Features associated with melanoma metastasis in Latvia.

Cutaneous melanoma (CM) is the most aggressive form of skin cancer, exhibits an increasing incidence worldwide and has a high potential to develop metastasis. The current study aimed to identify a set of parameters that may aid in predicting the probability and timing of the onset of CM metastasis. A retrospective analysis was performed using the archive data of 2,026 patients with CM that were treated at the Riga East University Hospital Latvian Oncology Centre, which is the largest oncological hospital in the country, between 1998 and 2015. A case-control study design was employed, where patients with metastasis (n=278) were used as the cases and patients without metastasis were used as the controls. The present study examined the associations between metastasis and potential risk factors and constructed multivariate models of features that predicted metastasis using stepwise regression. Time until metastasis was analyzed using negative binomial regression models. The results of the present study indicated an increase in the number of melanomas that developed metastases during 1998-2015. Tumor Breslow thickness was demonstrated to be significantly larger in patients with metastasis compared with those without (P=0.012). The presence of ulceration significantly increased the risk of metastases [odds ratio (OR), 1.66; 95% CI, 1.07-2.59; P=0.033]. The absence of pigment in melanoma tissues was indicated to lead to a greater likelihood of metastasis (OR, 2.14; 95% CI, 1.10-4.19; P=0.035). Shorter times from diagnosis until the onset of metastases were observed in older patients (incident rate ratio (IRR), 6.85; 95% CI, 2.43-19.30; P=2.78×10-4), and a borderline significant association was observed in those with ulcerated tumors (IRR, 1.33; 95% CI, 0.98-1.80; P=0.064). Therefore, the main features associated with the development of melanoma metastasis in Latvia were indicated to be tumor ulceration, absence of pigment and Breslow thickness.

Melanoma risk associated with MC1R gene variants in Latvia and the functional analysis of rare variants.

To evaluate the association of melanocortin 1 receptor gene (MC1R) variants with melanoma risk in a Latvian population, the MC1R gene was sequenced in 200 melanoma patients and 200 control persons. A functional study of previously uncharacterized, rare MC1R variants was also performed. In total, 26 different MC1R variants, including two novel variants Val165Ile and Val188Ile, were detected. The highest risk of melanoma was associated with the Arg151Cys variant (odds ratio (OR) 4.47, 95% confidence interval (CI) 2.19-9.14, P<0.001). A gene dosage effect was observed, with melanoma risk for carriers of two variants being twice (OR 3.98, 95% CI 2.15-7.38, P<0.001) that of carriers of one variant (OR 1.98, 95% CI 1.26-3.11, P=0.003). After stratification according to the pigmentation phenotype, the risk of melanoma remained in groups with otherwise protective phenotypes. Functional analyses of eight previously uncharacterized MC1R variants revealed that a subset of them is functionally relevant. Our results support the contribution of MC1R variants to a genetic predisposition to melanoma in Latvia.

Analysis of Latvian familial melanoma patients shows novel variants in the noncoding regions of CDKN2A and that the CDK4 mutation R24H is a founder mutation.

Hereditary cutaneous melanoma is associated with mutations in the high-risk CDKN2A gene in about 40% of melanoma-prone families. Mutations in the CDK4 gene are the cause in only a few pedigrees. In this study, we analyzed 20 Latvian familial melanoma probands and carried out a comprehensive analysis of CDKN2A including sequencing of its promoter/intronic regions and deletion screening. We also analyzed the critical second exon of the CDK4 gene. One novel intronic variant (IVS2+82C>T) of the CDKN2A gene and a small deletion (c.-20677_-20682delGTACGC) in its promoter region were found. Genotyping of the novel variants in larger melanoma and control groups indicated that the deletion increases the risk of melanoma (odds ratio=6.353, 95% confidence interval: 1.34-30.22, P=0.0168). The CDK4 gene analysis showed a Latvian melanoma family with the mutation R24H carried on the same haplotype as in two previously described Latvian CDK4-positive families. Our study suggests that the main risk gene in Latvian families with a strong family history of melanoma is CDK4 and that most of the other cases analyzed could be sporadic or associated with low-penetrance risk genes.

Prognostic factors and epidemiological characteristics of cutaneous and mucosal head and neck melanoma.

OBJECTIVE. To describe the prognostic factors and epidemiological characteristics of cutaneous and mucosal head and neck melanoma and to identify the variables associated with mortality from this disease. MATERIAL AND METHODS. Patients treated for head and neck melanoma in the Oncology Centre of Latvia, Riga during a 10-year period were identified. Records from 124 cases were analyzed in a descriptive, retrospective study. For each patient, information regarding age, sex, tumor anatomic site, as well as ulceration, histological tumor subtypes, Breslow thickness and Clark invasion level was viewed. Disease specific survival rates were calculated. The frequencies of all study variables and their 95% confidence intervals were determined. Kaplan-Meier survival curves were produced to illustrate the survival differences for each variable. RESULTS. The patients' mean age was 67.36 years. The study included 81 females (65.32%) and 43 males (34.67%). The prevalent anatomical site for cutaneous head and neck melanoma was the cheek - 49% (n=55) and the intraocular site for mucosal melanoma (61.5%). A high percentage of thick cutaneous melanoma was detected. In 53 cases (47.3%) out of 112 cutaneous melanoma the tumor ulceration was found. Nodular melanoma subtype was predominating (38%). The incidence of cutaneous melanoma has increased unequally whereas mucosal melanoma of the head and neck is an uncommon cancer and the incidence rates in Latvia during a ten year period are decreasing. CONCLUSION. Female sex, advanced age, facial skin, tumor thickness, nodular subtype and ulceration carried a relevant risk of poor prognosis.

Identification of a CDK4 R24H mutation-positive melanoma family by analysis of early-onset melanoma patients in Latvia.

We have analysed 47 early-onset (< or =40 years) Latvian melanoma patients for the involvement of the melanoma susceptibility loci CDKN2A and CDK4. We observed no disease-related mutations in CDKN2A, but one patient had a CDK4 R24H mutation and strong family history of melanoma. Haplotype analysis using microsatellite markers and single nucleotide polymorphisms showed that the Latvian haplotype is unique compared with that of other melanoma families with the R24H mutation. This finding supports the proposal that codon 24 is a mutational hotspot in the CDK4 gene.