Melanoma: Differences between Asian and Caucasian Patients


2012-02-14 | Admin MKKI

Original Article

Melanoma: Differences between Asian and Caucasian Patients
Haur Yueh Lee,MBBS, MRCP (UK), FAMS, Wen Yee Chay,MBBS, MRCP (UK), Mark BY Tang,MBBS, MRCP (UK), FAMS, Martin TW Chio,MB Ch B (Bristol), MRCP (UK), FAMS, Suat Hoon Tan,MMed (Int Med), DipRCPath (DMT), FAMS

Abstract
Introduction: Cutaneous melanoma is rare in Asia and the clinical presentation and outcome of melanoma is not well described in Southeast Asia. In addition, it is unclear if ethnic variations exist between the various racial groups. The objective of our study is to present the clinical characteristics of melanoma in Singapore and to highlight ethnical differences between Asians and Caucasians living in Singapore. Materials and Methods: Data were retrospectively collected from 48 patients with histological confirmation of melanoma who were seen in both the National Skin Centre and National Cancer Centre of Singapore. Results: Acral lentiginous melanoma (ALM) was the most common subtype of melanoma in Singapore (50%). A higher proportion of non-ALM subtypes of melanoma compared to ALM were diagnosed at stage 1 (48% vs. 25%). The delay in diagnosis of ALM was 27 months compared to 12 months in other subtypes. Compared to Caucasians, there was a trend towards Asian patients being older, having a higher proportion of ALM and a longer delay to diagnosis. Conclusion: Geographical and ethnic variations in the clinical presentation of melanoma exist. Specially adapted programmes are necessary to increase awareness of the different clinical presentation of melanoma in Asia and to encourage examination of the palms and soles in order to reduce the delay in diagnosis.

Ann Acad Med Singapore 2012;41:17-20
Key words: Acral, Pigmented lesions, Singapore, Skin cancer

Introduction
Cutaneous melanoma is the most common cause of mortality amongst skin cancer in Caucasian populations and incidence rates per 100,000 patient years vary between 21.9 in the United States to 55.9 in Australian males. In contrast, the incidence of melanoma in Asia is significantly lower with incidence rates of 0.2 to 0.5 per 100,000 patient years. In addition, the most common histological subtype in Asians is acral lentiginous melanoma (ALM) which accounts for approximately 50% of all cases, compared to Caucasians populations where it constitutes only 2% to 3% of all cases.

Singapore is a multi-ethnic country, located in equatorial Southeast Asia with a resident population of 3.8 million consisting of Chinese (77%), Malays (14%), Indians(8%) and 1% of other races, as well as a non-resident population of 1.2 million of various ethnicities. There have been few reports on the features of melanoma in Asia, particularly in Southeast Asia. Our current study aims to clarify the clinical presentation of cutaneous melanoma in Singapore and to evaluate if ethnic variations exist.

Materials and Methods
All cases of cutaneous melanoma seen at both the National Skin Centre and the National Cancer Centre (which are tertiary referral centres for skin diseases and cancers respectively) between 1998 and 2008 were retrospectively analysed. Patients with a coded diagnosis of melanoma were obtained from the institution’s computer database. Only cases with histological diagnosis of melanoma were included in this study. The medical records and histological reports were systematically reviewed and information pertaining to demographics, clinical presentation, histological features, other clinical investigations, treatment modalities and follow-up data were recorded. Staging of the melanoma was carried out according to the American Joint Committee on Cancer staging system (2002).

The time-interval to diagnosis was defined as the duration between the onset of the new pigmented lesion, change in an existing mole or previous normal surveillance and the diagnosis of melanoma.

To evaluate if histological subtypes and ethnicity influenced the presentation and outcome of disease, subgroup analysis of ALM versus non-ALM cases as well as Asian cases (consisting of both residents and non-residents) versus Caucasian cases were performed.

Statistical analyses were performed using Statplus for Macintosh. In the analysis of cases, Fisher’s exact test was utilised for qualitative variables and the Student’s T test for quantitative variables. P values were double sided with P <0.05 taken for statistical significance. The small sample size precluded further multi-variable analyses.

Results
From the initial database of patients coded for melanoma, 17 cases were excluded (benign histology n = 13, unavailable histological reports/specimens n = 4) and a total of 48 cases were eventually included in the study. The clinical and pathological features are summarised in Table 1. The mean age of the patients was 60 years with range between 29 and 95 years). There were 27 males and 21 females with a male to female ratio of 1.3 : 1. Thirty-eight cases were diagnosed in the resident ethnic population (37 Chinese and 1 Indian) and the remaining 10 cases were diagnosed in the non-residential expatriate population (consisting of 3 Asians and 7 Caucasians). Distribution of the lesions include the palms and soles (n = 21), limbs (n = 10), trunk (n = 9), head and neck (n = 4) and nails (n = 4).

ALM was the most common histological subtype (Fig. 1), accounting for 50% of all cases (n = 24), followed by superficial spreading melanoma 37.5% (n = 18) and nodular melanoma 12.5% (n = 6). The mean Breslow’s tumour thickness was 2.3 ± 2.0 mm. When stratified according to histological subtypes, the mean thickness of ALM subtypes was 2.5 ± 2.3 mm in comparison with non-ALM subtypes which was 1.7 ± 2.0 mm (P = 0.30). Thirty-six percent of patients presented with early stage melanoma (Stage I), when stratified according to histological subtypes, 48% of non-ALM were diagnosed at stage I compared to 25% of ALM (P = 0.07) (Table 2).

Surgical excision was the primary treatment modality in all patients. Ten patients (21%) who initially presented with stage I-III disease recurred after primary excision (Stage I: n = 3, Stage II: n = 5, Stage III: n = 2). Mean duration to tumour recurrence following initial diagnosis of melanoma was 25 months (range, 4 to 60 months).

The mean duration to diagnosis of melanoma for the total group of melanoma was 20 months (range, 1 to 120 months). The mean duration prior to diagnosis of ALM was 27 ± 33 months compared to 12 ± 14 months in other subtypes (P = 0.05). When stratified against ethnicity, the delay was 22 ± 28 months versus 7 ± 5 months for Asians versus Caucasians (P = 0.09) (Table 3).

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