Proton Therapy for Lung Cancer

Proton therapy is a type of cancer therapy that uses beams of protons to destroy and shrink tumors. The idea of proton therapy was first proposed in 1946 by the American physicist Robert R. Wilson.

How traditional radiation therapy works

In traditional radiation therapy, targeted concentrations of high energy waves are used to damage cancer cells. The high energy waves are a form of radiation made from negatively charged particles called electrons. When electrons are accelerated quickly by a special machine, they emit high energy particles called photons. Photons are the basic units of light.

According to 2015 research, these photons contain so much energy that they can break the molecules that make up the DNA of cancer cells. This damage can inhibit the ability of cancer cells to make copies of themselves and grow.

How proton therapy works

Proton therapy works in a similar way as traditional radiation therapy, but it uses beams of protons instead of high energy waves to damage the DNA of cancer cells. The National Cancer Institute suggests that proton therapy may be just as effective, but causes less damage to healthy cells.

Protons are about 800 times bigger than electrons, according to a 2018 review. During proton therapy, protons are sped up with special machines called synchrotrons or cyclotrons.

The high mass and acceleration of these protons give them enough momentum to penetrate your lungs to the depth of the cancer cells. Due to a property of the protons called the Bragg peak, they release most of their energy around the cancer cells while causing minimal damage to surrounding tissues and organs.

Proton therapy is improving rapidly as more research comes out. The main advantage of proton therapy over traditional radiation therapy is that it causes less radiation damage to healthy tissues and fewer side effects.

The development of side effects is often a limiting factor for the amount of radiation therapy that can be delivered. A 2017 review suggests that by reducing the number of side effects, proton therapy may allow for a greater dose of radiation therapy to be administered. According to 2018 research, this may improve the survival rate.

As researchers continue to examine the potential benefits of proton therapy, they’re learning more about how it can be used to treat lung cancer. As of now, a limited number of clinical studies have compared the effects of proton therapy to traditional radiation therapies.

So far, researchers have found that proton therapy may:

• Reduce damage to vital organs. A 2018 study has found that treating lung cancer with proton therapy may decrease damage to vital organs such as the esophagus, healthy lung tissue, and heart compared with traditional radiation therapy.
• Improve survival rate of locally advanced non-small cell lung cancer. A 2021 study found evidence that proton therapy yields low rates of side effects and increased overall survival in people with locally advanced non-small cell lung cancer.
• Reduce toxicity in early stage non-small cell lung cancer. A 2017 study suggests that proton therapy may achieve similar outcomes as surgery and traditional radiation therapy, with potentially less toxicity in early stage non-small cell lung cancer.
• Be an alternative to surgery. A 2020 study found that proton therapy may be a good alternative to surgery in people with ground glass opacity lung cancer when surgery isn’t feasible.
• Allow for the intensification of chemotherapy. Some early studies performed on people with lung cancer suggest that compared with traditional radiation therapies, proton therapy may prolong survival, lower the risk of cancer reoccurrence and severe toxicity, and allow for the intensification of chemotherapy.

Proton therapy is available for people:

• with lung cancer that hasn’t spread outside of the chest
• with returning lung cancer that hasn’t spread outside of the chest

According to Northwestern Medicine, people who should consider proton therapy:

• have a locally advanced lung cancer
• also need chemotherapy
• have had prior radiation therapy
• have limited or poor lung function

At the time a 2019 study was published, there were 31 proton therapy facilities in the United States, 13 more under construction, and 49 other facilities worldwide.

According to the researchers, candidacy for proton therapy may be driven by insurance status rather than clinical factors, since the cost of proton therapy is 2 to 3 times higher than nonproton radiation therapy. People without insurance may have trouble affording proton therapy.

Common side effects of proton therapy include fatigue, hair loss around the treatment site, and skin symptoms such as:

• redness
• irritation
• swelling
• blistering
• peeling
• dryness

In a 2021 study, researchers concluded that proton therapy led to low rates of side effects. In 195 people with a median age of 70 treated with proton therapy for non-small cell lung cancer, the researchers reported:

Both cardiac events were in people with multiple risk factors. The first person died after the cancer invaded his heart and major blood vessels. The second person had a heart attack 10 months after his treatment ended.

Proton therapy is a type of radiation therapy that involves using beams of protons to destroy and kill cancer cells. It’s thought to cause fewer side effects than traditional radiation therapy and may lead to improved survival rates.

There’s still a limited number of studies comparing the outcomes of proton therapy with traditional radiation therapy in people with lung cancer, but early research has found promising results. You can talk with your doctor to find out if you make a good candidate.