Helium ion radiotherapy benefited pediatric patients

In patients with pediatric cancers, helium ion beam therapy appeared to offer precise tumor-targeted therapy while sparing healthy organs at risk, according to recent findings.

“Particle beam therapy involving protons or carbon ions has advantages over conventional radiotherapy,” Hermann Fuchs, a PhD student at the Medical University of Vienna, said in a press release. “Helium ions may represent another kind of particle that can improve radiotherapy treatment. Due to their increased mass, spreading of the beam is reduced by a factor of two as compared with protons. Moreover helium ions have an increased biological effectiveness at the end of their range.”

In the treatment planning study, researchers formulated treatment plans for 10 pediatric patients based on a pencil beam algorithm. The patients consisted of five children with pediatric neuroblastoma and five with Hodgkin’s lymphoma. The investigators used the same beam arrangement (two beams from anteroposterior or lateral direction) for both helium ion therapy and proton beam therapy.

The clinical target volume for patients with neuroblastoma included the gross tumor volume and nearby areas of lymph node enlargement. The clinical target volume for patients with Hodgkin’s lymphoma included lymph nodes at diagnosis, adjusted based on post-chemotherapy anatomy. The planning target volume size was 163 cm to 232 cm for patients with neuroblastoma and 443 cm to 1,521 cm for patients with Hodgkin’s lymphoma.

Dose prescription to the planning target volume was 21 Gy for the patients with neuroblastoma and 19.8 Gy for patients with Hodgkin’s lymphoma. Based on the tumor position myelon, the organs at risk were the kidneys, liver, heart, lungs and thyroid. Quality analysis of treatment plans were formulated based on dose difference maps conformity and homogeneity index.

The researchers found that the helium ion beam therapy plan could be optimized for stricter organs at risk limitations than proton beam therapy. Because of overlapping volumes of the kidneys and the planning target volume in patients with neuroblastoma, there were variations in 50% dose between 0.1 Gy and 6.9 Gy, whereas the average helium ion beam treatment delivered 26% less dose to the kidneys vs. proton beam therapy. Sparing of the liver was equal in helium ion beam and proton beam therapy with 50% dose <1 Gy.

Due to the large planning target volume sizes used in patients with Hodgkin’s lymphoma compared with the volumes of organs at risk, helium ion beam and proton beam therapy performed similarly in these patients.

“After 3 years of extensive research and validation efforts, we were able to produce a treatment planning algorithm that enabled us to investigate the possibilities for using helium ion therapy in children treated with low-dose radiation,” Fuchs said. “We would now like to investigate its potential in patients being treated with higher doses; for example, those with brain tumors. The good results that have been achieved so far warrant the verification of the model in order to investigate the real clinical potential of helium ions.”

For more information:
Fuchs H. Presented at: European Society for Radiotherapy and Oncology (ESTRO) 33 Congress; April 4-8, 2014; Vienna.

Disclosure: The researchers report no relevant disclosures.