Radioligand therapy in patients with unknown point of origin, other than gastroenteropancreatic or G3 grading neuroendocrine neoplasms

Grzegorz Kamiński; Adam Durma; Marek Saracyn; Maciej Kołodziej; Katarzyna Joźwik-Plebanek; Beata Dmochowska; Adrianna Mroz; Wawrzyniec Żmudzki; Grzegorz Kaminski

doi:10.1530/endoabs.99.EP265

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Endocrine Abstracts (2024) 99 EP265 | DOI: 10.1530/endoabs.99.EP265

ECE2024 Eposter Presentations Pituitary and Neuroendocrinology (214 abstracts)

Radioligand therapy in patients with unknown point of origin, other than gastroenteropancreatic or G3 grading neuroendocrine neoplasms

Grzegorz Kamiński ¹ , Adam Durma ¹ , Marek Saracyn ¹ , Maciej Kołodziej ¹ , Katarzyna Jóźwik-Plebanek ¹ , Beata Dmochowska ¹ , Adrianna Mróz ¹ , Wawrzyniec Żmudzki ¹ & Grzegorz Kaminski ¹

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¹Military Institute of Medicine - National Research Institute, Endocrinology and Radioisotope Therapy, Warszawa, Poland

Background: Neuroendocrine neoplasms (NENs) are rare group of tumors with a different clinical course, prognosis and location. Radioligand therapy (RLT) is currently registered in gastroenteropancreatic (GEP) G1-G2 NENs. Tumors with an unknown point of origin, diagnosed outside the gastrointestinal tract and pancreas, or with Ki-67 >20%, do not qualify in many countries to standard RLT.

Materials and Methods: 48 patients with progressive NENs of unknown primary site, non-GEP-NENs, and G3 with good somatostatin receptor expression were qualified to the study. 32 patients received Lutetium-177 (7.4 GBq), while 16 received tandem therapy with Lutetium-177 and Yttrium-90 with equal activities (1.85 + 1.85 GBq) in 4 cycles every 10 weeks.

Results: Progression-free survival (PFS) before RLT was 34 months (IQR=36) for the whole study group. In subgroups of patients with an unknown tumor location (n = 25), the median PFS was 19 months (IQR = 23), with ‘other’ locations (n = 21) 31 months (IQR = 28), and with NEN G3 (n = 7) 18 months (IQR = 40). Just after the RLT, disease stabilization or regression was observed in 42 (87.5%) patients. 43 patients reported to follow-up visit (median time after RLT - 14 months; IQR=18). In 8 we noted progression, 9 patients died, and stabilization was noted in 26 individuals. PFS and OS probability (%) of surviving 12, 24, 36, 48 months (with 95% CI) were calculated. RLT did not cause statistically significant changes in creatinine or GFR values. Hematological parameters (RBC, WBC, PLT, HGB) as well as chromogranin A concentration decreased significantly during the treatment. There were no statistical differences between both subgroups regarding the type of radioisotope used (177-Lutetium vs 177-Lutetium and 90-Yttrium).

Conclusions: Patients with NENs who do not qualify for standard RLT at this moment due to a lack of registration could benefit from such therapy. There were no significant negative impacts on renal parameters. The reductions in blood counts were noticeably, but not clinically significant, which was acceptable in relation to the positive treatment outcomes.