A population-based study of cutaneous melanoma in Alberta, Canada (1993-2002)

Background: There is evidence to suggest that melanoma incidence rates continue to rise in Canada and the United States.

Objective: Our objective was to determine cutaneous melanoma trends from 1993 to 2002 in the province of Alberta and to compare the results to previously published provincial analyses for the decade of 1967-1976.

Methods: A retrospective study of 3479 patients with cutaneous melanoma diagnosed in Alberta between 1993 and 2002 was conducted. Estimates of relative survival compared the survival of melanoma patients with the Alberta population to derive the likelihood of surviving melanoma in the absence of other causes of death. Further comparison to published Canadian data was also conducted.

Results: For the period 1993-2002, the annual melanoma age-standardized incidence rates per 100,000 person-years ranged between 11.1 and 15.9 and between 9.8 and 14.1 among men and women, respectively. These rates are considerably higher than the previously reported (1976) highest Alberta incidence rates of 4.1 and 4.8 in men and women, respectively. The rates increased slightly for the period 1993-1999 with an average annual percentage change of +3.5%, but appeared to decrease for the interval 1999-2002 with an average annual percentage change of -6.4%. The majority of the tumors were less than 1.0 mm in thickness for both genders. On univariate analysis the following parameters were associated with decreasing patient survival: male gender, increasing age, head and neck tumors, Clark level of invasion, and Breslow tumor thickness. Multivariate analysis demonstrated that the strongest determinant of survival was Breslow tumor thickness.

Limitations: Melanomas in-situ were not included in this study.

Conclusions: Although melanoma incidence rates in Alberta are higher than previously reported, the incidence rates over the study period of 1993 to 2002 appear to have leveled and may in fact be declining over the past several years.