Vasu Divi and Misha Amoils
Although neck dissection is one of the most common procedures in head and neck surgery, there are no well-accepted quality outcome measures for this operation. There are many opportunities to develop measures that demonstrate the quality and value of care provided and allow for benchmarking and improvement initiatives. This chapter explores the evidence behind potential metrics and the strengths and weaknesses of using them on a national scale. Finally, it discusses the steps needed to develop them for use across diverse practices.
Keywords: quality, outcomes, metrics, lymph node yield, quality of life, complication rates, regional recurrence
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
While the evidence is fairly consistent across single institutional, multi-institutional, and large database studies, there remains some controversy when discussing implementation of LNY as a quality metric. The most notable is that LNY is a function of both the surgeon and the pathologist analyzing the specimen. Therefore, one must be careful to not attribute the entire performance on this metric to the surgeon. The LNY is only associated with improved overall survival and no causative mechanism can be assumed, since there are many components of care which may also be associated with higher LNY. In particular, patients who are treated by surgeons with higher LNY may also receive better perioperative care or better adjuvant treatment, both of which may have a survival impact. However, even in single institution studies which have more consistent process of care, the LNY was seen to associate with survival.8,12
Patient biology may also theoretically contribute. Patients with higher lymph node counts may have a more robust immune response to the tumor, leading to both higher lymph node counts and potentially better outcomes. Finally, patients with matted nodes with gross extranodal extension may have a lower nodal count if multiple nodes make a single conglomerate mass. These patients are known to have a worse outcome, although this is a minority of patients in these studies.
It is important to emphasize that all of the prior studies have been done in untreated necks, and therefore use of the metric would be limited to this patient population since prior radiation therapy is known to decrease LNY.
Ultimately, how a quality metric is implemented has a significant impact on its utility. Expecting that all patients would achieve a minimum of 18 nodes is not reasonable since—as discussed above—patient factors and tumor factors may impact the ultimate nodal yield. LNY should likely be evaluated at a hospital level, with a benchmark or minimum performance threshold for the percentage of cases that meet the metric. The Quality Integration Committee of the ACS Commission on Cancer establishes expected estimated performance rates (EPRs) for metrics monitored by their quality program. In colorectal cancer, the EPR is 85% for LNY, meaning that this percentage of eligible patients at the hospital has 12 or more lymph nodes removed and analyzed. For gastric cancer, the EPR is 80%.17 While there is no standard set for neck dissections, there is some evidence that an 80% threshold at the hospital level is an appropriate cutoff. Patients treated at hospitals meeting this threshold had better survival outcomes than those treated at hospitals that fell below this threshold.18
28.3 Intraoperative and Postoperative Complications
During and after a neck dissection, there are a number of potential complications that can occur. Intraoperatively, unexpected injury of a major vessel or nerve can potentially leave a patient with significant sequela. Postoperatively, patients may develop a hematoma, surgical site infection, or chyle leak. While these are known risks of the surgery, and can potentially be avoided, the risks of each complication are highly dependent on the patient and the disease, in addition to the skill of the surgeon.
For the rates of postoperative complications to be used as a quality measure, a formal process of “operationalizing” the measure needs to be undertaken. One example of how to do this is outlined by the Measures Management System (MMS) Blueprint maintained by the Center for Medicare and Medicaid Services.19 Prior to developing a measure, a known performance gap must first be identified, and the strength of evidence and business case (cost of implementation vs. anticipated benefit) must be evaluated. Measures should be considered for feasibility, reliability, and validity. In order to develop the measure, specifications must be determined, which include the measure description, population the metric applies to (denominator), expected outcome or process (numerator), sampling method, risk adjustment, and calculation algorithm. Testing and implementation of the measure then follow.
This process highlights some of the important challenges in developing new quality measures. In particular, deciding which patients meet inclusion criteria and performing appropriate risk adjustment is important, and would need to take into account additional factors such as disease type. A neck dissection for thyroid cancer would have very different risks and outcomes than a postradiation salvage neck dissection. Converting rates of postoperative complications into true quality measures is possible, but would require a more in-depth analysis of the data, and once implemented, each patient would need to be risk adjusted before reporting the metric. Comparing raw, unadjusted rates would likely have little face validity to clinicians, who may feel their patients are different than the “average” case.
28.4 Functional Outcomes and Quality of Life
Most QOL tools in HNC research rely on questionnaires to assess disease or treatment-related symptoms. Examples of general surveys used in cancer populations include the Medical Outcomes Study-Short Form 36 (MOS SF-36) and the Sickness Impact Profile (SIP).20,21 Instruments specific to HNC include the head and neck subscale of the Functional Assessment of Cancer Therapy (FACT-HN), the University of Washington QOL Questionnaire (UWQOL), and the 35-item head and neck questionnaire from the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ- H&N35).21.22.23. 24 These types of surveys focus on domains specific to HNC such as speech, swallowing, and eating. However, while these are useful tools to assess QOL in patients with HNC in general, none were specifically developed to focus on QOL assessment in patients after neck dissection.
Important variables to consider in QOL measurement after neck dissection include nerve injury (great auricular, marginal mandibular branch, hypoglossal, and spinal accessory nerves), lymphedema, scar appearance or cosmetic disfigurement, sensory function, and shoulder function. Shoulder function represents one of the most commonly studied QOL outcomes given its potential to result in significant morbidity and interference with many activities of daily living. A number of studies have suggested improved QOL in patients who undergo more limited neck dissections, related to better shoulder function.21 25 26 27
Tools that have been used to evaluate postoperative shoulder function include the Neck Dissection Impairment Index (NDII) and Constant’s Shoulder Assessment. The NDII is a validated questionnaire that consists of 10 items with a 5-point Likert scale; lower scores correspond with worse QOL impairment. Questions focus on neck or shoulder pain, stiffness, difficulty with self-care, ability to lift objects or reach overhead, overall activity level, participation in social activities, ability to participate in leisure or recreational activities, and ability to work.28 The Constant Shoulder Assessment is a test that combines patient symptom scores with objective measures of active shoulder function, such as range of movement, rotation, and strength. Patient symptoms represent 35% of the sum and include pain, sleep, recreation, and vocational activities; active shoulder function represents 65%.22,25,28
Similar to the NDII and Constant’s Assessment, the self-administered neck dissection questionnaire (NDQ) and arm abduction test (ABT) are tools that Japanese authors have used to focus on postoperative QOL after neck dissection. QOL variables taken into account for NDQ questions included neck stiffness, constriction, pain, numbness, shoulder drop, reach, and neck appearance. The ABT requires patients to rate their arm abduction on a scale of 0 to 5. Similar to other authors, these tools suggest that preservation of the spinal accessory nerve and sternocleidomastoid muscle results in significantly improved QOL.29,30
Consistent evaluation of shoulder dysfunction after neck dissection using tools such as the NDII and Constant’s Assessment, or NDQ and ABT, may provide a QOL score that is amenable to comparison across providers. Outcomes would also need to take into account factors such as the level of disease burden, and the extent of neck dissection for appropriate risk adjustment. Implementation of this metric would require widespread adoption of these tools by providers, and additional resources to collect and record survey data, which may significantly limit their use.
28.5 Regional Recurrence Rates
The most important oncologic outcome of a neck dissection is long-term regional control of disease. Similar to creating quality metrics around perioperative complications, developing an outcome measure around regional recurrence rates poses a few challenges. First, rates of regional recurrence would need to take into account different histologies, nodal stage, local recurrence, and cancer biology (e.g., extracapsular extension). In addition, adjuvant treatment with radiation—with or without chemotherapy— would also affect regional recurrence rates. Therefore, a more careful study and risk adjustment of patients would be required. While it is a worthwhile goal to create nationally recognized benchmarks for regional recurrence rates, ultimate implementation would be challenging. Each patient would need to be risk adjusted prior to comparing their outcomes, requiring significant data collection and reporting by providers. Regional recurrence rates for the nodal basin at risk would need to be reported, along with any concurrent local recurrence. Another possible approach would be to use the regional recurrence rates of a single disease (e.g., T1/T2N0 oral cavity disease) as a marker for all sites and stages. This would allow for easier risk adjustment, but it would be harder for any individual provider to generate sufficient case numbers to provide feedback in this setting.
There are many potential outcome quality measures for neck dissection. Many of these measures would require significant development to allow for comparison across different providers and different institutions. Nevertheless, in an era of value-based medicine, it is important for head and neck surgeons to define what constitutes high-quality care in their field.
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 Divi V, Chen MM, Nussenbaum B, et al. Lymph node count from neck dissection predicts mortality in head and neck cancer. J Clin Oncol. 2016; 34 (32):3892-3897
 Graboyes EM, Gross J, Kallogjeri D, et al. Association of compliance with process-related quality metrics and improved survival in oral cavity squamous cell carcinoma. JAMA Otolaryngol Head Neck Surg. 2016; 142(5):430-437
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 Shrime MG, Bachar G, Lea J, et al. Nodal ratio as an independent predictor of survival in squamous cell carcinoma of the oral cavity. Head Neck. 2009; 31 (11):1482-1488
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