The volume of inpatient neck dissections increased over 25% from 2000 to 2006, and much of this increase occurred with treatment of non-upper aerodigestive tract primary neoplasms: salivary gland, thyroid and parathyroid gland, and skin. Thyroid and parathyroid-related neck dissections showed an increase in volume that was even greater than that for neck dissections on the whole. The increases in neck dissections for salivary gland and cutaneous disease were not different from the overall trend. Among the upper aerodigestive tract subsites only, neck dissections performed for oral cavity neoplasms (tongue and non-tongue) accounted for the majority of the increase in volume over this time period.
We hypothesized that there would be a decrease in the number of neck dissections for primary tumor sites for which chemoradiotherapy had assumed a more prominent role as a primary treatment modality. These subsites include squamous cell carcinomas of the oropharynx. Our results, however, suggested a different trend, with an increase in neck dissections over the period 2000 – 2006 for both oropharynx and oral tongue. Because the NIS does not include diagnosed neoplasms (to determine whether there was a change in the proportion of neoplasms for which a neck dissection was performed), we examined the Surveillance Epidemiology and End Results (SEER) published incidence tables that do contain this information.18
The SEER tables, as opposed to raw data that can be obtained, groups incident diagnosed tumors of the oropharynx and oral tongue subsites within the category of “oral cavity and pharynx” that includes tumors of the tongue, floor of mouth and gum, oropharynx and tonsil, salivary gland, and lip. From 1992 to 2006, there was a statistically significant decrease in the delay-adjusted incidence rate for oral cavity and pharynx tumors (decrease of 1.3 cases per 100,000).18
Although we cannot comment specifically on oropharynx and oral tongue neoplasms, we acknowledge the limitation of the NIS but have no reason to believe that the increase in the number of neck dissections for these two subsites reflects an increase in the number of newly diagnosed neoplasms. There are several potential reasons for the increase in neck dissections related to these subsites in spite of a larger role for treatment with chemoradiotherapy. Some surgeons perform planned neck dissections following primary chemoradiotherapy, and neck dissections may be recommended as primary treatment for small primary tumors that have nodal involvement.
Our analysis showed that a higher proportion of neck dissections was performed by high-volume providers over time. This regionalization to high-volume providers was also demonstrated for specific subgroups of patients who have been shown to have low access to high-quality or high-volume care, suggesting that they were not being denied access to high-volume providers. High-volume providers and hospitals have been shown to have better outcomes and higher quality for a wide range of surgical procedures,4-7
although there are some limitations to the evidence describing this relationship.19
In a study by Morton et al., it was found that there was a strong correlation between surgeon procedure volume and both nodal yield and a lower incidence of regional recurrence.7
Regionalization can also be used to assess issues of workforce in head and neck cancer surgery. While there may be concerns for declining interest and numbers of head and neck cancer surgeons, trends in neck dissection regionalization indicate that it may be possible for fewer highly-trained surgeons, who each perform a higher volume of procedures, to meet the neck dissection needs in the United States.8, 9
The converse would argue that regionalization is the result of a current head and neck cancer surgeon shortage, which occurred due to fewer head and neck surgeons, each performing more neck dissections by necessity.
Another explanation for the extent of regionalization could relate to financial incentives. It is generally considered that the valuation of head and neck cancer procedures, including neck dissection, may not reflect the complexity and time required to perform these procedures; this concern contributed to a recent reweighting (increase) of the relative value units for many head and neck cancer procedures. With a primarily low-income patient population and low relative value unit valuation, patients that require head and neck cancer surgery may be referred to urban, teaching hospitals more frequently, thus contributing to regionalization.
The NIS has the standard limitations of all administrative databases, including its lack of certain clinical information (tumor size, lymph node involvement, and metastases) and the fact that billing information may not accurately reflect the performance of specific procedures. Because neck dissection is a major surgical procedure, we suggest that this procedure is not often overlooked in billing records and, therefore, would be included in this database. One possible exception may be central neck dissection performed in conjunction with thyroid surgery, where the changes we observed may reflect a change in coding practices rather than practice patterns.
Use of the database requires ICD-9 procedure codes rather than the more-specific Current Procedural Terminology (CPT) codes that describe separately the specific type of neck dissection: radical, modified, or selective. The most important implication is that selective neck dissections that may have been coded with the generic ICD-9 procedure code 40.3 (lymph node excision) without a neck-specific diagnosis code would not have been counted in our analysis. In spite of these limitations, another strength is that the NIS database has been used in many previous studies based on its completeness and the rigor with which it and the weighting algorithms are assembled.
Finally, we do not have detailed information on the incidence of neoplasms of specific subsites and in patient subgroups defined by the specific variables we have examined in this analysis. Ultimately, the strongest conclusions about access to neck dissection care require clinical information and incidence data that are lacking.