28 Quality Outcome Measures in Neck Dissection

As health care costs continue to escalate and health care reform has been unable to change the nature of the incentive system, addressing value in health care has become even more urgent. In January 2015, the Department of Health and Human Services outlined specific goals in transitioning health care from rewarding volume to value. One of the key objectives is that 90% of Medicare payments be tied to quality or value by 2018.¹ The provisions of the Medicare Access and CHIP Reauthorization Act of 2015 (MACRA) have defined the framework for how this will occur for Medicare physicians.

One difficulty with a value-based health care system is effectively defining what we mean by “high-quality” care. One of the most well-known frameworks for quality was first proposed in 1966 by Avedis Donabedian, MD, MPH, a professor at the University of Michigan School of Public Health. His framework defined three domains of quality: structure, process, and outcomes.

Structural measures assess the overall context where care is delivered and includes the facilities, resources, and organization of care. Process measures are the individual actions that occur in the course of patient care, such as whether a patient received a recommended treatment. Outcomes measures are the end result of care and can be evaluated by a clinical outcome or change in health status.

In the context of neck dissection in head and neck cancer (HNC), structural quality measures could include the number of neck dissections performed (volume) at a given institution or by a given surgeon. Subspecialty training of the surgeon is also a structural measure. Process measures could include adherence to clinical guidelines for when a neck dissection is indicated, performing the correct levels of neck dissection or correct laterality. Process measures may also comprise more generic measures of quality such as administration of preoperative antibiotics.

Quality outcomes measures in neck dissections can be broadly categorized into intermediate outcomes and end outcomes. End outcomes are the most important ones to patients and affect them directly. Important end outcomes include perioperative complications, function and quality of life (QOL), and regional recurrence rates.

Intermediate outcomes are results that are on the pathway to the desired end outcome. One example is measuring hemoglobin A1c on a patient whose end outcome may be the number of diabetic complications. These are particularly important since they may provide a more tangible way to affect the end outcomes, and can be more frequently monitored or modified. Intermediate outcomes in neck dissections include lymph node yield (LNY) from neck dissections.

28.2 Lymph Node Yield in Neck Dissection

Using the number of lymph nodes counted and analyzed in a regional nodal basin dissection was first popularized in colorectal cancer, where studies demonstrated that in patients with stage II or III colorectal cancer, the removal of 12 or more lymph nodes is associated with increased overall survival.^2,3,4 Since then, additional disease sites have investigated this concept and established quality metrics around LNYs. These metrics have been adopted by the American College of Surgeons Commission on Cancer Measures for Quality of Cancer Care, with recommended minimum nodal yields now established for bladder, gastric, kidney, and lung cancer.⁵

In neck dissections, the concept of a minimum nodal yield was introduced into the American Joint Cancer Commission (AJCC) staging manual. The manual states that “a selective neck dissection will ordinarily include 10 or more lymph nodes, and a radical or modified radical neck dissection will ordinarily include 15 or more lymph nodes.” This was increased from the 6 and 10 nodes, respectively, recommended in the seventh edition.^6,7 The purpose of achieving these nodal counts was to adequately stage the neck for prognostic and treatment purposes.

The above numbers, however, were not based on statistical evidence of an appropriate cutoff for minimum number of nodes. The first study in head and neck surgery to look at the idea of a cutoff was by Ebrahimi et al in 2011. They analyzed 225 patients from a single institution who had elective neck dissections performed for N0 disease. They found that an LNY less than 18 was associated with reduced overall survival (hazard ratio [HR], 2.0; 95% confidence interval [CI], 1.1–3.6; p = 0.020) and lower disease-specific survival.⁸ This was followed by a multi-institutional study with 1,567 patients, which again demonstrated reduced overall survival (HR, 1.69; 95% CI, 1.22–2.34; p = 0.002) in patients with less than 18 nodes.⁹

Divi et al performed the first study in node-positive disease. Using data from the RTOG 9501 and RTOG 0234 trials, the authors analyzed 572 patients with 98% N + disease who underwent therapeutic neck dissection. An overall survival benefit (HR, 1.38; 95% CI, 1.09–1.74; p = 0.007) was shown for patients with 18 nodes or more, and this was largely driven by higher rates of local-regional failure. Interestingly, this study independently calculated the optimal cut-point for survival difference and also found 18 nodes as the best threshold.¹⁰ In a subsequent analysis of the National Cancer Database, instead of calculating a new optimal cutoff, Divi et al tested the 18 LNY cutoff across 63,978 patients. In both N0 and N + patient populations, achieving LNY of 18 nodes or more was associated with a significant improvement in overall survival¹¹ ( Fig. 28.1).

Fig. 28.1 Adjusted overall survival probability for adult patients with head and neck cancer stratified by < 18 and ≥ 18 lymph nodes examined. Survival curves adjusted for sex, age group, race, comorbidities, pathologic stage, head and neck subsite, margins, extracapsular extension, positive nodes, adjuvant therapy, insurance, socioeconomic status, hospital volume, and hospital type.

Several other studies have supported this LNY metric. For example, Graboyes et al performed a retrospective analysis of their patients with clinically N0 oral cavity cancer, and found that LNY was one of four quality metrics associated with improved outcomes.¹² A few other studies with limited analyses did not find the same correlation; however, these authors were evaluating lymph node ratios and did not design studies to identify an optimal LNY for improved outcomes.^13,14,15,16

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