Raffaella Barone

Therapy using labelled somatostatin analogues : comparison of the absorbed doses with 111In-DTPA-D-Phe1-octreotide and yttrium-labelled DOTA-D-Phe1-Tyr3-octreotide

ObjectiveWe estimated the absorbed doses for 111In-DTPA-D-Phe1-octreotide and 90Y-DOTA-D-Phe1-Tyr3-octreotide in the same patients in order to compare the potential effectiveness (tumour dose) and safety (kidney and red marrow dose) of these drugs for peptide-targeted radiotherapy of somatostatin receptor positive tumours. MethodsSix patients with neuroendocrine tumours underwent quantitative 111In-DTPA-D-Phe1-octreotide SPECT and 86Y-DOTA-D-Phe1-Tyr3-octreotide PET scan at intervals of 1 week. All studies were performed with a co-infusion of amino acids for renal protection. PET and SPECT were reconstructed using iterative algorithms, incorporating attenuation and scatter corrections. Tissue uptakes (IA%) were measured and used to calculate residence times. Absorbed doses to tissues were estimated and the maximal allowed activity, defined as either the activity delivering 23 Gy to the kidneys (MAAK) or 2 Gy to the red marrow (MAARM), was calculated and the resulting tumour absorbed doses were computed. ResultsFor the MAAK the mean absorbed dose to the red marrow was lower for 90Y-DOTA-D-Phe1-Tyr3-octreotide than for 111In-DTPA-D-Phe1-octreotide (1.8±0.9 Gy vs. 6.4±1.6 Gy; P<0.001). The median absorbed dose to tumours for the MAAK was two-fold higher for 90Y-DOTA-D-Phe1-Tyr3-octreotide as compared to 111In-DTPA-D-Phe1-octreotide (30.1 vs. 12.6 Gy; P<0.05). The median absorbed dose to tumours estimated for the MAARM was 10-fold higher for 90Y-DOTA-D-Phe1-Tyr3-octreotide than for 111In-DTPA-D-Phe1-octreotide (35.1 Gy vs. 3.9 Gy; P<0.05). ConclusionsThis direct intra-patient comparison confirms that the use of 90Y-DOTA-D-Phe1-Tyr3-octreotide is more appropriate for therapy of somatostatin receptor bearing tumours. When using 111In-DTPA-D-Phe1-octreotide, the red marrow represents the major critical organ; this can result in significant toxicity if high activities have to be administered to obtain efficient tumour irradiation.

Relevance of early poststress variation in left ventricular function studied by gated-SPECT: evaluation in different clinical settings and relationship with angiography results.

BackgroundStress-induced ischemia may cause a decrease in left ventricular ejection fraction (EF). We evaluated the variation in early postexercise EF (S-EF) compared with rest EF (R-EF) in different clinical settings to detect ventricular dysfunction. We also correlated ventricular dysfunction with an angiographic score, the Syntax score, in a subgroup of ischemic patients. Materials and methodsGated-SPECT images were acquired 12 min after exercise stress and at rest in 1481 patients. Patients were classified as controls, negative for ischemia, mildly ischemic, moderately/severely ischemic, necrotic, and necrotic with ischemia. Mean end-diastolic volume, end-systolic volume, and EF were compared in each group. The ratio between stress to rest EF was indicated as the functional score. Angiography results were collected for 55% of moderately/severely ischemic patients. Sixty-one angiographies were also completed with Syntax score evaluation. ResultsIn negative, necrotic, and mildly ischemic patients no differences were found between S-EF and R-EF. An opposite trend was observed in moderately/severely ischemic patients with a decrement of S-EF compared with R-EF (54.80±11.33 vs. 57.79±11.14; P<0.0001). Coronary artery disease was confirmed by angiography in 93% of moderately/severely ischemic patients. In 61 patients who underwent Syntax score evaluation, significant correlation was observed with functional score. Significant decrease in functional score was found in patients with coronary artery bypass graft indication compared with patients with percutaneous coronary intervention or medical indication. ConclusionEarly poststress gated-SPECT acquisition allows the detection of ventricular dysfunction in moderately/severely ischemic disease and provides additional information when directing patients to angiography and revascularization.