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Melanoma in situ incidences increase at faster rate than invasive melanoma

Incidence of melanoma in situ increased at a faster rate than invasive melanoma, with the two melanomas displaying epidemiological and clinical differences, according to recently published study results.

Researchers used the Nurses’ Health Study, an ongoing prospective of cohort of 121,700 female registered nurses (1976-2010), and the Health Professionals Follow-up Study, which includes 51,529 men (aged 40 to 75 years) in the health care profession to prospectively collect incident cases of melanoma (1986-2010).

The study included analysis of 1,609 incident cases of invasive melanomas and 1,047 incident cases of melanoma in situ.

“[Melanoma in situ] incidence increased from 2 to 42 per 100,000 person-years among women, and from 11 to 73 per 100,000 person-years among men, exceeding the rate of increase of invasive melanomas,” the researchers wrote.

For women, the absolute incident cases of melanoma in situ began to exceed that of invasive melanoma in 2001 through 2002. In men, the absolute incident cases of melanoma in situ began to exceed invasive melanomas in 2007 to 2008.

Melanoma mortality had an initial increase over time but plateaued by the end of follow-up.

In situ melanomas on the upper half of the body were common among men (P <. 001). Invasive melanomas were more likely to be diagnosed at a younger age (P < .001), and were more likely to be found on the lower extremities of women and men (P < .001, both).

“This study revealed interesting epidemiologic and clinical features of [melanoma in situ],” the researchers wrote. “First, the increase in [melanoma in situ] detection relative to 30 years (women) and 20 years (men) of cohort follow-up did not correspond to a reduction in melanoma mortality. In addition, invasive and in situ melanomas showed distinct anatomic distribution, which may have greater implications on biologic behavior in distinct anatomic sites.”

“The lack of improvement in mortality despite the increase in detection of in situ relative to invasive lesions further highlights the need to improve invasive melanoma-specific clinical screening features,” the researchers concluded. – by Bruce Thiel

Disclosure: The researchers report no relevant financial disclosures.