Increasing Incidence of Merkel Cell Carcinoma in Queensland, Australia
In a study reported in JAMA Dermatology, Youlden et al found that the incidence of Merkel cell carcinoma in Queensland, Australia, a known high-risk area, increased by 2.6% annually between 1993 and 2010. Five-year relative survival was 41%, with significantly better survival found in patients aged < 70 years at diagnosis, those with tumors on the face or ears, and those with stage I disease.
Study Details
This retrospective cohort study used population-based administrative data for Merkel cell carcinoma collected by the Queensland Cancer Registry and supplemented by histopathologic data. Relative survival was calculated by dividing observed survival probability for the study group by the expected survival in the Queensland population, matched for age group, sex, and year.
Characteristics
A total of 879 eligible cases occurring between 1993 and 2010 were included in the study. Men accounted for 68% of cases, and median age at diagnosis was 75.5 years in men and 78.0 years in women. Diagnosis was made at stage I in 50% of cases, stage III in 12%, and stage IV in 15%, with the most common body sites being face/ears (35%; 38% of men, 29% of women), lower limbs (16%; 11% of men, 26% of women), and upper limbs/shoulders (14%). Immune suppression was present in 1.4% of patients and 36% had another primary cancer (12% in same year as diagnosis or subsequent years), including 2% with lymphoma and 1% with chronic lymphocytic leukemia.
Incidence
In total, 340 cases of Merkel cell carcinoma were diagnosed in Queensland between 2006 and 2010, corresponding to an incidence rate of 1.6 per 100,000 population. The incidence was higher in men (2.5/100,000 population) than in women (0.9/100,000 population) and age-related rates peaked at 20.7/100,000 population in persons aged ≥ 80 years.
Overall incidence increased by an average of 2.6% per year from 1993 to 2010, representing a 54% increase over the period. Annual increases were 2.5% in men, 2.1% in women, 3.1% for head cancers and 1.3% for other body sites, and 3.6% for stage I lesions and 2.9% for other stages. Annual incidence decreased by 1.4% in persons aged 0 to 59 years and increased by 2.0%, 2.3%, and 3.7% in those aged 60 to 69, 70 to 79, and ≥ 80 years.
Survival
Median follow-up for cases prevalent between 2006 and 2010 was 2.8 years. Cause-specific survival was 88% (95% confidence interval [CI] = 84%–91%) at 1 year and 66% (95% CI = 60%–71%) at 5 years. Relative survival was 77% (95% CI = 71%–81%) at 1 year and 41% (95% CI = 34%–48%) at 5 years, with 5-year relative survival being significantly better in patients aged < 70 years vs older at diagnosis (56%–60%, P < .001), those with tumors on the face/ears vs other sites (51%, P = .04), and those with lesions of stage I vs other stages (49%, P = .04).
Adjusted hazard ratios for 5-year mortality were 3.0 (95% CI = 1.8–5.1) for patients aged ≥ 80 years vs those aged 60 to 69 years, 2.2 (95% CI = 1.2–4.1) for those with lesions on the trunk and 1.8 (95% CI =1.1–3.0) for those with lesions on the lower limbs vs those with lesions on the face/ears, and 1.8 (95% CI = 1.1–3.2) for those with stage II disease and 2.3 (95% CI = 1.2–4.4) for stage IV disease vs stage I disease. No significant survival differences were observed for those with lesions on the scalp/neck or upper limbs/shoulders vs the face/ears, and no significant differences were found according to sex, remoteness of residence, level of invasion, surgical margins, or presence of multiple primary cancers.
The investigators concluded: “Incidence rates for [Merkel cell carcinoma] in Queensland are at least double those of any that have been previously published elsewhere in the world. It is likely that Queensland’s combination of a predominantly white population, outdoor lifestyle, and exposure to sunlight has played a role in this unwanted result. Interventions are required to increase awareness of [Merkel cell carcinoma] among clinicians and the public.”
Danny R. Youlden, BSc, of Cancer Council Queensland, is the corresponding author for the JAMA Dermatology article.
The study was supported by fellowships from the National Health and Medical Research Council and Cancer Council of Western Australia. The authors indicated no conflicts of interest.
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