Investigating Absorbed Dose Response in 177Lu-DOTATATE for GEP-NETs

For patients with progressive and inoperable gastroenteropancreatic neuroendocrine tumors (GEP-NETs) that overexpress somatostatin receptors, 177Lu-DOTATATE is an approved therapy option. Researchers can quantify absorbed doses through serial postinfusion scintigraphy measurements of the γ-emissions.

A study from Kévin Hebert, MD, and colleagues published in The Journal of Nuclear Medicine sought to determine the potential of postinfusion 177Lu-DOTATATE dosimetry to affect clinical management through predicting treatment efficacy, including tumor shrinkage and survival, as well as toxicity.

Researchers evaluated the data of patients with GEP-NETs who received treatment with 177Lu-DOTATATE and underwent dosimetry between 2016 and 2022. Using PLANET Dose and the local energy deposition method, they calculated the absorbed doses for healthy organs and tumors.

The 35 dosimetric studies were conducted in patients with grade 2 (77%) tumors and metastasis in the liver (89%), lymph nodes (77%), and bone (34%). Of the 146 analyzed lesions, there were 1 to 9 per patient, with a majority being liver metastasis (65%) and lymph nodes (25%).

Dr. Hebert and colleagues found that the median total absorbed dose by tumors was 94.4 Gy, with the absorbed doses by tumors lessening significantly between cycles. Three months following treatment end, researchers observed a connection between the absorbed dose by tumors and tumor volume variation (P<.001). The absorbed dose by tumors was also found to be a notable prognostic factor for survival.

A relationship between a reduction in hematologic parameters, including lymphocytes or platelet concentrations and the absorbed doses by the spleen or bone marrow was identified through toxicity analysis.

No connection was identified between the mean absorbed dose by the kidneys and nephrotoxicity throughout the study.

“In patients treated with 177Lu-DOTATATE for GEP-NETs, tumor and healthy organ dosimetry can predict survival and toxicities, thus influencing clinical management,” the investigators wrote.