Surgery for Primary Brain Tumors
Surgery has traditionally been, and remains, the first line of therapy for patients with primary brain tumors. For some tumors, complete surgical removal is often possible. However, even for tumors that cannot be completely removed, surgery can have a major beneficial effect on symptoms and on the effectiveness of other treatments, such as radiation therapy and chemotherapy.
The Role of Surgery
Surgery has several goals in the treatment of all primary brain tumors, and these include the following:
a. Complete tumor removal: Tumors which can often be removed entirely include some meningiomas, grade I astrocytomas, and ependymomas. However, complete removal does not mean the patient can forget about the tumor completely, because these tumors can come back even if all visible signs of the tumor are removed by the surgeon. For this reason, it is important that you follow up regularly with your neurosurgeon so any tumor recurrence can be detected early.
b. Partial tumor removal: Even for tumors that cannot be completely removed, partial removal has a role. There is increasing evidence that the more tumor removed during surgery, the better your chances that other therapies, including radiation therapy and chemotherapy, will be effective. Neurosurgeons in general will recommend as complete a surgical resection as possible, so long as the tumor can be removed safely—i.e., without leaving you with an unacceptable neurological deficit. Tumors that are in deep parts of the brain or which involve critical brain structures, such as those that allow you to speak and understand, however, may not be even partially resectable. Furthermore, tumor debulking is a major surgical procedure, and like any other major operation, has certain risks which become significant if your general medical condition is severely compromised (such as congestive heart failure, kidney failure, severe lung disease, and so on). In these cases, the surgeon may recommend a stereotactic biopsy instead. In this procedure, the surgeon uses a pencil-thin biopsy probe to remove a small amount of tissue, under computer guidance. This small amount of tissue is used for pathological evaluation, under minimally invasive conditions that, in general, places the body under far less stress than surgery. There are however, two general risks of stereotactic biopsy. First, because it removes only a small amount of tissue, it is possible to miss the tumor entirely or remove a fragment of tissue that is not representative of the overall tumor. Second, it is possible to produce local bleeding from the procedure. Both of these problems can be dealt with effectively, however. When you first meet with your neurosurgeon, be sure to discuss the pros and cons of partial removal versus stereotactic biopsy in your particular case.
c. Pathological identification: As our treatments of primary brain tumors become more sophisticated and tailored to the individual tumor, it is becoming increasingly important to have adequate amounts of tissue for review by neuropathologists. For example, over the last several years, specific markers that predict how well you will respond to specific treatments have become routinely available, and this technology will certainly be expanded as we learn more about tumors and their appropriate treatments. The only way to access this information, however, is by examining tumor tissue, which is provided by the neurosurgeon during an operation, either by partially removing the tumor or by a stereotactic biopsy.
d. Removal of hypoxic tissue: As primary brain tumors grow, their ability to nourish themselves with nutrients and oxygen (provided by blood flow) becomes increasingly compromised. As the oxygen delivery decreases, these tumors become more and more deficient in oxygen—a condition called “hypoxia.” Hypoxic tissue is remarkably resistant to other forms of therapy, particularly radiation therapy. The only way to get rid of this especially dangerous part of the tumor is for the neurosurgeon to remove it during an operation.
e. Symptomatic improvement: Primary brain tumors cause symptoms in part by compressing the normal brain and thereby interfering with normal brain function. By partially removing the tumor, neurosurgeons can relieve this compression and markedly improve symptoms and the quality of life. This is true even in situations where the tumor has become resistant to all other forms of treatment.
Surgery Risks and Side Effects
Surgery on the brain is a major procedure, and depending on the extent of the procedure, can be associated with a variety of risks and side effects. Fortunately, these are all relatively uncommon, but you should nonetheless discuss them with your neurosurgeon before your operation.
a. Infection: An infection of the surgical site or brain is very uncommon. More common are infections of other parts of the body that may develop because you are staying in bed after the procedure, such as lung infections or bladder infections. This is why it is important to be mobile—spend as much time out of bed as possible—as soon as your surgeon feels it is safe. All of these infections are generally treatable with antibiotics, but an infection can still prolong your hospital stay (see below).
b. Blood clots: Having a brain tumor by itself increases your risk of developing a blood clot in your legs, and staying in bed after an operation markedly increases that risk. Blood clots in the veins of the legs can be carried by the
bloodstream to the lungs, where they are called “pulmonary thromboemboli.” This is a serious problem that can be fatal if not prevented or adequately treated. This underscores the importance of being mobile as soon as it is safely possible. If this cannot be done, your surgeon may prescribe compression to your legs, to prevent blood from pooling there, or may administer some blood thinners to keep your blood from clotting.
c. Temporary neurological deficits: It is not uncommon for the surgical procedure itself to increase the amount of swelling in the surrounding normal brain tissue. Depending on where in the brain this occurs, this may lead to a temporary worsening of your neurological symptoms. This will often improve over time, particularly with the use of steroids, such as Decadron or prednisone.
d. Permanent neurological deficits: There is always the risk of damaging part of your normal brain tissue during the surgery, and depending on the location of this injury, this could leave you with a permanent neurological deficit. Neurosurgeons work very hard to prevent this, but you should still discuss what the chances of this happening are in your case. In certain circumstances, when the neurosurgeon feels that this is an appreciable risk, he/she may elect to perform your surgery with you awake (see below).
e. Bleeding into the surgical site: Several types of primary brain tumors have abnormal blood vessels that are easily damaged and can bleed. Some bleeding typically can occur after any brain tumor operation, but this is usually minor, temporary, and causes no appreciable problems. On rare occasion, however, this can become more serious, and can require another operation.
f. Seizures: Blood is very irritating to the brain, and even a trivial amount of bleeding can induce seizures. Your surgeon may choose to start you on anti-seizure medication before the operation in order to prevent this problem from occurring.
g. Prolonged hospitalization: Typically, a stereotactic brain biopsy requires one day of hospitalization, and a tumor resection requires three to five days in the hospital. However, any of the above complications will increase the time you have to spend in the hospital. Prolonged hospitalization by itself is a problem, since it increases your risk of acquiring a hospital-acquired infection (typically more resistant to antibiotics than a community-acquired infection) and can make it harder for you to readjust emotionally and physically to life at home. If your hospitalization has been prolonged for any reason, your neurosurgeon may prescribe a brief stay in a rehabilitation hospital or may have you do home rehabilitation. This can significantly accelerate your return to a normal life.
Newer Surgical Methods
Surgical Navigation: As with any other type of surgery, neurosurgery continues to make technological advances in the procedures used for brain tumor biopsies and resections. Many of the recent advances involve marrying neurosurgical techniques with a variety of sophisticated brain imaging methods. These advances give the surgeon detailed, real-time anatomic views of the tumor and surrounding brain in the operating room that can guide how the surgery is performed. In addition, several of these imaging techniques provide the surgeon with information on where certain important neurological functions are controlled in the brain and how close these regions are to the tumor.
Surgical Drug Delivery: Another area of neurosurgical advances involves marrying surgical technology to drug delivery technology. One of the problems in effectively treating brain tumors with chemotherapy is the “blood brain barrier.” This is a normal feature of the blood vessels in the brain, which are surrounded by cells that prevent many substances in the blood from entering the brain. This barrier exists so that the brain can be insulated from a variety of chemicals that circulate in your blood and which could impair normal brain function if they got into the brain. However, this barrier also blocks the entry of a variety of chemotherapeutic agents that are active against brain tumors in the laboratory. Several methods of getting around this problem through the use of neurosurgical techniques are either available or under active investigation. These include the following:
a. Gliadel®: During a brain tumor removal procedure, the neurosurgeon generates a “resection cavity”—i.e., a hole in the brain where the visible tumor used to be. In most primary brain tumors, however, we know that malignant tumor cells are left behind within a centimeter or less from the edge of the resection cavity. One option now available to the surgeon is to line this cavity with a biodegradable wafer that contains high concentrations of BCNU, a chemotherapy drug. As the wafer is slowly dissolved by the surrounding brain tissue, it releases high local concentrations of BCNU. This preparation was approved by the Food and Drug Administration over a decade ago for use in patients with malignant gliomas, and it is marketed under the name Gliadel®. While this is a very promising technology, Gliadel® use is associated with some complications, and prior use of this agent may prevent you from enrolling in certain investigational clinical trials.
b. Convection enhanced delivery: In this procedure, a small catheter is inserted into or surrounds the brain tumor, and chemotherapy is slowly pumped into the tumor directly. This method of drug delivery has the advantage over Gliadel® because it covers large areas of brain tissue surrounding the tumor, where microscopic nests of tumor cells frequently can be found. It is still considered an investigational procedure, however, and whether it will find its way into the mainstream of neurosurgical techniques will depend on a number of clinical trials that are ongoing. If you are interested in considering this option, you should ask your neurosurgeon for the nearest center that is investigating this technology.
Cortical Mapping: Sometimes, removing or partially removing a tumor involves operating on a regions of the brain that are involved in critical functions, such as moving parts of the body, speaking or reading. In these situations, the neurosurgeon may elect to remove the brain tumor under local anesthesia, with you at least partially awake. During such a procedure, he/she will map exactly where your ability to speak or move is controlled in the brain and where these brain regions are located relative to the tumor. During the tumor removal, the surgeon will monitor your ability to perform these normal functions. This procedure has the potential to significantly reduce your risk of suffering a permanent neurological deficit during the surgery. While the prospect of having your brain operated on while you are awake may sound gruesome, patients are typically treated with sufficient medication to be completely
Surgery for Secondary Brain Tumors
It used to be assumed that surgical removal had no role in the treatment of cancers that had metastasized (i.e., spread) to the brain, and that the only appropriate treatment for this problem is radiation therapy. However, several studies performed in the late ’80s and early ’90s have clearly shown that removal of brain metastases, when they are limited in number, can significantly improve survival and quality of life in patients with brain metastases, particularly when combined with radiation therapy. More recent studies in patients with spinal cord compression—another complication of metastatic cancer—have also shown that surgery has a definite role in well-selected patients. It is now standard practice to remove large or symptomatic brain metastases in patients whose cancer elsewhere (e.g., lung, bone, breast, etc.) is under good control.