RT Journal Article SR Electronic T1 Peptide receptor radiotherapy (PRRT) as a potential tool of neoadjuvant therapy in patients with inoperable neuroendocrine tumors (NETs) JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1743 OP 1743 VO 52 IS supplement 1 A1 Sowa-Staszczak, Anna A1 Pach, Dorota A1 Stefanska, Agnieszka A1 Tomaszuk, Monika A1 Mikolajczak, Renata A1 Pawlak, Dariusz A1 Trofimiuk, Malgorzata A1 Chrzan, Robert A1 Hubalewska-Dydejczyk, Alicja YR 2011 UL http://jnm.snmjournals.org/content/52/supplement_1/1743.abstract AB 1743 Objectives Surgical eradication is the main aim in the treatment of NETs, which becomes impossible in the case of large tumors or infiltration into other tissues and/or important blood vessels. Neoadjuvant therapy might be helpful in decreasing neuroendocrine tumor’ size also. Methods Within the group of 47 patients treated with PRRT, 6 patients were chosen with large, inoperable tumors, for whom enabling of complete surgical excision of the lesions might be the prospect for a cure. There were 5 patients with foregut tumors and 1 with midgut tumor). Every patient received a dose of 7.4 GBq/m2 90Y-DOTA TATE in 4-5 cycles every 6-9 weeks. The mean dose was 13.6 GBq (min 11.1 GBq, max 14.8 GBq). Response to the therapy was assessed according to RECIST criteria. Results After the treatment, mean tumor size decreased to 6.9 cm with SD 2 cm (min 3.1 cm, max 9.6 cm). According to RECIST criteria, stabilization of the disease was observed in 4, partial responses in 2 patients. In two patients, reduction of the tumor size enabled surgical intervention. Conclusions 1. PRRT might be considered a neoadjuvant therapy in primary inoperable neuroendocrine tumors. 2. According to RECIST criteria stabilization of the disease was observed in the majority of patients. 3. We suggest that not only tumor’ diameter changes, but also tumor’ volume and contrast enhancement changes in CT should be taken into consideration in assessment of the response to the therapy