Epidemiological trends in dermal sarcoma in Australia

Background: Sarcomas comprise a heterogenous group of malignant tumours of mesenchymal origin and can arise in the skin. Definitive management of skin sarcoma usually entails surgical resection with wide margins, often requiring reconstruction. The incidence and demographics of these neoplasms in Australia are poorly understood. Method: Incidence, gender and age distribution data for skin sarcomas for the period 1982–2009 were obtained from the Australian Cancer Database (ACD). Morphology and topographical region coding via the International Classification of Diseases for Oncology third edition (ICD-O-3)1 were used to identify the data. Results: A total of 5453 cases of skin sarcoma in the Australian population were identified over the 28-year period. Anatomically, 1610 cases (29%) occurred on the limbs, 1416 (26%) on the head and neck area, 957 (18%) on the trunk and 1470 (27%) had an unspecified skin origin. Overall incidence was 2.09 per 100,000 population. Males were more commonly affected (70%), most commonly in the 30–49 years and 70+ years age groups. The most common pathological subtypes were fibromatous sarcoma (including dermatofibrosarcoma protuberans), Kaposi’s sarcoma and pleomorphic dermal sarcoma. Conclusion: The Australian Cancer Database data used to describe the pattern and epidemiological trends for skin sarcoma in Australia demonstrated variation from international trends and highlight the need for further research into the aetiology of these

These changes should improve future data collection but it will take time to see the effects due to the low incidence/rarity of dermal sarcomas. This paper aims to report epidemiological information about dermal sarcomas in Australia, using Australian Cancer Database (ACD) data, and compare this with international trends.

Methods
A retrospective analysis was conducted on data obtained from the ACD for the years 1982-2009 for dermal sarcomas. The ACD requires mandatory reporting of every episode of malignancy that generates a histopathology report, for all of the Australian population. 35 The data cover approximately 97 per cent of the population, as statistics for the Australian Capital Territory and the Northern Territory were not available. 35 The ICD-O-3 coding system 1 was used by the ACD to identify sarcomas originating in the skin and which regions of the body they affected (codes C44.0-9). Initial analyses examined gender, age, year and pathological subtype for trends. Incidence per 100,000 population was calculated using Australian Bureau of Statistics (ABS) historical population numbers and dividing the observed frequency by the population then multiplying by 100,000. 36 An average incidence across the length of the study was also calculated. These data were further categorised by pathological subtypes, anatomical location and trends over time.

Results
The data collected from the ACD reported a total of 5453 cases of dermal sarcoma in the Australian population over a 28-year period. Fibromatous sarcoma, which includes dermatofibrosarcoma (DFSP), was the most common dermal sarcoma subtype, followed by Kaposi's sarcoma (Figure 1).
During the period of the study there was a steady increase in the number of cases of myomatous sarcoma, which includes leiomyosarcoma and pleomorphic dermal sarcoma, while Kaposi's sarcoma had the greatest frequency during the early 1990s before declining thereafter. Other forms of cutaneous sarcoma had stable incidence during the study period.
Overall, dermal sarcomas occurred more commonly in males (male:female=2.3:1). An increase in prevalence and incidence was observed during the study period, with males being particularly affected (Figure 2). The average incidence of dermal sarcomas across the study was 2.09 per 100,000.
The highest incidence of dermal sarcomas was

Discussion
This is the first study to describe the epidemiology of dermal sarcomas in Australia and is one of the largest series in the world. The increased incidence area. Kaposi's sarcoma had greatest incidence in the lower limbs in this Australian study while the trunk was more common in previous international studies. 29 The incidence of different pathological subtypes in this study contrasts with epidemiological trends from other countries. Kaposi's sarcoma is the most commonly reported type of cutaneous sarcoma globally, although this may be skewed by the inclusion of several geographic regions with particularly high rates of HIV. 30,31 In this Australian dataset, Kaposi's sarcoma was the second most common subtype and noted to be on the decline. This may be due to the relatively low prevalence of HIV in Australia, as well as access to antiviral therapies. 40 Fibromatous sarcoma is the most common type of dermal sarcoma overall in Australia and the second most common in all age groups in the US. 29 Fibromatous sarcoma appears to affect men and women equally and is observed in all age brackets but particularly in the 30-50 age group. This contrasts with pleomorphic dermal sarcoma, myomatous sarcoma and angiosarcoma, which are observed more frequently in those over 60 years of age. Our data demonstrated an increasing incidence of pleomorphic dermal sarcoma, particularly in elderly males, which was not evident in the US. 29 This study used ACD data, which requires compulsory registration of cancers and uses standardised coding information. As such, this study has a large number of cases and a high degree of data accuracy. However, there are limitations to these data. The data represent 97 per cent of the Australian population as data from the Australian Capital Territory and the Northern Territory were not available. The ethnic makeup of Australia changed significantly during the period of the study but unfortunately data relating to racial heritage were not accessed, limiting epidemiological analysis. Finally, as with most cancer registries, the ACD does not collect information pertaining to exposure to carcinogens or patient comorbidities and it was therefore not possible to include these in this study.

Conclusion
This is the first paper to describe the epidemiology of dermal sarcomas in the Australian population.
Compared with published data from Europe and North America, this study demonstrated variation in anatomical distribution and incidence in pleomorphic dermal sarcoma among elderly males. 29 These findings are in keeping with the hypothesis of a causal link between pleomorphic dermal sarcoma and UV radiation. 37 Further research to establish the epidemiology of dermal sarcomas in particular racial groups, and the role of genetics and aetiological agents, may lead to improved understanding of this disease. This in turn may lead to identification of potential preventive strategies and targeted treatments. This paper provides a foundation and reference point on which further research can be based and to ultimately improve outcomes for patients affected by dermal sarcoma.