Solitary Parathyroid Adenoma Localization in Technetium Tc99m Sestamibi SPECT and Multiphase Multidetector 4D CT

BACKGROUND AND PURPOSE

Minimally invasive parathyroid surgery relies critically on image guidance, but data comparing the efficacy of various imaging modalities are scarce. Our aim was to perform a blinded comparison of the localizing capability of technetium Tc99m sestamibi SPECT, multiphase multidetector 4D CT, and the combination of these 2 modalities (technetium Tc99m sestamibi SPECT + multiphase multidetector 4D CT).

MATERIALS AND METHODS

We reviewed the records of 31 (6 men, 25 women; median age, 56 years) consecutive patients diagnosed with biochemically confirmed primary hyperparathyroidism between November 2009 and March 2010 who underwent preoperative technetium Tc99m sestamibi SPECT and multiphase multidetector 4D CT performed on the same scanner with pathologic confirmation by resection of a single parathyroid adenoma. Accuracy was determined separately for localization to the correct side and quadrant using surgical localization as the standard of reference.

RESULTS

Surgical resection identified 14 left and 17 right parathyroid adenomas and 2 left inferior, 12 left superior, 11 right inferior, and 6 right superior parathyroid adenomas. For left/right localization, technetium Tc99m sestamibi SPECT achieved an accuracy of 93.5% (29 of 31), multiphase multidetector 4D CT achieved 96.8% accuracy (30 of 31), and technetium Tc99m sestamibi SPECT + multiphase multidetector 4D CT achieved 96.8% accuracy (30 of 31). For quadrant localization, technetium Tc99m sestamibi SPECT accuracy was 67.7% (21 of 31), multiphase multidetector 4D CT accuracy was 87.1% (27 of 31), and technetium Tc99m sestamibi SPECT + multiphase multidetector 4D CT accuracy was 93.5% (29 of 31). Reader diagnostic confidence was consistently ranked lowest for technetium Tc99m sestamibi SPECT and highest for technetium Tc99m sestamibi SPECT + multiphase multidetector 4D CT.

CONCLUSIONS

For left/right localization of parathyroid adenomas, all modalities performed equivalently. For quadrant localization, technetium Tc99m sestamibi SPECT + multiphase multidetector 4D CT is superior to technetium Tc99m sestamibi SPECT.

PET/CT today and tomorrow in veterinary cancer diagnosis and monitoring: fundamentals, early results and future perspectives

Functional imaging using positron emission tomography (PET) plays an important role in the diagnosis, staging, image-guided treatment planning and monitoring of malignant diseases. PET imaging complements conventional anatomical imaging such as computed tomography (CT) and magnetic resonance imaging (MRI). The strength of CT scanning lies in its high spatial resolution, allowing for anatomical characterization of disease. PET imaging, however, moves beyond anatomy and characterizes tissue based on functions such as metabolic rate. Combined PET/CT scanners were introduced commercially in 2001 and a number of technological advancements have since occurred. Radiolabelled tracers such as (18)F-fluorodeoxyglucose (FDG) and (18)F-fluorothymidine (FLT) allow visualization of various metabolic processes within cancer cells. Many studies in human oncology evaluating the utility of PET/CT have demonstrated clinical benefits. Few veterinary studies have been performed, but initial studies show promise for improved detection of malignancy, more thorough staging of canine cancer and determination of early response and disease recrudescence.

Circulating Tumor Cells and FDG-PET/CT for the Therapeutic Monitoring of Bone Metastases from Breast Cancer

Background: Circulating tumor cells (CTCs) and [18F]fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) are two promising new tools for monitoring therapy in patients with metastatic breast cancer. The two modalities showed high sensitivity in detection of bone relapse/progression from breast cancer (De Giorgi U et al. Ann Oncol 2009). In this study, we sought to evaluate the prognostic significance of two different modalities represented by the detection of CTC and FDG-PET/CT in patients with bone metastases from breast cancer treated with standard therapies. Our objective was to compare the two modalities to identify which technology could be more sensitive in prospectively monitoring such patients.Patients and Methods: This is a retrospective study of 54 patients with bone metastases from breast cancer without visceral metastases treated at The University of Texas M. D. Anderson Cancer Center from September 2004 to May 2008. CTC were detected and enumerated using the CellSearch system (Veridex LLC, Rariten NJ, USA). Patients were categorized according to first follow-up CTC counts as having a favorable (< 5 CTC/7.5 mL of blood) or unfavorable (≥ 5 CTC) outcome. Reassessment of disease status by CTC count and FDG-PET/CT was performed approximately 2-3 months after initiation of the new treatment, depending on treatment type and schedule. Progression-free survival (PFS) and overall survival (OS) were estimated by Kaplan-Meier product limit method, and compared between groups with the log-rank test.Results: In 54 evaluable patients, the median overall survival time was 17 months (range, 3 to >36). Follow-up CTC levels and FDG-PET/CT response predicted both PFS (p = 0.02 and p = 0.0001, respectively) and OS (p = 0.01 and p = 0.02, respectively), while baseline CTC predicted neither PFS (p = 0.8) nor OS (p = 0.76). In patients with either CTC or FDG-PET/CT response PFS has been 13 months, while in patients with discordant CTC and FDG-PET/CT response PFS has been 6 months and in patients with neither CTC nor FDG-PET/CT response PFS has been 5 months (p = <0.00002). In patients with either CTC or FDG-PET/CT response, OS has not been reached (>31 months); in patients with discordant CTC and FDG-PET/CT response, OS has been 24 months; and in patients with neither CTC nor FDG-PET/CT response, OS has been 18 months (p = 0.02).Conclusions: CTC and FDG-PET/CT are useful tools for therapeutic monitoring of bone metastases from breast cancer. Prospective studies in this specific clinical context are needed to assess the critical roles that CTC and FDG-PET/CT individually as well as collectively play in the prognostic and therapeutic monitoring of bone metastases from breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1109.

Phase I study combining an IGFR inhibitor (IMC-A12) and an mTOR inhibitor (temsirolimus) in patients with solid tumors or lymphoma

e14535

Background: IMC-A12 is a fully humanized IgG1/ lambda monoclonal antibody directed at the type I Insulin-Like Growth Factor Receptor (IGF-IR). Temsirolimus, an ester of the macrocyclic immunosuppressive agent sirolimus, is a cytostatic cell cycle inhibitor, which specifically inhibits the mammalian target of rapamycin (mTOR). A paradoxical increase in AKT activation by an mTOR inhibitor through an IGF-1R-dependent mechanism may compromise the therapeutic effect of mTOR inhibitors. Hence we evaluated the combination of temsirolimus and IMC-A12. Methods: This standard “3+3” design used a fixed dose of 25 mg IV weekly of temsirolimus with an escalating weekly dose of IV IMC-A12 at 3 mg/kg, 4 mg/kg and 6 mg/kg with no intrapatient dose escalation. The goal of this study is to define the MTD and to evaluate the biologic effects and metabolic activity of IMC-A12 and temsirolimus, individually and in combination. Patients with advanced solid tumors and lymphoma are eligible. No history of diabetes is allowed in dose escalation cohorts. Results: To date, 11 patients (4 males and 7 females, median age 47) with various solid tumor histologies have been enrolled across 3 dose cohorts with the current dose cohort at 6 mg/kg weekly IV of IMC-A12 and 25 mg weekly IV of temsirolimus. The MTD has not been determined. The most common grade 1 and grade 2 toxicities have been dysgeusia (n=5), fatigue (n=5), hyperglycemia (n=6), hypertriglyceridemia (n=6), leucopenia (n=4), mucositis (n=4), and ocular flashes of light (n=3). No grade 3 or 4 toxicity lasted more than 7 days (nausea n=1; vomiting n=1; thrombocytopenia n=1). Two patients (metastatic prostate cancer and metastatic breast cancer) demonstrated prolonged stable disease for 4 and 6 months, respectively. Conclusions: Preliminary data suggest that the combination is well tolerated and that it warrants further investigation. The expansion phase of this study will evaluate the biologic effects and metabolic activity of IMC-A12 and temsirolimus, individually and in combination, through the use of RPPA (Reverse Phase Protein Assays) and PET scans.

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Circulating tumor cells and FDG-PET/CT: biological and functional methods for therapeutic monitoring in metastatic breast cancer

Abstract #6052

Introduction: The combination of Computed Tomography (CT) and [18F] Fluorodeoxyglucose - Positron Emission Tomography (FDG-PET) scanning technologies provides a more complete picture of disease activity than CT alone. Circulating tumor cell (CTC) levels were shown to be more predictive than standard imaging (CT) when used to monitor disease progression in women with metastatic breast cancer (MBC). We performed a retrospective study to compare the ability of combined FDG-PET/CT to CTC to predict clinical outcomes in patients treated for MBC.
 Methods: One hundred and two MBC patients with either measurable or evaluable disease starting a new line of therapy had CTC counts and FDG-PET/CT scans done at baseline (BL) and at mid-therapy. CTC: 7.5mL of blood collected in CellSave tubes at both time points was assayed for CTC using the FDA approved CellSearch® System. Patients were categorized as having a favorable (<5CTC) or unfavorable (≥5CTC) outcome. Imaging: non-contrast-enhanced CT images were acquired first, then FDG-PET/CT scans were performed after administering a mean dose of 555 MBq FDG (range 444-740 MBq) to fasting patients. CT, PET, and co-registered CT-PET images were reviewed independently by 2 radiologists. The highest recorded FDG uptake was semi-quantitatively analyzed and maximum standardized uptake value (SUV) calculated with response = SUV of <50% in target lesions and no response = SUV of >50%. Changes in CTC and SUV at mid-therapy were compared to progression free survival (PFS) and overall survival (OS).
 Results: CTC: 50% (51/102) patients had ≥5 CTC at baseline (BL). At mid-therapy (median 2.5 months from BL), 21/102 progressed (≥5CTC) with a median PFS of 2.8 months vs. 7.8 months for those with no progression (<5CTC) (p<0.0001). OS was 10.0 months for patients with ≥5CTC at mid-therapy vs. 29.6 months for those with <5CTC (p<0.0001). PET/CT: 48% (49/102) patients showed no response at mid-therapy with median OS = 17.4 months vs. 29.6 months for those responding (p=0.0020). Overall, there was approximately 75% concordance in predicting outcomes between imaging and CTC assay changes [Table 1]. The majority of patients with discordant results had more advanced aggressive disease, i.e., >2nd line chemotherapy and triple-negative disease.
 
 Conclusion: ≥5 CTC and/or no response at FDG-PET/CT at mid-therapy accurately predicted significantly shorter OS.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6052.