Proton therapy for cancer lowers risk of side effects

by Julia Evangelou Strait, Washington University School of Medicine

Proton therapy results in fewer side effects than traditional X-ray radiation therapy for many cancer patients, according to a new study led by Washington University School of Medicine in St. Louis and the Perelman School of Medicine at University of Pennsylvania. Even with reduced side effects, proton therapy resulted in cure rates similar to those of X-ray radiation therapy.

Proton therapy for cancer lowers risk of side effects
A new study led by Brian Baumann, M.D., of Washington University School of Medicine in St. Louis, found that proton therapy (bottom) is associated with fewer severe side effects than conventional X-ray radiation therapy (top) for many cancer patients. Credit: Brian Baumann/Mike Worful

The study is the first major side-by-side comparison of side effects related to proton therapy and X-ray radiation therapy. It included almost 1,500 patients receiving combined chemotherapy and radiation therapy for lung, brain, head and neck, gastrointestinal and gynecologic cancers that had not yet spread to other parts of the body. Such patients receive both radiation and chemotherapy, a treatment regimen that often cures nonmetastatic cancer. But it also causes severe side effects—such as difficulty swallowing, nausea and diarrhea—that reduce quality of life and can, in some cases, require hospitalization.

After controlling for differences between the groups, such as age and additional medical problems, the researchers found that patients receiving proton therapy experienced a two-thirds reduction in the relative risk of severe side effects within 90 days of treatment, compared with patients receiving X-ray radiation therapy. Forty-five of 391 patients receiving proton therapy experienced a severe side effect in the 90-day time frame (11.5 percent). In the X-ray radiation therapy group, 301 of 1,092 patients experienced a severe side effect in the same period (27.6 percent). Patient data on side effects were gathered as the trial was ongoing, rather than after the fact.

“Proton therapy was associated with a substantial reduction in the rates of severe acute side effects—those that cause unplanned hospitalizations or trips to the emergency room—compared with conventional photon, or X-ray, radiation for patients treated with concurrent radiation and chemotherapy,” said Baumann, an assistant professor of radiation oncology at Washington University and an adjunct assistant professor of radiation oncology at Penn. “The opportunity to reduce the risk of severe side effects for patients and thereby improve their quality of life is very exciting to me. While there have been other studies suggesting that proton therapy may have fewer side effects, we were somewhat surprised by the large magnitude of the benefit.”

The researchers focused their study on what are called grade 3 adverse events, which are severe enough to require hospitalization. These can include pain, difficulty swallowing that might result in weight loss, difficulty breathing, and nausea and diarrhea severe enough to cause dehydration.

The researchers also found no differences between the two groups in survival, suggesting that proton therapy was just as effective in treating the cancer even as it caused fewer side effects. Overall survival at one year for the proton therapy group was 83 percent of patients versus 81 percent for the X-ray radiation therapy group. This difference was not statistically significant.

This study is the first large review of data across several cancer types to show a reduced side-effect profile for proton therapy compared with X-ray radiation therapy for patients receiving combined chemotherapy and radiation. Both types of radiation therapy are approved by the Food and Drug Administration for cancer treatment. Protons are relatively heavy, positively charged particles that hit their target and stop. X-ray beams consist of photons, which are much smaller particles that have almost no mass, allowing them to travel all the way through the body, passing through healthy tissue on the way out.

https://medicalxpress.com/news/2019-05-proton-therapy-cancer-lowers-side.html

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Montefiore Study May Help Establish Patient Criteria for Proton Therapy

N. Patrik Brodin, PhD

Data supporting the efficacy of proton therapy are robust for pediatric cancers, brain and base-of-skull tumors, and complex-shaped tumors near critical structures (…)

Proton therapy has emerged as an attractive option for patients with head and neck cancer. This is due to proton therapy beam technology, which precisely destroys cancers with an unmatched ability to stop at precise locations within the body.

Protons also have significantly fewer adverse effects (AEs) and toxicities than most other cancer therapies, because of the protons’ unique ability to sculpt radiation doses according to the shapes and sizes of tumors. This is particularly important for head and neck cancers, which frequently are close to or impeding on vocal cords, air passageways, swallowing muscles, salivary glands, and the oral mucosa. The opportunity to preserve healthy tissue is considerable.

AEs estimated to be significantly less prominent include swallowing difficulties, inflammation of the esophagus, and reduced saliva production. For people suffering from head and neck cancer and their families, the ability to avoid these types of complications makes an overwhelmingly important difference in QoL.

Younger patients, non-smokers, and patients with HPV p16- positive tumors will most likely benefit from proton therapy (…)

The highest expense in cancer therapy involves the regrowth of cancer—large sums are required to prolong survival and maintain QoL. By increasing cure rates and improving patients’ QoL, we can increase cost-effectiveness.

It is important for healthcare providers not only to educate our patients and their families about each treatment’s ability to destroy cancers, but also to manage expectations about different treatments and what life may look like “post cancer.”

Proton therapy is one of the most modern therapies available, and its ability to minimize AEs such as trouble swallowing, reduced ability to eat, dental problems, and difficulty digesting food can’t be understated for some of our patients (…) By increasing cure rates and improving patients’ Quality of Life, we can increase cost-effectiveness.

https://www.onclive.com/publications/oncology-live/2019/vol-20-no-11/montefiore-study-may-help-establish-patient-criteria-for-proton-therapy

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What are the general eligibility criteria for proton therapy ?

Proton therapy works well for localized solid tumors, whether benign or malignant, so we can address and cure the tumor by treating that location. We try to limit ourselves to curative patients who have a good quality of life because they need to come daily for the treatments over potentially a long period. Some patients require as many as 45 treatments ; some as few as 4 or 5. Generally, it is a four- to eight-week course of treatment.

Many patients have previously been treated with conventional therapy, and the tumors came back. They have no options at this point, but we may be able to re-radiate those patients with proton therapy. 

There is no age restriction. Our patient population ranges from babies to very spry 95-year-olds. Proton therapy is becoming a mainstay for treating pediatric tumors. By sparing still-growing tissue in children, proton therapy can reduce growth defects and secondary tumors caused by traditional radiation. 

Learn more about the cancers we treat with Proton Therapy
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Proton Therapy is highly effective at treating numerous cancers and tumors.

Proton Therapy was pioneered in the United States more than 50 years ago. By the end of 2018 it had been used to treat more than 170,000 patients.

Over the past decade, Proton Therapy has emerged as the most effective treatment method for a variety of cancers. Because it is a more accurate method for delivering radiation to the site of a tumor, proton therapy allows doctors to use a higher dose of radiation, without the risk of damage to surrounding healthy tissue and organs. Proton therapy patients experience relatively few harmful side effects and are able to maintain a high quality of life during and after treatment.

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Proton Therapy Delivery and Its Clinical Application in Select Solid Tumor Malignancies

ABSTRACT

Radiation therapy is a frequently used modality for the treatment of solid cancers. Although the mechanisms of cell kill are similar for all forms of radiation, the in vivo properties of photon and proton beams differ greatly and maybe exploited to optimize clinical outcomes. In particular, proton particles lose energy in a predictable manner as they pass through the body. This property is used clinically to control the depth at which the proton beam is terminated, and to limit radiation dose beyond the target region. This strategy can allow for substantial reductions in radiation dose to normal tissues located just beyond a tumor target. However, the degradation of proton energy in the body remains highly sensitive to tissue density. As a consequence, any changes in tissue density during the course of treatment may significantly alter proton dosimetry. Such changes may occur through alterations in body weight, respiration, or bowel filling/gas, and may result in unfavorable dose deposition. In this manuscript, we provide a detailed method for the delivery of proton therapy using both passive scatter and pencil beam scanning techniques for prostate cancer. Although the described procedure directly pertains to prostate cancer patients, the method may be adapted and applied for the treatment of virtually all solid tumors. Our aim is to equip readers with a better understanding of proton therapy delivery and outcomes in order to facilitate the appropriate integration of this modality during cancer therapy.

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Triple-Gaussian model improves proton therapy plans

Because the depth at which a proton beam is halted by tissue depends on its initial energy, intensity-modulated proton therapy (IMPT) allows the radiation field to conform closely to the 3D shape of the tumour while sparing surrounding tissue. This makes IMPT the method of choice for intricately shaped tumours in complex physiological settings. The narrow margins in these situations mean that a robust quality assurance procedure is needed so that clinicians can be confident that the planned dose is the one that is delivered to the patient. 

Simulated prostate treatment plan in the simple heterogeneous phantom. (Courtesy: J. Appl. Clin. Med. Phys. 10.1002/acm2.12535/CC BY 4.0)

(…) As the TPS and phantom are both commercially available, any clinic that uses IMPT based on pencil-beam scanning can use the procedure and the team’s phantom-specific correction table to verify their treatment plans. As long as absolute dose measurements are taken for each beam angle — to mitigate uncertainty related to measurement points and gantry rotation — the method provides an accurate, reproducible basis for quality assurance. “Our motivation was to realize equal access to high-quality spot-scanning proton therapy in Japan and all over the globe,” says Yasui.

https://physicsworld.com/a/triple-gaussian-model-improves-proton-therapy-plans /

https://aapm.onlinelibrary.wiley.com/doi/full/10.1002/acm2.12535

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Which Radiation Therapy technics for which patients ? How to Optimize survivorship ?

« There are certain patients with brain tumors who can live many years to decades. And we think that Radiotherapy for those patients with brain tumors can have long lasting side-effects. Proton Therapy allows us to treat the brain tumor and completely avoid radiation to normal brain tissue. Not just lowering the dose, but literally eliminating irradiation in these areas. Study showed that children treated with Proton Therapy had better cognitive functions down the road, better IQ (…) That’s a really meaningful improvement that we see with Proton Therapy (…)

Some adults with glioma can live many years to decades (…) we’re using Proton therapy to try treat that tumor, avoid as much unnecessary radiation dose to normal brain tissue, and see if we can help preserve their cognitive functions. »

https://www.itnonline.com/videos/video-advancements-radiation-therapy-brain-cancer

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