¹⁷⁷Lu‐[DOTA0,Tyr3] octreotate therapy in patients with disseminated neuroendocrine tumors: Analysis of dosimetry with impact on future therapeutic strategy

Abstract

BACKGROUND: 177 Lu-(DOTA0,Tyr3) octreotate is a new treatment modality for disseminated neuroendocrine tumors. According to a consensus protocol, the calculated maximally tolerated absorbed dose to the kidney should not exceed 27 Gy. In commonly used dosimetry methods, planar imaging is used for determination of the residence time, whereas the kidney mass is determined from a computed tomography (CT) scan. METHODS: Three different quantification methods were used to evaluate the absorbed dose to the kidneys. The first method involved common planar activity imaging, and the absorbed dose was calculated using the medical internal radiation dose (MIRD) formalism, using CT scan-based kidney masses. For this method, 2 region of interest locations for the background correction were investigated. The second method also included single-photon emission computed tomography (SPECT) data, which were used to scale the amplitude of the time-activity curve obtained from planar images. The absorbed dose was calculated as in the planar method. The third method used quantitative SPECT images converted to absorbed dose rate images, where the median absorbed dose rate in the kidneys was calculated in a volume of interest defined over the renal cortex. RESULTS: For some patients, the results showed a large difference in calculated kidneyabsorbed doses, depending on the dosimetry method. The 2 SPECT-based methods generally gave consistent values, although the calculations were based on different assumptions. Dosimetry using the baseline planar method gave higher absorbed doses in all patients. The values obtained from planar imaging with a background region of interest placed adjacent to the kidneys were more consistent with dosimetry also including SPECT. For the accumulated tumor absorbed dose, the first 2 of the 4 planned therapy cycles made the major contribution. CONCLUSIONS: The results suggested that patients evaluated according to the conventional planar-based dosimetry method may have been undertreated compared with the other methods. Hematology and creatinine did not indicate any restriction for a more aggressive approach, which would be especially useful in patients with more aggressive tumors where there is not time for more protracted therapy. Cancer 2010;116(4 suppl):1084-92.

Lutetium 177 PSMA radionuclide therapy for men with prostate cancer: a review of the current literature and discussion of practical aspects of therapy

“…The preferential means of performing dosimetry is with 3D imaging, namely quantitative SPECT/CT. Whilst 2D absorbed dose estimates can be made from planar data, limitations do exist, primarily in the form of structure overlap, and will most likely lead to overestimates of absorbed dose 34, 35. The planar approach to dosimetry is, however, far more readily available without the need for specialised software, and is generally performed on geometric mean whole body data with attenuation and scatter correction, combined with a whole organ MIRD approach (model‐based estimate of absorbed dose).…”

Production of 177Lu for Targeted Radionuclide Therapy: Available Options

“…The in vivo applications of key 177 Lu radiopharmaceuticals for a variety of therapeutic procedures include peptide receptor radionuclide therapy [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], bone pain palliation [27][28][29][30][31][32][33], radiation synovectomy [34][35][36][37][38][39] and radioimmonutherapy [40][41][42][43][44][45][46]. There is a steadily expanding list of 177 Lu-labeled radiopharmaceuticals that is currently being evaluated at the preclinical research or at product development stages; these may potentially be used in vivo in humans for evaluation for radionuclide therapy [1][2][3].…”

Individualized Dosimetry of Kidney and Bone Marrow in Patients Undergoing 177Lu-DOTA-Octreotate Treatment

“…Several studies have reported dosimetry data for the kidney based on 2-dimensional (2D) (1,8,16,18) or 3-dimensional (3D) (19)(20)(21)(22) imaging and attempted to tackle the question of the dose-limiting organ. In conventional external-beam radiotherapy, an absorbed dose limit of 23 Gy is used for the kidney (23).…”