Thallium-201 single photon emission tomography after injecting an antimuscarinic agent compared with computed tomography for the diagnosis of recurrent colorectal cancer. Report of three cases.

Thallium-201 chloride ((201)TlCl) is frequently used for imaging of a variety of malignant tumors viz., thyroid, lung, brain, bone and breast, however in patients with colorectal cancer, its role is not well established. In this case report we present three patients with colorectal cancer recurrence, with inconclusive computed tomography (CT) findings while (201)TlCl single photon emission tomography (SPET) after injecting an anti-muscarinic agent, showed findings corroborating with the final diagnosis. Correlating CT with (201)TlCl-SPET findings, recurrence of the colorectal cancer was diagnosed in two cases; surgical treatment accordingly planned, confirmed the diagnosis. In the third case, CT was falsely positive while (201)TlCl-SPET was negative, compatible with the final diagnosis.