A. Sarkisian1, M. Ojong-Ntui2, S. Goyal3, and Y. J. Rao3; 1George Washington University School of Medicine and Health Sciences, Washington D.C., DC, 2The George Washington University, Washington, DC, 3Radiation Oncology, George Washington University School of Medicine and Health Sciences, Washington, DC
Purpose/Objective(s): Stereotactic body radiotherapy (SBRT) has become more widely accepted as a standard treatment regimen for oligometastatic and oligoprogressive cancer. At our institution, tumors greater than 5cm, invading major blood vessels, invading or touching bowel, invading bladder, invading or touching major airway, and/or invading or touching skin have not been treated with SBRT due to concerns about toxicity. We evaluated an alternative hypofractionated intensity-modulated radiation therapy (IMRT) (typically 45 Gy in 15 fractions) for the treatment of oligometastatic cancers (1-5 sites) not amenable to SBRT.The primary objective was to assess the use of hypofractionated IMRT in patients with oligometastatic or oligoprogressive cancer.Materials/
Methods: We retrospectively reviewed and analyzed the data for 30 patients with oligometastatic or oligoprogressive cancer not amenable to SBRT who began radiation therapy using the aforementioned alternative regimen of hypofractionated IMRT between 2018 and 2023. Results: Of the 30 patients who received hypofractionated IMRT, 63% were male. The median follow up was 10 months (range, 2-53) overall and 17 months in surviving patients. The mean age (± SD, range) was 67 (±13, 37-91) years. The mean tumor size (± SD, range) treated was 6cm (±4, 1.2-23) and mean planning target volume (PTV) (±SD, range) was 689cc (±623, 28-2022). The majority of patients (76%) received 45 Gy in 15 fractions. The main indications for this treatment was a tumor size greater than 5cm (36%), bladder invasion by tumor (16%), tumors touching or invading skin, tumors invading major blood vessels (both 13%), tumors adjacent to the airway (10%), and tumors touching or invading bowel, bladder, or a major joint (3%). The cancer primary sites were GU (43%), GYN (16%), GI (13%), thorax (13%), head and neck (10%), and breast (3%). The IMRT treatment sites were the pelvis (40%), thorax (22%), abdomen (20%), head and neck (10%), and bone (6%). The abdomen was the treatment site with the largest mean tumor size (9.9cm), and bone was the site with the smallest mean tumor size (1.8cm). The local controls at 1 and 2-years were 94% and 72%, respectively. The overall survival at 1 and 2-years were 61% and 48%, respectively. Conclusion: Hypofractionated IMRT might be a suitable treatment method for oligometastatic and oligoprogressive cancer not amenable to SBRT. Future studies are warranted to further evaluate this technique and report on toxicity.
