CLINICAL VALIDATION OF SPECT AND CT MRI IMAGE REGISTRATION IN RADIOLABELED MONOCLONAL-ANTIBODY STUDIES OF COLORECTAL-CARCINOMA/

Registration methods combine the anatomic localizing ability of CT or MRI with SPECT images of radiolabeled monoclonal antibodies (Mabs), al lowing the accurate staging of patients prior to surgery or following treatment. Methods: Twenty-four patients (15 males and 9 females, mean age 55 yr, range 29-70 yr) were studied with this technique. Ten pati ents had suspected colorectal cancer recurrence and were infused with 10 mCi of I-131-CC49 prior to staging laparotomy. Fourteen patients tr eated in a Phase I radioimmunotherapy study with I-131-CC49 were also studied. All patients underwent SPECT imaging of the abdomen and pelvi s 5-7 days following infusion of Mab. Results: Phantom studies demonst rated a 3.6-mm surface fitting mean accuracy of datasets for the liver and 1.8 mm for an intrahepatic tumor. In the presurgical group, SPECT and CT/MRI registration allowed more accurate identification of uptak e abnormal sites. Areas of metastatic disease >1 cm confirmed at surge ry were found in six of nine patients with liver lesions and in two pa tients with extrahepatic (including one patient with pelvic) disease. In patients imaged following radioimmunotherapy, all lesions >1.5 cm s een on CT/MRI were identified, and activity distribution in tumor and normal tissue could be more accurately assessed. Conclusions: Routine registration of SPECT and CT/MRI images is feasible and allows more ac curate anatomic assessment of sites of abnormal uptake in radiolabeled Mab studies.