Lung Metastases

What Do Metastases in the Lungs Mean?

Lung metastases are secondary malignant tumors that originate from another primary malignant tumor, which can vary in distance from the lung metastases and be either outside or inside the lungs. Lung metastases are caused by malignant tumor cells that travel from the primary tumor to the lungs via the bloodstream or lymphatics and grow there uncontrollably. Unlike lung cancer, in which only lung tissue becomes malignant, different types of cells can be carried ("metastasize") to the lungs, depending on the origin of the primary tumor.

Where Do Metastases in the Lungs Originate?

The Most Common Primary Tumors That Metastasize to the Lungs Are:

• Colorectal cancer
• Breast cancer
• Kidney cancer
• Prostate cancer
• Stomach cancer
• Thyroid cancer
• Ovarian cancer
• Bone cancer
• Skin cancer
• Cancer of the head and neck areas.

Treatment Options for Lung Metastases

Lung metastases can be removed using a variety of techniques, which can vary widely in their radicality.

Radiofrequency Ablation

A less invasive therapeutic approach is radiofrequency ablation, in which a special needle is inserted directly into the tumor under radiological control (CT). An electric current is then passed through the needle tip into the tumor, which heats up to the extent that the surrounding malignant tumor tissue is destroyed. The advantage of this method is that the current flow can be controlled very precisely and adapted to the size of the tumor so that healthy and functional lung tissue is preserved as far as possible. However, a disadvantage of this method is the possibility of recurrence, i.e., the reappearance of lung metastases. In such cases, radio-ablation can be repeated.

Microwave Ablation

Microwave ablation, a similar minimally invasive removal technique, also uses heat to destroy malignant tumor tissue. However, unlike radiofrequency ablation, it does not use direct heat but electromagnetic oscillations of a specific frequency that cause hydrogen molecules of the tumor cells to rub against each other. This indirectly generates heat and causes the tumor cells to die.

Minimally Invasive Video-Assisted Thoracic Surgery (VATS).

If the tumor is located up to 1 cm away from the chest wall, minimally invasive video-assisted removal is an option. The advantage is reduced surgical risk and accelerated healing after surgery, plus a more appealing cosmetic result.

Lung Metastases Surgery

Surgical removal of metastases represents the best chance of cure. In the surgery, larger or smaller lung segments or even entire halves of the lungs are removed to eliminate the metastases as far as possible. This method is particularly radical and, while considered promising in therapeutic success, carries an increased risk of complications. In addition, a surgical resection is only an option for a small number of patients (approximately 25-30% in the early stage). However, every patient with lung metastases should be presented to a thoracic surgeon, says Dr. Kleine in an interview.

Before surgery, extensive diagnostics must be carried out. The extent and localization of individual tumor foci in the lungs are recorded using various imaging techniques such as X-ray, MRI, computer tomography, or nuclear medicine examinations (PET, PET-CT ). If the patient is known to have another tumor outside the lung, it must also be determined whether the tumor has metastasized to the lung or is a lung tumor. For this purpose, tissue samples are taken, which are examined histologically to determine the characteristics of the cells.

Then, based on certain criteria, a decision is made as to whether the patient is suitable for surgical removal of the lung metastases. Several factors are decisive, among others, whether the initial tumor can be removed, whether the lung metastases are easily accessible and can be removed, whether other metastases are known, and whether the patient is fit enough to compensate for the loss of parts of their lung.

Treatment Options for Inoperable Lung Metastases

We speak of inoperable lung metastases when specific criteria, such as the localization, number, and size of the metastases, metastases outside the lung or concomitant diseases of the patient, make surgical removal of the lung metastases impossible because the operation is technically unfeasible or it is associated with too high a risk of complications compared with the prospects of success. In such cases, the treating physician may resort to other therapeutic options that consider the patient's situation.

In principle, the minimally invasive therapy approaches mentioned above can be considered an alternative to surgical removal, taking into account the individual situation. However, the size, differentiation, or localization of the metastases, for example, and the primary tumor stage are often responsible because the metastases cannot be removed minimally invasively.

Cyberknife

As an alternative to surgery, non-invasive radiation therapy using cyberknife can also be considered. In this therapy, the metastases are irradiated with pinpoint accuracy in several settings and thus destroyed while the surrounding healthy tissue is preserved. The limiting factor here is that the metastases must not be too large and clearly demarcated from healthy tissue.

Transpulmonary Chemoembolization (TPCE)

Transpulmonary chemoembolization (TPCE), in which artificial pulmonary circulation is created to deliver the chemotherapeutic substance to the lungs in isolation, is considered promising. This can reduce the side effects to the rest of the body and increase the dose of the chemotherapeutic agent accordingly and destroy more tumor tissue.

Palliative chemotherapy is an option for advanced lung metastases with shorter life expectancy.

Lung Metastases Process

Pulmonary metastases occur in up to 30% of all cancers. Still, unfortunately, they often go undetected for more extended periods because they do not cause symptoms in the patient early in their course. In most cases, symptoms originate from the primary tumor, and lung metastases are random during tumor diagnostics.

Unfortunately, this means that lung metastases are often detected late and are then already more advanced. Typical symptoms in later stages are caused by damage to the lung tissue and can include breathing difficulties, bloody cough, and pneumonia.

Life Expectancy and Chances of Cure for Lung Metastases

Life expectancy for lung metastases depends on many factors and cannot be quantified across the board. In particular, the condition and type of the primary tumor, the number and extent of other metastases, and the patient's state of health strongly influence their individual therapeutic prospects.

If the patient proves to be operable and all lung metastases can be removed and tumor-free conditions created, the prognosis can improve in principle. However, many other factors are important, such as the primary tumor type and sensitivity to chemotherapy.

In some cases, however, pulmonary metastases are associated with an unfavorable prognosis. In such cases, palliative chemotherapy is a particular option.

Sources:

Deutsche Gesallschaft für Pneumologie

https://www.aerzteblatt.de/archiv/131466/Lungenmetastasen-Moeglichkeiten-chirurgischer-Intervention

Limmer, Stefan; Lungenmetastasen. Heidelberg: Springer Medizin 2015