Relationship of 99mtechnetium labelled macroaggregated albumin (99mTc-MAA) uptake by colorectal liver metastases to response following Selective Internal Radiation Therapy (SIRT)

58 patients with colorectal hepatic metastases received SIRT. All had pre-treatment MAA planar images and CT scans which were retrospectively reviewed. Tumours were qualitatively considered "cold", "equivocal" or "hot" based on MAA uptake and the ratio of uptake in tumour and normal liver tissue was calculated (TNR). Following SIRT (which included the administration of hepatic arterial Angiotensin 2) tumour response was assessed by CEA changes one to two months after treatment and by serial CT.Uptake was classified as "hot" in 37 patients (Group 1) and "equivocal" or "cold" in 21 (Group 2). CEA levels fell dramatically in over 90% of patients. The falls were not significantly different between the groups. There was no correlation between TNR and tumour response based on CEA changes (r2 = 0.004). CT responses after 3 months were not different in the 2 Groups.The pattern of MAA uptake by colorectal liver tumours after arterial injection is not a predictor of tumour response after treatment by SIRT. The results suggest the doses of 90Y microspheres used may be greater than is necessary.Colorectal cancer (CRC) is a particularly common cancer encountered worldwide. Although the primary site is resectable in the majority of instances, metastatic disease will be present or develop in some 50% of those affected within 5 years of presentation. As a result of the portal venous route of spread, the liver is the commonest site of metastases and is frequently the only evident site [1]. This feature of CRC, coupled with the disappointing results achieved with systemic chemotherapy, has lead to interest in the development of effective regional liver therapies. Such regional approaches include liver resection, cryotherapy or radiofrequency ablation, regional chemotherapy and selective internal radiation therapy (SIRT).SIRT has been shown to be a particularly effective form of local treatment of CRC liver metastases even when large volumes of tumour are present in multiple sites [2,