The Association of Smoking and Socioeconomic Status on Cutaneous Melanoma

A Population-based, Data-linkage, Case-control Study

J.A.G. Gibson; T.D. Dobbs; R. Griffiths; J. Song; A. Akbari; S. Whitaker; A. Watkins; S.M. Langan; H.A. Hutchings; R.A. Lyons; I.S. Whitaker

Disclosures

The British Journal of Dermatology. 2020;182(5):1136-1147. 

In This Article

Results

Between 2000 and 2015, 9636 patients were diagnosed with melanoma in Wales.

Stage One: Case–Control Study

Patient demographics and clinical characteristics of the cases and controls are outlined in Table 2. Data relating to smoking status were available for 7124 (73·9%) of the melanoma cohort; 1460 current smokers (20·5%), 3065 (43·0%) ex-smokers and 2599 (36·5%) nonsmokers.

Smoking. After adjusting for sex, age and socioeconomic status, current smokers had 30% reduced odds for developing melanoma compared with nonsmokers, (OR 0·70, 95% CI 0·65–0·76) (Table 3). There was no association between being an ex-smoker or nonsmokers and melanoma (OR 1·05, 95% CI 0·98–1·12).

Socioeconomic Status. We observed an inverse relationship between socioeconomic status and melanoma, whereby patients from higher socioeconomic WIMD quintiles were more likely to develop melanoma. Those in the highest socioeconomic quintile (WIMD 5) were 1·58 times more likely to develop melanoma as opposed to the lowest (HR 1·58, 95% CI 1·44–1·73) (Table 3).

Stage Two: Survival Analysis of the Melanoma Cohort

Demographic Data. Table 4 displays the demographics of the melanoma cohort. The median age at diagnosis was higher in nonsmokers (66·7 years) and ex-smokers (64·5 years) than in current smokers (62·4 years). Socioeconomic status had significant variation among groups, with the current and ex-smokers being more likely to have lower socioeconomic status WIMD quintiles. Stage at diagnosis was not significantly different between smoking groups or socioeconomic status. No differences between the mean Charlson Comorbidity Index scores were noted between the smoking groups or between WIMD quintiles (Table 4).

Mortality. A total of 3103 (32·2%) patients with melanoma died during the study period. Of these, 1688 (54·4%) died from melanoma (melanoma listed as the primary cause of death on their death certificate) and 1415 (45·6%) deaths were unrelated to melanoma. For patients who died from any cause, median time to death was 2·36 years. For patients who died of melanoma, median time to death was 1·73 years.

Univariate Survival Analysis. Median follow-up duration of the entire cohort was 5·22 years (range: 0–18 years). Overall survival rates were different across the three smoking status groups, with ex-smokers having lower survival than current or nonsmokers (P ≤ 0·001). In contrast, no difference was observed across the three smoking status groups for disease-specific mortality (P = 0·88). Overall and melanoma-specific survival rates by smoking status are shown in Table S3 (see Supporting Information). Figures 2 and 3 shows the overall and disease-specific survival curves, respectively, by smoking status. Overall and disease-specific survival rates differed significantly across the WIMD quintiles (Table S4; see Supporting Information). Figures 4 and 5 show the overall and disease-specific survival curves, respectively, by socioeconomic status.

Figure 2.

Overall survival by smoking status.

Figure 3.

Disease–specific survival rates by smoking status.

Figure 4.

Overall survival by socioeconomic status. WIMD, Welsh Index of Multiple Deprivation.

Figure 5.

Disease–specific survival by socioeconomic status. WIMD, Welsh Index of Multiple Deprivation.

Multivariable Survival Analysis. After adjusting for the aforementioned factors, current smokers had an increased overall risk of death as compared with nonsmokers (HR 1·30, 95% CI 1·09–1·55) (Table 5). There was no association between current smoking and melanoma-specific mortality. Increased odds of survival was noted in the highest socioeconomic WIMD quintile (quintile 5), compared with the lowest (quintile 1) (HR 0·67, 95% CI 0·56–0·81). A similar trend was observed with disease-specific mortality (HR 0·69, 95% CI 0·53–0·90).

Men had an increased risk of overall and melanoma-specific death compared with women (overall HR 1·28, 95% CI 1·13–1·46; disease-specific HR 1·35, 95% CI 1·12–1·62). Tumour location was an important predictor of survival. For overall survival, tumours located on the upper limb were associated with increased survival compared with those on the trunk (HR 0·73, 95% CI 0·61–0·88), with no association between tumours on the head and neck, and lower limbs. With regards to melanoma-specific mortality, tumours located on the trunk were associated with an increased risk of mortality when compared with those in other locations.

Age was associated with a small increased risk of overall and melanoma-specific mortality (overall HR 1·06, 95% CI 1·05–1·06, P ≤ 0·001; disease-specific HR 1·02, 95% CI 1·01–1·03, P ≤ 0·001). Melanoma morphology was not associated with overall survival, however, melanoma-specific mortality was increased in those with nodular melanoma (HR 1·23, 95% CI 0·98–1·54) whereas those with lentigo maligna melanoma had improved survival (HR 0·43, 95% CI 0·21–0·89). The Charlson Comorbidity Index was not association with overall (HR 1·01, 95% CI 1·00–1·02) or melanoma-specific survival (HR 1·00, 95% CI 0·99–1·02).

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