A new report assessed existing staging systems for cutaneous squamous cell carcinoma (cSCC) for their ability to predict metastasis and highlighted the strengths and weaknesses of each system. The researchers reported their findings in the British Journal of Dermatology.
The study examined 4 staging methodologies used with cSCC: the American Joint Committee on Cancer 8th edition (AJCC8) system, the Brigham and Women’s Hospital (BWH) system, the Tübingen University staging system, and the Salamanca T3 refinement, which had been designed as a refinement of the AJCC8 T3 system. The analysis consisted of a nested case-control study based on data from the National Disease Registration Service of England.
Data were evaluated from cases of metastatic cSCC that were matched 1:1 with data from nonmetastatic control patients, with cSCC from both cases and control patients staged according to each system. The performance of each system at predicting metastasis was evaluated in terms of specificity, positive predictive value (PPV), negative predictive value (NPV), concordance index (c-index), distinctiveness, homogeneity, and monotonicity. Distinctiveness involved differences in outcomes between each category of a staging system, homogeneity involved outcome similarity within each category of a staging system, and monotonicity was a measure of sensitivity.
A total of 887 cases of metastatic cSCC and 887 nonmetastatic cSCC control patients, were included in the analysis. In an analysis of cSCC across all body sites, the BWH system performed the best in terms of specificity, PPV, and c-index. This system’s specificity was 92.8% (95% CI, 90.8%-94.3%), its PPV was 13.2% (95% CI, 10.6%-16.2%), and its c-index was 0.84 (95% CI, 0.82-0.86).
Compared with the BWH and Tübingen systems, the AJCC8 system showed better NPV, homogeneity, and monotonicity when analyzing cSCC across all body sites. NPV with the AJCC8 system was 99.2% (95% CI, 99.2%-99.3%). Tübingen tumor diameter and co-risk factor classification systems showed better monotonicity and homogeneity than the BWH system did. There was not an improvement over the AJCC8 system with the Salamanca T3 refinement for tumors of all body sites.
The AJCC8 had originally been developed for head and neck cSCC; however, this system performed more poorly in analysis of cSCC in the head and neck than it did in the analysis of all body sites.
The study investigators considered the PPV of each system to be low. They also noted that the BWH system had the best c-index of the systems, which they considered to be the best indicator of a system’s predictive capacity. “We showed that BWH and AJCC8 are both superior to Tübingen staging systems and that each staging system has its own strengths, with BWH showing the highest overall discriminative ability,” the researchers concluded.
Disclosures: Some authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
Venables ZC, Tokez S, Hollestein LM, et al. Validation of four cutaneous squamous cell carcinoma staging systems using nationwide data. Br J Dermatol. Published online December 3, 2021. doi:10.1111/bjd.20909