Table 3.

Clinical applications of ctDNA.

Cancer Types	Clinical Management	Conclusion	References
Breast Cancer	Assessment of early ctDNA dynamics in 149 patients	Assessment of early dynamic changes in ctDNA can predict the efficacy of targeted therapy	[106]
	Prediction of recurrence of cancer	Predicted metastatic relapse with high accuracy	[103]
	Detection of PIK3CA mutations	CtDNA can be used for the detection of PIK3CA mutations	[107]
Lung cancer	Cancer diagnosis and therapeutics	EGFR L858R and T790M mutations can be detected in ctDNA using NGS and ddPCR	[108]
	Detection of cancer at IA, IB, and IIA stages	Found an association among tumor stage, subtype, and cfDNA concentration, and demonstrated the utility and feasibility of targeted sequencing for ctDNA monitoring	[109]
	Monitoring treatment response and drug resistance	Proved the decrease of mutant copies after treatment and monitored the emergence of secondary mutations	[110]
	Detection of copy number variations in tumor cells	Copy number changed in BAX, P53, CASP3, SOX2, GRB2, SOS1, MAPK1, and a few other genes of cancer patients	[111,112]
	Diagnostic marker	The presence of ctDNA in cancer patients was found to be eight times higher than in healthy persons	[113]
Colon cancer	Adjuvant therapy	Provided evidence of the potential use of ctDNA with adjuvant novel drugs for cancer patients	[114]
Colorectal cancer	Marker for cancer recurrence	Postoperative ctDNA positivity may be associated with the recurrence of cancer	[115]
	Predicting response to neoadjuvant chemoradiotherapy	Combination of MRI and ctDNA potentially improves the predictive performance of cancer	[116]
	Novel biomarker Optimizing chemotherapy	Described that ctDNA can potentially be utilized for diagnosis and personalized medicine for colorectal cancer	[117]
Melanoma	Monitoring of relapse in stage III	ctDNA identified the highest risk stage III melanoma patients and helped in adjuvant therapy decisions	[118]
	Detection of ctDNA levels in patients treated with anti-PD1 therapy	The evaluation of ctDNA during anti-PD1 antibody therapy provided reliable information	[119]
Leiomyosarcoma	Detection of genetic variants using Guardant360	The identification of molecular alterations can help develop therapy, targeting TP53, cell cycle, and kinase signaling pathways	[120]