Table 1.

Patient characteristics, treatment detail, and dose modifications for thrombocytopenia.

Age & gender	Race	Breast cancer subtype	Agent	Line of therapy	Delays	Dose reductions	Cycle of 1st reduction for TCP	Cycle of 2nd reduction for TCP	Platelet nadir	Met CIT criteria*
57F	White	ER-/PR-/HER2 3+	T-DM1	2nd line metastatic	0	2	6	8	52	yes
53F	White	ER-/PR-/HER2 2 + (ISH+)	T-DXd	3rd line metastatic	0	1	1	N/A	91	no**
36F	Asian	ER+/PR+/HER2 3+	T-DXd	4th line metastatic	3	3	5	10	24	yes
57F	White	ER+/PR-/HER2 3+	T-DM1	2nd line metastatic	0	1	18	N/A	50	yes
58F	White	ER-/PR-/HER2 3+	T-DXd	3rd line metastatic	1	2	7	21	57	yes
80F	White	ER-/PR-/HER2 3+	T-DM1	Adjuvant	2	2	4	6	50	yes

^*Chemotherapy-induced thrombocytopenia (CIT) criteria: platelet count < 100 000/mcL for ≥ 3 weeks following last antibody-drug conjugate administration.

^**1 individual did not meet CIT criteria while on T-DXd; however, the individual had disease progression on dose-reduced and dose-delayed T-DM1, and the reason for therapy delays and reductions was thrombocytopenia and the clinician made decision to dose-reduce the next line of therapy, T-DXd, as a result.

Abbreviations: TCP, thrombocytopenia; F, female; ER, estrogen receptor; PR, progesterone receptor; HER2, human epidermal growth factor receptor 2; 2+, 2 + by immunohistochemistry; 3+, 3 + by immunohistochemistry; ISH, in situ hybridization; T-DM1, trastuzumab emtansine; T-DXd, trastuzumab deruxtecan.