Redefining skin cancer staging reveals previously hidden cases

The eighth edition of the American Joint Committee on Cancer (AJCC-8) guidelines will soon be implemented expanding the scope of a T3 classification for cutaneous squamous cell carcinoma (cSCC) to include three independent risk factors.

A new analysis shows that by expanding the definition of T3 staging, cases that would not have been included in previous editions of the guidelines, are now included.

“The new AJCC-8 guidelines are significantly impactful upon the practice of the Mohs surgeon. 13 of the 18 tumors [we] identified as T3 were only identified at the time of Mohs surgery; cases like these should be referred for nodal disease evaluation,” according to a study presented by Michael Montuno, M.D., of the University of Florida, at the 2017 American Society for Dermatologic Surgery annual meeting in Chicago on Oct. 7.

Previous editions of the guidelines did not include independent risk factors of large caliber perineural invasion (PNI), clinical size of at least 4 cm and invasion beyond the subcutaneous fat layer - but AJCC-8 does include these risk factors which are typically identified during Mohs surgery.

Dr. Montuno and colleagues conducted a review of cSCC staging based on the results of excision specimens and tissue stages from Mohs surgery under both the AJCC-7 and AJCC-8 guidelines.

Researchers reviewed the records of patients who underwent Mohs surgery for invasive cSCC on the head or neck with no evidence of nodal or metastatic disease detected by Mohs surgery.

The analysis included the results of Mohs surgery specimens and corresponding biopsies that were conducted between July 2015 and April 2017. The data included results from the anatomic site, pre-operative clinical diameter, tumor thickness and depth of invasion, tumor differentiation, PNI and caliber of largest nerve affected, and bony invasion.

STAGING TUMORS

In staging tumors according to AJCC-7 guidelines, 66 T1 tumors were recorded and 30 T2 tumors, but no T3 tumors. When staging tumors according to AJCC-8 guidelines, 67 T1 tumors were found, 11 T2 tumors and 18 T3 tumors.

In cases that followed AJCC-8 guidelines, 18 of 182 (9.9%) Mohs surgery cases and 5 of 170 (2.9%) biopsy specimens were stage T3 tumors. A T3 stage was determined by clinical size in all but one of biopsies. One biopsy was determined to be T3 after a punch biopsy showed high risk histological features.

There was a statistically significant correlation between AJCC-8 staging and higher tumor stage (T3 vs T2).

“When staging cSCC lesions according to AJCC-8 versus AJCC-7, there is a statistically significant increase in the likelihood of upstaging of tumors in AJCC-8 when evaluating a pool of stage T2 and T3 tumors,” researcher stated.

Previously, under the AJCC-7 guidelines, cutaneous squamous cell carcinomas (cSCC) were often upgraded to T3 only after a biopsy revealed a large caliber PNI, clinical size of at least 4 cm and/or invasion beyond subcutaneous fat tissue. The authors of this analysis showed these factors for T3 staging were more conclusively derived at by Mohs surgeons during micrographic surgery.

“The new AJCC-8 guidelines are significantly impactful upon the practice of the Mohs surgeon. 13 of the 18 tumors identified as T3 were only identified as such at the time of Mohs surgery; cases like these should be referred for nodal disease evaluation,” researchers stated.

EDITOR’S NOTE

The eighth edition of AJCC will be implemented on Jan. 1, 2018, according to the the American Joint Committee on Cancer (AJCC). Until then, clinicians should continue to use "the latest information for patient care, including scientific content of the 8th Edition Manual. All newly diagnosed cases through December 31st, 2017 should be staged with the 7th edition.  The time extension will allow all partners to develop and update protocols and guidelines and for software vendors to develop, test, and deploy their products in time for the data collection and implementation of the 8th edition in 2018."

-     8th Edition Implementation Project, https://cancerstaging.org

Reference

Michael Montuno, MD, Brandon Brown, MD, Sailesh Konda, MD, Kiran Motaparthi, MD. “The Impact of Mohs Micrographic Surgery on Tumor Staging of Cutaneous Squamous Cell Carcinoma: A Comparison and Evaluation of the 7th and 8th Editions of the American Joint Committee on Cancer Guidelines,” ASDS 2017. Oct. 7, 2017.