Predictive Factors of Persistent Thrombocytopenia after Peptide Receptor Radioligand Therapy in Enteropancreatic Neuroendocrine Tumors

Romain Ferrara¹Christophe Zemmour²Thibaut Reichert¹Daniel Ouk¹Patricia Niccoli³JEMIMA MANIRY-QUELLIER³Isabelle Brenot-Rossi¹Nathalie Charrier¹Sandrine Oziel-Taieb^3*

• ¹Department of Nuclear Medicine, Institut Paoli-Calmettes, Marseille, Provence-Alpes-Côte d'Azur, France
• ²Department of Clinical Research and Investigation, Biostatistics an Methodology Unit, Institut Paoli-Calmettes, Marseille, Provence-Alpes-Côte d'Azur, France
• ³Department of Medical Oncology, Institute Paoli Calmettes, Marseille, France

Introduction: Peptide Receptor Radionuclide Therapy is an effective and well tolerated treatment for advanced Neuroendocrine Tumors (NETs). However, Persistent Thrombocytopenia been reported and may compromise further therapies and outcomes. This study aimed to identify predictive factors of PT defined as a platelet count <100 x 10 9 /L, two months after the end of PRRT. Methods: We performed a single center retrospective analysis of clinical, biological and imaging parameters of metastatic NET patients undergoing [177Lu]Lu-DOTATATE. Bone metastatic volume was quantitatively measured and converted into an Osteo-Medullary Invasion Score (OMIS). The Initial Decline of Platelet Count (IDPC) was defined as the relative change (%) in platelet count between the baseline and the nadir value before the second cycle. Results: 47 patients (25 female, 22 male, median age 68y) were included. 15 patients (31.9%) had bone metastases and five (10.6%) had an OMIS ≥ 30%. Six patients (15.4%) presented a spleen length ≥ 100 mm. Median follow up was 50.1 months. Median IDPC was 26%. Eight patients (17%) presented a PT. PT was associated with an OMIS ≥ 30% (p < 0.001; odds ratio not estimable) a spleen length ≥ 100 mm (p = 0.04; odds ratio = 7), an IDPC ≥ 30% (p= 0.014: odds ratio = 15.8) and was unrelated to age, gender, previous cancer, previous therapies and cumulative activity. Conclusion: We found 17% of PT incidence correlated with relative high bone metastatic burden and spleen length. Physicians should be vigilant in the event of a significant drop in platelet count after the first cycle of PRRT.