Intrathecal (IT) chemotherapy delivers anti-cancer drugs directly into the cerebrospinal fluid (CSF). This fluid surrounds and cushions the brain and spinal cord, forming the central nervous system (CNS). By injecting medication into this fluid-filled space, healthcare providers ensure the drugs reach cancer cells within the CNS, a region often difficult to treat with standard chemotherapy methods.
Why Intrathecal Chemotherapy is Necessary
The brain and spinal cord are protected by a natural defense mechanism known as the blood-brain barrier (BBB). This barrier is composed of tightly packed cells lining the blood vessels in the brain, which restrict the passage of many substances from the bloodstream into the CNS. While this barrier is beneficial for protecting the brain from harmful toxins, it also prevents many conventional chemotherapy drugs, which are often large molecules, from reaching cancer cells within the brain and spinal cord.
Systemic chemotherapy, administered intravenously or orally, circulates throughout the entire body but often cannot cross the BBB in sufficient concentrations to treat CNS cancers effectively. This limitation necessitates a different approach for cancers that have spread to or originated in the CNS. Intrathecal chemotherapy bypasses this protective barrier by delivering drugs directly into the cerebrospinal fluid, allowing the medication to bathe the brain and spinal cord and directly target cancer cells.
Methods of Administration
Intrathecal chemotherapy is administered through two primary methods, each chosen based on the patient’s specific needs and the frequency of treatment required. One common method is a lumbar puncture, often referred to as a spinal tap. During this procedure, the patient typically lies on their side with knees pulled towards the chest or sits leaning forward, positions that help to widen the spaces between the vertebrae in the lower back.
After cleaning the skin with an antiseptic solution, a local anesthetic is injected to numb the area, minimizing discomfort. A thin needle is then carefully inserted between two vertebrae in the lower spine, entering the intrathecal space where the cerebrospinal fluid is located. A small amount of CSF may be withdrawn for diagnostic testing before the chemotherapy drug is slowly injected.
For patients requiring frequent or long-term intrathecal chemotherapy, an Ommaya reservoir may be implanted. This is a small, dome-shaped device, approximately the size of a quarter, surgically placed under the scalp. A thin tube, called a catheter, extends from the reservoir into one of the brain’s ventricles, which are fluid-filled spaces where CSF is produced and circulates.
The Ommaya reservoir provides a secure and repeated access point to the cerebrospinal fluid without the need for multiple lumbar punctures. When chemotherapy is needed, a healthcare professional inserts a needle through the skin of the scalp directly into the reservoir, and the medication flows into the CSF. This method offers convenience for ongoing treatment.
Conditions Treated
Intrathecal chemotherapy is employed for cancers that involve the central nervous system (CNS), either originating there or spreading from other parts of the body.
One common application is in treating leukemias, particularly Acute Lymphoblastic Leukemia (ALL). In ALL, cancer cells have a significant risk of spreading to the CNS, making intrathecal chemotherapy a standard part of the treatment protocol, often used as a preventive measure. Certain types of lymphomas, such as Burkitt lymphoma, lymphoblastic lymphoma, and diffuse large B-cell lymphoma, may also require intrathecal chemotherapy if they have spread to the CNS or are at high risk.
Intrathecal chemotherapy is also utilized for leptomeningeal carcinomatosis, a condition where cancer cells spread to the leptomeninges, the membranes covering the brain and spinal cord. This can occur with various solid tumors, including breast cancer and lung cancer, and the direct delivery of chemotherapy into the CSF helps to manage these widespread cancer cells.
Potential Side Effects and Management
Like all chemotherapy treatments, intrathecal chemotherapy can lead to a range of side effects, some related to the medication itself and others to the administration procedure. The most common side effect is a headache, which can vary in intensity from mild to severe. This headache is often associated with a post-lumbar puncture headache, especially when the treatment is given via spinal tap, and may be accompanied by nausea, vomiting, or fever.
Patients may also experience back pain, dizziness, or a temporary feeling of weakness or tiredness. These symptoms might worsen when standing up and improve when lying down. To manage headaches, resting flat after the procedure is often recommended, as this can help prevent their occurrence. Pain relievers can also provide relief for headaches and other discomfort.
While less common, more serious side effects can occur, including seizures, confusion, or difficulty with walking or talking. There is also a small risk of infection or bleeding at the injection site, or in rare instances, more significant neurological damage or spinal fluid leakage. Healthcare providers closely monitor patients for these side effects and offer supportive care, such as anti-nausea medications, pain relief, and close observation, to manage symptoms and address any complications promptly.