A methodology for incorporating functional bone marrow sparing in IMRT planning for pelvic radiation therapy

Background and purposeThe purpose of this study was to design a radiation therapy treatment planning approach that would spare hematopoietically active bone marrow using [18F]FLT PET imaging.Materials and methodsWe have developed an IMRT planning methodology to incorporate functional PET imaging using [18F]FLT scans. Plans were generated for two simulated cervical cancer patients, where pelvic active bone marrow regions were incorporated as avoidance regions based on the ranges: SUV4 ⩾ 4; 4 > SUV3 ⩾ 3; and 3 > SUV2 ⩾ 2. Dose objectives were set to reduce bone marrow volume that received 10 (V10) and 20 (V20) Gy.ResultsActive bone marrow regions identified by [18F]FLT with an SUV ⩾ 2, SUV ⩾ 3, and SUV ⩾ 4 represented an average of 43.0%, 15.3%, and 5.8%, respectively of the total osseous pelvis for the two cases studied. Improved dose–volume histograms for all identified bone marrow SUV volumes and decreases in V10, and V20 were achieved without clinically significant changes to PTV or OAR doses.ConclusionsIncorporation of [18F]FLT PET in IMRT planning provides a methodology to reduce radiation dose to active bone marrow without compromising PTV or OAR dose objectives in pelvic malignancies.