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Original Investigation
February 2018

Comparison of Tumor Classifications for Cutaneous Squamous Cell Carcinoma of the Head and Neck in the 7th vs 8th Edition of the AJCC Cancer Staging Manual

Author Affiliations
  • 1Department of Dermatology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts
  • 2Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
  • 3Division of Otolaryngology–Head and Neck Surgery, University of California, San Diego, La Jolla
JAMA Dermatol. 2018;154(2):175-181. doi:10.1001/jamadermatol.2017.3960
Key Points

Question  How well does the AJCC Cancer Staging Manual, 8th edition (AJCC 8), tumor (T) classification for head and neck cutaneous squamous cell carcinoma (HNCSCC) stratify disease-related outcomes and how does its performance compare with the 7th edition (AJCC 7)?

Findings  In a cohort of patients with HNCSCC, 17.8% of tumors were classified in AJCC 8 as high tumor categories (T3/T4), and this small subset accounted for 70.4% of the cohort’s poor outcomes. Comparatively via AJCC 7, few tumors (0.7%) and poor outcomes (16.9%) were classified as T3/T4.

Meaning  AJCC 8 demonstrates superior homogeneity and monotonicity compared with AJCC 7.

Abstract

Importance  Previous studies have shown that the AJCC Cancer Staging Manual, 7th edition (AJCC 7), tumor classification for cutaneous squamous cell carcinoma (CSCC) failed to accurately stratify disease-related outcomes. The recently released 8th edition (AJCC 8) features a revised tumor classification for only head and neck CSCC (HNCSCC).

Objective  To compare AJCC 7 and AJCC 8 tumor classifications for HNCSCC and to validate AJCC 8.

Design, Setting, and Participants  This was a 10-year retrospective cohort study (2000-2009) at an academic tertiary care center reviewing 680 primary HNCSCC tumors in 459 patients.

Main Outcomes and Measures  Primary HNCSCC tumors were reviewed for disease-related outcomes (DROs): local recurrence (LR), nodal metastasis (NM), and disease-specific death (DSD). Tumors were stratified by AJCC 7 and AJCC 8 tumor classification. Distinctiveness (outcome differences between categories), homogeneity (outcome similarity within categories), and monotonicity (outcome worsening with increasing categories) were assessed for both classifications.

Results  Most of the 459 patients were white (451 [98.3%]) and male (312 [68.0%]). AJCC 8 high tumor categories (T3/T4) accounted for 121 (17.8%) of total cases but 50 of 71 DROs (70.4%) (22 of 34 of LRs [64.7%], 17 of 24 NMs [70.8%], and 11 of 13 of DSDs [84.6%]). This was a significant improvement over AJCC 7, where only 12 of 71 DROs (16.9%) (4 of 34 LRs [11.8%], 3 of 24 NMs [12.5%], and 5 of 13 DSDs [38.5%]) occurred in T3/T4 categories. However, AJCC 8 T2 and T3 were indistinct, with overlapping 95% CIs for 10-year cumulative incidences of LR, NM, and DSD. The 10-year cumulative incidence of DROs in the 119 AJCC 8 T3 cases were 19.7% (95% CI, 13.0%-29.7%) for LR, 14.1% (95% CI, 9.7%-20.7%) for NM, and 9.3% (95% CI, 6.8%-14.0% for DSD).

Conclusions and Relevance  AJCC 8 demonstrates superior homogeneity and monotonicity compared with AJCC 7. It now may be possible for AJCC 8 HNCSCC T2, T3, and T4 cases to be recorded and tracked by tumor registries because they represented a 23.1% subset in this study, which includes nearly all poor outcomes (85.9%). Further work is needed to validate AJCC 8 with population-level data and to compare AJCC 8 performance against alternative tumor classifications.

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