The investigators will detect circulating tumor DNA in blood of patients with lung metastases from colorectal cancer using NGS technology and intend to use it for predicting the outcome of local treatment (surgery or radiation) and recurrence of lung metastases.

The investigators produce customized gene target panel by selecting genes that are commonly found in colorectal cancer and metastasis from existing literature.

In patients diagnosed with lung metastases from colorectal cancer, 20mL of whole blood is collected before and after local treatment (surgery or radiation) and cell-free DNA (cfDNA) is extracted from the collected blood. Thereafter, 20 mL of whole blood is additionally collected once after 3 months (±2 months) and once after 6 months (±2 months) during follow-up and cfDNA is extracted. The investigators perform sequencing from the extracted cfDNA.

The investigators compare the mutations detected in cfDNA before and after local treatment and identify the trend of reducing mutations in cfDNA after local treatment. So The investigators discover biomarkers for the outcome of local treatment. The investigators also search for mutations for target drugs from mutation profiling of cfDNA.

Inclusion Criteria:

1. adults over 19 years of age
2. those who understand research and have written consent
3. cases diagnosed with lung metastases from colorectal cancer

Exclusion Criteria:

1. pregnant women, nursing women
2. those who lack the ability to voluntarily agree
3. participation in other clinical trials where drugs for clinical trials are administered within the past four weeks as of the date of participation in clinical trials

They were diagnosed with lung metastases from colorectal cancer and are Korean. They are also treated in severance hospital during the study period.