Lung cancer is the largest cancer in my country, with high morbidity and mortality. One of the major causes of lung cancer death is brain metastasis. Among the metastatic sites of advanced lung cancer, the central nervous system (CNS) is the most common site. Statistics show that 20% to 65% of lung cancer patients will develop brain metastases during the course of the disease. Compared with non-small cell lung cancer, small cell lung cancer has a higher incidence of brain metastases. About 20% of patients have brain metastases at the time of diagnosis, and the incidence of brain metastases in the autopsy of small cell lung cancer patients is as high as 80%. .
Why is lung cancer so prone to brain metastases?
First of all, the lungs are extremely rich in blood vessels. The human body has two major circulatory systems, one is the systemic circulation and the other is the pulmonary circulation. Except for the heart, no organ in the human body is full of blood vessels and blood like the lungs. Because of the rich capillary network, lung cancer cells have a greater probability of breaking through the blood vessel wall and entering the pulmonary blood vessels. Secondly, there are anastomotic branches between the pulmonary blood vessels and the vertebral veins. After the cancer cell emboli enter the veins, they can enter the brain directly through the systemic circulation retrograde without being filtered by the pulmonary capillaries. This is very different from malignant tumors in other parts. The metastasis path of malignant tumors of other organs generally reaches the lungs first, and then can enter the brain. Most tumor cells are filtered out by pulmonary capillaries, and the probability of entering the brain is much lower.
In non-small cell lung cancer, up to 50% of Asian patients carry EGFR mutations. Such advanced patients can be said to be very lucky, because they can control the disease with oral targeted drugs, and the targeted drugs for the EGFR gene are the most complete. However, God opens a door for you and may close a window. A large number of studies have shown that patients with EGFR mutations have a higher incidence of cumulative brain metastases compared with patients with other mutations and no sensitive gene mutations.
In addition to common brain tissue metastases, there is also a special type of brain metastases, that is, meningeal metastases. The incidence in advanced non-small cell lung cancer is 3% to 9.4%, and it carries EGFR mutations. The incidence of meningeal metastases was also higher in patients with In a retrospective study of 5,387 lung cancer patients, meningeal metastases with EGFR mutations (9.4%) were significantly higher than those with wild-type EGFR (1.7%).
Lung cancer with brain metastases has a very poor prognosis. What should I do if a brain metastasis occurs? Are you going to give up treatment?
Lung cancer brain metastases do shorten the patient’s survival period and make it more difficult for patients to obtain a good quality of life. However, brain metastases are not impossible, and the choice can be made according to the actual situation of the patient. Radiotherapy, targeted therapy with small molecule drugs and even local brain surgery can achieve certain curative effects.
Due to the existence of the blood-brain barrier, it is difficult for macromolecular drugs to enter the brain, and chemotherapy is generally ineffective for brain metastases. However, small-molecule oral targeted drugs have a strong ability to enter the brain, which is more reflected in drugs such as osimertinib, almetinib, alectinib, and lorlatinib. There are indeed some brain metastases in clinical practice. The patient’s condition has been stably controlled for a long time through the comprehensive treatment of targeted drugs and brain radiotherapy. As for the effect of macromolecular immunotherapy drugs on brain metastasis, there is still no definite conclusion, and large sample studies are still needed to demonstrate.