Dr Kathleen Morrisroe

Australia has the highest reported prevalence of systemic sclerosis (SSc) worldwide (233/million cases in 1999). SSc, an autoimmune disease characterised by vasculopathy and fibrosis, is arguably the most devastating of the rheumatological diseases, with a potential to irreparably damage multiple organ systems and shorten life expectancy by an average of two decades. Until recently, the majority of research has focused on the leading causes of SSc-related death, namely pulmonary arterial hypertension and interstitial lung disease. With the emergence of improved treatment and reduced mortality of these manifestations, interest is shifting to the major cause of non SSc-related death, namely cancer.

My research project proposed to quantify the true ‘burden’ of cancer in SSc, including its epidemiology, health service utilisation and impact on health-related quality of life (HRQoL), which had not previously been reported.

Through a data linkage methodology, my project specifically set out to (i) quantify the incidence and prevalence of cancer in SSc; (ii) identify clinical risk factors associated with the development of cancer in SSc, such as immunosuppression and individual organ involvement; (iii) quantify direct healthcare costs associated with cancer in SSc by hospital, emergency department and ambulatory care utilisation and associated cost in SSc patients with cancer; and (iv) quantify health related quality of life in SSc patients.

Our work confirmed that the presence of systemic sclerosis carries an over a two-fold increased risk of developing cancer compared with the background Australian population (standardised incidence ratio (SIR) 2.15 (95% confidence interval (CI) 1.84-2.49), particularly for cancer diagnosed within 5 years of SSc disease onset. Cancer was diagnosed in 14.2% of our cohort, with 43 individuals having more than one cancer type. Specific cancer types with a higher incidence than the background population included breast cancer, lung cancer and melanoma. Additionally, SSc patients with cancer had a higher all-cause mortality than the Australian population, over three fold higher [standardised mortality rate (SMR) 3.13 (95%CI 2.39-4.02)] and higher than SSc patients without cancer [SMR 2.19 (95%CI 1.87-2.54)]. In those with cancer, the primary cause of death was non-SSc related in 58.1%, most commonly due to their cancer (77.1%), followed by ischemic heart disease (5.7%) and sepsis (5.7%). In terms of healthcare utilisation, cancer patients were admitted to hospital more frequently and utilized more ambulatory care services then those without cancer but there was no difference in the frequency of emergency department presentations. SSc patients with cancer compared to those without cancer had an increased healthcare cost with an annual excess healthcare cost per patient of AUD$1,496 (p<0.001). Furthermore, our SSc cohort reported lower health related quality of life than the general population. Cancer patients reported an even lower HRQoL than those without cancer (53.5 vs 38.7, p<0.001).

Our results provide comprehensive cancer data that are essential for designing SSc-specific cancer screening guidelines and for allocation of resources to improve patient care in this devastating disease.

As a clinical researcher I will continue with my research in the field of SSc and hope to share our findings with the wider international community.