Treatment Options

Radiation therapy is a type of cancer and tumor treatment that uses beams of energy to destroy or damage cancer cells. It works by damaging the DNA within the cancer cell, which provides the cancer cell the instructions for how to grow and divide. Without these instructions, the cancer cells die and the tumors can stop growing and sometimes shrink.

Note: Radiation may be called different names, but they all mean the same thing: radiotherapy, irradiation, x-ray therapy, radiation treatment or radiation therapy.

Radiation therapy is delivered in 3 ways: external beam radiation, internal radiation implants, or radiopharmaceutical injection. The most common kind for cancer treatment, and specifically leptomeningeal cancer, is external radiation.

External Beam Radiation Therapy

Linear accelerators (linacs) or cyclotrons are machines used for external beam radiation therapy. They send high-energy beams to a precise point on your body without ever touching you. There are several types of external radiation:

• 3D conformation radiation therapy (3DCRT)
• Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT)
• Image guided radiation therapy (IGRT)
• Stereotactic radiosurgery (SRS) or stereotactic body radiation therapy (SBRT). These involve high doses of focused radiation with surgical precision, but no actual surgery is involved. You may hear terms such as gamma knife, cyberknife and x-knife, all of which are types of stereotactic radiation therapy with different brand names

The most common form of external radiation uses photon beams, which is the same type of radiation used during an x-ray but at a higher energy and more focused dose. The radiation is delivered from multiple angles to optimize the dose to the tumor and minimize the dose to the rest of your body.

Another type of external radiation is called proton therapy or particle beam therapy. This type of radiation uses charged particles called protons instead of an x-ray beam. There are some advantages and disadvantages of this approach, depending on the scenario. Proton therapy is very specialized and only available at certain centers. Your doctor can explain whether and why protons may or may not be appropriate for your case. Proton therapy delivers a specific dose of focused radiation and can limit exposure to nearby tissues. The protons stop at a certain distance, so the tissue behind the tumor is exposed to very little radiation. There are some other nuances to this type of treatment, however, so it is not ideal for all cases. 

Photon vs. Proton Radiation Therapy

Photon radiation therapy has traditionally been used as the standard of care for brain tumors because of its effectiveness at destroying cancer cell DNA. Although any type of radiation may affect nearby normal healthy tissues, modern photon techniques, such as intensity modulated radiation therapy (IMRT) and volumetric arc therapy (VMAT), are highly effective at sparing nearby normal tissues.

Proton therapy has a similar effectiveness at destroying cancer cell DNA. It also may deposit a higher energy at the tumor site or next to the tumor, which may or may not be helpful. Protons also allow for better sparing of tissues farther away from the target. This may result in fewer side effects than photon therapy, but this depends on the scenario and the area targeted by radiation.

Radiation Therapy for Leptomeningeal Cancer

Radiation therapy is a useful and common treatment for people with leptomeningeal spread. It can be used to treat the cancer in the brain and spine by stopping further spread and it can be used to treat symptoms caused by advanced cancer. Because most systemic therapies like chemotherapy do not penetrate the leptomeningeal space, radiation therapy can be particularly useful as it delivers its effect into any part of the body that is targeted.

Ways in which radiation therapy (photon or proton) is used in leptomeningeal cancer treatment includes:

• Targeted radiation such as SRS or SBRT: Targeted radiation can be used to control a limited number of growths (nodules) in the brain or spine or help with symptoms like pain or neurologic symptoms and/or to prevent development of symptoms. Since targeted radiation does not treat the entire leptomeningeal compartment, it therefore does not treat the leptomeningeal cancer cells outside of the targeted radiation fields.
• Involved-field radiation therapy (IFRT) such as whole brain radiation therapy (WBRT) or focal spine radiation therapy: IFRT is the most common form of radiation therapy for leptomeningeal cancer. It is used to help with/prevent symptoms from leptomeningeal cancer and to decrease the tumor burden. Since IFRT does not treat the entire leptomeningeal compartment, it therefore does not treat the leptomeningeal cancer cells outside of the IFRT fields.
• Craniospinal Irradiation (CSI): CSI targets the entire brain and spine and the leptomeningeal compartment at the same time to better control spread of leptomeningeal cancer. It aims to treat all the leptomeningeal cancer cells.
  • Photon-based CSI using older techniques such as 3DCRT can help control spread but may often be too toxic. The radiation doses that spread to tissues in front of the spine can cause symptoms, and the radiation dose within the bones of the spine may affect bone marrow function. Modern photon-based types of radiation therapy, such as IMRT and VMAT, can be used for CSI while reducing radiation dose to normal tissues, including the bone marrow. This technique is likely to be less toxic than standard photon CSI.
  • Proton-based CSI, with less dose going to parts of the body in front of the spinal canal, may be a safer approach than the standard photon-based CSI, and when compared with IFRT, has been shown to improve survival in patients with leptomeningeal cancer. This survival benefit also depends on many factors (such as the type of leptomeningeal cancer, how much disease is present, cancer in other parts of the body and if the patient has a lot of symptoms from the leptomeningeal spread). A clinical trial found that for people with leptomeningeal cancer from breast cancer or non-small cell lung cancer who received proton CSI, the cancer is controlled for more than three times longer than those who received IFRT to just the whole brain or portions of the spine. Those who received proton CSI also lived more than two times longer than those who received IFRT. In addition, people who received proton CSI reported improved daily function. Importantly, there is no current evidence in a clinical trial comparing proton-based CSI with modern photon-based CSI techniques.

One of the difficulties with proton radiation therapy is access. Proton therapy isn’t offered at all hospitals or cancer centers, although there are more facilities opening. So, you may have to travel for this type of therapy. The National Association for Proton Therapy keeps an updated list of all centers. You can search by type of center or location, or you can use the interactive map to find a center near you.

Who should receive what type of radiation therapy depends on many factors, including your previous radiation history, distribution of disease in your body, symptoms from the tumor and imaging findings, so it is important to discuss with your physician.

Planning for Radiation Therapy

Before radiation therapy, you will meet with a radiation oncologist, a doctor who specializes in using radiation to treat cancer. The radiation oncologist will plan exactly how they will do the radiation, the amount of radiation they will use, and the schedule for treatment. Planning can take a few weeks and includes:

• Imaging: A CT scan will be performed to map out a custom radiation plan for your treatment. This will help guide the treatment machine to target the area getting radiation accurately and keeps tissue and organs as protected as possible.
• Radiation simulation: During simulation, you will be positioned on a scanner, and the technicians will work with you to find a comfortable position for the actual radiation treatment. Cushions and props may be used to be sure you will be comfortable for the length of time needed for you to be still during treatment. You will be fitted for a custom-made mesh face mask and body mold to help keep you in place. Your radiation therapists may put marks on your skin to know exactly where the radiation will be used on your body.
• Dose planning: The radiation oncologist and their team determine how much radiation will be delivered, the best way to deliver the radiation dose, how to position the beam and beam angles and how deep the beams will travel.

You may also need to stop any systemic or intrathecal therapies during radiation therapy because of possible interactions with radiation.

What to expect during treatment

Radiation is most done as an outpatient procedure and usually done over the course of several sessions. Usually, it will be five days a week over several weeks. Each session will take anywhere from 10 to 30 minutes, with most of the time being used to position your body perfectly.

During a session:

• Your radiation team will help position you on the table. If you have a mask or mold, they will be used to hold you in position.
• The machine is lined up with the marks on your mask and/or skin.
• You’ll need to lie very still as the machine moves around you. You will not feel the radiation as it is being delivered; however, some people find they smell unusual odors or get a metallic or bitter taste in their mouth.
• The machine will make a buzzing sound during treatment. Some people find that watching a video or listening to music helps them pass the time.

Side Effects of Radiation

The side effects from radiation therapy depends on where the treatment is being delivered and what other therapies you may have received. Most of the side effects can happen during or shortly after completion of radiation therapy and usually go away after a few weeks. These may include:

• Fatigue or feeling exhausted
• Hair loss
• Short-term memory or concentration problems
• Nausea and vomiting
• Skin irritation from brain and/or spine radiation could include redness, itchiness, and dryness.
• Exacerbation of symptoms related to leptomeningeal cancer, such as headaches, vision changes, hearing changes, seizures.
• Drop in blood counts when treating large areas of the spine or the brain and spine together

It is often difficult to tell if the side effects are from the treatment and cancer cells reacting to the treatment, or symptoms from the cancer itself.

Sometimes there are delayed side effects that happen 6 or more months after radiation. Most of these symptoms are uncommon and may include:

• Problems with short-term memory, concentration, or thinking.
• Inflammation or tissue damage that is seen on the MRI, which can sometimes cause symptoms that are specific to the areas of the brain or spine with these changes. Some of the symptoms may be, dependent on the part of brain or spine affected, weakness, sensation changes, vision or hearing changes, trouble speaking.
• Increased risk of having another tumor in the area (this is very rare and not likely to occur in people with leptomeningeal cancer)

To help manage your symptoms, make sure you get plenty of rest and continue to eat a healthy diet. A dietician can help you choose foods to manage nausea and vomiting while keeping up your strength. Be gentle with the area that received radiation – don’t use any topical creams or powders on irritated skin that aren’t approved by your medical team. Your providers may also prescribe other medications to reduce the risks of or to treat your symptoms, such as steroids, anti-nausea medications, and medications to helps protect brain cells from damage.

Early side effects usually go away a few weeks after treatment ends. Delayed side effects might not happen for a few months or even years after treatment. Talk to your healthcare provider about what to expect and how to manage your specific side effects.