Brain metastases in patients with cancer of an unknown primary tumour in the Netherlands, A status update.

Abstract

Background: Cancers of unknown primary (CUP) are metastatic tumours of which the site of origin cannot be identified. Guidelines regarding care for CUP patients are limitedly available, particularly for those who present with (synchronous) single or multiple brain metastases (BM-CUP). Knowledge on the incidence, approach and survival is scarce but is urgently needed to reveal current challenges and points for improvement in care for patients with BM-CUP. Methods: We performed a literature search on CUP patients and brain metastases in PubMed using the terms “CUP” OR “primary unknown tumour” AND “brain metastases”, focusing on reports published between 2017 and 2021. Variables considered were age, gender, presence and localisation of brain metastases, and prognosis. Also, information from the Dutch National Cancer Registry (NCR) was collected to review current practices in The Netherlands. Results: Ten international publications were identified on BM-CUP via the literature search, indicating a shortage of research on this subject. From the NCR, clinical metadata could be retrieved for a total of 1,419 BM-CUP patients. An increase in the proportion of BM-CUP patients from 8.1% to 10.1% was observed between 2009 and 2018. Incidence was slightly higher in men (54%). Cancer histology was not determined in most cases (42.7%). Presentation with multiple brain lesions was slightly more prevalent (52.9%). Among cases with known localization, most lesions were located in supratentorial areas (24.7%). Statistically significant associations were found for gender, age, and tumour histology in relation to BM-CUP incidence, and for age, histology, and tumour localisation in relation to survival (p <0.01). Discussion: Our search showed how little literature is currently available on BM-CUP. Our analyses of BM-CUP in The Netherlands showed significant associations in relation to incidence and survival. This research aims to contribute to better knowledge on the current challenges in the care for patients with BM-CUP. This should aid improvement of the diagnostic approach, clinical decision making, and quality of life for patients with BM from CUP.