Two new studies support the safety of proton therapy. The first study, published in Pediatric Blood and Cancer, shows that very young children who received proton therapy for medulloblastoma had higher rates of overall survival and recurrence-free survival compared to patients who received intense chemotherapy without radiation therapy.
The second study, published in Oncology Act, has shown that children with tumors of the central nervous system who received proton therapy with a newer technique called pencil scanning experienced a significantly lower rate of brain stem damage than patients treated with older proton techniques.
Both studies were directed by Christine Hill-Kayser, associate professor of Radiation Oncology at the Perelman School of Medicine of the University of Pennsylvania, and pediatric oncologist in the Philadelphia Children's Hospital Cancer Center (CHOP).
Proton therapy is an FDA-approved treatment that directs positively charged protons to the tumor, where they deposit most of the radiation dose, with minimal residual radiation delivered beyond the target, potentially reducing side effects and damage to surrounding tissue.
The first study focused on children with newly diagnosed medulloblastoma. Older children, between the ages of four and 18, with the disease usually receive radiation throughout the brain and spine, but this treatment can be very toxic for very young children, less than four years old, who receive chemotherapy cycles Intense instead of radiation, with a higher frequency of racaids and previous studies have shown that the greatest risk of relapse is related to the posterior fossa, where the tumor is mainly located.
The researchers evaluated 14 young children who received proton therapy after surgery and chemotherapy. They found that the overall five-year survival rate was 84 percent, while the recurrence-free survival rate was 70 percent. Historical data shows that both rates are generally between 30 and 60 percent in very young patients who do not receive radiotherapy.
“Our study, although small, shows promising results when we use proton therapy directed only to the area of surgery instead of irradiating the entire brain and spinal areas,” says the study's lead author, Amardeep Grewal.
The second study deals with a new proton technique called pencil beam scanning (PBS), which is more effective in preserving healthy tissue than older proton techniques, such as scattered or uniform double scanning.
This study evaluated 166 patients with pediatric tumors of the central nervous system and found that at 24 months, the rate of patients experiencing damage to brain stem tissue by proton therapy PBS is 0.7 percent.
This is much lower than the rates of severe brain stem toxicity reported after treatment with double dispersion proton therapy.
“Our data shows that proton therapy with pencil scanning does not increase the risk compared to conventional photon techniques,” says lead study author Jennifer Hyatt Vogel. These data justify additional studies, especially in high-risk patients and patients who have received prior radiotherapy, concludes Hyatt.
“Regardless of the technique, experience in proton therapy planning and strict compliance with safety restrictions are essential, particularly in the treatment of tumors near the brainstem,” says Hill-Kayser.