When colon cancer spreads, the lungs are the second most common place it goes, after the liver. Lung spread is not always a sign that nothing can be done, because a few spots in the lungs can often be removed or destroyed the way a single tumour can. The choice of treatment depends less on the diagnosis itself than on how many spots there are, where else the cancer is, and how long it took to come back.
Why Colon Cancer Spreads to the Lungs
Blood from the colon and upper rectum drains first to the liver, then passes through the heart to the lungs.1PubMed Central. Patterns of metastasis in colon and rectal cancer That is why spread often shows up in the liver first, then the lungs, then other organs.2PubMed. Haematogenous metastatic patterns in colonic carcinoma: an analysis of 1541 necropsies Blood from the lower rectum skips the liver and reaches the lungs first, so rectal cancer spreads to the chest more often than colon cancer does.3PubMed Central. Patterns of metastasis in colon and rectal cancer
Spots in the lung are colon cancer cells that travelled there, not a new lung cancer. They are treated with colon cancer drugs, not lung cancer drugs, which is why doctors work hard to confirm which cancer it is.
Many colorectal tumours carry a change in a gene called KRAS, which your tumour test report may list as KRAS mutant or KRAS wild-type. KRAS changes turn up in about 6 in 10 lung metastases but only about 3 in 10 liver metastases.4PubMed. KRAS mutation is associated with lung metastasis in patients with curatively resected colorectal cancer People whose colon tumour has a KRAS change are also about twice as likely to have the cancer return in the lungs.5PubMed. KRAS mutation is associated with lung metastasis in patients with curatively resected colorectal cancer
Cells can sit unnoticed in the lungs after the colon tumour is removed. They may grow slowly and only show up on a later follow-up scan, sometimes years afterward. Lung spots often cause no symptoms at first, so scans find most of them.
How Lung Metastases Are Diagnosed
A chest CT is the main scan for finding lung spots. In people being checked for lung spread, CT found about 9 in 10 spots later removed at surgery, compared with about 3 in 4 for PET-CT.6PubMed Central. Role of 18F-FDG PET/CT vs CT-scan in patients with pulmonary metastases previously operated on for colorectal liver metastases CT also flags more harmless spots, so about half of its suspicious findings in that setting were not cancer.7PubMed Central. Role of 18F-FDG PET/CT vs CT-scan in patients with pulmonary metastases previously operated on for colorectal liver metastases PET-CT, on the other hand, found spread outside the lungs, such as in lymph nodes or the liver, that CT missed in some people.8PubMed Central. Role of 18F-FDG PET/CT vs CT-scan in patients with pulmonary metastases previously operated on for colorectal liver metastases Many people therefore have both scans before treatment is planned.
Scans often undercount the spots. Both CT and PET counted the number of lung metastases correctly only about 6 times in 10.9PubMed. Low Accuracy of Computed Tomography and Positron Emission Tomography to Detect Lung and Lymph Node Metastases of Colorectal Cancer About 1 in 5 people thought to have a single spot turned out to have more at surgery.10PubMed. Low Accuracy of Computed Tomography and Positron Emission Tomography to Detect Lung and Lymph Node Metastases of Colorectal Cancer
When a needle sample is taken, the lab stains it for markers that show where the cells came from. A marker called CDX2 identified colon cancer in about 95 of 100 biopsy samples from lung spots.11PubMed. CDX2 as a useful marker of colorectal adenocarcinoma metastases to lung in pre-operative biopsy specimens Without CDX2, about 4 in 10 biopsies would have been unclear between lung cancer and colon cancer.12PubMed. CDX2 as a useful marker of colorectal adenocarcinoma metastases to lung in pre-operative biopsy specimens Another marker, CK7, is usually present in lung cancer but absent in colon cancer spread, which helps tell them apart.13PubMed. The utility of the lineage specific immunohistochemical stains SATB2, CDX2, and villin, and the mucin glycoproteins MUC2, MUC5AC, and MUC6 to distinguish pulmonary invasive mucinous adenocarcinoma from metastatic colorectal carcinoma
In a CT-guided needle biopsy, you lie in a CT scanner while a thin needle is guided into the spot. It is usually done with local numbing as an outpatient. A small air leak around the lung is the most common complication. Results with marker stains usually take several days.
Doctors sometimes skip the biopsy. Spots that are small or hard to reach may not be sampled. If several spots appear in someone with known colon cancer, doctors may treat based on the scans, and watching a spot on a repeat scan can show whether it grows. It is reasonable to ask whether a biopsy would change your treatment plan.
Some doctors also use blood tests that look for tumour DNA, but people with lung spread tend to shed less of it into the blood.14PubMed Central. Circulating Tumor DNA and Management of Colorectal Cancer A low or negative result does not rule out lung spots.
Surgery to Remove Lung Metastases
UK national guidance says surgery, ablation or focused radiation should be considered for anyone whose lung spots can be treated locally.15National Institute for Health and Care Excellence. Colorectal cancer (update): evidence review for treatment for metastatic colorectal cancer in the lung The decision should be made by a team that includes a chest surgeon and a specialist in non-surgical treatments.16National Institute for Health and Care Excellence. Colorectal cancer (update): evidence review for treatment for metastatic colorectal cancer in the lung People are chosen for surgery when removing all the cancer looks possible.17PubMed Central. Prognostic factors after pulmonary metastasectomy of colorectal cancers: a single-center experience It is worth asking whether your case has been reviewed by such a team.
The operation, called metastasectomy, can be done through a large cut between the ribs or by keyhole surgery with a camera. After either approach about half of people are alive five years later, around 46 to 51 percent.18PubMed Central. Video-assisted thoracoscopic surgery versus open resection of lung metastases from colorectal cancer Keyhole surgery causes less blood loss, though it takes longer.19PubMed Central. Video-assisted thoracoscopic surgery versus open resection of lung metastases from colorectal cancer The chance of the cancer coming back in the lungs is similar with both methods, around 1 in 4.20PubMed. Management of lung metastases from colorectal cancer: video-assisted thoracoscopic surgery versus thoracotomy–a case-matched study
Most often only a small wedge of lung around each spot is removed. Larger or central spots may need a bigger piece or a whole lobe. The hospital stay is usually a few days, shorter after keyhole surgery, and a chest tube drains air and fluid for a day or more.
Surgery does not guarantee better well-being for everyone. In a trial that compared surgery with no surgery, people’s overall sense of well-being over two years was about the same in both groups.21PubMed Central. Pulmonary metastasectomy in colorectal cancer: health utility scores by EQ-5D-3L in a randomized controlled trial show no benefit from lung metastasectomy
Focused Radiation and Heat Ablation
SBRT, or stereotactic body radiation therapy, aims very high doses of radiation at a spot over a few sessions. About 8 in 10 spots treated with focused radiation were still under control two years later.22PubMed Central. Stereotactic body radiation therapy for lung metastases from colorectal cancer: outcomes and prognostic factors in a series of 109 patients In one hospital, two-year control of treated spots was about 7 in 10 for both radiation and surgery.23PubMed Central. Stereotactic Body Radiotherapy versus Surgery for Lung Metastases from Colorectal Cancer: Single-Institution Results In another comparison, though, the treated spot grew back in about 1 in 3 people after radiation versus about 1 in 6 after surgery.24PubMed. Comparison of the Long-term Survival Outcome of Surgery versus Stereotactic Body Radiation Therapy as Initial Local Treatment for Pulmonary Oligometastases from Colorectal Cancer: A Propensity Score Analysis
In ablation, a needle is guided through the skin under CT and heats the spot until the cancer cells die. After microwave ablation in selected people, about half were alive five years later.25PubMed Central. Long-term outcome following microwave ablation of lung metastases from colorectal cancer Outlook was better in people who had no liver spread when the lung spots were found.26PubMed Central. Long-term outcome following microwave ablation of lung metastases from colorectal cancer Radiofrequency and microwave ablation work about equally well for spots up to 3 cm.27Journal of Vascular and Interventional Radiology. Radiofrequency and Microwave Ablation of Colorectal Cancer Lung Metastases: A Retrospective Comparison
Surgery may be preferred for fit people because the spot comes back less often. Radiation suits people with weak lungs or heart, or spots near the centre of the chest. Ablation suits small spots near the edge of the lung. Many people have a mix, such as surgery for one spot and radiation for another.
Focused radiation is painless and usually takes three to eight short visits. Tiredness and a cough for a few weeks are common. Ablation usually needs one overnight stay and light sedation. Both can be repeated if new spots appear later.
Chemotherapy and Targeted Drugs
Chemotherapy combinations such as FOLFIRI are the main treatment when lung spots are too many or spread is wider. In people with spread limited to the liver or lungs, about a quarter to a third had their tumours shrink enough to have surgery after chemotherapy with a targeted drug.28Springer Link / Journal of Cancer Research and Clinical Oncology. Conversion surgery after cetuximab or bevacizumab plus FOLFIRI chemotherapy in colorectal cancer patients with liver- and/or lung-limited metastases The targeted drug bevacizumab improves survival in people with spread, though its benefit appears smaller when the lungs are involved along with other sites.29Journal of Clinical Oncology. Bevacizumab in first-line therapy in lung metastases of colorectal cancer: An ARCAD pooled analysis
Chemotherapy may come first to see whether new spots appear before surgery, or follow surgery or radiation to lower the chance of return. Some people get treatment breaks when the cancer is stable. The order is individual and decided by the team.
Tumour testing guides drug choice. Drugs such as cetuximab work only in tumours without a KRAS or related RAS gene change. Tumours with a high level of a pattern called MSI, shown as MSI-high on reports, often respond to immunotherapy.30Journal of Case Reports and Images in Oncology. Pembrolizumab leading to complete resolution of non-small cell lung cancer and microsatellite instability stable colon adenocarcinoma; two birds one stone Ask whether your tumour has been tested for KRAS and MSI.
When treatment aims to control the cancer rather than cure it, many people still live for years on rounds of treatment. Scans every few months show whether the drugs are still working, and doctors switch drugs when one stops. Clinical trials are an option worth asking about.
What Affects Your Outlook
Having more than three lung spots predicts a higher chance of the cancer coming back after surgery.31PubMed. Predictors of recurrent pulmonary metastases and survival after pulmonary metastasectomy for colorectal cancer So does the cancer returning less than one to two years after the first treatment.32PubMed. Prognostic factors for recurrence after pulmonary resection of colorectal cancer metastases Among people with one spot found more than a year after first treatment, about half were free of cancer three years after surgery.33PubMed. Prognostic factors for recurrence after pulmonary resection of colorectal cancer metastases Of people with three or more spots found within a year, none was cured by surgery.34PubMed. Prognostic factors for recurrence after pulmonary resection of colorectal cancer metastases Spots larger than 14 mm also point to a poorer outlook.35PubMed. Recurrence-free survival curve for pulmonary metastasectomy in colorectal cancer plateaus at 3 years
People with spread to both liver and lungs can sometimes have both removed, usually the liver first and the lungs later.36PubMed. Oncological benefit of complete metastasectomy for simultaneous colorectal liver and lung metastases Results were poor, though, when both tumour blood markers, CEA and CA19-9, were high.37PubMed. Longterm results after resection of simultaneous and sequential lung and liver metastases from colorectal carcinoma
These factors describe groups, not what will happen to you. One poor factor does not rule out benefit from treatment.
Recovery After Lung Treatment
In the first three months after lung surgery, people often report more breathlessness, cough, tiredness and chest pain.38PubMed. Quality of life evolution after pulmonary metastasectomy: a prospective study comparing isolated lung perfusion with standard metastasectomy Shoulder stiffness on the operated side and difficulty with daily tasks are common at first.39PubMed. Quality of life evolution after pulmonary metastasectomy: a prospective study comparing isolated lung perfusion with standard metastasectomy By six months, these usually return to how they were before surgery.40PubMed. Quality of life evolution after pulmonary metastasectomy: a prospective study comparing isolated lung perfusion with standard metastasectomy Plan for reduced activity and help at home for the first few weeks.
Walking daily and breathing exercises help the lung re-expand, and gentle shoulder movement prevents stiffness. Take pain relief regularly so you can cough and breathe deeply. Call your team for fever, worsening breathlessness or coughing blood.
Some people with lung spread develop fluid around the lung, which causes breathlessness.41Froedtert & the Medical College of Wisconsin. Colon Cancer Lung Metastasis It can be drained with a small tube left in the chest that empties into a vacuum bottle at home.42Froedtert & the Medical College of Wisconsin. Colon Cancer Lung Metastasis
Follow-Up Scans After Treatment
In a large trial, scans or CEA tests every few months led to more people having treatment aimed at cure when the cancer came back.43PubMed. Effect of 3 to 5 years of scheduled CEA and CT follow-up to detect recurrence of colorectal cancer: the FACS randomized clinical trial A typical schedule was the CEA blood test every 3 months for 2 years then every 6 months, and CT every 6 to 12 months for 5 years.44PubMed. Effect of 3 to 5 years of scheduled CEA and CT follow-up to detect recurrence of colorectal cancer: the FACS randomized clinical trial About 4 in 10 people with stage 2 or 3 colon cancer will have a return, which is why close follow-up is advised.45PubMed Central. Colorectal Cancer: Postoperative Follow-up and Surveillance New lung spots are common after lung surgery and can often be treated again.
Where you get care can matter. Younger people and those who travelled farther for care were more likely to have surgery. If surgery was ruled out, a second opinion from a specialist centre is reasonable, and you can ask how many of these operations your hospital does each year.