Changes in Eosinophil as potential marker for immune-related changes associated with PRRT in NET

Ziel/Aim Eosinophils (E) have been shown to accumulate under Check Point Inhibitors (CPI) in cancer patients’ blood. It has been postulated that Peptide Receptor Radionuclide Therapy (PRRT) can induce conducive tumor environment for CPI in G1/G2 neuroendocrine tumor patients. With this background we evaluated a) the changes in E as well as neutrophil (N) to E ratio pre and post PRRT and b) correlation with PET/CT-based response.

Methodik/Methods 61 G1/G2 NET patients (F:M 26:35; 68 ±11 y) treated with PRRT (median 4 cycles; administered radioactivity of 6.89 ± 0.93 GBq/Lu-177-DOTAiTATE) were included. Response assessment was performed using Ga-68 Somatostatin Receptor (SSTR) PET/ceCT. The values (E, N, N/E) collected before the first PRRT and after the first and second PRRT were compared.

Ergebnisse/Results Most frequent site of primary was midgut (39%) followed by pancreas (30%). E values n (%) increase after PRRT in 13 (50) of patients with partial remission (PR, 41%), in 6 (27) stable disease (SD, 36%) and in 6 (46) progressive disease (PD, 23%) patients. E counts increased by 22 ± 1 % after PRRT, however this difference was not significant. In patients achieving PR, SD and PD, E increased by 11%, 16% and 25% (difference not significant). The N counts decreased by 17% after PRRT. There was also a corresponding change in the ratio median (range) value of N/E from 34.5 (20.4-84.2) to PRRT 27.1 (17.9-53.0) after PRRT with a trend towards significance (p = 0.06).

Schlussfolgerungen/Conclusions In this preliminary study we observed eosinophil accumulation in blood in total of 25/61 (41%) of patients after PRRT. However, unlike immunotherapy this eosinophil enrichment did not show any negative or positive predictive value. Future studies are planned to correlate the changes in E and N/E with immune-related changes in the tumor microenvironment after PRRT to ascertain the optimal time point for initiation of CPI therapy.

Publication History

Article published online:
08 April 2021