Survival in 31 670 patients with thin melanomas: a Swedish population-based study.

BACKGROUND: The incidence of cutaneous malignant melanoma (CMM) continues to increase in most countries worldwide and the majority are diagnosed with thin tumours (≤ 1 mm). OBJECTIVES: The aim of the present study was to investigate the melanoma-specific survival (MSS) as well as conditional MSS (CMSS) in patients with thin CMM in Sweden. PATIENTS AND METHODS: Clinical and histological parameters were obtained from the Swedish Melanoma Registry for patients diagnosed with thin CMM between 1990 and 2017. Patients were followed until the end of 2017. MSS as well as CMSS for different thickness groups were calculated using the Kaplan-Meier method and Cox regression analyses were used to calculate for survival differences between thickness groups. RESULTS: There were 31 670 patients included for final analyses. The overall 10- and 20-year MSS for thin CMMs was 97% [95% confidence interval (CI) 97-97] and 95% (95% CI 95-96), respectively. From 0·7 mm and above, MSS decreased significantly with increasing thickness level. All thickness groups had an increased survival over time. The lowest CMSS was confirmed for men with 1·0 mm in thickness but their 10-year CMSS increased steadily over time. Women had overall better MSS as well as CMSS than men. However, the relation between MSS and CMSS was similar for both sexes. CONCLUSIONS: MSS was confirmed as excellent for patients with thin CMMs in Sweden. Although we could show a decreased MSS for patients with 0·7 mm thickness and above, the long-term survival and, in addition, a very favourable CMSS for those patients do not support more extended follow-up programmes than the current recommendations in Sweden.

Prognostic instrument for survival outcome in melanoma patients: based on data from the population-based Swedish Melanoma Register.

BACKGROUND: Several major analyses have identified a consistent set of independent risk factors for cutaneous malignant melanoma (CMM). A few prognostic models have been presented but some are based on a limited number of patients and others are based on selected groups of patients referred to major institutions. No nationwide population-based prognostic instrument for survival of CMM has been presented. The Swedish Melanoma Register (SMR) database covers 99% of CMM diagnosed in Sweden and includes today >50,000 cases. OBJECTIVES: To create a prognostic instrument based on SMR data to give highly reliable risk profiles for patients diagnosed with localised CMM. METHODS: Clinicopathological data were linked to the cause of death registry for calculation of CMM-specific survival. A generalised gamma method was used to derive 1, 5 and 10year probabilities of death for each combination of patient and tumour data: age, sex, tumour site, tumour thickness, tumour ulceration, Clark's level of invasion and when applicable also outcome of sentinel node biopsy (SNB). RESULTS: Tumour thickness had the highest prognostic impact, explaining 77% of the model. Women had 30% lower risk of death because of CMM than men. Presence of ulceration nearly doubled the risk. If the patient had a positive SNB status the risk of death due to CMM increased three times versus a negative SNB status. CONCLUSION: This unique population-based prognostic model for primary CMM shows better survival than the American Joint Commission on Cancer prognostic model widely used. The reason is probably that the referral bias is eliminated in a population-based cohort.