Changing Therapeutic Paradigms: Predicting mCRC Lesion Response to Selective Internal Radionuclide Therapy (SIRT)...

A 65 year old male with metastatic colorectal cancer (mCRC) in the liver was referred for selective internal radionuclide therapy (SIRT) following a history of extensive systemic chemotherapy. ⁹⁰Y PET imaging was performed immediately after treatment and used to confirm lesion targeting and measure individual lesion absorbed doses. Lesion dosimetry was highly predictive of eventual response in the follow-up FDG PET performed 8 weeks after therapy. The derived radiation dose map was used to plan a second SIRT procedure aiming to protect healthy liver by keeping absorbed dose below the critical dose threshold, whilst targeting the remaining lesions that had received sub-critical dosing. Again, ⁹⁰Y PET was performed immediately post-treatment and used to derive absorbed dose measures to both lesions and healthy parenchyma. Additional follow-up FDG PET imaging again confirmed the role of the ⁹⁰Y PET dose map as an early predictor of response, and a tool for safe repeat treatment planning.