RT Journal Article SR Electronic T1 Bone Marrow Absorbed Doses and Correlations with Hematologic Response During 177Lu-DOTATATE Treatments Are Influenced by Image-Based Dosimetry Method and Presence of Skeletal Metastases JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1406 OP 1413 DO 10.2967/jnumed.118.225235 VO 60 IS 10 A1 Linn Hagmarker A1 Johanna Svensson A1 Tobias Rydén A1 Martijn van Essen A1 Anna Sundlöv A1 Katarina Sjögreen Gleisner A1 Peter Gjertsson A1 Peter Bernhardt YR 2019 UL http://jnm.snmjournals.org/content/60/10/1406.abstract AB This study aimed to compare different image-based methods for bone marrow dosimetry and study the dose–response relationship during treatment with 177Lu-DOTATATE in patients with and without skeletal metastases. Methods: This study included 46 patients with advanced neuroendocrine tumors treated with at least 2 fractions of 177Lu-DOTATATE at Sahlgrenska University Hospital. High- and low-uptake compartments were automatically outlined in planar images collected at 2, 24, 48, and 168 h after injection. The bone marrow absorbed doses were calculated from the cross doses of the high- and low-uptake compartments and the self-dose, using the time–activity concentration curve for the low-uptake compartment. This time–activity concentration curve was adjusted using a fixed constant of 1.8 for the planar dosimetry method and using the activity concentrations in vertebral bodies in SPECT images at 24 h after injection of 177Lu-DOTATATE in 4 hybrid methods: L4-SPECT used the activity concentration in the L4 vertebra, whereas V-SPECT, L-SPECT, and T-SPECT used the median activity concentration in all visible vertebrae, lumbar vertebrae, and thoracic vertebrae, respectively. Results: Using the planar method, L4-SPECT, V-SPECT, L-SPECT, and T-SPECT, the estimated median bone marrow absorbed doses were 0.19, 0.36, 0.40, 0.39, and 0.46 Gy/7.4 GBq, respectively, with respective ranges of 0.12–0.33, 0.15–1.44, 0.19–1.71, 0.21–1.60, and 0.18–2.12 Gy/7.4 GBq. For all methods, the bone marrow absorbed dose significantly correlated with decreased platelet counts. This correlation increased after treatment fraction 2: the Spearman correlation (rs) were −0.49 for the planar method, −0.61 for L4-SPECT, −0.63 for V-SPECT, −0.63 for L-SPECT, and −0.57 for T-SPECT. A separate analysis revealed an increased correlation for patients without skeletal metastases using the planar method (rs = −0.67). In contrast, hybrid methods had poor correlations for patients without metastases and stronger correlations for patients with skeletal metastases (rs = −0.61 to −0.74). The mean bone marrow absorbed doses were 3%–69% higher for patients with skeletal metastases than for patients without. Conclusion: The estimated bone marrow absorbed doses by image-based techniques and the correlation with platelets are influenced by the choice of measured vertebrae and the presence of skeletal metastases.