Where traditional radiation fails in treating mesothelioma, proton radiation succeeds. Even compared to new-age techniques such as intensity-modulated radiation therapy, proton beams seem to provide the same tumor-killing effects and less damage to healthy tissue.
Those are the revelations from a recent consensus statement on proton radiation therapy in pleural mesothelioma. The report, a 37-page document written by 16 radiation experts spanning 12 hospitals, examines the benefits and drawbacks of each radiation approach.
The conclusion? Proton radiation is the recommended approach.
We at Mesothelioma Guide interviewed Dr. Charles Simone, the chief medical officer of the newly created New York Proton Center. He’s also one of the 16 authors for the consensus statement, which has been in the works since 2017. He provided context on why proton radiation therapy is so beneficial in combating pleural mesothelioma — and why, most importantly, it’s the safest radiotherapy option.
“I think people are now more comfortable delivering (proton radiation),” Dr. Simone said. “I think it’s more evident that mesothelioma is a radiosensitive cancer.
“I think radiation is coming back in favor.”
If you’d like to visit the New York Proton Center for mesothelioma radiation therapy, please contact our team. Patient advocate and registered nurse Karen Ritter can assist you in setting up an appointment with Dr. Simone and his staff. Please email Jenna at firstname.lastname@example.org.
Mesothelioma Radiation and the Effect on the Lungs
The long-standing issue with mesothelioma radiation is the therapy can damage healthy tissue, even that of essential organs. Traditional photon radiation, and even the more-targeted and more-effective intensity-modulated radiation therapy (IMRT), can lead to a condition called pneumonitis.
Pneumonitis involves damage to healthy lung tissue. Mesothelioma radiation inevitably leads to damage to the lung closest to where pleural mesothelioma forms. What should be restricted is damage to the lung on the opposite side of the thorax.
This lung is called the “contralateral lung.” Contralateral is defined in medical terminology as the opposite side of the body. The contralateral lung is the organ on the opposite side of the chest from where pleural mesothelioma originates.
That lung is essential to long-term survival and quality of life for mesothelioma patients. There are two primary surgeries for this type of mesothelioma: extrapleural pneumonectomy (EPP) and pleurectomy with decortication (P/D).
EPP removes the nearby lung from the body. P/D spares the lung and primarily focuses on removing the pleura, which is the narrow space near the lung where this cancer forms.
If a patient undergoes EPP, then the health of the remaining lung is vital. Even after P/D, radiation therapy must be directed on or close to the ipsilateral lung. At least some tissue damage is nearly a foregone conclusion.
“To some extent, we can’t avoid damage,” Dr. Simone said. “That lung never is as ‘good’ as it was before their diagnosis of mesothelioma. Their lung elasticity is never as good as it was before.”
At high doses, radiation oncologists have difficulty reducing damage to the contralateral lung with traditional radiation and IMRT. According to the consensus statement, which cites multiple studies:
- IMRT after EPP led to a 15% rate of severe pneumonitis to the contralateral lung
- IMRT after P/D resulted in a 20% rate of grade 3 or higher pneumonitis to the contralateral lung
“The problem historically has been it’s harder to deliver radiation for mesothelioma because it’s a big area,” Dr. Simone said. “We need to treat the entire hemithorax. … We usually can’t deliver that high of a dose with traditional radiation, even photon radiation or IMRT.
“We either underdose the tumor or lower the dose we are prescribing. Both of those can lead to lower control rates.”
How Proton Radiation Avoids Lung Damage
Proton radiation originated in the middle of the 20th century. However, proton radiation centers started emerging in the last 30 years.
The benefit of proton therapy, compared to traditional radiation or even IMRT, is the proton beams stop at the intended target. IMRT is a more targeted approach that limits damage to healthy tissue. It has its benefits, especially compared to traditional X-ray photon radiation, but it still can lead to lung tissue damage.
Proton radiation is the next evolution in this treatment. The proton beams limit excess radiation to surrounding tissue and organs, allowing radiation oncologists to deliver higher doses to the mesothelioma tumors.
“Higher doses have better outcomes and better survival for mesothelioma,” Dr. Simone said.
The paper cites four studies, three involving proton radiation after P/D surgery and one using proton radiation after EPP surgery. In combining the results of the four studies:
- Grade 3 pneumonitis was the most severe amount of damage to the contralateral lung
- Only two of the 39 patients (5.1%) had grade 3 pneumonitis
- Only three of the 39 patients (7.7%) had grade 2 pneumonitis
The pneumonitis rates for proton radiation were lower than those of traditional photon radiation. This is while using the same dose for treatment.
In addition to the contralateral lung, radiation can damage tissue on or in the:
- Spinal cord
The consensus statement shows that proton radiation minimizes the risk for all of these organs and body areas. In every cited study comparing proton radiation and traditional methods, proton radiation delivered a lower amount of scattered radiation to the heart, liver and kidneys.
All of this is evidence that proton radiation can deliver life-extending, tumor-killing effects while minimizing severe side effects. A shift to using this form of radiotherapy seems inevitable in the years to come.
Sources & Author
- Consensus Statement on Proton Therapy in Mesothelioma. Practical Radiation Oncology. Retrieved from:
https://www.practicalradonc.org/article/S1879-8500(20)30117-X/pdf. Accessed: 06/10/2020.
Sources & Author