Conventional radiation therapy There are still many controversies about radiotherapy for brain metastases, such as whether whole brain radiotherapy or local radiotherapy is needed, whether radiotherapy is required after total excision of the lesion, and the radiation dose. One part of the retrospective studies confirmed that surgery plus postoperative radiotherapy did not reduce recurrence and prolong survival, while another part of the studies came to the opposite conclusion. Currently, most scholars believe that although surgery plays an important role in the treatment of brain metastases, since most brain metastases are multiple, surgical removal of every metastasis or even undetected lesions is undoubtedly impossible, and postoperative radiotherapy is still required, therefore radiotherapy is suitable for most patients and is another common means of treatment after surgery. The indications are: ① postoperative brain metastases; ② tumors sensitive to radiotherapy, such as small cell lung cancer, lymphoma, breast cancer; ③ tumors less sensitive to radiotherapy, such as non-small cell lung cancer, adrenal tumors, malignant melanoma; ④ prophylactic head radiotherapy: it is suitable for small cell lung cancer and non-small cell lung cancer that are highly susceptible to brain metastases, and has become an important part of standard treatment for lung cancer. It has been found to significantly reduce the incidence of metastasis and mortality.
Whole Brain Radiotherapy (WBRT) is the most commonly used treatment. Because CT and MRI examinations of the brain are similar to autopsy findings, i.e., brain metastases that cannot be detected by CT and MRI are still rare, and because whole brain radiotherapy can cause complications such as dementia, local radiotherapy has also been advocated. In recent years, more units are using intensity-modulated conformal radiotherapy equipment, and after 30-40 Gy of whole brain radiotherapy, the local dose is increased by 10-20 Gy. The dose plan used for radiotherapy varies from family to family. Since radiotherapy can cause early (occurring within a few days after the start of radiotherapy, such as headache, nausea, vomiting, fever, etc.) and late (such as dementia, ataxia, etc.) radiation reactions, the use of high-dose radiotherapy regimens has been discouraged. Single high-dose regimens have been discouraged. In recent years, cognitive dysfunction caused by whole brain radiotherapy has received much attention, and a variety of improved radiotherapy regimens have been introduced, among which the most studied is Hippocampal Avoidance WBRT (HiBRT). A new drug, memantine, has been used during and after radiotherapy to improve memory function, with significant results, and is recommended to be started within 3 days of radiation treatment at 20 mg daily for 24 weeks.
It has been found that peritumor cells are sensitive to radiotherapy, while cells in the core of the tumor are insensitive to radiation due to hypoxia. The use of radiotherapy booster can increase the sensitivity of hypoxic cells to radiation and thus improve the therapeutic effect. For whole brain radiation therapy of non-small cell lung cancer intracranial metastases, motexafin can be used. Many prospective studies have found that about 43%-64% of patients started to show effect at 2 weeks of radiation therapy, and 66% of patients had symptom relief at a radiation therapy dose of ≥25Gy. In general, radiotherapy alone can prolong the mean survival time of patients with brain metastases by 4-6 months, and for individual patients it can prolong the survival time by 12-24 months, which is even better when combined with hormonal therapy. Recent randomized controlled studies have found that the combination of whole brain radiotherapy after surgical resection of a single lesion or after radiosurgical treatment significantly improves survival. In patients with fewer than four metastases, radiosurgery combined with whole-brain radiotherapy significantly improved control of intracranial lesions. Several RTOG clinical studies have suggested that good radiotherapy outcomes are often associated with (i) a KPS (Karnofsky Performance Scale) ≥70; (ii) no primary tumor detected or controlled; (iii) patient age <60< span=""> years; and (iv) brain metastases only.
Stereotactic Radiosurgery includes Gamma Knife, Linear Accelerator Radiosurgery (X Knife and Radio Knife or Cyber Knife), and Particle Beam Knife (Proton Knife and Heavy Particle Therapy), among which Gamma Knife is more commonly used. Gamma knife treatment of brain metastases is different from the principle of ordinary radiotherapy, the former is through a one-time high dose of radiation to reach the diseased tissue and destroy it, while the latter mainly relies on the sensitivity of the tissue to radiation, through the radiation to achieve the purpose of inhibiting tumor growth. Gamma knife has a wide range of indications for the treatment of brain metastases, and there is an increasing trend of using radiosurgery to treat brain metastases in recent years. Class 1 evidence supports stereotactic radiosurgery combined with whole brain radiotherapy for single metastases that can be surgically resected, and Class 2B evidence supports the use of stereotactic radiosurgery alone for a limited number of brain metastases. However, surgery should still be preferred for larger brain metastases (>3.5 cm in diameter) with significant occupancy signs or bleeding. Data confirm that the local control rate of gamma knife treatment of brain metastases is 80% to 90%, with a mean survival time of 8 to 11 months, and for single brain metastases, the treatment effect is similar to surgery plus whole brain radiotherapy (Figure 68-6). 33 cases with 52 metastases treated by Adler, 27 of which had conventional radiotherapy, were followed up for 5.5 months, and the local control rate was found to be 81%, and the KPS score The follow-up was 5.5 months and the local control rate was found to be 81% and the KPS score was found to be 21% improved, 49% unchanged, and 30% diminished. Between October 1993 and December 1995, the Department of Neurosurgery of Huashan Hospital treated 206 patients with brain metastases (501 lesions) with Gamma Knife, aged 28-78 years (average 57 years), with a male to female ratio of 2.7:1, 48% with single lesions and 33% with more than 3 lesions. The mean dose was 41±8 Gy (11-70 Gy) in the center and 22±4 Gy (10-53 Gy) in the periphery. Before or after Gamma Knife treatment, 20% of patients received whole brain conventional radiotherapy, 51% received chemotherapy, and 33% received surgical treatment of the primary tumor. And follow-up from 24 to 39 months showed that the local control rate of the tumor was 93%, the recurrence rate in situ was 1%, and the mean survival time was 8.5 months. Although the effectiveness of surgery plus postoperative radiotherapy in the treatment of single brain metastases has been affirmed, gamma knife treatment is gradually accepted by patients because of its advantages such as less trauma and shorter hospital stay. The main complication that may occur after Gamma Knife is the exacerbation of cerebral edema (related to volumetric effects and treatment dose), which can often be controlled with treatments such as dehydration and hormones. As with surgery, Gamma Knife does not prevent the development of new intracranial metastases, and for this reason most advocate supplementing Gamma Knife with 20-30 Gy of whole brain radiotherapy, but this is highly controversial, as some studies have found no significant effect on mean survival time with pre-Gamma Knife radiotherapy, concurrent radiotherapy, or Gamma Knife treatment alone.
Radiofrequency knife (Cyber Knife) is a new radiosurgery tool that is commonly used to treat certain larger tumors with less variation in dose distribution within the tumor because it can be used in a fractionated approach, and the irradiation dose can be increased for certain important sites such as tumors within the brainstem with mild postoperative adverse effects (Figure 68-7). From January 2008 to July 2011, 67 cases of single brain metastases were treated with radiofrequency knife at Huashan Hospital, with a follow-up of 12 to 45 months, with a mean of 26 months, and the tumor local control rate was 92% at 1 year and 85% at 2 years. The mean survival was 20 months. The mean survival was 20 months. In 20 cases of multiple brain metastases, the 1-year tumor control rate was 87%, the 1-year OS was 93%, and the mean survival was 16 months.