Patient income also makes a difference, with poorer patients getting diagnosed with thicker melanomas, the researchers said.
"Survival for patients with melanoma is dependent on stage at diagnosis. As Breslow (depth of tumor cells in the skin) thickness increases, overall survival decreases," wrote Dr. Karyn B. Stitzenberg, of the School of Public Health at the University of North Carolina at Chapel Hill, and her colleagues.
"Consequently, early diagnosis may substantially improve patient outcomes," the researchers added. But, "because melanoma can only be definitively diagnosed based on biopsy findings, diagnosis requires detection of the suspicious lesion and biopsy. Some primary care providers perform diagnostic biopsies, but many prefer to refer patients to dermatologists or surgeons."
Among the patients in this study, the median distance to a diagnosing physician was eight miles, and the median Breslow thickness was 0.6 millimeters. For each one-mile increase in distance to the doctor, there was a 0.6 percent increase in Breslow thickness, the study found.
Patients who had to travel more than 15 miles to see their doctor had about 20 percent greater Breslow thickness than those who were less than 15 miles away.
Compared to those in metropolitan counties, patients in rural counties traveled an average of 2.4 miles farther to their diagnosing doctor. Patients in counties with at least one dermatologist traveled an average of 8.3 miles less than those in counties without a dermatologist.
The study also found an association between Breslow thickness and age and poverty.
"For each one percent increase in poverty rate, Breslow thickness increased by one percent. Breslow thickness was 19 percent greater for patients aged 51 to 80 years than for those aged 0 to 50 years and was 109 percent greater for patients older than 80 years than for those aged 0 to 50 years," the study authors wrote.
The study is published in the August issue of the journal Archives of Dermatology.
HealthDay News, August 22, 2007