Why the lung
After the liver, the lung is the second most common site of colorectal cancer metastases: it happens in 10-20 % of patients, and more often in rectal cancer (part of its blood drains directly into the general circulation, bypassing the liver). They often appear as small nodules, one or a few, on a follow-up CT scan, years after the primary tumour and without symptoms.
Not every lung nodule is a metastasis: nodules of a few millimetres are common in the general population (scars, old infections). That is why, when they are very small, the usual approach is to repeat the CT in 2-3 months to see whether they grow before deciding anything. A PET-CT or a biopsy help when there is doubt.
When surgery makes sense
Surgery for lung metastases (metastasectomy) is considered with curative intent when, broadly, these conditions are met:
- The primary tumour is controlled (removed, with no local recurrence).
- There is no disease elsewhere that cannot also be treated (an operable liver metastasis is not an obstacle: both are treated).
- All the lesions can be removed while leaving enough lung: in practice, usually few lesions (one to three or four) and not too large.
- Your lung function and general health allow the operation (measured with spirometry).
Factors linked to better outcomes: a single metastasis, a long interval since the primary tumour (more than 1-2 years), a normal CEA before surgery, and uninvolved mediastinal lymph nodes. None of these alone rules out surgery; they are weighed together.
How it is operated on
The most common operation is a wedge resection (the nodule is removed with a margin of healthy lung) or a segmentectomy; a lobectomy (a whole lobe) is reserved for large or central lesions. Today most are done by minimally invasive surgery (VATS or robotic), with a 2-4 day stay and recovery within a few weeks. If there are metastases in both lungs they can be operated on in two stages. The loss of breathing capacity after a wedge resection is small.
Alternatives to surgery
- Stereotactic radiotherapy (SBRT): 3-8 high-precision sessions, with no admission or anaesthesia. It controls the treated lesion in more than 80-90 % of cases. It is the option when surgery is not possible because of lung function, age or other illnesses, or when the patient prefers it. For small, peripheral lesions the medium-term results are comparable to surgery, although they have not been directly compared in large trials.
- Ablation (radiofrequency, microwave, cryoablation): a CT-guided needle destroys the nodule. For lesions under 2-3 cm, away from large vessels. One day in hospital.
- Chemotherapy: before surgery (to "test" that the disease is not racing ahead and to shrink the lesions) or afterwards; its added benefit in resected lung metastases is not clearly proven, and the decision is individualised.
What the evidence says (and what it does not)
To be honest: lung metastasectomy rests on series of operated patients, with 5-year survival of 40-60 %, but there is no large trial comparing it with not operating. The only one that tried, PulMiCC, could not recruit enough patients and left the question open: part of the good outcome may be due to selecting the patients with the slowest disease. Even so, European and American guidelines recommend it in well-selected patients, because it is the only option with a chance of cure and the surgical risk is low. What matters is that the selection is made by a multidisciplinary board with a thoracic surgeon, and not decided in a single consultation.
Afterwards
Follow-up is with a CT scan every 3-6 months in the first years. New lung metastases appear in around half of those operated on; many can be treated again (a second operation, SBRT or ablation). The disease can thus become something treated in episodes, with long treatment-free periods in between.
What to ask at your appointment
- Are we sure these are metastases, or should the CT be repeated in a few months?
- Has my case been discussed at a board with a thoracic surgeon?
- Surgery, SBRT or ablation: which do you recommend for me, and why?
- Is chemotherapy needed before or after, and what is expected from it?
- What happens if more nodules appear later: can they be treated again?