Pilot Study Of Dose Escalation Using Cyberknife Stereotactic Radiotherapy (Ck Srt) For Liver Metastasis In Adenocarcinoma In Rodents: Preliminary Results

BackgroundThe linear quadratic model (LQM) is not appropriate for large fraction doses, such as those used for CK SRT. Furthermore, data on CK SRT efficacy in rodents are scarce.Purpose/Objective(s)We conducted a pilot/phase I study to correlate early CT response with histological response in rodents treated with dose escalated CK SRT for liver metastasis of colorectal adenocarcinoma (ADK). The dose escalation scheme consisted of three arms: 7 Gy, 8 Gy or 9 Gy × 3 fractions.Materials/MethodsThe experiment was carried out on six rats. The Table shows D0 tumor cells were injected into the right and left liver lobes. One tumor was irradiated (TT), while the other was used as a control (TC).Meanwhile, a golden sterile fiducial was placed into the rat liver to allow for respiratory motion tracking during radiotherapy planning.– Rats were maintained with tumors for three weeks up to a tumor size of 1 cm in diameter.D20: We performed a pre-treatment post-contrast CT scan (contrast injected intra-peritoneally) for dosimetry/conformal radiotherapy planning. External contours were used for proper repositioning of the rats. An expert delineated tumor and organs at risk. Two rats were treated with three 7 Gy-fractions, as defined in the first arm of the dose escalation protocol. D34: Response was evaluated using a new CT scan under similar conditions as pre-treatment CT scan. Then rats were sacrificed. Tumors were removed and placed into one limps containing formol and blind labeling. Quantification of tumor cells necrosis was evaluated to assess HSR efficacy.ResultsFor rats treated in the first arm (7 Gy × 3 fractions):ConclusionsCK SRT (7 Gy × 3) resulted in an 60% tumor volume reduction on CT scan 2 weeks after treatment.Tabled 1D20% of liver in D20D34% of liver in D34Mean of volume TT (mm3)2663.14024.7Mean of volume TC (mm3)2462.9120514.2 Open table in a new tab BackgroundThe linear quadratic model (LQM) is not appropriate for large fraction doses, such as those used for CK SRT. Furthermore, data on CK SRT efficacy in rodents are scarce. The linear quadratic model (LQM) is not appropriate for large fraction doses, such as those used for CK SRT. Furthermore, data on CK SRT efficacy in rodents are scarce. Purpose/Objective(s)We conducted a pilot/phase I study to correlate early CT response with histological response in rodents treated with dose escalated CK SRT for liver metastasis of colorectal adenocarcinoma (ADK). The dose escalation scheme consisted of three arms: 7 Gy, 8 Gy or 9 Gy × 3 fractions. We conducted a pilot/phase I study to correlate early CT response with histological response in rodents treated with dose escalated CK SRT for liver metastasis of colorectal adenocarcinoma (ADK). The dose escalation scheme consisted of three arms: 7 Gy, 8 Gy or 9 Gy × 3 fractions. Materials/MethodsThe experiment was carried out on six rats. The Table shows D0 tumor cells were injected into the right and left liver lobes. One tumor was irradiated (TT), while the other was used as a control (TC).Meanwhile, a golden sterile fiducial was placed into the rat liver to allow for respiratory motion tracking during radiotherapy planning.– Rats were maintained with tumors for three weeks up to a tumor size of 1 cm in diameter.D20: We performed a pre-treatment post-contrast CT scan (contrast injected intra-peritoneally) for dosimetry/conformal radiotherapy planning. External contours were used for proper repositioning of the rats. An expert delineated tumor and organs at risk. Two rats were treated with three 7 Gy-fractions, as defined in the first arm of the dose escalation protocol. D34: Response was evaluated using a new CT scan under similar conditions as pre-treatment CT scan. Then rats were sacrificed. Tumors were removed and placed into one limps containing formol and blind labeling. Quantification of tumor cells necrosis was evaluated to assess HSR efficacy. The experiment was carried out on six rats. The Table shows D0 tumor cells were injected into the right and left liver lobes. One tumor was irradiated (TT), while the other was used as a control (TC). Meanwhile, a golden sterile fiducial was placed into the rat liver to allow for respiratory motion tracking during radiotherapy planning.– Rats were maintained with tumors for three weeks up to a tumor size of 1 cm in diameter. D20: We performed a pre-treatment post-contrast CT scan (contrast injected intra-peritoneally) for dosimetry/conformal radiotherapy planning. External contours were used for proper repositioning of the rats. An expert delineated tumor and organs at risk. Two rats were treated with three 7 Gy-fractions, as defined in the first arm of the dose escalation protocol. D34: Response was evaluated using a new CT scan under similar conditions as pre-treatment CT scan. Then rats were sacrificed. Tumors were removed and placed into one limps containing formol and blind labeling. Quantification of tumor cells necrosis was evaluated to assess HSR efficacy. ResultsFor rats treated in the first arm (7 Gy × 3 fractions): For rats treated in the first arm (7 Gy × 3 fractions): ConclusionsCK SRT (7 Gy × 3) resulted in an 60% tumor volume reduction on CT scan 2 weeks after treatment.Tabled 1D20% of liver in D20D34% of liver in D34Mean of volume TT (mm3)2663.14024.7Mean of volume TC (mm3)2462.9120514.2 Open table in a new tab CK SRT (7 Gy × 3) resulted in an 60% tumor volume reduction on CT scan 2 weeks after treatment.