Descriptive epidemiological study of rare, less common and common cancers in Western Australia.

Background: There are no epidemiological studies describing rare cancers in Western Australia (WA). We aimed to fill this gap by estimating the incidence and five-year survival of rare, less common and common cancers in WA, based on definitions for rarity used by the Australian Institute of Health and Welfare and cancer groupings from the project on Surveillance of Rare Cancers in Europe (RARECARE). This research will enable policy- and decision-makers to better understand the size and nature of the public health problem presented by rare cancers in WA. It is anticipated that this study will inform improved health service design and delivery for all WA cancer patients, but particularly those with rare and less common cancers.

Methods: We estimated incidence and five-year survival rates of rare, less common and common cancers in WA using data sourced from the WA Cancer Registry for the 2013-2017 period. Cancers were defined as rare (< 6), less common (6-12), or common (> 12) based on their crude incidence rate per 100,000 people per year.

Results: Rare cancers make up 21.5% of all cancer diagnoses in WA, with a significantly poorer five-year survival of 58.2% (95% confidence interval (CI) 57.3-59.1%), compared to patients diagnosed with a common cancer, whose five-year survival was 87.8% (95% CI 87.3-88.3%). Survival for less common cancers was significantly poorer than both rare and common cancers, at 48.1% (95% CI 47.3-49.0%). Together, rare and less common cancers represent 48.4% of all cancer diagnoses in WA.

Conclusions: While rare cancers are individually scarce, collectively over one in five cancer patients in WA are diagnosed with a rare cancer. These patients experience significantly worse prognoses compared to patients with common cancers.