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Tumor Volume: An Adjunct Prognostic Factor in Cutaneous Melanoma

Cutis. 2014 November;94(5):226-230
November 6, 2014|Cutis
Robert G. Walton, MD;Jinah Kim, MD, PhD;Cruz Velasco, PhD
Author and Disclosure Information

Robert G. Walton, MD; Jinah Kim, MD, PhD; Cruz Velasco, PhD; Susan M. Swetter, MD

Drs. Walton, Kim, and Swetter are from the Department of Dermatology, Stanford University Medical Center, California. Dr. Kim also is from the Department of Pathology. Dr. Swetter also is from the Stanford Cancer Institute as well as the Dermatology Service, VA Palo Alto Health Care System, California. Dr. Velasco is from the Biostatics Program, School of Public Health, and the Stanley S. Scott Cancer Center, Louisiana State University Health Sciences Center, New Orleans.

The authors report no conflict of interest. Dr. Walton’s research was supported in part by a grant from the Ronald and Ann Williams Charitable Foundation.

Correspondence: Susan M. Swetter, MD, Department of Dermatology/Cutaneous Oncology, Stanford University Medical Center and Cancer Institute, 900 Blake Wilbur Dr, W3045, Stanford, CA 94305-5356 (sswetter@stanford.edu).

Measurement of tumor volume may be a helpful adjunct to established prognostic factors in cutaneous melanoma, including Breslow depth, presence or absence of ulceration, mitotic index, lymphovascular invasion, and microsatellites. This report expands on the theory that a tumor volume cutoff point of 250 mm3 as measured by surface area of the lesion (ie, longest vertical and horizontal measurements either based on clinical or gross pathological assessment) multiplied by the Breslow depth could serve as a potentially relevant predictor of sentinel lymph node (SLN) metastasis in both thin and thick invasive cutaneous melanomas, which prompted investigation of a larger sample size using the pathology database at our institution.

     Practice Points

  • Measurement of melanoma tumor volume using clinical area (length • width of the lesion before diagnostic biopsy) multiplied by Breslow depth may provide additional prognostic information.
  • Further study is needed to validate the use of tumor volume as an adjunct to established histopathologic prognostic factors in cutaneous melanoma.

Univariate analysis demonstrated that Breslow depth was the best prognostic indicator of metastasis (AUC=0.946) but that tumor volume (as a continuous variable) was nearly equally predictive (AUC=0.940)(Table 3). Tumor volume alone (categorized as <250 mm3 vs >250 mm3) had lower prognostic value (AUC=0.855). Mitotic index, presence or absence of ulceration, inflammatory host reaction, and surface area also had lower prognostic values, though all were significant factors (P values ranging from <.0001 to .0077)(Table 3).

Importantly, the addition of surface area, mitotic index, presence or absence of ulceration, and inflammatory host reaction to the model to Breslow depth did not improve predictive ability for metastasis, and AUC values did not increase significantly after adding these factors (Table 4). In particular, the change in AUC for adding surface area to the model with Breslow depth was 0.023 (P=.1095). Models in Table 4 were checked for interaction of these 2 predictors, and the interaction term for thickness and surface area was not statistically significant (P=.0932)(data not shown).

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