Evaluation of primary and recurrent colorectal cancer patients with Tc99m IMMU-4 (Fab' fragment) radioimmünoscintigraphy

Colorectal malignancies rank fourth in frequency among all cancers and second in mortality following lung cancers.Nowadays, of the conventional methods , CT is the most commonly used fort he diagnosis and follow-up of colorectal cancers.However, in cases with recurrent colorectal cancers , the interpretation to differentiate between scar and recurrence or metastasis through CT findings poses significant challenges since post-operative/ post-radiation anatomy alters.In this study, we aimed to compare CT findings by Tc99m anti-CEA (IMMU-4) monoclonal antibody sycintigraphy in patients with primary or recurrent colorectal cancers.A total of 18 patients (10 male and 8 female; mean age: 50.57+13.93) with colorectal mass, suspected of colorectal cancer and with recurrrent colorectal cancer, who applied to General Surgery Clinic of Medical Faculty, Dicle University ,were included into the study.The definitive diagnosis of all cases were confirmed histopathologically.Of 18 cases, 7 were with colorectal cancer and 8 were with recurrent disease ; of the remaining 3 cases , 2 were with bone metastasis and 1 was malign melanoma.The average serum CEA levels of the patients were determined to be 42.89+ 155.2ng/ml.Of the cases, 5 were with Duke?s B, 10 with Duke?s C and 2 with Duke?s D.On separate days, patients abdominopelvic CT and radioimmunosycintigraphy were taken by GE Millenium gama camera through intravenous infusion of 25 mCi(925 MBq) Tc 99m IMMU-4 (anti-CEA) antibody.Following injection, the whole body imaging was performed at hours 3 and 24 in anterior and posterior positions.In patients with suspected activity involvement in pelvis and abdomen, SPECT imaging was achieved at the 3th hour.Post-operative histopathology of a case, in whose RIS no pathologic activity was noted, came as malign melanoma.In 2 cases, who had earlier been diagnosed to have colorectal cancer, upon the detection of increased osteoblastic activity involvement in femur during routine bone sycintigraphy, RIS was performed to find out whether there was metastasis or not.Upon the observation of increased Tc 99m IMMU-4 (anti-CEA) antibody involvement in the same sites, these sites were interpreted as metatasis.Though any activity involvement that might be evaluated pathologically in rectosigmoid region and rectum in monoclonal antibody sycintigraphy performed in 2 cases with rectal mass, abdominopelvic CT was observed to be within the normal limits.In the diagnosis of primary and recurrent colorectal cancers in abdominopelvic region , sensitivity of RIS was determined as 93.75%, specifity as 100% and accuracy rate as 94.4%, while sensitivity of CT was found as 87.5%, specifity as 50% and accuracy rate as 88.8%.In abdominopelvic CT of two patients with colon and primary rectal cancer together with bone metastasis, 1.5cm. hypodense lesions were observed in the liver.However, in Tc 99m anti-CEA monoclonal antibody sycintigraphy, liver lesions defined in CT could not be evaluated due to increased physiological activity involvement in kidney ,liver and spleen.Since the patients did not give consent fort he biopsies of liver,of malign/benign differentiation of lesions could not be histopathologically avhieved.Of 17 patients, the results of radioimmunosycintigraphy and post-operative histopathology were found to be compatible with each other in 15 patients.No significant difference was found between patients? serum CEA levels and pathologic activity involvements determined in marked antibody sycintigraphy(p> 0.05).As a result , we concluded that RIS, performed with technetium-marked anti-CEA antibody fragments, was more sensitive than CT in the diagnosis of primary, recurrent and distant metastases (particularly bone) ,since it ensures the whole body screening but that CT could be more useful than RIS in the detection of liver metastases.