Browse Tag: brain metastasis

Brain Tumors

More than 18,000 new cases of primary brain tumors are treated each year in the United States. Metastases are even more frequent and contribute considerably to suffering and death from systemic cancer. The diversity of brain tumors makes it important to attend to what is characteristic about each histologic type. Biologic specificity guides therapy to some extent now, and will be the key to successful treatment in the future.

The classification of brain tumors is a subject with confusing terminology. This text employs the simple approach of classifying brain tumors into metastatic, primary extra-axial, and primary intra-axial . These categories include all of the primary brain tumors listed in the World Health Organization classification , and adds pituitary and metastatic tumors. Although obviously simple, it follows practical clinical thinking. This chapter deals with the general biology, clinical features, and treatment of brain tumors as an overall problem.

GENERAL CONSIDERATIONS

“Is it benign or malignant?” is invariably the first question asked by patients, families, and physicians when confronted with a diagnosis of brain tumor. About a third of primary brain tumors can be called benign. Meningiomas and acoustic neuromas are good examples. They grow slowly, often can be removed completely, and rarely recur.

The concept of malignancy in the central nervous system (CNS) has a different meaning from that which applies to systemic cancers. The term “malignant” has nothing to do with metastasis out of the CNS, which is extraordinarily rare. It has everything to do with anatomic location and the possibility of complete surgical removal. Unless a tumor can be completely excised to the last cell, all intracranial neoplasms are potentially malignant in that they may recur, and often do.

Brain metastasis from an unknown primary

The last thing I’d like to just mention about, and it’s an important point, is the issue of brain metastasis from an unknown primary.If one looks at a series from M.D. Anderson, 220 patients with brain metastasis. Approximately 39 of those patients, or 18%, were without a known systemic site. The median age of these patients is approximately 55. Most of them had good performance status. About half of those lesions were multiple, however half of them were single. One actually looked at the histology of those tumors.

Approximately 31% were adenocarcinomas, representing by far the greatest number. In the few patients where a primary was eventually found, usually at autopsy, lung represented the most common primary site. The important thing to know about these tumors however is that there is a subset of these patients who can actually do quite well. All these patients were treated with whole brain radiation, 30 gray, and that intracranial disease-free survival at five years was 72% of these patients. And that the overall median survival of these patients was well over a year, whereas 12% of these patients surviving eight years and probably effectively cured of their disease.

What this says is that, particularly if you have a young middle aged person, good performance status, who has a solitary metastasis with no known primary, that that patient should indeed be treated very aggressively, both with surgery and radiation. Because that patient has a very good chance of having a long term disease-free survival, and potentially even cured.

Primary CNS lymphoma relative to chemotherapy

Just to give you an idea of what types of responses you can have. This is a 52-year-old man, presented with a huge mass in his right temporal parietal lobe. This was found on biopsy to be a CNS lymphoma and after two cycles on a regimen that we use, consisting of high dose methotrexate, cyclophosphamide and vincristine, after two cycles this was his scan.

This is before radiation therapy. So again a very satisfying disease to treat.

There remain a number of questions of primary CNS lymphoma relative to chemotherapy, such as who benefits from chemotherapy? We talked about the issue of immunocompetent versus immunodeficient patients. Prognostic factors seem to make a difference, with age being the most important. That elderly patients do not tolerate the chemotherapy as well or they don’t tolerate the chemotherapy side effects, and indeed they do not appear to benefit as much as younger patients. But what the age cut-off is and why this should be the case remains totally unknown. Issues relative to performance status, pathology and extent of disease appear to be less significant, at least for immunocompetent patients being treated with chemotherapy. There also continue to be significant and growing questions about the appropriate role for radiotherapy, such as what is the optimal dose and fractionation scheme, since combining chemotherapy and radiation now patients are living longer, one begins to have to worry about long term neuro-cognitive sequelae. One is beginning to question, with optimal chemotherapy, does one even need to use radiation therapy. So these are questions that still remain outstanding in primary CNS lymphoma. Again, a difficult problem in answering these questions given the relative rarity of the disease.

I’d like to just finish up by talking a little bit about, and mentioning a few of the recent developments, in the treatment of brain metastasis. A problem that medical oncologists obviously see quite frequently. The reason for that is that 20-40% of all cancer patients will develop brain metastases, accounting for 170,000 cases per year. The majority of these patients have lung cancer. Most of the metastases occur in the gray white matter, of which 80% is supratentorial. The few tumor types that can metastasize to the dura are breast and prostate, while the two tumor types that appear as hyperdense lesions without contrast are renal cell carcinoma, melanoma and actually sarcoma. But most of the other metastases appearing as hypo or iso-dense lesions.