RT Journal Article SR Electronic T1 Radioimmunotherapy prevents local recurrence of colon cancer in rats JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1552 OP 1552 VO 50 IS supplement 2 A1 Gabie De jong A1 Robert Bleichrodt A1 Sandra Heskamp A1 Frits Aarts A1 Thijs Hendriks A1 Wim Oyen A1 Otto Boerman YR 2009 UL http://jnm.snmjournals.org/content/50/supplement_2/1552.abstract AB 1552 Objectives Since radioimmunotherapy (RIT) is particularly suited to treat small lesions, the objective of this study was to determine the potential role of RIT as an adjuvant after colon cancer surgery. Methods In male Wag/Rij rats an anastomosis was constructed after intraluminal injection of 2 x 106 CC531 tumor cells. The biodistribution of 111In-labeled anti-CC531 antibody MG1 after intraperitoneal administration was assessed in this model. Subsequently, the therapeutic efficacy of 177Lu-labeled MG1 (74 MBq per rat) was compared with that of the carrier only (n=13). RIT was administered either at the day of surgery (D0, n=13) or 5 days postoperatively (D5, n=13). Primary endpoint was peri-anastomotic tumor growth 28 days after surgery (Figure 1). Results 111In-labelled MG1 preferentially accumulated in peri-anastomotic CC531 tumors (2.5 ± 0.2 %ID/g), while uptake in normal organs did not exceed 1%ID/g. Mortality rate due to surgery was 1/54 rats. No macroscopic or microscopic peri-anastomotic tumor growth was found in 8/11 rats in the D0-group and 11/13 rats in the D5-group, while in the control group 11/13 rats did had peri-anastomotic tumors (P=0.011 and P=0.001 versus control groups respectively). RIT resulted in transiently lower body weight in both treatment groups (P<0.05), compared to the control group. However, no other signs of clinical discomfort were registered. Conclusions This study indicates that RIT can be an effective adjuvanttreatment modality to prevent local recurrence afterresection of colon cancer.