Is there a correlation between peptide receptor radionuclide therapy-associated hematological toxicity and spleen dose?

Aim: The spleen receives a high mean absorbed radiation dose during peptide receptor radionuclide therapy (PRRNT). The aim of this study is to correlate the radiation dose to spleen with the effect on blood cell count after PRRNT. Methods: Fifty-three neuroendocrine tumor (NET) patients were treated with 3.8-8.5 GBq ¹⁷⁷Lu-DOTATATE or ¹⁷⁷Lu-DOTATOC. Dosimetry was performed according to MIRD scheme. Eleven NET patients who had undergone splenectomy before PRRNT and who received 4.7-7.6 GBq ¹⁷⁷Lu-DOTATATE or ¹⁷⁷Lu-DOTATOC were selected as controls. RBC, WBC (total and differential), and platelet counts before and after each cycle of PRRNT were documented. Results: The median dose to the spleen in the study group was 6.34 Gy (2.32-20.06 Gy). There was no significant difference in the posttherapy changes in the blood cell counts (RBC, WBC, or platelets) between the study group and the control group. Mild hematological toxicity was found in 7 of the 53 (13.2%) patients in the study group and in 1 out of the 11 patients (9.1%) in the control group. However, there was no correlation between the incidence or grade of hematological toxicity and the dose to the spleen. Conclusion: This study demonstrates for the first time that hematological toxicity after PRRNT is not related to the radiation dose to the spleen.