Yttrium-90 radioembolization for unresectable hepatic metastases of breast cancer: A systematic review

BACKGROUND: Liver metastases secondary to breast cancer are associated with unfavourable prognosis. Radioembolization with ytrrium-90 is an emerging option for management of liver metastases of breast cancer when other systemic therapies have failed to achieve disease control. However, unlike the case of other liver tumours (colorectal/melanoma metastases/cholangiocarcinoma), its role in the management of breast liver metastases is yet to be elucidated. AIM: The aims of this systematic review were to (1) assess the effect of radioembolization with yttrium-90 on tumour response; and (2) to estimate patient survival post radioembolization. METHODS: The review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. A systematic literature search was performed using the PubMed and EMBASE databases from January 2007 to December 2018. The initial search yielded 265 reports which were potentially suitable for inclusion in this review. Studies published in English reporting at least one outcome of interest were considered to be suitable for inclusion. Conference abstracts; case reports, animal studies and reports not published in English were excluded from this review. Data was retrieved from each individual report on the name of primary author, year of publication, patient demographics, type of microspheres used, radiation dose delivered to tumour, duration of follow-up, disease control rate (%), tumour response, and overall patient survival. RESULTS: The final number of studies which met the inclusion criteria was 12 involving 452 patients. There were no randomized controlled trials identified after the literature search. The age of the patients included in this review ranged from 52 to 61 years. The duration of the follow up period post-radioembolization ranged from 6 to 15.7 mo. The total number of patients with breast metastases not confined to the liver was 236 (52.2%). Cumulative analysis revealed that radioembolization with yttrium-90 conferred tumour control rate in 81% of patients. Overall survival post-radioembolization ranged from 3.6 to 20.9 mo with an estimated mean survival of 11.3 mo. CONCLUSION: Radioembolization with ytrrium-90 appears to confer control of tumour growth rate in most patients, however its effect on patient survival need to be elucidated further. Furthermore, quality evidence in the form of randomized trials is needed in order to assess the effect of radioembolization in more depth.