OTHR-07. ESTIMATING INCIDENCE PROPORTION OF BRAIN METASTASES AT DIAGNOSIS AND LIFETIME INCIDENCE AMONG CANCER PATIENTS DIAGNOSED FROM 2010–2015 IN CANADA

INTRODUCTION: The incidence of brain metastases (BM) among Canadian cancer patients is unknown. We aimed to estimate the incidence proportion (IP) of BM at the time of all cancer diagnoses and during follow-up of cancer patients with the top six primary tumours that are most likely to metastasize to the brain. METHODS: Data on BM at diagnosis from 2010–2015 was obtained from the Canadian Cancer Registry (CCR). Site-specific IPs of BM was estimated for patients from provincial registries that achieved ≥90% complete data. These estimates were applied to the total number of newly diagnosed primary cancers to estimate total number of BM at diagnosis from 2010–2015 in Canada. To estimate the number of lifetime BM that arise from six selected primary cancers including lung, breast, skin melanoma, colorectal, kidney/renal pelvis and esophagus, we applied IP estimates reported in the literature. RESULTS: We identified 1,105,905 cancer cases in the CCR from 2010–2015, of which 519,950 (47%) were from the six primaries. The annual average number of patients with BMs at diagnosis from all cancer sites was approximately 2,800 and was highest for lung cancer(2,400).The site-specific IPs of BM at diagnosis were: lung (9.6%;95% CI: 9.3–10.0%), esophageal (2%;95%CI:1.5–2.7%), kidney/renal pelvis (1.3%;95%CI:1.0–1.5%), skin melanoma (1.1%;95%CI:0.9–1.3%), colorectal (0.3%;95%CI:0.2–0.3%), and breast (0.2%;95%CI:0.2–0.3%).Using clinical and population data from the literature, we estimated that nearly 7,400 lifetime BM cases occur annually for these six primaries. CONCLUSIONS: Each year in Canada, approximately 2,800 BMs from all primary cancers are found at the time of diagnosis and approximately 7,400 lifetime BM occur annually from the six selected primary tumours.