SBRT-based PArtial Tumor Irradiation of HYpoxic Segment

This study uses an unconventional radiotherapy schedule developed at our institute, consisting of a short course high-dose partial irradiation targeting exclusively the hypoxic segment of a bulky tumors, which in our preliminary study has shown to be capable of inducing abscopal and bystander effects. This approach is delivered by using a stereotactic radiotherapy technique so as to spare nearby organs at risk including the peritumoral immune microenvironment from irradiation as much as possible. Our approach consists of a single or up to 3 radiotherapy doses of at least 10 Gy per fraction prescribed to the 70% isodose line encompassing the hypoxic target volume. Radiotherapy will be administered at the precise timing determined specifically for each patient based on the serially mapped homeostatic immune fluctuations by monitoring the blood levels of the cytokines and inflammatory markers over the 2 weeks prior to irradiation. This is done in order to synchronize the radiation treatment with the favorable, most active anti-tumor immune system phase, so as to stimulate and increase anti-tumor immune system activity. This is a monocentric, prospective, two-arm, phase I proof of principle study in which the investigator will enroll subjects with oligometastatic and/or locally advanced (N+) cancers with at least one "bulky" lesion (maximum diameter of at least 6 cm or greater). Patients with life expectancy of at least 3 months, who are ineligible for systemic therapy or experience disease progression with systemic therapies will be included. Radiotherapy will be administered to arm 1 at an estimated "less favorable time-position in immune cycle", while the second arm will have it administered at the estimated "most favorable time-position in immune cycle". The primary endpoint will be the response rate of the non-targeted effects both bystander (local, at the level of the partially treated bulky tumor) and abscopal (distant, at the non-treated metastatic sites), def