The head and/or neck area is the most common region for squamous cell carcinoma, according to new findings, and the next most common is the upper limbs.¹

This study was conducted to determine the anatomic locations of keratinocyte carcinomas (KCs) in Medicare beneficiaries in the US. Additionally, the investigators sought to learn how keratinocyte carcinoma locations differ by sex and by tumor type.²

The research was authored by Lucy J. Navsaria, MBBCh, BAO, MPH, from the Department of Health Services Research at the University of Texas MD Anderson Cancer Center in Houston.

“Keratinocyte carcinomas are the most common cancers in the US,” Navsaria and colleagues wrote. “However, keratinocyte carcinomas are not included in US national cancer registries, and information on the anatomic locations of keratinocyte carcinomas is lacking.”

Background and Findings

The investigators conducted the cohort study, utilizing deidentified and randomly-selected Medicare claims data from the period between 2009 and 2018. They evaluated 4,999,999 beneficiaries that were aged 65 years or older and had continuous Parts A, B, and D coverage and no Medicare Advantage coverage.

The researchers’ study was approved by the MD Anderson Cancer Center institutional review board. All of the beneficiaries with at least a single procedurally-treated KC were featured in the study, and data from all cases of procedurally-treated KCs were collected, including beneficiaries who had more than 1 KC.

In this study, the investigators sought to evaluate KC distribution across various kinds of anatomic locations, also taking into account patients’ gender and type of tumor. To improve their accuracy, they divided squamous cell carcinomas (SCCs) into two categories: SCC and SCC in situ.

The researchers accounted for differences in skin surface areas in different locations and enabled comparisons with other studies by calculating the relative tumor densities (RTDs) by dividing the proportion of lesions by the proportion of skin surface area using the Wallace Rule of Nines.

Additionally, the investigators used logistic regression to examine the relationship between subtypes of the KCs (SCC vs basal cell carcinoma [BCC]) and body location, while controlling for demographic variables including race, sex, age, ethnicity, and region of census.
The team noted that among the 792,393 Medicare beneficiaries reporting a minimum of 1 treated KC, mean (SD) age at initial diagnosis of KC was found to be 76.6 (8.1) years. They added that 51.8% of them were women and 96.7% of the group were White.

In the end, they identified a total of 2,415,514 procedurally-treated KCs. The majority of the KCs were subtyped into basal cell carcinoma for 33.0% of the KCs, or squamous cell carcinoma for 38.4%, with 28.6% being untyped by the team.

The investigators found that the most observed location of squamous cell carcinomas was found to be the head and/or neck for 44.3% of the KCs, then the upper limbs for 26.7%. Additionally, the team noted that the most common location for basal cell carcinomas was the head and/or neck for 63.8% followed by the trunk for 14.9% of them.

Regarding demographic differences, the investigators reported that the most common location of KCs for women had been found to also be the head and/or neck for 47.3%, followed then by the upper and lower limbs (18.5% and 16.6%, respectively).

They added that the most common region for KCs in men was also the head and/or neck (58.7%), followed by the upper limbs and trunk region (17.3% and 11.4%, respectively).

“Further studies detailing the use of KC ICD codes and prevalence of codes not specifying BCC or SCC should be pursued to further characterize the anatomic locations of keratinocyte carcinomas in the US,” they wrote.

References

1. ^{Navsaria LJ, Li Y, Tripathy S, et al. Anatomic Locations of Procedurally Treated Keratinocyte Carcinomas in the US Medicare Population. JAMA Dermatol. Published online April 19, 2023. doi:10.1001/jamadermatol.2023.0611.}
2. ^{National Cancer Institute Seer Training Modules - Reportable List. National Institutes of Health. Accessed February 04, 2023. Published 2022.}