Comparison of Keratinocyte Cancer Tumour and Defect Sizes Treated by Mohs Micrographic Surgery: Sydney Versus Outside Metropolitan Sydney.

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Australia and New Zealand face the world's highest skin cancer rates, with non-metropolitan regions bearing a greater burden. Mohs micrographic surgery (MMS) is the gold-standard treatment for keratinocyte cancers (KCs) due to high cure rates and tissue-sparing benefits. This study evaluates whether Outside Metropolitan Sydney (OMS) patients present with larger tumours and defects than Sydney Metropolitan Area (SMA) patients. This retrospective study examined MMS cases at The Skin Hospital in 2017. Patients were divided into Sydney Metropolitan Area (SMA) and Outside Metropolitan Sydney (OMS), with OMS sub-grouped into Non-Sydney Metropolitan (NSM) and Regional, Rural and Remote (RRR). Tumour and defect sizes were compared between OMS, SMA, and RRR and NSM, with additional exploratory analyses assessing surgical outcomes and tumour characteristics. Of 2073 patients undergoing MMS, 1870 basal cell carcinomas and 203 squamous cell carcinomas were included. Tumours and defects were significantly larger in OMS patients (median tumour size: 0.8 cm2, defect size: 2.1 cm2) compared to SMA patients (median tumour size: 0.7 cm2, defect size: 1.8 cm2). No correlation was found between distance travelled and tumour or defect size. SMA patients also had greater flap and primary closures than OMS. Subgroup analysis of RRR and NSM showed no significant difference in tumour or defect sizes. Patients from OMS presented with larger KCs, suggesting barriers to earlier access to specialised care. This highlights geographic disparities in skin cancer management outside major cities in Australia in the context of MMS, emphasising the need for improved access and dermatological workforce distribution.