Higher doses of proton beam radiation may be a worthwhile treatment alternative for some lung cancer patients.
Radiation oncologists at MD Anderson Cancer Center and MD Anderson Proton Therapy Center in Houston, Texas, are taking a lead in evaluating the use of fewer, larger-sized fractions of a total proton dose to treat early and more advanced lung cancers. This clinical approach is called hypofractionated proton therapy.
“Hypofractionated proton therapy has the potential to offer better tumor control because you’re using higher doses per day,” said Daniel Gomez, M.D., a radiation oncologist at MD Anderson Proton Therapy Center. “It also may be a convenience benefit for patients because they’re getting fewer fractions and a cost benefit to the health system because you’re doing fewer fractions, as well.”
In one clinical trial led by Joe Y. Chang, M.D., a radiation oncologist and director of the stereotactic radiotherapy program at MD Anderson Cancer Center, hypofractionated proton therapy is being compared with stereotactic ablative body radiation (SABR) in the treatment of patients with early-stage lung cancers. More specifically, these are centrally located or recurrent non-small cell lung cancer.
SABR uses hypofractionated photon radiation. Hypofractionated proton therapy is also called stereotactic ablative proton therapy (SAPT).
While protons and photons are equally effective at killing cancer cells, it’s the amount of unintentional radiation going to healthy tissue and critical organs that can cause problems down the road for some cancer survivors. And protons tend to stay to the tumor target much more so than photons, reducing the doses of harmful, spillover radiation.
But will that hold true for early-stage lung cancer patients treated with hypofractionated proton radiation?
That’s the question Dr. Chang and other researchers at MD Anderson and at Massachusetts General Hospital in Boston, Massachusetts, hope to answer.
They will monitor side effects experienced by early-stage lung cancer patients for two years following randomized treatment with either hypofractionated proton beams or SABR.
About 30 lung cancer patients have been recruited so far, Dr. Gomez said. Clinicians in Houston and Boston are looking to enroll a total of 120 patients in the clinical trial. More information can be found at clinicaltrials.gov.
About a year ago, phase I research by Dr. Gomez identified the potential for using hypofractionated proton therapy to treat those patients with locally advanced lung cancer who are not good candidates for chemotherapy alone or in combination with photon radiation.
The 25-patient study, published in the International Journal of Radiation Oncology • Biology • Physics, found that patients tolerated higher doses of protons delivered over a three-week schedule and experienced few severe side effects. Conventional proton treatments for lung cancer are typically conducted over a longer period of time.
“Much more information is needed regarding the safety of hypofractionated proton therapy before it can be widely adopted for some lung cancers,” Dr. Gomez cautioned. “That means long-term follow up is needed to assess toxicities appearing a year or more after treatment.”