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.
Keywords: 177Lu-DOTATATE; PRRT; mesenteric mass; neuroendocrine tumor; objective response.
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