Table 1.

ESR1 mutation frequency in primary or metastatic tumors, or ctDNA.

Reference	Sequencing Method	ESR1 Mutation Prevalence	Mutations Detected
Primary tumor
Toy et al.15	NGS	3.3% (6/183)	E380Q, V392I, L536R, Y537C, Y537N, D538G
Toy et al.12	Targeted sequencing	3.5% (11/313)	S329Y, G344D, E380Q, V418E, S463P, S432L, F461D, L466Q, V478L, N532K, V534E, L536H, L536P, L536R, Y537S, Y537N, Y537C, Y537D, D538G, E542G, A576D
Liang et al.31	ddPCR	3.4% (3/89)	Mutations not specified
Metastatic tumor
Toy et al.12	Targeted sequencing	14% (84/616)	S329Y, G344D, E380Q, V418E, S463P, S432L, F461D, L466Q, V478L, N532K, V534E, L536H, L536P, L536R, Y537S, Y537N, Y537C, Y537D, D538G, E542G, A576D
Toy et al.15	NGS	25% (9/36) and 11% (5/44)	S463P, V534E, L536R, Y537N, Y537S, D538G
Robinson et al.16	NGS	55% (6/11)	L536Q, Y537S, D538G
Takeshita et al.36	ddPCR	17% (6/35)	Y537C, Y537N, Y537S, D538G
ctDNA
Schiavon et al.26	ddPCR	14% (24/171) 4.1% (2/49) 22% (4/18)	L536R, Y537C, Y537N, Y537S, D538G
Clatot et al.27	ddPCR	31% (44/144)	Y537C, Y537N, Y537S, D538G
Spoerke et al.28	ddPCR	37% (57/153)	E380Q, S463P, P535H, L536Q, L536R, L536H, L536P, Y537C, Y537N, Y537S, D538G
Chandarlapaty et al.10	ddPCR	29% (156/541)	Y537S, D538G
Fribbens et al.9	ddPCR	39% (63/161) and 25% (91/360)	E380Q, S463P, L536R, Y537C, Y537N, Y537S, D538G
Chung et al.35	NGS	34% (67/197)	T347A, R352M, H356D, M357V, L379I, E380Q, M388I, M388L, T431S, G442R, S463P, H476N, H524L, H524Y, P535T, L536F, L536H, L536P, L536R, L536V, Y537S, Y537N, Y537C, Y537D, D538G, L539P, L541M, E542D, E542K
Takeshita et al.36	ddPCR	14% (5/35)	Y537C, Y537N, Y537S, D538G
Cristofanilli et al.84	BEAMing ddPCR	27% (106/396)	Mutations not specified
O’Leary et al.43	ddPCR	31% (61/195)	E380Q, S463P, L536R, Y537C, Y537N, Y537S, D538G
Lok et al.85	ddPCR	30% (10/33)	E380Q, S463P, I514V, Y537C, Y537S, D538G
Allouchery et al.86	ddPCR	33% (7/21)	Y537C, Y537N, Y537S, D538G
Fribbens et al.34	ddPCR	56% (22/39)	E380Q, S463P, L536R, Y537C, Y537N, Y537S, D538G