Prognostic Case Volume Thresholds in Patients With Head and Neck Squamous Cell Carcinoma

Abstract

Importance: Though described as an important prognostic indicator, facility case volume thresholds for patients with head and neck squamous cell carcinoma (HNSCC) have not been previously developed to date.

Objective: To identify prognostic case volume thresholds of facilities that manage HNSCC.

Design, setting, and participants: Retrospective analysis of 351 052 HNSCC cases reported from January 1, 2004, through December 31, 2014, by Commission of Cancer-accredited cancer centers from the US National Cancer Database. Data were analyzed from August 1, 2018, to April 5, 2019.

Exposures: Treatment of HNSCC at facilities with varying case volumes.

Main outcomes and measures: Using all-cause mortality outcomes among adult patients with HNSCC, 10 groups with increasing facility case volume were created and thresholds were identified where group survival differed compared with each of the 2 preceding groups (univariate log-rank analysis). Groups were collapsed at these thresholds and the prognostic value was confirmed using multivariable Cox regression. Prognostic meaning of these thresholds was assessed in subgroups by category (localized [I/II] and advanced [III/IV]), without metastasis (M0), with metastasis (M1), and anatomic subsites (nonoropharyngeal HNSCC and oropharyngeal HNSCC with known human papillomavirus status).

Results: Of 250 229 eligible patients treated at 1229 facilities in the United States, there were 185 316 (74.1%) men and 64 913 (25.9%) women and the mean (SD) age was 62.8 (12.1) years. Three case volume thresholds were identified (low: ≤54 cases per year; moderate: >54 to ≤165 cases per year; and high: >165 cases per year). Compared with the moderate-volume group, multivariate analysis found that treatment at low-volume facilities (LVFs) was associated with a higher risk of mortality (hazard ratio [HR], 1.09; 99% CI, 1.07-1.11), whereas treatment at high-volume facilities (HVFs) was associated with a lower risk of mortality (HR, 0.92; 99% CI, 0.89-0.94). Subgroup analysis with Bonferroni correction revealed that only the moderate- vs low- threshold had meaningful differences in outcomes in localized stage (I/II) cancers, (LVFs vs moderate-volume facilities [MVFs]: HR, 1.09 [99% CI, 1.05-1.13]; HVF vs MVF: HR, 0.95 [99% CI, 0.90-1.00]), whereas both thresholds were meaningful in advanced stage (III/IV) cancers (LVF vs MVF: HR, 1.09 [99% CI, 1.06-1.12]; HVF vs MVF: HR, 0.91 [99% CI, 0.88-0.94]). Survival differed by prognostic thresholds for both M0 (LVF vs MVF: HR, 1.09 [99% CI, 1.07-1.12]; HVF vs MVF: HR, 0.91 [99% CI, 0.89-0.94]) and nonoropharyngeal HNSCC (LVF vs MVF: HR, 1.10 [99% CI, 1.07-1.13]; HVF vs MVF: HR, 0.93 [99% CI, 0.90-0.97]) site cases, but not for M1 (LVF vs MVF: HR, 1.00 [99% CI, 0.92-1.09]; HVF vs MVF: HR, 0.94 [99% CI, 0.83-1.07]) or oropharyngeal HNSCC cases (when controlling for human papillomavirus status) (LVF vs MVF: HR, 1.10 [99% CI, 0.99-1.23]; HVF vs MVF: HR, 1.07 [99% CI, 0.94-1.22]).

Conclusions and relevance: Higher volume facility threshold results appear to be associated with increases in survival rates for patients treated for HNSCC at MVFs or HVFs compared with LVFs, which suggests that these thresholds may be used as quality markers.

Figure 1.. Flow Diagram

AJCC indicates American Joint Committee on Cancer; HNSCC, head and neck squamous cell carcinoma; HPV, human papillomavirus; M0, without distant metastases; and M1, with distant metastases.

Figure 2.. Proportion of Patients Treated Stratified by Facility Volume

The number of cases per year is defined in the Results subsection Facility Volume Thresholds.

Figure 3.. Kaplan-Meier Curve Stratified by Facility Volume

The number of cases per year is defined in the Results subsection Facility Volume Thresholds.

Figure 4.. Adjusted Hazard Ratios of Stratified Facility Volume by Specific Subset of Patients

The number of cases per year is defined in the Results subsection Facility Volume Thresholds. Moderate-volume facilities (MVFs) were the reference for comparison. CoC indicates Commission on Cancer; Nonoropharyngeal HNSCC, nonoropharyngeal head and neck squamous cell carcinoma; HPV, human papillomavirus; HVF, high-volume facility; LVF, low-volume facility; oropharyngeal HNSCC, oropharyngeal head and neck squamous cell carcinoma. Full Cox regressions may be found in eTables 6, 9, 12, and 15 in the Supplement.

Figure 5.. Kaplan-Meier Curve Stratified by Facility Volume for Head and Neck Squamous Cell Carcinoma (HNSCC)