[¹8F-FDG PET/CT. Its correlation with carcinoembryonic antigen in patients with colorectal carcinoma]. / Tomografía por emisión de positrones-tomografía computarizada con 18F-2-fluoro-2-deoxi-D-glucosa (18F-FDG PET/CT) y su correlación con el antígeno carcinoembrionario en pacientes con carcinoma colorrectal.

BACKGROUND: ¹8F-FDG PET has been shown to be highly accurate for recurrent and metastatic disease as well as in restaging. The carcinoembryonic antigen (CEA) can be used as a marker of prognosis and recurrence. OBJECTIVE: To evaluate the association between the presence of lesions detected with 18F-FDG PET/CT and CEA values in patients with colorectal carcinoma. MATERIAL AND METHODS: We reviewed the records of 2,051 patients who underwent PET/CT to identify all the patients with colorectal carcinoma and previous CEA. RESULTS: We included a total of 101 patients, 51 women and 50 men, with an average age of 60.21 years. The clinical stage that prevailed was ECIIA, with moderately differentiated adenocarcinoma histology (88.12%). There was agreement between the elevation of CEA and lesions detected by PET/CT in 73.9%. From the patients with normal values of CEA, in 42% the PET/CT study was positive for tumoral recurrence or metastases. CONCLUSIONS: Our study revealed that 18F-FDG PET/CT can provided additional information in up to 42% of patients with normal ranges of carcinoembryonic antigen, detecting early recurrence or metastases.

Kit preparation and biokinetics in women of 99mTc-EDDA/HYNIC-E-[c(RGDfK)]2 for breast cancer imaging.

BACKGROUND: In breast cancer, α(ν)ß(3) and/or α(ν)ß(5) integrins are overexpressed in both endothelial and tumour cells. Radiolabelled peptides based on the Arg-Gly-Asp (RGD) sequence are radiopharmaceuticals with high affinity and selectivity for these integrins. The RGD-dimer peptide (E-[c(RGDfK)]2) radiolabelled with (99m)Tc has been reported as a radiopharmaceutical with a 10-fold higher affinity for the α(ν)ß(3) integrin compared with the RGD-monomer. Ethylenediamine-N,N'-diacetic acid (EDDA) is a hydrophilic molecule that may favour renal excretion when used as coligand in the (99m)Tc labelling of hydrazinonicotinamide (HYNIC) peptides and can easily be formulated in a lyophilized kit. AIM: The aim of this study was to establish a biokinetic model for (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2 prepared from lyophilized kits and evaluate its dosimetry as a tumour-imaging agent in seven healthy women and three breast cancer patients. MATERIALS AND METHODS: (99m)Tc labelling was performed by adding sodium pertechnetate solution and 0.2 mol/l phosphate buffer (pH 7.0) to a lyophilized formulation containing E-[c(RGDfK)]2, EDDA, tricine, mannitol and stannous chloride. The radiochemical purity was evaluated using reverse-phase high-performance liquid chromatography and instant thin-layer chromatography on silica gel analyses. Stability studies in human serum were carried out using size-exclusion high-performance liquid chromatography. In-vitro cell uptake was tested using breast cancer cells (MCF7, T47D and MDA-MB-231) with blocked and nonblocked receptors. Biodistribution and tumour uptake were determined in MCF7 tumour-bearing nude mice with blocked and nonblocked receptors, and images were obtained using a micro-SPECT/PET/CT. Whole-body images from seven healthy women were acquired at 0.5, 1, 3, 6 and 24 h after (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2 administration with radiochemical purities greater than 94%. Regions of interest were drawn around the source organs at each time frame. Each region of interest was converted to activity using the conjugate view counting method. The image sequence was used to extrapolate the (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2 time-activity curves of each organ to adjust the biokinetic model and 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. In three breast cancer patients with histologically confirmed cancer, static images were obtained at 1 h in the supine position with hands placed behind the head. RESULTS: (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2 obtained from lyophilized kits demonstrated high stability in human serum and specific cell receptor binding. The biodistribution data from mice showed rapid blood clearance, with both renal and hepatobiliary excretion, and specific binding towards α(ν)ß(3) integrins in the MCF7 tumours. In women, the blood activity showed a half-life value of 1.60 min for the fast component (T1/2α = ln2/26.01) and half-life values of 1.0 h for the first slow component (T1/2ß = ln2/0.69) and 4.03 h for the second slow component (T1/2γ = ln2/0.16). Images from patients showed an average tumour/heart (blood) ratio of 3.61 ± 0.62 at 1 h. The average equivalent doses calculated for a study using 740 MBq were 4.9, 6.2, 20.7, 34.5 and 57.0 mSv for the liver, intestines, spleen, kidneys and thyroid, respectively, and the effective dose was 6.1 mSv. CONCLUSION: All absorbed doses were comparable to those known from most of the (99m)Tc studies. (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2 obtained from kit formulations showed high tumour uptake in patients with malignant lesions, making it a promising imaging radiopharmaceutical for targeting site-specific breast cancer. The results obtained in this study warrant further clinical studies to determine the specificity and sensitivity of (99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2.

Staging, response to therapy, and restaging of lymphomas with 18F-FDG PET.

BACKGROUND: We undertook this study to determine the diagnostic accuracy of (18)FDG after three cycles and at the end of chemotherapy in non-Hodgkin's lymphoma (NHL) or Hodgkin's lymphoma (HL). We also evaluated the role of (67)Ga, bone marrow aspiration (BMA), and computed tomography (CT) in monitoring lymphoma treatment. METHODS: (18)FDG, (67)Ga, BMA, and CT were performed before chemotherapy on 40 untreated patients. (18)FDG and CT data were also obtained in 28/40 patients after 3 cycles of chemotherapy and at the end of chemotherapy. Patients had a median follow-up of 18 months, 21 had NHL, 7 had HL. Age range was from 15 to 74 years. Histopathology considered the standard reference at the initial stage. Follow-up was a comparative study of all exam results. RESULTS: Initial staging for PET and CT was as follows: sensitivity (Se) was 100%, specificity (Sp) 100%, positive predictive value (PPV) 100%, negative predictive value (NPV) 0%, and accuracy (Ac) 100%. (67)Ga was Se, 64%; Sp, 0%, PPV, 100%; and Ac, 64%. After the third cycle of chemotherapy and at the end of chemotherapy, Se, Sp, PPV, NPV, and Ac were always higher with PET than with CT. Eighteen patients had complete response, and seven had partial or no response. CONCLUSIONS: (18)FDG had greater prognostic values than CT after the third and last cycle of chemotherapy. PET after three cycles of chemotherapy is predictive of 18-month outcome in patients with intermediate and aggressive NHL and HL and may help in the identification of patients who would benefit from more intensive treatment or from a change in chemotherapy.