Proton therapy: the current status of the clinical evidences – by Dongryul Oh

Precision and Future Medicine 2019

Proton Therapy Clinical Evidences – Dongryul Oh

The dosimetric advantages of proton therapy—compared with photon therapy—have been clearly defined in many comparison studies involving various tumor sites. There are now accumulating clinical data demonstrating that this dosimetric advantage can lead to better outcomes such as reduced RT toxicity and improved treatment outcomes. 

Pediatric Tumors

RT has an important role in treating pediatric tumors including central nervous system (CNS) tumors, extra-cranial sarcomas, neuroblastoma, and hematopoietic tumors. Long-term toxicities, including secondary malignancies, neurocognitive dysfunctions, growth and musculoskeletal problems, and cardiac problems, are major concerns in pediatric patients who undergo RT. There have been many efforts to reduce the RT dose and volume to avoid these RT-related toxicities.

Proton therapy is one of the best options to reduce unnecessary irradiation dose and volume in pediatric patients.

More than 30 pediatric tumor types were treated, mainly with curative intent: 48% were CNS, 25% extra-cranial sarcomas, 7% neuroblastoma, and 5% hematopoietic tumors

Head and Neck Tumors

Retrospective data have demonstrated better local control (LC) and overall survival (OS) with proton therapy than with photon therapy including IMRT and stereotactic body radiation therapy (SBRT).

Proton therapy has also demonstrated better survival rates in nasal cavity and paranasal sinus tumors.

In oropharyngeal cancers, proton therapy can reduce toxicity to normal tissues.

Proton therapy can also reduce toxicities in unilateral irradiation, such as in cases involving major salivary gland tumor and oral cavity cancers, because the exit dose of the proton beam is essentially negligible

CNS tumors

Cognitive impairment has been one of major concerns following RT for CNS tumors. Proton therapy has a potential benefit to reduce the irradiated dose to normal brain tissue to prevent cognitive dysfunction. In addition, a dose escalation could be possible in radioresistant brain tumors such as high-grade gliomas.

Gastrointestinal tumors

Proton therapy can spare the surrounding normal tissues when it is used to treat gastrointestinal tumors. In the management of hepatocellular carcinoma (HCC), it is very important to spare liver function. Because the liver is an organ with parallel functional subunit in the model of radiation response of normal tissues, liver toxicity is more sensitive to irradiated volume. Proton therapy has a major advantage in reducing the irradiated volume of remnant liver when irradiating the tumor. In many retrospective trials, proton therapy resulted in favorable outcomes.

Re-irradiation

Proton therapy has the advantage of irradiating the target while reducing the dose to the surrounding normal tissues; thus, it has a potential benefit in re-irradiation. Many retrospective studies investigating re-irradiation in various tumor sites have been reported.

Non-Small Cell Lung Cancer

Low-dose shower is a major risk for radiation pneumonitis (RP) when treating non-small cell lung cancer (NSCLC) with photon therapy. If the lateral beam placement is avoided to reduce the lung dose, the irradiated dose to heart is consequently increased and results in increased cardiac death in long-term follow-up. In many dosimetric studies, proton therapy demonstrated advantages in lung and heart dose compared with photon therapy. Several clinical studies have reported treatment outcomes and toxicities of proton therapy in early-stage disease, locally advanced disease, re-irradiation, and in postoperative settings 

Indications for Proton Therapy

American Society for Radiation Oncology (ASTRO)  has updated the recommendations for insurance coverage. The ASTRO recommendation is based on four selection criteria:

  1. a decrease in dose inhomogeneity in a large treatment volume is required to avoid an excessive dose “hotspot” within the treated volume to lessen the risk for excessive early or late normal tissue toxicity;
  2. the target volume is in close proximity to ≥1 critical structure(s), and a steep dose gradient outside the target must be achieved to avoid exceeding the tolerance dose to the critical structure(s);
  3. a photon-based technique would increase the probability of clinically meaningful normal tissue toxicity by exceeding an integral dose-based metric associated with toxicity;
  4. and, finally, the same or an immediately adjacent area has been previously irradiated, and the dose distribution in the patient must be carefully modelled to avoid exceeding the cumulative tolerance dose to nearby normal tissues.

Based on the above medical necessity requirements and published clinical data, group 1, which is recommended coverage is listed as follows:

  • ocular tumors, including intraocular melanomas;
  • skull base tumors, primary or metastatic tumors of the spine, where spinal cord tolerance may be exceeded with conventional treatment or where the spinal cord has previously been irradiated;
  • hepatocellular cancer;
  • pediatric tumors;
  • patients with genetic syndromes making total volume of radiation minimization crucial;
  • malignant and benign primary CNS tumors;
  • advanced and/or unresectable H&N cancers;
  • the paranasal sinuses and other accessory sinuses cancers;
  • non-metastatic retroperitoneal sarcomas;
  • and cases requiring re-irradiation.

Read the full study on Precision and Future Medicine 2019

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You’re welcome !

Our Patients Coordinators are our heroes. And when we thank them for the tremendous work they perform every day for our patients, they simply answer “You’re welcome !”.

They answer any single request about Proton Therapy and take care of our patients and their families.

They collect the full set of medical records which we need to analyse the situation correctly and advise rightly.

They coordinate the best treatment plan with our medical teams worldwide.

They manage the day to day operations for all patients traveling abroad for treatment, including coordination of proton therapy and other ancillary treatments.

Upon request, they can provide assistance with transportation, accommodation, translation, or any other tiny service that helps our patients feel comfortable so they can concentrate on getting better.

Once the treatment abroad is completed, they make sure our patients travel safely back home, and they ensure the follow-up plan defined by the medical staff is provided by local physicians with the high level of quality care all patients deserve. 

We sincerely thank all our Patients Coordinators for treating each patient like family, and for placing them in our hands to get them safely to timely treatment.


“Once the decision is made for proton therapy, we usually send the patient to the overseas committee which will collaborate with SAH in the United States. The process is very, very simple, quick and easy. The patient, within one to two weeks of the decision making, will be sent abroad to the United States for the treatment. He or she will stay there and receive great care from the SAH team.
Every patient who returns from treatment praises the team at SAH Care. From their departure from Bahrain to their arrival in the States and throughout the course of their treatment, patients praise the team.
They talk about the good company they had, the good treatment they received, the perfect communication with the staff, the doctors, and the therapists – with everything. When we see patients who have fully recovered, cured from the cancer, we are more than excited. It’s a present for us. We don’t need anything else. The patient is happy.”

Dr Hanadi Malik, M.D., MSc.Radiation Oncologist, SMC, The Kingdom of Bahrain

You can read more patients stories and physicians’ testimonials on SAHcare.com


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The complexity of designing, developing and operating a Proton Therapy cancer center.

This TV production by BBC highlights the complexity of designing, developing and operating a Proton Therapy cancer center.

Proton beam therapy is the one of the most technologically advanced though expensive cancer treatments in the world – but it has the potential to save the lives of children with otherwise incurable cancers.

Over two years, Horizon follows the engineers, scientists and medics as they race to build two new centres.

At the cutting edge of particle physics, proton beam therapy involves splitting hydrogen atoms to create a beam of protons travelling at two-thirds the speed of light, which target tumours with millimetre precision. But doing this in the heart of two of our biggest cities is no easy feat. The process generates so much radiation it needs to be housed in a maze-like nuclear bunker, with walls four metres thick. 2,000 tonnes of precision instruments are installed – more than four jumbo jets worth – and it all has to work perfectly.

This special BBC Two programme goes behind the scenes on the £250 million cancer cure – from digging the big and wide hole to the treatment of the first patients.

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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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