PT - JOURNAL ARTICLE AU - Al Mansour, Laure AU - De Mestier, Louis AU - Haissaguerre, Magalie AU - Afchain, Pauline AU - Hadoux, Julien AU - Lecomte, Thierry AU - Morland, David AU - Cottereau, Anne Segolene AU - De Rycke, Ophelie AU - Tlili, Ghoufrane AU - Tordo, Jérémie AU - Janier, Marc AU - Deville, Agathe AU - Walter, Thomas TI - Outcome on Mesenteric Mass Response of Small-Intestinal Neuroendocrine Tumors Treated by <sup>177</sup>Lu-DOTATATE Peptide Receptor Radionuclide Therapy: The MesenLuth Study, a National Study from the French Group of Endocrine Tumors and Endocan-RENATEN Network AID - 10.2967/jnumed.123.266063 DP - 2024 Feb 01 TA - Journal of Nuclear Medicine PG - 258--263 VI - 65 IP - 2 4099 - http://jnm.snmjournals.org/content/65/2/258.short 4100 - http://jnm.snmjournals.org/content/65/2/258.full SO - J Nucl Med2024 Feb 01; 65 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 &lt; 5%). However, it allows MM stability, with few MM-related side effects, and has a relevant impact on MM-related symptoms.