Assessing incidence rates and secular trends in nonmelanocytic skin cancer: which method is best?

Incidence of Nonmelanoma Skin Cancer in New Brunswick, Canada, 1992 to 2001

Background:

Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), collectively referred to as nonmelanoma skin cancer (NMSC), cause significant morbidity and generate a substantial cost to the health care system. Canadian data on the incidence of NMSC are lacking.

Objective:

To study the incidence and characteristics of NMSC in New Brunswick, Canada (population 729,498 people in 2001), by using the Provincial Cancer Registry.

Method:

Data were obtained from 1992 to 2001 from the New Brunswick Provincial Cancer Registry, to which reporting of all cancers is mandatory. Multiple tumors of a given histologic type are recorded only once in the registry per individual per lifetime. A descriptive analysis of incidence rates of BCC and invasive SCC of the skin was performed in relation to gender, age, and anatomic location. The main outcome measures were the age- and sex-specific incidence rates of BCC and SCC. Age standardization was performed using the Canadian, US, and world standard populations.

Results:

When adjusted to the world standard population, the age-standardized incidence rates (ASIRs) per 100,000 population for BCC from 1992 through 2001 were 87 for males and 68 for females. For invasive SCC, the ASIRs per 100,000 population were 34 for males and 16 for females. There was an increasing incidence trend for both BCC and invasive SCC over the 10-year study period, with minimal change in the incidence of SCC in women. The overall ratio of BCC to invasive SCC in the population was 2.8 to 1. The approximate lifetime probabilities of developing BCC and invasive SCC were 13% and 5%, respectively.

Conclusions:

The incidence of NMSC in the province of New Brunswick is similar to that reported from 1973 through 1987 in the province of British Columbia, higher than those reported in most parts of Europe, and lower than all published rates in the United States and Australia. Owing to the inability of the registry to account for tumor multiplicity, the actual annual number of all NMSC lesions in this population is likely much higher.

40-year trends in skin cancer in British Columbia, Canada, 1973 to 2003

BACKGROUND

Skin cancer is common in North America. Incidence rate trends are potentially important in the assessment of the effects of measures to increase sun awareness in the population as well as measures to reduce sun damage.

OBJECTIVE

To determine the incidence of basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and cutaneous malignant melanoma (CMM) in a geographically defined Canadian population over a 40-year period.

METHODS

Data were obtained from the BC Cancer Registry for the calendar years 1973, 1983, 1993, and 2003.

RESULTS

Age-standardized incidence rates increased significantly from 1973 to 2003 for BCC, SCC, and CMM.

LIMITATIONS

The ethnic makeup of British Columbia has changed over time, and a novel method of accounting for the effect of this on skin cancer rates is presented.

CONCLUSION

The incidence rate for skin cancers continued to rise in British Columbia, but there appears to have been a decline in the incidence of CMM and BCC in the youngest cohorts.

Cancer risk in multiple sclerosis: findings from British Columbia, Canada

Findings regarding cancer risk in people with multiple sclerosis have been inconsistent and few studies have explored the possibility of diagnostic neglect. The influence of a relapsing-onset versus primary progressive course on cancer risk is unknown. We examined cancer risk and tumour size at diagnosis in a cohort of patients with multiple sclerosis compared to the general population and we explored the influence of disease course. Clinical data of patients with multiple sclerosis residing in British Columbia, Canada who visited a British Columbia multiple sclerosis clinic from 1980 to 2004 were linked to provincial cancer registry, vital statistics and health registration data. Patients were followed for incident cancers between onset of multiple sclerosis, and the earlier of emigration, death or study end (31 December 2007). Cancer incidence was compared with that in the age-, sex- and calendar year-matched population of British Columbia. Tumour size at diagnosis of breast, prostate, colorectal and lung cancers were compared with population controls, matched for cancer site, sex, age and calendar year at cancer diagnosis, using the stratified Wilcoxon test. There were 6820 patients included, with 110 666 person-years of follow-up. The standardized incidence ratio for all cancers was 0.86 (95% confidence interval: 0.78-0.94). Colorectal cancer risk was also significantly reduced (standardized incidence ratio: 0.56; 95% confidence interval: 0.37-0.81). Risk reductions were similar by sex and for relapsing-onset and primary progressive multiple sclerosis. Tumour size was larger than expected in the cohort (P = 0.04). Overall cancer risk was lower in patients with multiple sclerosis than in the age-, sex- and calendar year matched general population. The larger tumour sizes at cancer diagnosis suggested diagnostic neglect; this could have major implications for the health, well-being and longevity of people with multiple sclerosis.