(P045) Involved-Nodal Radiation Therapy Leads to Lower Doses to Critical Organs at Risk Compared With Involved-Field Radiation Therapy

David J. Mulvihill, MD, Kevin McMichael, BA, Sharad Goyal, MD, Richard Drachtman, MD, Aaron Weiss, DO, Atif J. Khan, MD; Rutgers Cancer Institute of New Jersey

Background: Involved-field radiotherapy (IFRT) after cytotoxic chemotherapy has become the standard of care in treating pediatric patients with Hodgkin disease. However, recent interest in shrinking the treatment volume to involved-node radiotherapy (INRT) may allow lower doses to critical organ structures. We dosimetrically compared IFRT and INRT treatment approaches.

Methods: INRT treatment plans were retrospectively constructed from 18 pediatric patients identified with Hodgkin disease who had been treated with conventional IFRT. The radiation doses delivered to organs at risk (OARs) with virtual INRT treatment plans based on INRT field design were then compared with the original treatment plans. Metrics for comparison included mean doses to organs and volumes of organ receiving at least 50% of the original prescription dose (V50). A one-tailed, paired t-test was then performed to verify statistical significance at an alpha level of .025.

Results: Three OARs that were compared in this investigation (thyroid, parotids, and lungs) had significantly lower doses of radiation with INRT when compared with IFRT (P < .025). Furthermore, the volume of breast receiving at least 50% of the initial prescription dose was statistically lower in the INRT plans. We did not find statistical improvements in dosimetrics for exposure to kidney and heart with INRT in our patients.

Conclusions: Utilizing the concept of INRT results in a reduction of radiation dose to critical organ structures in pediatric patients with Hodgkin disease when compared with the more traditional method of IFRT.