Distance to Diagnosing Specialist Increases Melanoma Thickness

CHAPEL HILL, N.C., Aug. 20 -- The farther patients must travel to reach a specialist who can diagnose melanoma, the more likely they are to have a thicker lesion, researchers here reported.

For each mile increase in distance to the specialist, Breslow thickness at diagnosis increased by a significant 0.6% (P=0.003), Karyn B. Stitzenberg, M.D., of the University of North Carolina here, and colleagues, reported in the August issue of the Archives of Dermatology.

Melanoma can be diagnosed definitively only through biopsy, the researchers wrote, so that primary-care providers often refer patients to dermatologists or surgeons.

In a study of 277 original providers from 42 North Carolina counties, there were 615 eligible cases with a median Breslow thickness 0.6 mm (range, 0.1-20.0 mm).

Only 15 original physicians diagnosed the melanomas in at least 1% of the patients. The median distance to the diagnosing specialist was eight miles (range, zero-386 miles).

For distances not exceeding 120 miles, each mile increase corresponded to 0.6% increase in Breslow thickness (P=0.003).

In other words, the researchers said, each 10-mile increase in distance corresponded to a 6% increase in Breslow thickness. Patients who traveled more than 15 miles had 20% thicker tumors on average than patients who traveled up to 15 miles (P=0.02).

Breslow thickness was also associated with age and poverty. Thickness was 19% greater for patients ages 51 to 80 than for those 50 or younger (P=0.02) and was 109% greater for patients older than 80 compared with those younger than 50 (P<0.001).

Poverty was also significantly associated with the Breslow score. For each 1% increase in poverty rate, Breslow thickness increased by 1% (P=0.04).

However, sex, rural origin for the primary tumor site, and supply of dermatologists were not associated with a more advanced tumor, the researchers reported.

Patients from rural counties traveled an average 2.4 miles farther to the diagnosing clinician than did those from metropolitan counties.

Those from counties with a least one dermatologist traveled an average of 8.3 fewer miles compared with those without a dermatologist in their counties. In other words, the researchers said, the presence of a dermatologist did not directly affect distance to a diagnosing provider, but rather is a marker of an increased supply of local health-care resources.

Many factors influence the distance to the diagnosing provider. Most important, the investigators concluded is the role of the referring provider and the effect of health insurance, although these elements could not be explored in this study.

In discussing the study's limitations, the researchers said that Euclidian distance was used for the study, which although not as precise as road distance, has been shown to be a meaningful measure of travel distance in areas without major topographical distances.

Referral bias may have confounded the effect of distance to the diagnosing provider, inasmuch as large tumors may be preferentially referred to high-volume centers. It is possible that some patients were referred to surgeons before a biopsy was done, simply on the basis of a worrisome clinical examination.

However, the researchers said, those diagnosed by surgeons traveled on average only 1.3 miles farther than did patients diagnosed by a dermatologist.

Finally, the researchers wrote that although survival data were lacking, it was reasonable to surmise that differences in Breslow thickness could translate into differences in overall survival.

"Further work is needed to characterize the determinant of distance to diagnosing provider, as well as the pathways and barriers to melanoma care," the authors wrote.

Once potential barriers are identified and interventions are developed to minimize the effect of travel distance, such interventions could potentially translate to other settings in which access to specialists is critical, Dr. Stitzenberg and colleagues concluded.