Impact of 177Lu-octreotate therapy on the spleen

1363 Objectives: The aim of this retrospective study was to evaluate the impact of 177Lu-octreotate therapy on the spleen, a cible organ of peptide receptor radionuclide therapy (PRRT) in patients treated for metastatic well differentiated gastro-entero-pancreatic endocrine cancers (WD GEP EC). Methods: Spleen volume was measured on diagnostic CT (5 mm thick slice) performed before (mean delay 10.7 month; range:0.3–47.9) and after (mean delay following last administration of PRRT: 5.7 month; range:1.9–10) treatment with 177Lu-octreotate. Spleen’s contours were semi-automatically delineated and spleen volume was calculated using an image processing workstation (Isogray, Dosisoft, France) in 7 patients (1 female, 6 male, mean age 57 years) referred to the Rotterdam group for PRRT. Five patients received a cumulated activity (CA) of 30 GBq in 4 administrations and 2 patients a mean CA of 21 GBq in 3 administrations. Results: Mean spleen volume was 222 cm3 (range:127-312) and 180 cm3 (range:89-237) before and after PPRT respectively. A reduction of the spleen volume was observed in all patients after PRRT with a mean reduction of 19 % (range 10-36%). No infectious event occurred after PPRT after a median follow-up of 17 months (range: 7.8-27.1). Conclusions: These preliminary data shows that 177Lu-octreotate therapy is probably responsible of a reduction in spleen volume. Whether there is a clinical impact will have to be determined on further studies.