Table 2.

CTCs in Clinical Disease Management.

Study	Study Population	Study Treatment	CTC Measurement	Results
Nemunaitis et al., 2009 [92]	Advanced NSCLC	Belagenpumatucel-L	CTC enumeration every 4 weeks	Median OS was significantly shorter in patients with ≥2 CTCs/7.5 mL
Riethdorf et al., 2010 [88]	Metastatic breast cancer	Neoadjuvant therapy	CTC enumeration	No association between tumor response and CTC detection
Punnoose et al., 2012 [86]	Advanced NSCLC	Erlotinib + Pertuzumab	CTC enumeration, EGFR expression in CTCs, oncogenic mutations in CTCs	Higher baseline CTC counts were associated with treatment response Larger CTC count decreases at days 14, 28, 56 associated with treatment response
Goldkorn et al., 2014 [91]	Metastatic castration-resistant Prostate Cancer	Docetaxel + Prednisone with or without Atrasentan	CTC Enumeration at baseline and day 21 post treatment	Median OS was significantly shorter in patients with ≥5 CTCs/7.5 mL of blood at day 0 Rising CTC counts from day 0 to day 21 were associated with shorter OS
Agelaki et al., 2015 [90]	Metastatic breast cancer + HER2-positive CTCs	Lapatinib	Immunofluorescent Microscopy stained for HER2/EGFR/Cytokeratin	“Effective in decreasing HER2-positive CTCs… irrespective of HER2 status”
Ignatiadis et al., 2018 [46,93]	High risk, HER2 nonamplified, early breast cancer	Trastuzumab	CTC enumeration at baseline and week 18	Trastuzumab did not decrease rate of CTC detection
Tan et al., 2018 [94]	Colorectal	Chemotherapy (broad)	CTC enumeration	CTC count trends can be used in place of uninformative CEA for monitoring patient response
Bidard et al., 2021 [87]	Hormone receptor-positive, ERBB2-negative metastatic breast cancer	CTC count-driven vs. Clinician-driven first line therapy	CTC enumeration (chemotherapy if ≥5 CTCs, endocrine therapy otherwise)	Median PFS was slightly longer in CTC-driven treatment compared with clinician-driven treatment
Bonvini et al., 2021 [85]	Inflammatory myofibroblastic tumor	Entrectinib	Longitudinal CTC enumeration during treatment (up to 24 months post treatment)	Antitumor activity was associated with elimination of CTCs from blood
Sperger et al., 2021 [96]	Metastatic prostate cancer	Enzalutamide or abiraterone	CTC androgen-receptor (AR) gene expression	CTCs clustered according to AR-gene expression Presence of CTCs enriched for AR-gene transcripts associated with shorter OS
Pang et al., 2021 [97]	Metastatic Breast Cancer	Surgery or Adjuvant Therapy	CTC enumeration	CTC counts will increase in the perioperative period for up to 14 days CTC positivity associated with shorter OS and PFS following adjuvant therapy