August 09, 2016
2 min read

De novo melanomas more aggressive than nevus-associated melanomas

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Patients with de novo primary cutaneous melanomas were more likely to have an adverse histopathology and poor OS compared with patients with nevus-associated melanomas, according to a review of two prospective cohorts.

Twenty percent to 30% of melanomas are histopathologically nevus associated, whereas 70% to 80% arise de novo, or, without a nevus. The lifetime risk for an individual nevus to turn into melanoma is estimated at less than one in 1,000.

Whether melanoma prognosis is influenced by an associated nevus is uncertain because previous trials have been limited by small samples sizes, retrospective designs and varying quality of follow-up data, according to Rachel M. Cymerman, MD, resident physician at The Ronald O. Perelman department of dermatology at New York University School of Medicine, and colleagues.

Cymerman and colleagues compared whether de novo melanomas and nevus-associated melanomas differed with regard to histopathologic features and survival outcomes.

The analysis included patient data from two prospective cohorts treated at New York University. One cohort consisted of 1,024 patients (48.8% male; median age, 53 years) treated from 1972 to 1982, and the other consisted of 1,125 patients (54.8% male; median age, 59 years) treated from 2002 to 2009. The proportion of patients with de novo melanomas was 80.7% in cohort 1 and 69% in cohort 2.

In cohort 1, patients with de novo melanomas also tended to have tumor thickness greater than 1 mm (OR = 1.96; 95% CI, 1.43-2.7), ulceration (OR = 1.65; 95% CI, 1.1-2.54), nodular subtype (OR = 3.26; 95% CI, 1.7-7.11) and stage II disease or higher (OR = 2.35; 95% CI, 1.65-3.4). These patients also were more likely to be older (OR = 1.64; 95% CI, 1.18-2.3) and have shorter OS (HR = 1.63; 95% CI, 1.22-2.18) than patients with nevus-associated melanomas.

Researchers used the data from cohort 2 to test the ability to reproduce these association, citing the 20-year gap as a means to increase confidence in the identified associations.

De novo melanomas were again associated with tumor thickness greater than 1 mm (OR = 2.24; 95% CI, 1.72-2.93), ulceration (OR = 2.88; 95% CI, 1.95-4.37), nodular subtype (OR = 2.41; 95% CI, 1.75-3.37), stage II disease or higher (OR = 2.42; 95% CI, 1.8-3.29), older patient age (OR = 1.68; 95% CI, 1.31-2.17) and shorter OS (HR = 2.52; 95% CI, 1.78-3.56).

In a multivariate analysis of cohort 2, de novo classification independently predicted poor prognosis (HR = 1.7; 95% CI, 1.19-2.44).

Among patients with de novo classification, men experienced significantly worse survival than women (cohort 1, P < .001; cohort 2, P < .001); however, there was no difference in outcome based on sex among patients with nevus-associated melanomas.

Researchers acknowledged that because cohort 1 was enrolled prior to the advent of sentinel node biopsy, they were unable to include an analysis of biopsy results.

“These findings suggest there are potentially important differences in the biology of nevus-associated and de novo melanomas,” Cymerman and colleagues wrote. “Moving forward, it may be useful to use the nevus-associated vs. de novo classification in analyses of melanoma risk factors, tumor biology and response to therapy.” – by Nick Andrews

Disclosure: The researchers report no relevant financial disclosures.