Pablo Pichardo-Romero

Targeted imaging of gastrin-releasing peptide receptors with 99mTc-EDDA/HYNIC-[Lys3]-bombesin: biokinetics and dosimetry in women.

BackgroundThe gastrin-releasing peptide receptor (GRP-R) is expressed in several normal human tissues and is overexpressed in various human tumors including breast, prostate, small-cell lung cancer and pancreatic cancer. Recently, 99mTc-EDDA/HYNIC-[Lys3]-bombesin (99mTc-HYNIC-BN) was reported as a radiopharmaceutical with high stability in human serum, specific cell GRP-R binding and rapid cell internalization. AimThe aim of this study was to determine the biokinetics and dosimetry of 99mTc-HYNIC-BN and the feasibility of using this radiopharmaceutical to image GRP-R in four early breast cancer patients and seven healthy women. MethodsWhole-body images were acquired at 20, 90, 180 min, and 24 h after 99mTc-HYNIC-BN administration. The same regions of interest were drawn around source organs on each time frame and regions of interest were converted to activity (conjugate view counting method). The image sequence was used to extrapolate 99mTc-HYNIC-BN time-activity curves in each organ to calculate the total number of disintegrations (N) that occurred in the source regions. N data were the input for the OLINDA/EXM code to calculate internal radiation dose estimates. Results99mTc-HYNIC-BN had a rapid blood clearance with mainly renal excretion. No statistically significant differences (P>0.05) in the radiation-absorbed doses among cancer patients and healthy women were observed. The average equivalent doses (n=11) were 24.8±8.8 mSv (kidneys), 7.3±1.8 mSv (lungs), 6.5±4.0 mSv (breast), 2.0±0.3 mSv (pancreas), 1.6±0.3 mSv (liver), 1.2±0.2 mSv (ovaries), and 1.0±0.2 mSv (red marrow). The effective dose was 3.3±0.6 mSv. The images showed well-differentiated concentration of 99mTc-HYNIC-BN in cancer mammary tissue. ConclusionAll the absorbed doses were comparable with those known for most of the 99mTc studies. 99mTc-HYNIC-BN shows high tumor uptake in breasts with malignant tumors so it is a promising imaging radiopharmaceutical to target site-specific early breast cancer. The results obtained warrant a further clinical study to determine specificity/sensibility of 99mTc-HYNIC-BN.

153Sm-EDTMP for Pain Relief of Bone Metastases from Prostate and Breast Cancer and Other Malignancies

BACKGROUND AND AIMS Approximately 85% of patients with cancer suffer severe metastatic bone pain for which radionuclide therapy has been employed for pain palliation. We undertook this study to evaluate the pain relief effect of (153)Sm-EDTMP in Mexican patients with severe and painful bone metastases from mainly prostate, breast, and renal cancer and other malignancies. METHODS Patients (277) with intense sustained pain caused by bone metastases were referred to the Nuclear Medicine Department of the Oncology Hospital of the Mexican Social Security Institute. The patients had to have acceptable physical conditions, a previous positive (99m)Tc-MDP scan and blood values within normal range. (153)Sm-EDTMP was prepared at the Instituto Nacional de Investigaciones Nucleares (ININ) and 37 MBq/kg of body weight was injected intravenously. Pain palliation was evaluated with a visual analogue scale (VAS) and a verbal rating scale (VRS) before treatment and 3 and 12 weeks after treatment was started. RESULTS The age interval of the patients was 24-92 years with a mean age of 64 ± 12 years. Mean values for hemoglobin, leukocyte and platelet counts did not statistically differ at zero time, 3 and 12 weeks after treatment. Pain intensity and relief assessment were statistically different: 9.1 ± 0.61 units initially; 4.2 ± 1.3 units 3 weeks later (54%) and after 12 weeks the pain diminished to 2.4 ± 1.4 units (74%) in the pain relief score scales. CONCLUSIONS (153)Sm-EDTMP was readily available, safe and well tolerated. We conclude that (153)Sm-EDTMP was an adequate palliative agent and was the best option for our Mexican patients to relieve their severe metastatic bone pain.