Overview of Palliative Radiation Therapy for Brain Metastases
When cancer spreads to the brain, it’s a serious and potentially fatal issue. In fact, this is the immediate cause of death for over half of the people it affects. It’s notable that the most common brain tumor in the United States is actually a metastasis, which means that it’s a cancer that started somewhere else in the body and then spread to the brain. There are a few types of cancer that are more likely to spread to the brain, including lung, breast, colon, melanoma (a type of skin cancer), and kidney cancer.
Unfortunately, the survival rates for people with cancer that has spread to the brain are low. Only about 8.1% of people are still alive after two years, and 2.4% after five years. We also believe that between 10 and 40% of all people with cancer will eventually have it spread to their brain, but this is harder to determine because studies often don’t report how far the cancer has spread at the time of enrollment, so we might be underestimating how common this is.
The most common way for cancer to spread to the brain is through the blood. This is called hematogenous spread. The brain tissue provides a unique environment that can both help and hinder the spread of cancer. On one hand, it encourages spreading; on the other, it limits the ability of our treatments to reach the brain.
That’s why if a patient has cancer that has spread to the brain, we usually use radiation therapy. This aims to improve survival and quality of life. We also work on developing better treatments that can reach the brain, limiting the side effects of radiation on cognition, and deciding the best times to use immunotherapy. When making a treatment plan, we consider the patient’s health, the specifics about the tumor, and any past treatments the patient has had.
Finally, the use of whole-brain radiotherapy as a method to alleviate symptoms in people with brain metastasis. This was first reported by a group called Chao et al., and Chao et al. also reported that many patients still had their cancer come back after treatment. Further research showed that different doses of radiation were equally effective. This text aims to help people understand when radiotherapy might be beneficial, the significance of it, how it works, and the recent improvements in this treatment.
Anatomy and Physiology of Palliative Radiation Therapy for Brain Metastases
The cells that make up the choroid plexus in the brain form an important barrier between the blood and the cerebrospinal fluid (CSF) which surrounds the brain and spinal cord. This barrier allows the movement of tiny particles between the blood and the central nervous system (CNS), the part of the body that includes the brain and spinal cord. There’s a component of our immune system called C3 complement that has been found to help certain signals enter the CNS. This component is thought to play a role in the spread of cancer in the membranes that cover the brain and spinal cord.
Cancer metastasis, or the spread of cancer from its original site to other parts of the body, involves several steps: Firstly, cancer cells break away from the main tumor and invade nearby tissues and blood vessels. Next, these cells leave the bloodstream and enter other tissues in the body. Sometimes, cancer cells might remain inactive at their new location, and at other times, they grow and multiply. Factors that make it more likely for cancer to spread to the brain include a dense network of tiny blood vessels and a higher blood flow compared to other organs. Certain interactions between cancer cells and the blood vessels can also increase the likelihood of cancer spread.
The treatment dose for radiation therapy, often used to treat cancer, depends on how a particular tissue responds to radiation. Some tissues are more sensitive to a single high dose of radiation than others. For instance, many malignant (cancerous) tumors are more sensitive to radiation, while benign (non-cancerous) tumors are less sensitive.
Why do People Need Palliative Radiation Therapy for Brain Metastases
When treating patients with brain metastasis, or spread of cancer to the brain, doctors take into account several factors. These include the size and number of the areas affected in the brain, the patient’s overall health, age, presence of cancer elsewhere in the body, the specific location of cancer in the brain, the patient’s wishes, the original location of the cancer, and other factors.
Whole-brain radiotherapy (WBRT) is a treatment option often favored for these situations. This involves using radiation to treat the entire brain. It can help control the cancer, manage small, undetectable areas of cancer, lower the chance of cancer coming back, and improve the overall life quality for the patient. It can also prevent a dangerous condition called brain compression syndrome.
Another method, known as hypofractionation dosing, can also be beneficial. It may be particularly useful for larger areas of cancer, areas near crucial brain structures, patients who have received radiation before, or patients with other conditions like stroke or dementia.
WBRT is often the choice when more targeted radiotherapies cannot be performed. This can happen if the patient has numerous metastases, has a low diagnosis-specific graded prognostic assessment (DS-GPA) score, or has certain medical conditions that make other treatments risky.
Doctors might also consider the speed of metastasis – how quickly the areas of cancer in the brain are increasing – to decide whether WBRT is the best choice.
However, there are concerns about WBRT, including limited survival benefits and potential cognitive decline. However, improvements in cognitive function can happen if the tumor shrinks after WBRT. Doctors must balance the amount of radiation delivered, specifically to certain parts of the brain like the hippocampus which is involved in memory, to reduce cognitive impacts.
Radiotherapy effects on brain function are measured using various tests, like the Hopkins verbal learning test, trail making tests, and others. There can be a decline in mental abilities after WBRT, or after radiation to other parts of the brain like the prefrontal cortex or striatum.
Several strategies are used to reduce the cognitive impacts of WBRT. Hippocampal avoidance WBRT, stereotactic radiosurgery, and spatially partitioned adaptive radiotherapy (SPARE), which delivers the radiation treatment over several days to minimize side effects, have been used.
Overall, in treating brain metastasis, doctors must balance the need to control the cancer with the risk of potential side effects. They use various tools and strategies to deliver treatment as effectively and safely as possible.
When a Person Should Avoid Palliative Radiation Therapy for Brain Metastases
Collagen vascular diseases, like lupus, scleroderma, Sjogren syndrome, and inflammatory bowel syndrome, are generally considered as reasons to not have certain treatments or procedures. However, some people debate that these shouldn’t universally stop a procedure from happening. Collagen vascular diseases are conditions that affect your connective tissues, which include the proteins collagen and elastin in your skin and joints.
So, if you have inherited cancers or related issues such as ataxia telangiectasia, Nijmegen breakage syndrome, Fanconi anemia, Gorlin syndrome, Cockayne syndrome, Down syndrome, Gardner syndrome, Usher syndrome, your doctor needs to thoroughly assess your situation. These are all different medical conditions that can increase a person’s risk of developing certain types of cancer. It’s important to understand and manage these risks with your doctor’s guidance.
Equipment used for Palliative Radiation Therapy for Brain Metastases
Stereotactic Radiosurgery is a type of radiation therapy that focuses high-powered x-rays on a small area of the body. This technique is often used to treat tumors and other abnormalities in the brain, spine, and other parts of the body.
The procedure can be done using various tools such as a Linear accelerator, a Gamma Knife unit or charged particles. The Gamma Knife, for instance, uses 192 Cobalt 60 sources. It also incorporates an MRI-friendly device, known as a stereotactic headframe, to keep the patient’s head still. This frame is fitted with three angles which allow for the adjustment of the patient’s position. Additionally, this frame can move in the x, y, and z directions, minimizing the time taken to adjust the patient’s position.
While performing the surgery, the headframe is safely attached to the patient’s skull using titanium pins. The exact positioning of the head frame relative to the Gamma Knife is determined by the coordinates X, Y, Z, and the gamma angle, which are calculated based on the treatment area and treatment plan.
To map out treatment, healthcare providers use a software which employs digital imaging and communication in medicine. This software takes into account recent technological advances with the Gamma Knife, like the use of automated radiation dose balancing algorithms. These algorithms efficiently distribute the radiation dose to the required targets while taking care to protect critical structures within the body. The radiation dose to be applied and the isodose, which is the region receiving the same dose of radiation, are determined by various factors such as the type and size of the target and whether the patient has undergone any prior radiation therapy or stereotactic radiosurgery.
Who is needed to perform Palliative Radiation Therapy for Brain Metastases?
When a patient undergoes radiation therapy to treat cancer, there are several different healthcare professionals involved in the process. According to the World Health Organization (WHO), these include:
Firstly, the radiation oncologist or clinical oncologist; this is a doctor specializing in treating cancer with radiation. The radiation oncologist is in charge of patient care and manages everything from planning and supervision of treatment to monitoring how a patient is responding. This doctor also takes care of managing any side effects from the treatment. Additionally, they play a key role in ensuring safety of the patient during the treatment by designing a plan that restricts the radiation exposure to essential areas, while protecting vital organs.
Secondly, a medical radiation physicist is involved. Their job is to carefully oversee the dose of radiation used in the therapy, help to identify and protect organs at risk, and manage the technical equipment used for the therapy. They are also in charge of the safety of the patient and staff, ensuring precautions are taken against electrical and mechanical hazards, and avoiding contamination from radiation.
Medical radiation therapy technicians or radiotherapy technologists form another group of important personnel. They are responsible for setting up the machines for treatment, putting the patient in the correct position for treatment, and ensuring that all safety measures are followed. They also play an important role in making sure the quality of the system is constantly managed.
A radiation technician helps in preparing equipment and assuring patients are correctly positioned. They also maintain treatment records and ensure safe use of radiation therapy substances.
Medical dosimetrists have a specific job on the team, with their main responsibilities includes planning the treatment, creating moulds to facilitate the radiation, and calculating the precise amount of radiation to be given.
Engineers are the ones who fix the machines when they break down, apply their technical knowledge and keep the radiation equipment functional. They usually get their training from the manufacturer of the machines.
Lastly, there are other individuals who provide their expert advice during the process.
The numbers of these specialized professionals have remained stagnant over the years, causing a shortage especially in the United States. This is a concerning issue, as it could worsen and may impact patient treatment in coming years.
Preparing for Palliative Radiation Therapy for Brain Metastases
When planning radiation therapy for the brain, a major concern is the close location of important parts of the brain that control vital functions. If these areas get exposed to radiation, it can lead to serious health problems. That’s why it’s crucial to keep the patient still during treatment and plan it accurately. This can help to reduce the chance of complications.
How is Palliative Radiation Therapy for Brain Metastases performed
When you undergo a procedure, it’s important that you’re secure and still — this is known as immobilization. Different materials and methods are used, and different amounts of these materials can make contact with your body. The type and amount can change how repeatable the procedure is. Sometimes things like masks are used to keep you still, but this can be frightening for patients with claustrophobia. If your case is like this, your doctor will work to identify these situations beforehand and determine the safest way to proceed.
Whether a procedure works may depend on a patient’s ability to stay still for a while. Things like nerves, neurological conditions, or nausea may make this hard. Multiple pictures may be taken during a procedure, and there can be some uncertainty when they’re combined. Each stage of image taking has a risk of mistakes, which could potentially affect treatment outcomes.
The reproducibility of a setup relies a lot on the immobilization technique used. Sometimes, errors may occur. For instance, with the use of certain systems such as the stereotactic frames or thermoacrylic systems, the errors could range from 1.3 mm to 5.5 mm. The material used in the formation of the masks can also have an impact on these errors.
Fortunately, brain movements inside the skull are minimal, so the effects of such motion are lesser and calculating such minor movements during the procedure might not be necessary.
The need and the frequency of taking images during brain treatment procedures needs to be standardized. Acquiring an image on the first day is critical to identify any gross errors and to set data. Also, to keep a check on any errors that might occur due to other reasons, daily images for the first three days are typical. Weekly imaging may be needed if the fit of the immobilization device might change due to factors such as the side effects of medication.
During the treatment procedure, care is taken to safeguard the critical structures in the brain. There might be times when the anatomy of the intracranial structures is not evident in one shot and multiple images from different angles may be required. These images will then provide good information when clear images cannot be achieved due to the structure of immobilization devices or the arrangement of the fields.
Before starting the treatment, a virtual planning Computed Tomography (CT) scan should be done for planning. This becomes much more necessary when only part of the brain is being irradiated. If the whole brain is treated, the use of parallel fields in enables coverage of the entire brain.
The plan for your treatment will depend on your specific situation. Whole-brain radiotherapy, stereotactic radiosurgery, or hypofractionated stereotactic radiotherapy might be suitable depending on the size and location of the tumors. There is an intent to minimize the exposure of vital structures while treating non-hazardous tumors. A plan may be made to target the site of interest while still avoiding any potential damage to nearby structures.
Doctors can also use CT and MRI imaging to outline the contours of the cerebellum, brainstem, and other areas to ensure optimal treatment. For brain metastasis, contrast-filled MRIs are a good choice for treatment planning. Critical structures have a tolerance dose beyond which they should not be exposed. Hence, planning the treatment volume and appropriate administration of dose become critical to the success of the treatment.
Possible Complications of Palliative Radiation Therapy for Brain Metastases
Whole-brain radiotherapy (WBRT) is a method used to treat problems in the brain. It can sometimes cause issues. For example, one risk of WBRT is radionecrosis, which is when brain tissue dies due to radiation. People might need another operation to remove this dead tissue in the future. It can also lead to seizures, especially for people who already have epilepsy. And the treatment requires the patient to keep their head still which can be a problem for people who are afraid of confined spaces.
Straight after the treatment, people might experience problems such as skin redness, hair loss, tiredness, changes in taste and smell or ear problems. Later on, they might have memory loss, confusion, and a condition called leukoencephalopathy, which is an unusual change in the white matter of the brain.
Other disadvantages of WBRT could include a decline in the person’s health-related quality of life, a loss of hair, and tiredness. There might also be a loss in cognitive abilities and the need for multiple trips to the hospital. There’s also a risk for damage to the bone marrow, inflammation in the gut and mouth sores. These risks prevent the use of WBRT in some patients with advanced solid tumor cancers.
Stereotactic radiosurgery (SRS), another treatment method, can cause some side effects too. These can be local (at the site of treatment) or systemic (affecting the whole body).
Local effects of the SRS procedure include trauma, bleeding, and infection at the site where the head frame is placed.
Systemic effects can appear soon after treatment (headache, nausea, vomiting, seizures, and worsening neurological deficits due to swelling) or many months later (brain bleeding, tissue death, and changes related to the treatment like increased contrast, tissue death, swelling and mass effect). Steroids, hyperbaric oxygen, a specific type of antibody (bevacizumab), and surgical removal might be necessary to treat these conditions. Similarly, there is a potential risk of cranial neuropathies which are disorders of the nerves in the brain. Other serious side effects of SRS are rare, but may include harm to the optic nerve, tissue death due to radiation, and injury to blood vessels.
What Else Should I Know About Palliative Radiation Therapy for Brain Metastases?
Doctors use various tools to predict how likely a patient is to get better, depending on their particular situation. One of these tools, called Recursive Partitioning Analysis (RPA), analyzes four different factors, such as the state of the original tumor, whether the disease has spread, the overall health and capabilities of the patient, and age. According to the RPA, patients are divided into three groups. Patients in groups I and II are recommended treatments like surgery or radiation. Those in grade III are usually suggested primarily supportive care, like pain management.
Recently, doctors have started to include changes at a molecular level to make these predictions more precise. For example, for lung cancer, they may look at genetic mutations, alongside other variables such as age and the extent of the disease spread. For cancers like breast cancer and melanoma, it may be other factors like specific hormone statuses and the presence of certain genetic mutations.
Doctors use imaging scans, like MRIs, to track how well treatment is working by comparing it to a series of established criteria. Things they look out for include whether the cancer has shrunk or spread, changes related to the cancer or the treatment, and how well the patient is physically doing.
Additionally, they assign labels to lesions based on their size and location. They might be ‘target lesions,’ which they specifically measure, or ‘non-target lesions,’ which they monitor for signs of disease progression. They use standard rules to judge whether the disease has responded to the therapy, is stable, or is growing. For example, if all lesions disappear for at least four weeks, they would say that the treatment has achieved a ‘complete response.’
One of the challenges in evaluating the effectiveness of treatments is achieving ‘standardization,’ which means getting everyone to measure and evaluate things the same way. This is particularly important when participating in clinical trials, where consistency in reporting is essential. To combat this issue, there are several definitions of survival that consider different aspects of a patient’s condition and are used in clinical trials.
The nature of the disease, the type of therapy, the effects on the patient’s quality of life, and the use of supportive therapies like steroids can all play important roles in judging treatment response. The paramount goal of these approaches is to ensure the best patient care, accurately predicting treatment outcomes, and continuously improving the standard of treatments based on these insights.
