Proton therapy for the treatment of lung cancer

Radiation therapy is one of the most common methods of treating lung cancer. It is often used in combination with other treatments such as surgery or chemotherapy.

Proton therapy, or proton beam therapy, is a type of radiation therapy. Unlike traditional radiation therapy, which uses high-energy waves to destroy and reduce tumors, proton therapy uses proton beams.

It is believed that proton therapy causes fewer side effects than traditional radiation therapy due to its ability to target cancer cells more specifically.

How traditional radiation therapy works

In traditional radiation therapy, concentrated high-energy waves of directed action are used to damage cancer cells. High-energy waves are radiation consisting of negatively charged particles called electrons.

When the electrons are accelerated by a special device, they begin to emit high-energy particles called photons. Photons are the basic units of light.

According to a 2015 study, the energy contained in photons can destroy the molecules that make up the DNA of cancer cells, suppressing their ability to divide and multiply.

How Proton Therapy works

Proton therapy works the same way as traditional radiation therapy, but it uses proton beams instead of high-energy waves. The US National Cancer Institute suggests that proton therapy may be just as effective, but it does less harm to healthy cells.

According to a 2018 study, protons are about 800 times larger than electrons. During proton therapy, protons are accelerated using special devices called synchrotrons or cyclotrons.

The large mass and acceleration of these protons give them sufficient momentum to penetrate into the lungs to the depth of malignant tissues. Due to a special property of protons called Bragg peak, they release most of their energy inside cancer cells, causing minimal damage to surrounding tissues and organs.

Proton therapy is rapidly improving as new research data becomes available. The main advantage of proton therapy over traditional radiation therapy is that it causes less radiation damage to healthy tissues.

Dosimetric comparisons between photonic [left (A, C, E) and proton right (B, D, F)] plans for a patient with stage III lung cancer. Radiation doses shown as color shades of warmer colors (red) represent higher doses compared to colder colors (blue). The first pair of axial sections (A and B) are at a level exceeding the axial sections C and D; It is obvious that more normal lung is irradiated on the left than on the right; E and F are coronal sections with dosimetry.

The development of side effects is often a limiting factor for the volume of radiation therapy. One 2017 study says that by reducing the number of side effects, proton therapy allows the use of large doses of radiation therapy. According to another 2018 study, this may have a positive effect on patient survival.

As researchers continue to explore the potential benefits of proton therapy, they will learn more about how it can be used to treat lung cancer. At the moment, there are a limited number of clinical studies comparing the effectiveness of proton therapy with traditional radiation therapy.

However, researchers have already confirmed that proton therapy can:

• Reduce damage to vital organs.
  A 2018 study found that treating lung cancer with proton therapy can reduce damage to vital organs, such as the esophagus, and healthy lung and heart tissues compared to traditional radiation therapy.
• Improve survival in locally advanced non-small cell lung cancer.
  A 2021 study demonstrated evidence that proton therapy provides a low level of side effects, increasing overall survival in people with locally advanced non-small cell lung cancer.
• Reduces toxicity in non-small cell lung cancer at an early stage.
  A 2017 study showed that proton therapy can produce the same results as surgery and traditional radiation therapy, but with potentially less toxicity in early-stage non-small cell lung cancer.
• It can be used as an alternative to surgery.
  A 2020 study showed that proton therapy could be a good alternative to surgery for inoperable people with lung cancer with frosted glass syndrome.
• Allows you to intensify chemotherapy.

Some early studies conducted on people with lung cancer suggest that, compared with traditional radiation therapy, proton therapy can prolong survival, reduce the risk of cancer recurrence and severe toxicity, and also allow for the intensification of chemotherapy.

Proton therapy is recommended for people:

• with lung cancer that has not spread beyond the chest;
• with recurrent lung cancer that has not spread beyond the chest.

According to the Northwestern Medicine medical network, proton therapy can be recommended as a therapeutic method:

• patients with locally advanced lung cancer
• patients in need of chemotherapy
• patients who have previously undergone radiation therapy
• patients with limited or poor lung function

At the time of publication of the 2019 study, there were 31 proton therapy centers in the United States, 13 facilities were under construction, and 49 more centers were operating around the world.

According to the researchers, the approval of a patient's candidacy for proton therapy may be due to his insurance status, rather than clinical factors, since the cost of proton therapy is 2-3 times higher than that of conventional radiation therapy. People without insurance may have problems paying for proton therapy services.

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

• redness
• irritation
• swelling
• formation of blisters
• peeling
• dryness

In a 2021 study, the authors concluded that proton therapy is accompanied by fewer side effects. After analyzing the data of 195 people with an average age of 70 years who received proton therapy for non-small cell lung cancer, the researchers recorded the following side effects:

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

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