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. 2022 Aug 1;5(8):e2225424.
doi: 10.1001/jamanetworkopen.2022.25424.

Analysis of Rates of Brain Metastases and Association With Breast Cancer Subtypes in Ontario, Canada

Xin Ye Wang  1 , Michael N Rosen  2 , Rania Chehade  1   3 , Arjun Sahgal  4 , Sunit Das  1   5 , Ellen Warner  3 , Refik Saskin  6   7 , Bo Zhang  6   7 , Hany Soliman  4 , Kelvin K W Chan  1   3 , Katarzyna J Jerzak  1   3
Affiliations

Analysis of Rates of Brain Metastases and Association With Breast Cancer Subtypes in Ontario, Canada

Xin Ye Wang et al. JAMA Netw Open. .

Abstract

Importance: Approximately 1 in 7 patients with metastatic breast cancer (MBC) will receive radiotherapy for brain metastases (BRM). Significant differences in cumulative incidence of BRM by breast cancer subtype may inform future BRM screening protocols.

Objective: To describe cumulative incidence of BRM among patients with de novo MBC.

Design, setting, and participants: In this population-based cohort study, population health administrative databases in Ontario, Canada, held at the ICES were used to identify patients diagnosed with de novo MBC between 2009 and 2018. Given that a code for BRM does not exist within ICES, we analyzed the incidence of radiotherapy for BRM. The median (IQR) follow-up was 19.3 (6.2-39.5) months. A total of 100 747 patients with a new diagnosis of breast cancer between January 2009 and December 2018 were identified. Of these patients, 17 955 were excluded because they had previous or subsequent malignant neoplasms, 583 were excluded because they were younger than 18 years, 974 were excluded because there was an invalid Ontario Health Insurance Plan number or a date of death on or before the index date. Among 81 235 remaining patients, 3916 were identified as having de novo MBC.

Exposures: Treatment with radiotherapy for breast cancer BRM.

Main outcomes and measures: Cumulative incidence of radiotherapy for BRM accounting for the competing risk of death, and time from MBC diagnosis to brain radiotherapy. Kaplan-Meier analyses were performed for time-to-event end points. Logistic regression was used to account for confounding variables.

Results: Among 3916 patients with MBC, 1215 (31.0%) had HR-positive/ERBB2 (formerly HER2)-negative cancer, 310 (7.9%) had ERBB2-positive/HR-positive cancer, 200 (5.1%) had ERBB2-positive/HR-negative cancer, 258 (6.6%) had TNBC, and the remaining 1933 patients (49.4%) had an unknown breast cancer subtype. The median (IQR) age at diagnosis was 63 (52-75). A total of 549 (14.0%) underwent stereotactic radiosurgery or whole brain radiotherapy for breast cancer BRM. Cumulative incidence of BRM was higher among patients with ERBB2-positive/HR-negative breast cancer (34.7%), ERBB2-positive/HR-positive breast cancer (28.1%), and triple-negative breast cancer (21.9%) compared to those with HR-positive/ERBB2-negative breast cancer (12.1%). The median (IQR) time from MBC diagnosis to brain radiotherapy ranged from 7.5 (2.3-17.4) months for patients with TNBC to 19.8 (12.2-35.1) months for those with ERBB2-positive/HR-positive breast cancer.

Conclusions and relevance: Incidence and time to development of BRM vary significantly by breast cancer subtype. A better understanding of the biology of intracranial metastatic disease may help inform potential screening programs or preventative interventions.

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Conflict of interest statement

Conflict of Interest Disclosures: Dr Sahgal reported receiving grants from Elekta and Varian outside the submitted work. Dr Sahgal reported being a consultant for Varian, Elekta, BrainLAB, Merck, Abbvie, and Roche, being a board member of the International Stereotactic Radiosurgery Society and co-chair of AO Spine Knowledge Forum Tumor, serving on the advisory board for VieCure, and participating in educational seminars from AstraZeneca, Elekta, Varian, BrainLAB, Medtronic Kyphon, and Accuray, and receiving personal fees from Elekta, Varian, and BrainLAB outside the submitted work. Dr Das reported serving on the advisory board for Subcortical Surgery Group and XPan, receiving grants from Alkermes, serving as a speaker for the Congress of Neurological Surgeons and the American Association of Neurological Surgeons, and receiving personal fees from Ontario Health and Oxford University Press outside the submitted work. Dr Zhang reported receiving grants from Eli Lilly during the conduct of the study. Dr Jerzak reported receiving grants from Eli Lilly during the conduct of the study and receiving grants from AstraZeneca and Seagen and personal fees from Amgen, AstraZeneca, Apobiologix, Knight Therapeutics, Merck, Myriad Genetics, F. Hoffman-La Roche, Purdue Pharma, Pfizer, Novartis, Seagen, Gilead Sciences, Genomic Health/Exact Sciences, Esai, Eli Lilly, and Viatris outside the submitted work. No other disclosures were reported.

Figures

Figure.
Figure.. Cumulative Incidence of Brain Metastases and Cumulative Incidence of Death Among Patients With Metastatic Breast Cancer by Breast Cancer Subtype
Cumulative incidence of brain metastases and survival among patients with metastatic breast cancer by breast cancer subtype. HR indicates hormone receptor; TNBC, triple-negative breast cancer.
See this image and copyright information in PMC

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