RT Journal Article SR Electronic T1 Outcome on Mesenteric Mass Response of Small-Intestinal Neuroendocrine Tumors Treated by 177Lu-DOTATATE Peptide Receptor Radionuclide Therapy: The MesenLuth Study, a National Study from the French Group of Endocrine Tumors and Endocan-RENATEN Network JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 258 OP 263 DO 10.2967/jnumed.123.266063 VO 65 IS 2 A1 Al Mansour, Laure A1 De Mestier, Louis A1 Haissaguerre, Magalie A1 Afchain, Pauline A1 Hadoux, Julien A1 Lecomte, Thierry A1 Morland, David A1 Cottereau, Anne Segolene A1 De Rycke, Ophelie A1 Tlili, Ghoufrane A1 Tordo, Jérémie A1 Janier, Marc A1 Deville, Agathe A1 Walter, Thomas YR 2024 UL http://jnm.snmjournals.org/content/65/2/258.abstract AB A mesenteric mass (MM), characterized by fibrotic reaction, is present in most small-intestinal neuroendocrine tumors (SI-NETs). 177Lu-DOTATATE peptide receptor radionuclide therapy (PRRT) has shown its efficacy in patients with progressive SI-NETs. However, because of specific tissue characteristics of desmoplastic MMs, we hypothesize that these lesions may be refractory to 177Lu-DOTATATE PRRT. Methods: From the national French Groupe d’étude des Tumeurs Endocrines database, we identified patients with an advanced SI-NET and a MM (≥2 cm with a retractile aspect) of a SI-NET treated by at least 1 course of 177Lu-DOTATATE PRRT. The primary endpoint was a MM objective response rate (ORR) of less than 5%. Secondary endpoints were metabolic response, MM-related safety, and clinical response, as well as MM progression-free survival (PFS) and non-MM PFS. Results: In total, 52 patients were included. The MM ORR was 4% (n = 2), and the non-MM ORR was 8% (n = 4). No patient had a MM metabolic response, and the non-MM metabolic response rate was 12% (n = 6). Among the 26 patients with baseline MM-related symptoms, 46% had a clinical response. Four patients presented with gastrointestinal complications during PRRT. The median MM-related PFS was not reached, and the non-MM PFS was 50.3 mo (95% CI, 38.2–61.7 mo). Conclusion: This study confirms that 177Lu-DOTATATE PRRT does not lead to morphologic response on MMs (ORR < 5%). However, it allows MM stability, with few MM-related side effects, and has a relevant impact on MM-related symptoms.