Children with craniopharyngiomas have better neurocognitive outcomes when they are treated with proton-beam radiation instead of the usual approach ― traditional photon radiation ― without loss of survival benefit, according to a study from researchers at St. Jude Children’s Research Hospital, Memphis.
“The results of this prospective clinical trial are likely to set a new gold standard for the treatment of childhood craniopharyngioma,” investigator and St. Jude neurosurgeon Frederick Boop, MD, said in a press release announcing the results.
Craniopharyngiomas are rare brain tumors that form in the central region of the brain. The general treatment is upfront surgery to remove as much of the tumor as possible, followed by photon radiation therapy.
“These results could be practice changing if they convince caregivers to recommend proton-beam therapy over radical surgery or referral of patients using proton-beam therapy instead of radiotherapy using photons,” commented principal investigator Thomas E. Merchant, DO, PhD, chair of the Department of Radiation Oncology at St. Jude.
“We have long recognized a theoretical benefit” of proton therapy for craniopharyngiomas, “but now have proof that [it] causes fewer cognitive side effects than photons,” Boop said.
The proof he referred to came in the form of almost five fewer points of IQ lost after 5 years among 94 children treated with proton-beam therapy at St. Jude and the University of Florida, in Jacksonville, in comparison with 101 historical control patients who were treated with conventional photon therapy.
Children treated with photon therapy also lost 7.34 more points on a parent-reported adaptive behavior scale.
“Improved intellectual and adaptive functioning afforded by proton therapy, in the context of maintained high survival rates, is a huge win for patients diagnosed with craniopharyngioma and their families,” co-investigator and St. Jude neuropsychologist Heather Conklin, PhD, said in the press release.
The study was published April 18 in The Lancet Oncology.
“These are important findings,” two experts comment in an accompanying editorial.
However, they add that “proton-beam therapy is an extremely expensive and complex technology, is not widely available,” and there is need to consider how using it for craniopharyngiomas – a novel indication – might limit its use for other pediatric tumors, write Ashley Grossmam, MD, PhD, a neuroendocrinology professor at Barts and the London School of Medicine, and oncologist Michael Kosmin, MD, a proton-beam therapy specialist at the University College London Hospitals.
Grossman and Kosmin were also concerned that the control group that was used for comparison was based on historical cases with varying protocols that might have fallen short of current standards for photon treatment.
“Nevertheless,” they said, “where proton-beam therapy is readily available, and patient numbers are not excessive such that other pediatric tumours are thereby excluded,” then proton-beam therapy for craniopharyngiomas “might have advantages, at least in terms of neurocognitive function.”
Study Details
Children in the photon therapy group were treated from 2011–2016 with passively scattered proton beams at a total dose of 54 Gy with a 0.5-cm clinical target volume margin.
Children in the historical control group were treated from 1998 through 2013 with photon-based conformal or intensity-modulated radiation at a dose of 54 Gy but with a target volume of 0.5–1 cm.
Overall, children treated with photons received more than twice the dose of radiation to their temporal lobes than those treated with protons, which might have played a role in later neurocognitive differences, the investigators say.
The median age of children in both groups was just over 9 years at baseline, but a greater percentage in the photon group had received cerebrospinal fluid shunts and had undergone two or more surgeries prior to radiation therapy. Surgeries were limited in the proton group. The extent of surgery in the photon arm was not reported.
Five-year progression-free survival was 93.6% in the proton group, which was not statistically different from that with photon therapy, at about 90.0%. Rates of treatment toxicities were also similar.
The work was funded by the National Cancer Institute, the American Lebanese Syrian Associated Charities, Research to Prevent Blindness, and others. The investigators and the editorialists have disclosed no relevant financial relationships.
Lancet Oncol. Published online 18 April 18, 2023. Abstract, Editorial
M. Alexander Otto is a physician assistant with a master’s degree in medical science and a journalism degree from Newhouse. He is an award-winning medical journalist who worked for several major news outlets before joining Medscape. Alex is also an MIT Knight Science Journalism fellow. Email: [email protected].
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