Proton therapy is a type of radiation therapy that’s more targeted than traditional radiation therapy. It may lower the risk of damage to surrounding tissue. However, more long-term research is needed.

Radiation therapy is a type of breast cancer treatment that uses high intensity energy beams to destroy cancer cells. Almost 65% of people who receive a breast cancer diagnosis receive radiation therapy treatment, according to a 2023 review.

A benefit of radiation therapy is that it can destroy cancer cells within a specific area. But in the process, it can affect nearby healthy tissue.

According to the National Cancer Institute, recent studies suggest proton therapy may be a more safe and effective treatment than traditional radiation therapy. However, there’s still limited long-term research that compares the two.

Keep reading to learn more about proton therapy for breast cancer.

Proton therapy is a type of radiation therapy that uses charged particles called protons. This allows for more precise targeting of the tumor compared with traditional radiation therapy, where the energy comes from X-rays.

In traditional radiation therapy, also known as photon therapy, the energy beams pass through the tumor and continue. This may harm nearby healthy tissues and organs, such as the heart or lungs.

However, in proton therapy, radiation stops where the tumor stops. This means a doctor can concentrate the energy beams directly on the tumor without letting it pass through to the underlying tissue.

As a result, proton therapy may reduce the risk of damage to the heart and lungs. This may be particularly helpful if you have breast cancer on your left side, closer to your heart.

Proton therapy may be used to help treat various types of breast cancer. Speak with your doctor about whether proton therapy is a good option for your treatment.

In a 2021 review, experts note there is no consensus about who proton therapy is best for specifically. However, they suggest it may be recommended for people at risk of cardiovascular diseases and lung diseases.

Research from 2018 suggests that people with breast cancer most likely to benefit from proton therapy over traditional radiation therapy are those expected to receive higher doses to the heart.

Factors that may increase radiation to the heart include:

  • having tumors on the left side
  • having tumors in the inner quadrant
  • having a mastectomy
  • receiving radiation therapy to regional lymph nodes

According to The Institute of Cancer Research, a clinical trial with 192 participants was launched in 2023 in the United Kingdom to compare the effectiveness of proton and traditional radiation therapies. The proton therapy group is intended for participants who are 2% more likely to develop heart problems later in life.

Research suggests proton therapy may be safer and more effective than traditional radiation therapy. For example:

  • A 2023 review suggests that proton therapy is more targeted and may help reduce damage to surrounding organs.
  • A 2022 study found that proton therapy did not affect cardiovascular biomarkers in 70 participants with breast cancer. Researchers concluded that proton therapy may have cardiac benefits compared with traditional radiation therapy.
  • A 2020 study found that proton therapy may decrease the risk of developing secondary lung and contralateral breast cancers compared with traditional radiation therapy.
  • A 2017 review suggests that proton therapy may help improve survival rates while decreasing potential side effects, like injury to organs.
  • A 2019 study followed 42 people who had proton therapy after a mastectomy for non-metastatic breast cancer. The median follow-up was almost 3 years, and the overall survival rate was 97.2%. This is equivalent to outcomes with traditional radiation therapy.
  • A 2019 phase 2 study suggests proton therapy for breast cancer has a similar rate of disease control as traditional radiation therapy.

Several ongoing clinical trials are comparing the effectiveness of proton and radiation therapies. However, there’s a consensus among the research that larger long-term studies are still needed.

Getting proton therapy is very similar to getting traditional radiation therapy.

The outpatient procedure takes just a few minutes. You’ll probably be in the procedure room for about 30 minutes. It’s usually administered five times a week for up to 6 weeks, the same as traditional radiation therapy.

Before starting, the radiation therapist finds the best position for treatment and marks your skin accordingly. These markings guide all future treatments.

It’s an open machine, so you won’t feel closed in. Once you’re properly positioned, the therapist goes to the control room to deliver the treatment. You need to remain perfectly still, but the treatment is painless.

The therapist can communicate with you through an intercom and let you know when it’s fine to move. You can leave when it’s over.

Side effects of proton therapy are similar to those of traditional radiation. These may include:

  • skin tenderness
  • hair loss in the treated area
  • redness that resembles a sunburn
  • fatigue

Research from 2019 suggests proton therapy has a favorable toxicity profile.

Similarly, a 2019 study found that proton therapy could be less likely to cause serious side effects than traditional radiation therapy.

Within 90 days of starting treatment, 28% of participants in the traditional radiation group experienced a side effect severe enough to need hospitalization. This compared with 12% of participants in the proton group.

It’s important to note it will take longer follow-up times and clinical trials to fully investigate proton therapy’s long-term effects.

What is the success rate of proton therapy for breast cancer?

A 2019 phase 2 study with 69 people found that the 5-year survival rate after proton therapy for breast cancer was 91%. That said, more long-term research is needed to better understand the success rate of proton therapy for breast cancer.

What are the disadvantages of proton beam therapy for breast cancer?

Some disadvantages of proton beam therapy for breast cancer are that it’s very expensive and only a limited number of centers do the therapy. There are also not many long-term studies to measure its effectiveness compared with traditional radiation therapy.

Is proton therapy better than surgery for breast cancer?

Since proton beams do not continue past the tumor site, it may lower the risk of radiation damage to healthy tissues. If you have breast cancer, that can mean reducing the chances of damage to the heart and lungs.

Does insurance cover proton therapy for breast cancer?

Medicare and some other insurance providers cover all or a portion of the cost of proton therapy. Not all do, though. It’s important to check with your insurance provider before starting the therapy so you’re not caught off guard. Call the doctor’s office if you don’t have insurance to see whether they offer payment plans or reduced rates for self-payers.

Proton therapy is an advanced type of external beam radiation therapy. It delivers high dose radiation directly to cancer cells. It’s more precise than traditional radiation therapy, so it’s less likely to harm nearby tissues and organs.

That said, more long-term research is needed to fully understand the effectiveness of proton therapy for breast cancer.

If your doctor recommends radiation treatment for breast cancer, ask if proton therapy is a good option for you.