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Calculated tumor area provides independent prognostic value for patients with melanoma

A new two-dimensional feature called calculated tumor area appears to have effective independent prognostic value in patients with melanoma, according to a retrospective cohort study published in JAMA Dermatology.

Researchers said that studying this feature further should become a priority.

“We have now devised a newer feature, the calculated tumor area (CTA), which yields an area in square millimeters of invasive melanoma cells on the same microscopic section used for measurement of Breslow thickness,” Gerald Saldanha, MRCP, FRCPath, PhD, consultant histopathologist and honorary senior lecturer in the Leicester Cancer Research Centre at University of Leicester, United Kingdom, and colleagues wrote. “Calculated tumor area was designed for speed and simplicity so that any pathologist could measure it prospectively during routine practice.”

Breslow thickness has been the optimal prognostic feature since 1970. However, it is measured in one dimension even though tissue sections have two dimensions.

In this study, Saldanha and colleagues sought to determine the association between CTA and melanoma-specific survival and how it compares to Breslow thickness in the survival analysis. They analyzed 918 patients with melanoma presenting at Leicester National Health Service Hospital and 321 patients with melanoma presenting at Nottingham National Health Service Hospital. Median age of all patients was 60 years, and 649 patients (52.4%) were women. Median Breslow thickness among all patients was 0.9 mm.

CTA demonstrated an ability to be an independent prognostic factor among patients in the Leicester cohort in Cox proportional hazard regression models after adjusting for Breslow thickness, age, sex, ulcer, mitotic rate and microsatellites (HR = 1.87; 95% CI, 1.49-2.34). These findings appeared to be validated among patients in the Nottingham cohort (HR = 1.55; 95% CI, 1.15-2.09). Among all patients, CTA demonstrated an HR of 1.70 (95% CI, 1.43-2.03).

Saldanha and colleagues performed a second check by taking 100 bootstrap samples from the entire cohort and performing a backward stepwise variable selection. Results demonstrated that CTA was retained in all 100 bootstrap sample models. Breslow thickness was retained in 53.

“This finding supports CTA as the most influential of these features,” Saldanha and colleagues wrote.

Systematic differences between Leicester and Nottingham hospitals, such as case mix, specimen handling and histopathologist reporting practices, were a limitation of the study. In addition, further confirmation that the measurement protocol and interobserver agreement can be replicated by others is needed.

If coupled with advances in digital pathology, CTA could become an “invaluable” element of melanoma staging, Timothy H. McCalmont, MD, professor of pathology and dermatology at University of California, San Francisco, wrote in an accompanying editorial.

“One beauty in the application of CTA is its utter simplicity, because the assessment can be completed in a timely fashion using conventional histopathologic sections,” McCalmont wrote. “One flaw is that it does include an estimated component, in that the area is precisely determined through measurements of width and thickness but the proportion involved by melanoma cells is gauged by visual inspection. It seems possible if not likely that this factor could lead to poor reproducibility with broader dissemination.” – by John DeRosier

Disclosures: Saldanha reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures. McCalmont reports no relevant financial disclosures.