Paudel, Y. R.

Estimating the Incidence of Brain Metastases at Diagnosis and Over the Lifetime of Canadian Cancer Patients diagnosed between 2010 and 2015
Paudel, Y.R., Walker, E., Smith, T., Yuan, Y., Nichol, A.M., & Davis, F.G.

The incidence of brain metastases among Canadian cancer patients is unknown. The goal of the current analysis was to estimate the frequency of brain metastases among Canadian cancer patients diagnosed between 2010-2015 at the time of the primary cancer diagnosis and over the lifetime of patients with primary cancers known to metastasize to the brain.

We used data on the presence of BM concurrent with the primary cancer diagnosis from 2010-2015 obtained from the Canadian Cancer Registry (CCR). Site-specific incidence proportions were estimated as measures of BM frequency at the time of the primary cancer diagnosis. BM incidence proportions from provinces with ≥90% complete data were applied to the population distribution in provinces/territories with incomplete data to estimate expected numbers at diagnosis of the primary cancer. Incidence proportions for BM over the life-course of patients were identified from the literature and used to estimate expected frequencies in the Canadian cancer population from 2010-2015.

We identified 1,105,930 cancer cases in the CCR from 2010-2015. The site-specific IPs of BM at diagnosis were: lung (9.64%;95% CI: 9.3-10.0%), esophageal (2.0%;95%CI:1.5-2.7%), kidney (1.25%;95%CI:1.0-1.5%), skin melanoma (1.07%;95%CI:0.9-1.3%), colorectal (0.28%;95%CI:0.2-0.3%), breast (0.24%;95%CI:0.2-0.3%), and other sites (0.1%;95% CI: 0.09-0.11). The annual estimated average number of patients with BMs at diagnosis from all cancer sites was approximately 2,850 and was highest for lung cancer(2,400). Using clinical and population data from the literature, we estimate that over 7,850 lifetime BM cases occur annually for cancer sites known to develop BM.

This analysis highlighted that BM are predominantly associated with 6 primary tumours. The highest incidence proportion of BM at diagnosis was among patients with lung cancer, specifically Small Cell lung cancer. With changes in patterns of primary cancer incidence, population dynamics, emerging treatment methods and access to care, population level BM incidence in Canada needs to be regularly monitored.