Comparison of different pathways to the diagnosis of melanoma in Waikato

Abstract

Background: In New Zealand, there have been increasing concerns about having the highest incidence and mortality rates of melanoma amongst the world with no signs of a decrease. Therefore, the factors that are associated with the diagnosis of melanoma in New Zealand need to be identified. Aim: The ultimate aim was to assess the impact of different patient pathways to the diagnosis of melanoma in Waikato, New Zealand. The efficiency of diagnosis as indicated by the depth (Breslow’s thickness) and diagnostic type of melanomas (invasive or in-situ) has been evaluated. This thesis also aimed to evaluate an aspect of the effectiveness of MoleMap, a recently established diagnostic and surveillance program, in terms of the results of biopsies following MoleMap recommendation. Methods: Two interrelated studies were conducted separately. The retrospective observational study analysed all invasive and in-situ melanomas diagnosed histopathologically in Waikato during 2010-2012 using descriptive statistics, multiple logistic and linear regression for categorical and continuous variables respectively. The cohort study assessed compliance rate and clinical outcomes of a cohort of MoleMap clients who were examined in Waikato during 2010-2012 and recommended for excision of lesions suspicious of melanoma. Results: In Waikato during 2010-2012, invasive melanoma was less likely to be lentigo maligna melanoma or unspecified melanoma and more likely to be excised in public specialist care compared with in-situ melanoma. Melanoma thickness was significantly greater in older patients, with lesions located on the lower limb and with nodular or unspecified melanoma. Eighty two percent of MoleMap clients in Waikato region during 2010-2012 had a biopsy or excision after receiving ‘very strong’ excision recommendation from MoleMap dermatologists. Of total biopsied lesions, 49 percent were malignant lesions. Melanoma accounted for 9 percent of total lesions biopsied and 19 percent of lesions that had ‘very strong’ recommendation for excision. Only 1 melanoma was given weak excision recommendation from MoleMap dermatologists. Conculsion: Depth of invasion was associated mainly with the biological factors but not healthcare or social factors. MoleMap recommendations have high compliance rates and clinical accuracy in diagnosis of suspicious skin lesion. A further investigation is required to investigate appropriate measures of diagnostic interval for melanoma. More thorough assessment on VLC and MoleMap services is needed to examine the benefits of specialised assessment services.