Erik Mittra

Phase 3 Trial of 177Lu-Dotatate for Midgut Neuroendocrine Tumors

Background Patients with advanced midgut neuroendocrine tumors who have had disease progression during first‐line somatostatin analogue therapy have limited therapeutic options. This randomized, controlled trial evaluated the efficacy and safety of lutetium‐177 (177Lu)–Dotatate in patients with advanced, progressive, somatostatin‐receptor–positive midgut neuroendocrine tumors. Methods We randomly assigned 229 patients who had well‐differentiated, metastatic midgut neuroendocrine tumors to receive either 177Lu‐Dotatate (116 patients) at a dose of 7.4 GBq every 8 weeks (four intravenous infusions, plus best supportive care including octreotide long‐acting repeatable [LAR] administered intramuscularly at a dose of 30 mg) (177Lu‐Dotatate group) or octreotide LAR alone (113 patients) administered intramuscularly at a dose of 60 mg every 4 weeks (control group). The primary end point was progression‐free survival. Secondary end points included the objective response rate, overall survival, safety, and the side‐effect profile. The final analysis of overall survival will be conducted in the future as specified in the protocol; a prespecified interim analysis of overall survival was conducted and is reported here. Results At the data‐cutoff date for the primary analysis, the estimated rate of progression‐free survival at month 20 was 65.2% (95% confidence interval [CI], 50.0 to 76.8) in the 177Lu‐Dotatate group and 10.8% (95% CI, 3.5 to 23.0) in the control group. The response rate was 18% in the 177Lu‐Dotatate group versus 3% in the control group (P<0.001). In the planned interim analysis of overall survival, 14 deaths occurred in the 177Lu‐Dotatate group and 26 in the control group (P=0.004). Grade 3 or 4 neutropenia, thrombocytopenia, and lymphopenia occurred in 1%, 2%, and 9%, respectively, of patients in the 177Lu‐Dotatate group as compared with no patients in the control group, with no evidence of renal toxic effects during the observed time frame. Conclusions Treatment with 177Lu‐Dotatate resulted in markedly longer progression‐free survival and a significantly higher response rate than high‐dose octreotide LAR among patients with advanced midgut neuroendocrine tumors. Preliminary evidence of an overall survival benefit was seen in an interim analysis; confirmation will be required in the planned final analysis. Clinically significant myelosuppression occurred in less than 10% of patients in the 177Lu‐Dotatate group. (Funded by Advanced Accelerator Applications; NETTER‐1 ClinicalTrials.gov number, NCT01578239; EudraCT number 2011‐005049‐11.)

Clinically Approved Nanoparticle Imaging Agents

Nanoparticles are a new class of imaging agent used for both anatomic and molecular imaging. Nanoparticle-based imaging exploits the signal intensity, stability, and biodistribution behavior of submicron-diameter molecular imaging agents. This review focuses on nanoparticles used in human medical imaging, with an emphasis on radionuclide imaging and MRI. Newer nanoparticle platforms are also discussed in relation to theranostic and multimodal uses.

Pilot Pharmacokinetic and Dosimetric Studies of 18F-FPPRGD2: A PET Radiopharmaceutical Agent for Imaging αvβ3 Integrin Levels

PURPOSE To assess the safety, biodistribution, and dosimetric properties of the positron emission tomography (PET) radiopharmaceutical agent fluorine 18 ((18)F) FPPRGD2 (2-fluoropropionyl labeled PEGylated dimeric RGD peptide [PEG3-E{c(RGDyk)}2]), which is based on the dimeric arginine-glycine-aspartic acid (RGD) peptide sequence and targets α(v)β(3) integrin, in the first volunteers imaged with this tracer. MATERIALS AND METHODS The protocol was approved by the institutional review board, and written informed consent was obtained from all participants. Five healthy volunteers underwent whole-body combined PET-computed tomography 0.5, 1.0, 2.0, and 3.0 hours after tracer injection (mean dose, 9.5 mCi ± 3.4 [standard deviation] [351.5 MBq ± 125.8]; mean specific radioactivity, 1200 mCi/mmol ± 714 [44.4 GBq/mmol ± 26.4]). During this time, standard vital signs, electrocardiographic (ECG) readings, and blood sample values (for chemistry, hematologic, and liver function tests) were checked at regular intervals and 1 and 7 days after the injection. These data were used to evaluate tracer biodistribution and dosimetric properties, time-activity curves, and the stability of laboratory values. Significant changes in vital signs and laboratory values were evaluated by using a combination of population-averaged generalized estimating equation regression and exact paired Wilcoxon tests. RESULTS The administration of (18)F-FPPRGD2 was well tolerated, with no marked effects on vital signs, ECG readings, or laboratory values. The tracer showed the same pattern of biodistribution in all volunteers: primary clearance through the kidneys (0.360 rem/mCi ± 0.185 [0.098 mSv/MBq ± 0.050]) and bladder (0.862 rem/mCi ± 0.436 [0.233 mSv/MBq ± 0.118], voiding model) and uptake in the spleen (0.250 rem/mCi ± 0.168 [0.068 mSv/MBq ± 0.046]) and large intestine (0.529 rem/mCi ± 0.236 [0.143 mSv/MBq ± 0.064]). The mean effective dose of (18)F-FPPRGD2 was 0.1462 rem/mCi ± 0.0669 (0.0396 mSv/MBq ± 0.0181). With an injected dose of 10 mCi (370 MBq) and a 1-hour voiding interval, a patient would be exposed to an effective radiation dose of 1.5 rem (15 mSv). Above the diaphragm, there was minimal uptake in the brain ventricles, salivary glands, and thyroid gland. Time-activity curves showed rapid clearance from the vasculature, with a mean 26% ± 17 of the tracer remaining in the circulation at 30 minutes and most of the activity occurring in the plasma relative to cells (mean whole blood-plasma ratio, 0.799 ± 0.096). CONCLUSION (18)F-FPPRGD2 has desirable pharmacokinetic and biodistribution properties. The primary application is likely to be PET evaluation of oncologic patients-especially those with brain, breast, or lung cancer. Specific indications may include tumor staging, identifying patients who would benefit from antiangiogenesis therapy, and separating treatment responders from nonresponders early.

Novel Strategy for a Cocktail 18F-Fluoride and 18F-FDG PET/CT Scan for Evaluation of Malignancy: Results of the Pilot-Phase Study

18F-FDG PET/CT is used for detecting cancer and monitoring cancer response to therapy. However, because of the variable rates of glucose metabolism, not all cancers are identified reliably. Sodium 18F was previously used for bone imaging and can be used as a PET/CT skeletal tracer. The combined administration of 18F and 18F-FDG in a single PET/CT study for cancer detection has not been reported to date. Methods: This is a prospective pilot study (November 2007–November 2008) of 14 patients with proven malignancy (6 sarcoma, 3 prostate cancer, 2 breast cancer, 1 colon cancer, 1 lung cancer, and 1 malignant paraganglioma) who underwent separate 18F PET/CT and 18F-FDG PET/CT and combined 18F/18F-FDG PET/CT scans for the evaluation of malignancy (a total of 3 scans each). There were 11 men and 3 women (age range, 19–75 y; average, 50.4 y). Results: Interpretation of the combined 18F/18F-FDG PET/CT scans compared favorably with that of the 18F-FDG PET/CT (no lesions missed) and the 18F PET/CT scans (only 1 skull lesion seen on an 18F PET/CT scan was missed on the corresponding combined scan). Through image processing, the combined 18F/18F-FDG scan yielded results for bone radiotracer uptake comparable to those of the 18F PET/CT scan performed separately. Conclusion: Our pilot-phase prospective trial demonstrates that the combined 18F/18F-FDG administration followed by a single PET/CT scan is feasible for cancer detection. This combined method opens the possibility for improved patient care and reduction in health care costs.

US Intergroup Trial of Response-Adapted Therapy for Stage III to IV Hodgkin Lymphoma Using Early Interim Fluorodeoxyglucose–Positron Emission Tomography Imaging: Southwest Oncology Group S0816

PURPOSE Four US National Clinical Trials Network components (Southwest Oncology Group, Cancer and Leukemia Group B/Alliance, Eastern Cooperative Oncology Group, and the AIDS Malignancy Consortium) conducted a phase II Intergroup clinical trial that used early interim fluorodeoxyglucose positron emission tomography (FDG-PET) imaging to determine the utility of response-adapted therapy for stage III to IV classic Hodgkin lymphoma. PATIENTS AND METHODS The Southwest Oncology Group S0816 (Fludeoxyglucose F 18-PET/CT Imaging and Combination Chemotherapy With or Without Additional Chemotherapy and G-CSF in Treating Patients With Stage III or Stage IV Hodgkin Lymphoma) trial enrolled 358 HIV-negative patients between July 1, 2009, and December 2, 2012. A PET scan was performed after two initial cycles of doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) and was labeled PET2. PET2-negative patients (Deauville score 1 to 3) received an additional four cycles of ABVD, whereas PET2-positive patients (Deauville score 4 to 5) were switched to escalated bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone (eBEACOPP) for six cycles. Among 336 eligible and evaluable patients, the median age was 32 years (range, 18 to 60 years), with 52% stage III, 48% stage IV, 49% International Prognostic Score 0 to 2, and 51% score 3 to 7. RESULTS Three hundred thirty-six of the enrolled patients were evaluable. Central review of the interim PET2 scan was performed in 331 evaluable patients, with 271 (82%) PET2-negative and 60 (18%) PET2-positive. Of 60 eligible PET2-positive patients, 49 switched to eBEACOPP as planned and 11 declined. With a median follow-up of 39.7 months, the Kaplan-Meier estimate for 2-year overall survival was 98% (95% CI, 95% to 99%), and the 2-year estimate for progression-free survival (PFS) was 79% (95% CI, 74% to 83%). The 2-year estimate for PFS in the subset of patients who were PET2-positive after two cycles of ABVD was 64% (95% CI, 50% to 75%). Both nonhematologic and hematologic toxicities were greater in the eBEACOPP arm than in the continued ABVD arm. CONCLUSION Response-adapted therapy based on interim PET imaging after two cycles of ABVD seems promising with a 2-year PFS of 64% for PET2-positive patients, which is much higher than the expected 2-year PFS of 15% to 30%.

Exploratory clinical trial of (4S)-4-(3-[18F]fluoropropyl)-L-glutamate for imaging xC- transporter using positron emission tomography in patients with non-small cell lung or breast cancer.

Purpose: (4S)-4-(3-[18F]fluoropropyl)-l-glutamate (BAY 94-9392, alias [18F]FSPG) is a new tracer to image xC− transporter activity with positron emission tomography (PET). We aimed to explore the tumor detection rate of [18F]FSPG in patients relative to 2-[18F]fluoro-2-deoxyglucose ([18F]FDG). The correlation of [18F]FSPG uptake with immunohistochemical expression of xC− transporter and CD44, which stabilizes the xCT subunit of system xC−, was also analyzed. Experimental Design: Patients with non–small cell lung cancer (NSCLC, n = 10) or breast cancer (n = 5) who had a positive [18F]FDG uptake were included in this exploratory study. PET images were acquired following injection of approximately 300 MBq [18F]FSPG. Immunohistochemistry was done using xCT- and CD44-specific antibody. Results: [18F]FSPG PET showed high uptake in the kidney and pancreas with rapid blood clearance. [18F]FSPG identified all 10 NSCLC and three of the five breast cancer lesions that were confirmed by pathology. [18F]FSPG detected 59 of 67 (88%) [18F]FDG lesions in NSCLC, and 30 of 73 (41%) in breast cancer. Seven lesions were additionally detected only on [18F]FSPG in NSCLC. The tumor-to-blood pool standardized uptake value (SUV) ratio was not significantly different from that of [18F]FDG in NSCLC; however, in breast cancer, it was significantly lower (P < 0.05). The maximum SUV of [18F]FSPG correlated significantly with the intensity of immunohistochemical staining of xC− transporter and CD44 (P < 0.01). Conclusions: [18F]FSPG seems to be a promising tracer with a relatively high cancer detection rate in patients with NSCLC. [18F]FSPG PET may assess xC− transporter activity in patients with cancer. Clin Cancer Res; 18(19); 5427–37. ©2012 AACR.

Positron Emission Tomography/Computed Tomography: The Current Technology and Applications

Positron emission tomography (PET) and combined PET/CT provide powerful metabolic and anatomical information together in a single exam. This article reviews the fundamentals of PET physics, the state of the art and future directions in PET technology, and the current clinical applications of PET. The latter is quite diverse and includes oncology, cardiology, neurology, and infection and inflammation imaging, all with FDG as the tracer. Additionally, novel radiopharmeuticals are under development, many of which are target cellular processes that are more specific than glucose metabolism.

Prospective comparison of combined 18F-FDG and 18F-NaF PET/CT vs. 18F-FDG PET/CT imaging for detection of malignancy

PurposeTypically, 18F-FDG PET/CT and 18F-NaF PET/CT scans are done as two separate studies on different days to allow sufficient time for the radiopharmaceutical from the first study to decay. This is inconvenient for the patients and exposes them to two doses of radiation from the CT component of the examinations. In the current study, we compared the clinical usefulness of a combined 18F-FDG/18F-NaF PET/CT scan with that of a separate 18F-FDG-only PET/CT scan.MethodsThere were 62 patients enrolled in this prospective trial. All had both an 18F-FDG-alone PET/CT scan and a combined 18F-FDG/18F-NaF PET/CT scan. Of the 62 patients, 53 (85%) received simultaneous tracer injections, while 9 (15%) received 18F-NaF subsequent to the initial 18F-FDG dose (average delay 2.2 h). Images were independently reviewed for PET findings by two Board-Certified nuclear medicine physicians, with discrepancies resolved by a third reader. Interpreters were instructed to only report findings that were concerning for malignancy. Reading the 18F-FDG-only scan first for half of the patients controlled for order bias.ResultsIn 15 of the 62 patients (24%) neither the 18F-FDG-only PET/CT scan nor the combined 18F-FDG/18F-NaF PET/CT scan identified malignancy. In the remaining 47 patients who had PET findings of malignancy, a greater number of lesions were detected in 16 of 47 patients (34%) using the combined 18F-FDG/18F-NaF PET/CT scan compared to the 18F-FDG-only PET/CT scan. In 2 of these 47 patients (4%), the 18F-FDG-only scan demonstrated soft tissue lesions that were not prospectively identified on the combined study. In 29 of these 47 patients (62%), the combined scan detected an equal number of lesions compared to the 18F-FDG-only scan. Overall, 60 of all the 62 patients (97%) showed an equal or greater number of lesions on the combined scan than on the 18F-FDG-only scan.ConclusionThe current study demonstrated that 18F-FDG and 18F-NaF can be combined in a single PET/CT scan by administering the two radiopharmaceuticals simultaneously or in sequence on the same day. In addition to patient convenience and reduced radiation exposure from the CT component, the combined 18F-FDG/18F-NaF PET/CT scan appeared to increase the sensitivity for detection of osseous lesions compared to the 18F-FDG-only PET/CT scan in the studied population.

Efficacy of 18F-FDG PET/CT in the evaluation of patients with recurrent cervical carcinoma

PurposeOnly a limited number of studies have evaluated the efficacy of 18F-FDG PET/CT for recurrent cervical carcinoma, which this study seeks to expand upon.MethodsThis is a retrospective study of 30 women with cervical carcinoma who had a surveillance PET/CT after initial therapy. Sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were calculated using a 2 × 2 contingency table with pathology results (76%) or clinical follow-up (24%) as the gold standard. The Wilson score method was used to perform 95% confidence interval estimations.ResultsThe sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of PET/CT for the detection of local recurrence at the primary site were 93, 93, 93, 86, and 96%, respectively. The same values for the detection of distant metastases were 96, 95, 95, 96, and 95%, respectively. Seventy-one percent of the scans performed in symptomatic patients showed true-positive findings. In comparison, 44% of scans performed in asymptomatic patients showed true-positive findings. But, all patients subsequently had a change in their management based on the PET/CT findings such that the effect was notable. The maximum standardized uptake value ranged from 5 to 28 (average: 13 ± 7) in the primary site and 3 to 23 (average: 8 ± 4) in metastases which were significantly different (p = 0.04).ConclusionThis study demonstrates favorable efficacy of 18F-FDG PET/CT for identification of residual/recurrent cervical cancer, as well as for localization of distant metastases.

Pulmonary Ventilation Imaging Based on 4-Dimensional Computed Tomography: Comparison With Pulmonary Function Tests and SPECT Ventilation Images

PURPOSE 4-dimensional computed tomography (4D-CT)-based pulmonary ventilation imaging is an emerging functional imaging modality. The purpose of this study was to investigate the physiological significance of 4D-CT ventilation imaging by comparison with pulmonary function test (PFT) measurements and single-photon emission CT (SPECT) ventilation images, which are the clinical references for global and regional lung function, respectively. METHODS AND MATERIALS In an institutional review board-approved prospective clinical trial, 4D-CT imaging and PFT and/or SPECT ventilation imaging were performed in thoracic cancer patients. Regional ventilation (V4DCT) was calculated by deformable image registration of 4D-CT images and quantitative analysis for regional volume change. V4DCT defect parameters were compared with the PFT measurements (forced expiratory volume in 1 second (FEV1; % predicted) and FEV1/forced vital capacity (FVC; %). V4DCT was also compared with SPECT ventilation (VSPECT) to (1) test whether V4DCT in VSPECT defect regions is significantly lower than in nondefect regions by using the 2-tailed t test; (2) to quantify the spatial overlap between V4DCT and VSPECT defect regions with Dice similarity coefficient (DSC); and (3) to test ventral-to-dorsal gradients by using the 2-tailed t test. RESULTS Of 21 patients enrolled in the study, 18 patients for whom 4D-CT and either PFT or SPECT were acquired were included in the analysis. V4DCT defect parameters were found to have significant, moderate correlations with PFT measurements. For example, V4DCT(HU) defect volume increased significantly with decreasing FEV1/FVC (R=-0.65, P<.01). V4DCT in VSPECT defect regions was significantly lower than in nondefect regions (mean V4DCT(HU) 0.049 vs 0.076, P<.01). The average DSCs for the spatial overlap with SPECT ventilation defect regions were only moderate (V4DCT(HU)0.39 ± 0.11). Furthermore, ventral-to-dorsal gradients of V4DCT were strong (V4DCT(HU) R(2) = 0.69, P=.08), which was similar to VSPECT (R(2) = 0.96, P<.01). CONCLUSIONS An 18-patient study demonstrated significant correlations between 4D-CT ventilation and PFT measurements as well as SPECT ventilation, providing evidence toward the validation of 4D-CT ventilation imaging.