Glioblastoma is an aggressive type of brain tumor that originates in the brain or spinal cord. This tumor grows rapidly and can spread quickly within the brain tissue. Radiation therapy is an important component of its treatment, often serving as a primary approach to manage the disease.
How Radiation Works for Glioblastoma
Radiation therapy employs high-energy rays, such as X-rays, gamma rays, or protons, to target and damage the genetic material, or DNA, within cancer cells. This damage prevents the cancer cells from successfully growing and dividing, ultimately leading to their death. For glioblastoma, the objective is to deliver a precise dose of radiation to the tumor and a small margin of surrounding tissue. This margin accounts for microscopic tumor cells that may have infiltrated nearby healthy brain areas.
The goals of radiation in glioblastoma treatment include controlling tumor growth, alleviating symptoms caused by the tumor’s presence, and extending the patient’s life expectancy.
Types of Radiation and Delivery
External Beam Radiation Therapy (EBRT) is the most common method for delivering radiation to glioblastoma. This approach involves conventional fractionation, where daily treatments are administered over several weeks, five days a week for six weeks. Each session delivers a small dose of radiation, allowing healthy tissues to recover between treatments while cumulatively damaging tumor cells.
More advanced techniques like Intensity-Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) offer precision. IMRT shapes the radiation beams to conform closely to the tumor’s three-dimensional shape, varying the intensity of the radiation within each beam. VMAT delivers radiation as the treatment machine continuously rotates around the patient, optimizing dose distribution and reducing treatment time. These methods help spare healthy brain tissue surrounding the tumor.
Stereotactic Radiosurgery (SRS) or Stereotactic Radiotherapy (SRT) provides a highly precise, high-dose radiation delivery, typically in one (SRS) or a few (SRT) sessions. These techniques are reserved for smaller tumors or recurrent glioblastoma, where precision is important. Proton therapy, an emerging option, uses protons instead of X-rays, which deposit most of their energy at a specific depth, potentially reducing the dose to healthy tissues beyond the tumor. Before treatment, a detailed planning process involves imaging like MRI and CT scans to precisely map the tumor and surrounding structures. This simulation ensures accurate positioning and beam alignment during each treatment session.
Managing Treatment and Side Effects
Patients undergoing radiation therapy for glioblastoma can expect daily treatment sessions, lasting only a few minutes each, though preparation time is longer. Before each session, the patient is positioned on a treatment table, often with a custom-made mask or headrest to ensure precise immobilization. This careful setup guarantees that radiation beams are directed accurately to the target area, minimizing movement during delivery. Monitoring by the radiation oncology team occurs throughout the entire course of treatment.
Common acute side effects associated with brain radiation include fatigue and skin irritation in the treated area, resembling a sunburn. Hair loss is common within the radiation field, though it may be temporary. Patients might experience a temporary worsening of neurological symptoms, such as headaches or seizures, due to brain swelling caused by the radiation.
These side effects are managed to improve patient comfort and safety. Brain swelling is often controlled with corticosteroids like dexamethasone. Supportive care, including rest and nutritional support, helps manage fatigue and maintain overall well-being. The medical team provides guidance on skin care and other supportive measures to alleviate discomfort throughout the treatment period.
Role in Overall Treatment Strategy
Radiation therapy integrates with other glioblastoma treatments, forming a comprehensive strategy against the disease. Following surgical removal of the tumor, radiation is initiated to target any remaining microscopic cancer cells that could not be surgically removed. This post-operative approach aims to reduce the likelihood of tumor recurrence.
Radiation therapy is commonly used concurrently with chemotherapy, most often with temozolomide, an oral chemotherapy drug. This combined approach, known as concomitant chemoradiation, has demonstrated improved outcomes by enhancing the effectiveness of radiation against tumor cells. Following the completion of radiation, patients often continue with adjuvant chemotherapy, temozolomide, for several cycles to further suppress tumor growth.
Radiation also plays a role in managing recurrent glioblastoma, either as a standalone treatment or in combination with other therapies, depending on the tumor’s location and previous treatments. The combination of radiation with surgery and chemotherapy represents the most effective approach to optimize patient outcomes.