rates was stressed routinely in weekly conferences in department A. Understanding mapping between the LN yield and outcomes urged the staff to perform a neck dissection to increase the LN yield in the hope to decrease regional recurrences later. Third, the average number of the LN yield in department A was announced regularly, and the individual data was not reported. According to behavior economics, the staff with lower LN yield compared with the average yield from all staff started to figure out how to improve LN yield [19]. Beyond surgical techniques and pathological analysis, increased LN yield was associated with an average delay in surgery over 15 days, skin involvement by tumor, and additional precancer lesions in oral cancer [20]. In our series, there was no significant difference in age, gender, and differentiation between groups. In the multivariate analysis, the above-mentioned symptoms were adjusted in the regression model.
The magnitude of the 64% increase in LN yield and decrease of regional recurrence in department A after implementation of the multiple-step action plan was significant (Tables 2 and 3). Increase of LN yield and decrease in regional recurrence in department A with multi-step action plan was summarized in Table 4. Besides multivariate linear and logistic regression, the impact of the multiple-step action plan was also evaluated with difference-in-difference analysis. The major policy change in department A over time was the intervention or policy change in period 2, which provided for a quasi-experimental chance. Using difference-in-difference analysis, the net effect or interaction term, intervention × period on LN yield and regional recurrence was evaluated with the linear model. The multiple-step action plan incurred a net impact of 13.78 increase in LN yield and a reduction of 11.6% in regional recurrence in the END group. We also analyzed the overall survival rates between different groups and periods (Additional file 2: Figure S1). Patients with local or loco-regional recurrence were excluded. There was no significant difference among these groups, which might be attributed to different follow-up periods and heterogenous surgical techniques.
All national and international guidelines have reported how adequate LN yield could significantly improve survival in patients with oral cancer, however there is no recommended intervention for clinical practice. Interventions based on the theories of behavior economics are summarized by the acronym NUDGE and has been explored in the healthcare field [21,22,23]. Penn Medicine, for example, has used this strategy widely. Changing the default choice for medications greatly increased the rate of prescriptions for generic medicine [22]. Using an active choice alert system in the electric medical record increased the influenza vaccination rate 37% in adults suitable for vaccination [24]. Ayala et al. also reported that moving from an "opt-in" to an "opt-out" system greatly increased the rate of providing aspirin prophylaxis for preeclampsia prevention [25]. An automated dashboard with active choices and peer comparison performance feedback to physicians was associated with increased statin prescriptions by primary care physicians [26]. In our institute, several feasible and low-cost strategies have been applied, such as weekly conferences used to explain the association between LN yield and recurrence since October 2015. Thereafter, surgeons were encouraged to confirm important landmarks during neck dissections. Furthermore, the average LN yield was announced each month in order to provide feedback to all surgeons. Multiple NUDGE-like interventions helped the target group to improve the cervical LN yield in oral cancer surgery.
There are several limitations in the current study. First, the study was not a prospective design. All these data were obtained retrospectively. Second, the common trend assumption was not well tested in our series for DID analysis. Third, we could only confirm that surgery oriented by landmarks was emphasized in department A during period 2; however, it could be a standard operative procedure in department B. Fourth, the spillover effects of the multiple-step action plan in the control group was not estimated. Although it was possible, the effect may be minimal because these two departments were located in different floors in our institute. Fifth, the time effect of diagnosis may also influence the LN yield. The estimated LN yield could be derived from the data between 2009 and 2015 (Additional file 1: Table S2). The gap between the real LN yield (37.5) and estimated LN yield (27.4) could be attributed to the multi-step intervention in department A. Furthermore, the annual LN increase was 0.4 since 2009 in SEER database (data not shown). The increase in LN yield was much than the annual increase by time. Finally, although this study only included Asian people, this observed activity improving the quality of neck dissections, is simple, and could be applied to a widespread patient population.