I. What is dural metastatic cancer? Dural metastases?
Dural metastases are seen in about 8-9% of patients with advanced cancer, about half of them involve only the dura mater, and the primary foci are commonly found in breast cancer, prostate cancer and lung cancer. In recent years, the detection rate of dural metastases has been increasing with the improvement of comprehensive cancer treatment, the prolongation of patient survival and the development of neuroimaging technology. Since some patients with dural metastases are combined with brain parenchymal metastases or soft meningeal carcinoma, and some patients do not show symptoms and are missed, and some patients are misdiagnosed due to occupying lesions resembling meningioma or combined with subdural hematoma, so they should be paid sufficient attention in clinical practice.
What kind of tumors are likely to cause dural metastasis?
The common primary foci of dural metastases include breast cancer, prostate cancer, lung cancer, gastric cancer, hematologic malignancies, neuroblastoma and head and neck cancer.
What symptoms indicate the possibility of dural metastasis?
1. About 11%-20% of patients with dural metastases do not appear asymptomatic, but are only discovered incidentally by radiological imaging or at autopsy.
2. Those who develop symptoms are mostly related to compression or invasion of brain tissue, or can be caused by combined subdural hematoma or fluid. Less commonly, they are caused by obstruction of blood return due to involvement of the dural venous sinus by the lesion, mainly due to.
(1) Symptoms associated with compression or invasion of adjacent brain tissue are the most common clinical manifestations in patients with dural metastases, with headache and cranial neuropathy in particular being common, followed by visual disturbances, altered mental status, hemiparesis, sensory abnormalities, epilepsy, gait abnormalities, and signs of cranial hypertension. Headache is usually helpful for localization; cranial neuropathy usually suggests dural metastases involving the skull base; local weakness or sensory loss usually helps to localize the tumor to the contralateral hemisphere.
(2) Dural metastases combined with subdural hematomas are most often chronic hematomas, with headache, contralateral limb weakness, and varying degrees of impaired consciousness as the main manifestations; occasionally, acute hematomas are seen, and more rarely, hemorrhagic internal dural meningitis.
3. Systemic active cancer is seen in most patients with dural metastases, with bone, lymph node, liver and lung involvement being the most common.
4. What tests are needed to confirm the diagnosis of dural metastatic cancer?
The imaging diagnosis of dural metastases mainly relies on CT scan and MRI imaging.
One of the advantages of CT scan is that the bone window image can help to clarify the skeletal involvement.
MRI is the imaging test of choice for dural metastases because it helps to differentiate between dural metastases and soft meningeal metastases, etc. MRI findings can be divided into three categories: (1) diffuse dural thickening, which is characterized by widespread, uniformly enhancing dural thickening; (2) subdural hematoma, which can be characterized by chronic subdural hematoma or a rarer subtype” hemorrhagic endodural laminitis”, the latter showing a slight, diffuse dural thickening distributed along the inner plate of the skull; (3) meningioma-like masses.
3. Other imaging features The most common sites of involvement are the parietal and frontal lobes. Half have brain parenchymal compression and vasogenic edema, 2/3 have visible cranial involvement, about half have dural caudal signs, and 1/3 have brain tissue invasion. In addition, a few dural metastases may involve venous sinuses and show manifestations of venous sinus occlusion.
V. How to diagnose dural metastatic cancer?
1. Firstly, patients should be asked in detail whether they have a history of related tumors. At present, the primary foci of dural metastases that can cause meningioma-like masses include follicular thyroid cancer, breast cancer, prostate cancer, hematologic malignancies, lung cancer, etc.; the primary foci of dural metastases that can cause subdural hematoma or effusion include stomach cancer, lung cancer, breast cancer, prostate cancer, etc. For those who have a history of the above mentioned tumors, once the relevant clinical and imaging manifestations appear, the possibility of dural metastases should be considered.
2. Dynamic testing of tumor markers can help to clarify the primary focus, and cytological examination of cerebrospinal fluid can help to exclude soft meningeal carcinoma.
3. For those who have no history of related tumors and have dural metastases as the first symptom, pathological examination should be used as the basis for diagnosis because of the lack of specificity of clinical and imaging manifestations. If the subdural hematoma is suspected to be caused by dural metastases, the drainage fluid should be retained and sent for cytological examination at the same time during surgery.
4. In general, the diagnosis of dural metastases should meet the following criteria: 1) MRI and CT imaging suggest dural metastases; 2) histopathological basis of the primary cancer; 3) cytological examination of lumbar puncture shows no tumor cells in the cerebrospinal fluid; 4) the resected dural metastases are consistent with the histopathology of the primary cancer; 5) no combined brain metastases or soft meningeal metastases.
What diseases need to be differentiated from dural metastases?
Some isolated dural metastases may also show intracranial extra-axial, well-defined, high-density or isointense meningioma-like lesions with meningeal tail sign and contrast enhancement, which are difficult to distinguish from meningioma. In particular, dural metastases caused by prostate cancer can also present with osteophytes, which are easily misdiagnosed as meningiomas before surgery. Thus, special imaging such as magnetic resonance spectral imaging, dynamic sensitive-contrast-enhanced perfusion-weighted imaging (PWI), T2 perfusion imaging, diffusion-weighted images, and apparent diffusion coefficient maps can help to distinguish dural metastases from brain metastases; 99mTc-methylene diphosphonic acid, 111 indium-octreotide brain imaging combined with FDG-PET scan, and 11C-methionine PET-CT for both The differential diagnosis also has some value.
2. Simple subdural hematoma should be differentiated from simple subdural hematoma or effusion for dural metastases with combined subdural hematoma or subdural effusion.
3. A few dural metastases may present as the rarer “hemorrhagic endodural inflammation”, which should be differentiated from soft meningeal carcinomatosis. Generally, the former often shows a slight diffuse dural thickening, resembling internal dural hemorrhage, but the enhanced MRI shows that the dural enhancement is distributed along the inner plate of the skull rather than along the sulcus, which can be used as a basis for differentiation from the latter.
VII. How to treat dural metastases?
There is no standard treatment plan for dural metastases, and surgery, radiotherapy, chemotherapy, combination therapy or supportive therapy can be used in general.
1. It is generally believed that for single metastases, easy to reach with clear boundaries, especially if the systemic lesions are controlled or not life-threatening in the short term, surgical resection of metastases is the best treatment; even if the patient’s systemic cancer is in the progressive stage, if the dural metastases cause severe symptoms and the patient can still tolerate surgery, surgical resection should also be attempted. Dural defects after tumor resection can be repaired by autologous fascia or artificial dura mater. If dural metastases cause subdural hematoma, timely hematoma removal or drilling and drainage should be performed.
Radiation therapy can be used for patients with dural metastases that are difficult to remove or extensive or who do not have a long life expectancy due to progression of systemic disease.
3. There is insufficient evidence to support intrathecal chemotherapy for dural metastases. Because dural metastases are located outside the blood-brain barrier, they have the potential to benefit from systemic chemotherapy because they avoid the limitations of the blood-brain barrier on the permeability of chemotherapeutic agents. In addition, patients with DM often have a combination of active systemic cancers that require chemotherapy, so the best regimen for patients with dural metastases suitable for systemic chemotherapy should be chosen for the primary cancer.
High-dose dexamethasone often helps to relieve symptoms in patients with dural metastases even if no significant brain edema is found on MRI.
VIII. What is the prognosis of dural metastases?
Current retrospective analysis suggests that the median overall survival of patients with dural metastases is 6 months (range 1 month to 7 years, varies by treatment!) , depends mainly on the progression of the primary cancer and the recurrence (especially in situ recurrence) of the dural metastases, but also on the pathological type of the primary tumor and the systemic progression. The overall survival of those with controlled systemic cancer and complete resection of metastases can be more than 2 years.
Univariate analysis showed that progression-free survival and overall survival were shorter in patients with older age, lower KPS scores, combined systemic disease and lung cancer at the primary site, and longer in those with surgical resection and chemotherapy.
Multifactorial analysis showed that progression-free survival and overall survival were shorter in those with low KPS score and lung cancer, and longer in those with surgical resection, while chemotherapy only improved progression-free survival.