. Author manuscript; available in PMC: 2021 Nov 2.

Published in final edited form as: Clin Breast Cancer. 2021 Mar 16;21(2):143–152. doi: 10.1016/j.clbc.2021.03.007

Table 1. Published trials combining radiotherapy and immune checkpoint blockade in metastatic breast cancer.

AE, adverse event; AST, aspartate aminotransferase; CI, confidence interval; CR, complete response; HR+/HER2−, hormone receptor-positive/human epidermal growth factor receptor 2-negative; mBC, metastatic breast cancer; mTNBC, metastatic triple negative breast cancer; ORR, objective response rate; PR, partial response; RT, radiation therapy; WBRT, whole brain radiotherapy.

Trial	Phase	N	Tumor Type	Intervention	ORR	Toxicity
McArthur et. al.⁴⁸	-	20	HER2+ or HER2− mBC with brain metastases	Concurrent WBRT and Tremelimumab	12-week non-CNS DCR 10% in HER2− mBC 33% in HER2+ mBC	15 grade 3 AE (fatigue, diarrhea, colitis), 0 grade 4 or 5 AE
Voorwerk et. al. (TONIC)⁴⁹	2	12	mTNBC	Sequential RT (24 Gy in 3 fractions) and Atezolizumab	12% (1 PR) 95% CI, 0.2-38.5%	3 grade 3 AE, 0 grade 4 AE, 1 grade 5 AE (nivolumab-related)
Ho et. al.⁵⁴	2	17	mTNBC	Concurrent RT (24 Gy in 3 fractions) and Pembrolizumab	17.6% (3 CR) 95% CI, 4.7-44.2%	3 grade 3 AE (fatigue, infection, lymphopenia), 1 grade 4 AE (lymphopenia), 0 grade 5 AE
Barroso-Sousa et. al.⁵⁵	2	8	HR+/HER2− mBC	Pembrolizumab prior (2-7 days) to RT (20 Gy in 5 fractions)	0%	1 grade 3 AE (AST elevation), 0 grade 4 or 5 AE