A comparison of prognostic factors and surgical results in 1,786 patients with localized (stage I) melanoma treated in Alabama, USA, and New South Wales, Australia

Abstract

Twelve clinical and pathologic parameters were compared in two series of Stage I melanoma patients treated at the University of Alabama in Birmingham, USA (676 patients) and at the University of Sydney in New South Wales, Australia (1,110 patients). Actuarial survival rates were virtually the same at the two institutions over a 25-year follow-up period. The incidence of thin melanomas (less than 0.76 mm) was also similar at both geographic locations (25% vs. 26%). Other similarities of these two patient populations included the following: 1) tumor thickness (Breslow Microstaging). 2) level of invasion (Clark Microstaging), 3) surgical results, 4) sex distribution, and 5) age distribution. The greatest differences between the two patient populations were their 1) anatomic distribution, 2) growth pattern, and 3) incidence of ulceration. The trunk was the most common site of melanoma, and occurred more frequently among Australian patients (37% vs. 28%). A multifactorial analysis (Cox's regression model) was then performed that included a comparison of the two institutions as a variable (Alabama vs. Australia). The dominant prognostic factors (p less than 0.0001) were 1) ulceration, 2) tumor thickness, 3) initial surgical management (wide excision +/- node dissection), 4) anatomic location, 5) pathologic stage (I vs. II), and 6) level of invasion. The benefit of elective lymph node dissection was demonstrated in both series for patients with intermediate thickness melanoma (0.76 to 3.99 mm.) For melanomas ranging from 0.76 to 1.5 mm in thickness, the benefit of node dissection was primarily in male patients. Survival rates for melanoma at the two institutions were not significantly different in the multifactorial analysis, even after adjusting for all other variable. Thus, the biologic behavior of melanoma in these two different parts of the world was virtually the same, with only minor differences that did not significantly influence survival rates. Long-term follow-up exceeding eight to ten years after surgery is critical in the interpretation of these prognostic factors and the surgical results.