title: 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 kidney-absorbed 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.
authors.affiliation: Department of Oncology, Lund University and Lund University Hospital, Lund, Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Garkavij
authors.forename: Mattias
authors.initials: M
authors.lastname: Nickel
authors.forename: Katarina
authors.initials: K
authors.lastname: Sjögreen-Gleisner
authors.forename: Michael
authors.initials: M
authors.lastname: Ljungberg
authors.forename: Tomas
authors.initials: T
authors.lastname: Ohlsson
authors.forename: Karin
authors.initials: K
authors.lastname: Wingårdh
authors.forename: Sven-Erik
authors.initials: SE
authors.lastname: Strand
authors.forename: Jan
authors.initials: J
authors.lastname: Tennvall
mesh_terms: D005544:Forecasting; D006801:Humans; D008187:Lutetium / Q000627:therapeutic use*; D009362:Neoplasm Metastasis; D018358:Neuroendocrine Tumors / Q000473:pathology / Q000532:radiotherapy; D015282:Octreotide / Q000031:analogs & derivatives* / Q000627:therapeutic use; D009942:Organometallic Compounds / Q000627:therapeutic use*; D011874:Radiometry / Q000379:methods; D019275:Radiopharmaceuticals / Q000627:therapeutic use*; D011879:Radiotherapy Dosage
chemical_list: D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; D008187:Lutetium; C447941:lutetium Lu 177 dotatate; D015282:Octreotide