Costs and effects of intra-operative fluorescence molecular imaging - A model-based, early assessment

Introduction

Successful breast conserving cancer surgeries come along with tumor free resection margins and account for cosmetic outcome. Positive margins increase the likelihood of tumor recurrence. Intra-operative fluorescence molecular imaging (IFMI) aims to focus surgery on malignant tissue thus substantially lowering the presence of positive margins as compared with standard techniques of breast conservation (ST). A goal of this paper is to assess the incremental number of surgeries and costs of IFMI vs. ST.

Methods

We developed a decision analytical model and applied it for an early evaluation approach. Given uncertainty we considered that IFMI might reduce the proportion of positive margins found by ST from all to none and this proportion is assumed to be reduced to 10% for the base case. Inputs included data from the literature and a range of effect estimates. For the costs of IFMI, respective cost components were added to those of ST.

Results

The base case reduction lowered number of surgeries (mean [95% confidence interval]) by 0.22 [0.15; 0.30] and changed costs (mean [95% confidence interval]) by €-663 [€-1,584; €50]. A tornado diagram identified the Diagnosis Related Group (DRG) costs, the proportion of positive margins of ST, the staff time saving factor and the duration of frozen section analysis (FSA) as important determinants of this cost.

Conclusions

These early results indicate that IFMI may be more effective than ST and through the reduction of positive margins it is possible to save follow-up surgeries–indicating further health risk–and to save costs through this margin reduction and the avoidance of FSA.

The effect of temperature on the development and reproduction of Busseola fusca (Lepidoptera: Noctuidae)

The effect of temperature on the reproduction and development of Busseola fusca was studied under laboratory conditions. Single male-female pairs were confined to oviposition chambers kept at 15, 20, 26 and 30 ± 1°C and a 14L:10D photoperiod. Data on reproduction parameters were captured daily. Oviposition occurred at all the mentioned temperatures but no fertility was recorded at 30°C. The total number of eggs laid per female moth was between 300 and 400 and the optimum temperature for oviposition and fertility was between 20 and 26°C. Larval development was studied at five different temperature regimes, i.e. 15, 18, 20, 26 and 30 ± 1°C and a 14L:10D photoperiod. The most favourable temperature as well as the upper threshold temperature for larval development was between 26 and 30°C. Total development period was 152.6-52.6 days, respectively, at 15°C, and 26-30°C. The thermal constants for B. fusca was 99.50, 536.48, 246.25 and 893.66°D and lower temperature thresholds were 10.36, 8.14, 8.99 and 8.84°C, for completion of the egg, larval, pupal and egg-to-adult stages, respectively. Results on the thermal constants and lower and upper threshold temperatures of B. fusca can be used to predict the impact of climate change on the distribution and population growth of this pest.

Threshold Analysis and Biodistribution of Fluorescently Labeled Bevacizumab in Human Breast Cancer

In vivo tumor labeling with fluorescent agents may assist endoscopic and surgical guidance for cancer therapy as well as create opportunities to directly observe cancer biology in patients. However, malignant and nonmalignant tissues are usually distinguished on fluorescence images by applying empirically determined fluorescence intensity thresholds. Here, we report the development of fSTREAM, a set of analytic methods designed to streamline the analysis of surgically excised breast tissues by collecting and statistically processing hybrid multiscale fluorescence, color, and histology readouts toward precision fluorescence imaging. fSTREAM addresses core questions of how to relate fluorescence intensity to tumor tissue and how to quantitatively assign a normalized threshold that sufficiently differentiates tumor tissue from healthy tissue. Using fSTREAM we assessed human breast tumors stained in vivo with fluorescent bevacizumab at microdose levels. Showing that detection of such levels is achievable, we validated fSTREAM for high-resolution mapping of the spatial pattern of labeled antibody and its relation to the underlying cancer pathophysiology and tumor border on a per patient basis. We demonstrated a 98% sensitivity and 79% specificity when using labeled bevacizumab to outline the tumor mass. Overall, our results illustrate a quantitative approach to relate fluorescence signals to malignant tissues and improve the theranostic application of fluorescence molecular imaging. Cancer Res; 77(3); 623-31. ©2016 AACR.

Tumor-Specific Uptake of Fluorescent Bevacizumab-IRDye800CW Microdosing in Patients with Primary Breast Cancer: A Phase I Feasibility Study

Purpose: To provide proof of principle of safety, breast tumor-specific uptake, and positive tumor margin assessment of the systemically administered near-infrared fluorescent tracer bevacizumab-IRDye800CW targeting VEGF-A in patients with breast cancer.Experimental Design: Twenty patients with primary invasive breast cancer eligible for primary surgery received 4.5 mg bevacizumab-IRDye800CW as intravenous bolus injection. Safety aspects were assessed as well as tracer uptake and tumor delineation during surgery and ex vivo in surgical specimens using an optical imaging system. Ex vivo multiplexed histopathology analyses were performed for evaluation of biodistribution of tracer uptake and coregistration of tumor tissue and healthy tissue.Results: None of the patients experienced adverse events. Tracer levels in primary tumor tissue were higher compared with those in the tumor margin (P < 0.05) and healthy tissue (P < 0.0001). VEGF-A tumor levels also correlated with tracer levels (r = 0.63, P < 0.0002). All but one tumor showed specific tracer uptake. Two of 20 surgically excised lumps contained microscopic positive margins detected ex vivo by fluorescent macro- and microscopy and confirmed at the cellular level.Conclusions: Our study shows that systemic administration of the bevacizumab-IRDye800CW tracer is safe for breast cancer guidance and confirms tumor and tumor margin uptake as evaluated by a systematic validation methodology. The findings are a step toward a phase II dose-finding study aimed at in vivo margin assessment and point to a novel drug assessment tool that provides a detailed picture of drug distribution in the tumor tissue. Clin Cancer Res; 23(11); 2730-41. ©2016 AACR.

Uniqueness in multispectral constant-wave epi-illumination imaging

Multispectral tissue imaging based on optical cameras and continuous-wave tissue illumination is commonly used in medicine and biology. Surprisingly, there is a characteristic absence of a critical look at the quantities that can be uniquely characterized from optically diffuse matter by multispectral imaging. Here, we investigate the fundamental question of uniqueness in epi-illumination measurements from turbid media obtained at multiple wavelengths. By utilizing an analytical model, tissue-mimicking phantoms, and an in vivo imaging experiment we show that independent of the bands employed, spectral measurements cannot uniquely retrieve absorption and scattering coefficients. We also establish that it is, nevertheless, possible to uniquely quantify oxygen saturation and the Mie scattering power-a previously undocumented uniqueness condition.

[Rehabilitation standards for follow-up treatment and rehabilitation of patients with ventricular assist device (VAD)]

The increasing use of ventricular assist devices (VADs) in terminal heart failure patients provides new challenges to cardiac rehabilitation physicians. Structured cardiac rehabilitation strategies are still poorly implemented for this special patient group. Clear guidance and more evidence for optimal modalities are needed. Thereby, attention has to be paid to specific aspects, such as psychological and social support and education (e.g., device management, INR self-management, drive-line care, and medication).In Germany, the post-implant treatment and rehabilitation of VAD Patients working group was founded in 2012. This working group has developed clear recommendations for the rehabilitation of VAD patients according to the available literature. All facets of VAD patients' rehabilitation are covered. The present paper is unique in Europe and represents a milestone to overcome the heterogeneity of VAD patient rehabilitation.

Molecular Fluorescence Endoscopy Targeting Vascular Endothelial Growth Factor A for Improved Colorectal Polyp Detection

Small and flat adenomas are known to carry a high miss-rate during standard white-light endoscopy. Increased detection rate may be achieved by molecular fluorescence endoscopy with targeted near-infrared (NIR) fluorescent tracers. The aim of this study was to validate vascular endothelial growth factor A (VEGF-A) and epidermal growth factor receptor (EGFR)-targeted fluorescent tracers during ex vivo colonoscopy with an NIR endoscopy platform.

METHODS

VEGF-A and EGFR expression was determined by immunohistochemistry on a large subset of human colorectal tissue samples--48 sessile serrated adenomas/polyps, 70 sporadic high-grade dysplastic adenomas, and 19 hyperplastic polyps--and tissue derived from patients with Lynch syndrome--78 low-grade dysplastic adenomas, 57 high-grade dysplastic adenomas, and 31 colon cancer samples. To perform an ex vivo colonoscopy procedure, 14 mice with small intraperitoneal EGFR-positive HCT116(luc) tumors received intravenous bevacizumab-800CW (anti-VEGF-A), cetuximab-800CW (anti-EGFR), control tracer IgG-800CW, or sodium chloride. Three days later, 8 resected HCT116(luc) tumors (2-5 mm) were stitched into 1 freshly resected human colon specimen and followed by an ex vivo molecular fluorescence colonoscopy procedure.

RESULTS

Immunohistochemistry showed high VEGF-A expression in 79%-96% and high EGFR expression in 51%-69% of the colorectal lesions. Both targets were significantly overexpressed in the colorectal lesions, compared with the adjacent normal colon crypts. During ex vivo molecular fluorescence endoscopy, all tumors could clearly be delineated for both bevacizumab-800CW and cetuximab-800CW tracers. Specific tumor uptake was confirmed with fluorescent microscopy showing, respectively, stromal and cell membrane fluorescence.

CONCLUSION

VEGF-A is a promising target for molecular fluorescence endoscopy because it showed a high protein expression, especially in sessile serrated adenomas/polyps and Lynch syndrome. We demonstrated the feasibility to visualize small tumors in real time during colonoscopy using a NIR fluorescence endoscopy platform, providing the endoscopist a wide-field red-flag technique for adenoma detection. Clinical studies are currently being performed in order to provide in-human evaluation of our approach.

Steady-state total diffuse reflectance with an exponential decaying source

The increasing preclinical and clinical utilization of digital cameras for photographic measurements of tissue conditions motivates the study of reflectance measurements obtained with planar illumination. We examine herein a formula that models the total diffuse reflectance measured from a semi-infinite medium using an exponentially decaying source, assuming continuous plane wave epi-illumination. The model is validated with experimental reflectance measurements from tissue mimicking phantoms. The need for adjusting the blood absorption spectrum due to pigment packaging is discussed along with the potential applications of the proposed formulation.

Video-rate optical flow corrected intraoperative functional fluorescence imaging

Intraoperative fluorescence molecular imaging based on targeted fluorescence agents is an emerging approach to improve surgical and endoscopic imaging and guidance. Short exposure times per frame and implementation at video rates are necessary to provide continuous feedback to the physician and avoid motion artifacts. However, fast imaging implementations also limit the sensitivity of fluorescence detection. To improve on detection sensitivity in video rate fluorescence imaging, we considered herein an optical flow technique applied to texture-rich color images. This allows the effective accumulation of fluorescence signals over longer, virtual exposure times. The proposed correction scheme is shown to improve signal-to-noise ratios both in phantom experiments and in vivo tissue imaging.

Robust overlay schemes for the fusion of fluorescence and color channels in biological imaging

Molecular fluorescence imaging is a commonly used method in various biomedical fields and is undergoing rapid translation toward clinical applications. Color images are commonly superimposed with fluorescence measurements to provide orientation, anatomical information, and molecular tissue properties in a single image. New adaptive methods that produce a more robust composite image than conventional lime green alpha blending are presented and demonstrated herein. Moreover, visualization through temporal changes is showcased as an alternative for real-time imaging systems.

Towards clinically translatable NIR fluorescence molecular guidance for colonoscopy

White-light surveillance colonoscopy is the standard of care for the detection and removal of premalignant lesions to prevent colorectal cancer, and the main screening recommendation following treatment for recurrence detection. However, it lacks sufficient diagnostic yield, exhibits unacceptable adenoma miss-rates and is not capable of revealing functional and morphological information of the detected lesions. Fluorescence molecular guidance in the near-infrared (NIR) is expected to have outstanding relevance regarding early lesion detection and heterogeneity characterization within and among lesions in these interventional procedures. Thereby, superficial and sub-surface tissue biomarkers can be optimally visualized due to a minimization of tissue attenuation and autofluorescence by comparison with the visible, which simultaneously enhance tissue penetration and assure minimal background. At present, this potential is challenged by the difficulty associated with the clinical propagation of disease-specific contrast agents and the absence of a commercially available endoscope that is capable of acquiring wide-field, NIR fluorescence at video-rates. We propose two alternative flexible endoscopic fluorescence imaging methods, each based on a CE certified commercial, clinical grade endoscope, and the employment of an approved monoclonal antibody labeled with a clinically applicable NIR fluorophore. Pre-clinical validation of these two strategies that aim at bridging NIR fluorescence molecular guidance to clinical translation is demonstrated in this study.

Concurrent video-rate color and near-infrared fluorescence laparoscopy

The visual identification and demarcation of tumors and tumor margins remains challenging due to the low optical contrast of cancer cells over surrounding tissues. Fluorescence molecular imaging was recently considered clinically for improving cancer detection during open surgery. We present herein a next step in the development of fluorescence molecular guidance by describing a novel video-rate imaging laparoscope capable of concurrently recording color and near-infrared fluorescence images and video. Video-rate operation is based on graphics processing unit-based image processing. We examine the optical characteristics of the system developed and provide performance metrics related to intra-operative endoscopic guidance, showcased on phantoms and endoscopic color and fluorescence molecular imaging of tumors in a mouse model of the human disease.

Enriching the interventional vision of cancer with fluorescence and optoacoustic imaging

Among several techniques considered for surgical and endoscopic imaging, novel optical methods are evolving as a promising approach for interventional guidance. Pilot clinical applications of fluorescence molecular imaging have demonstrated the benefits of using targeted fluorescent agents in cancer surgery. This premise can be extended broadly to interventional guidance through an increasing number of targeted agents and detection techniques. Beyond epi-illumination fluorescence imaging, optoacoustic (photoacoustic) methods are emerging to offer high-resolution cross-sectional optical imaging through several millimeters to centimeters of depth. We present an overview of key recent developments in optical interventional imaging and outline the potential for a paradigm shift in surgical and endoscopic visualization.

[Cardiac rehabilitation with a structured education programme for patients with chronic heart failure--illness-related knowledge, mental wellbeing and acceptance in participants]

BACKGROUND

Chronic heart failure is a severe disease with increasing importance and difficult prognosis. Patient education is an essential component of medical rehabilitation, which is aimed at increasing self-management abilities and reducing mental symptom load in these patients. A newly developed patient education programme for heart failure was implemented as part of a three-week cardiac rehabilitation programme. The present study dealt with patients' acceptance of this programme, changes in disease-related knowledge, perceived health- and illness-related quality of life, and mental symptoms over the treatment course.

METHOD

During inpatient cardiac rehabilitation, 64 patients (79.7% male) participated in this competence-focused programme for patients with chronic heart failure. Before, directly after and 6 months after participation in the programme, they filled in self-rating questionnaires on their mental wellbeing (HADS anxiety and depression), quality of life (SF-36, KCCQ), and a test of their knowledge on heart-related disease behavior. Additionally they were given an evaluation-questionnaire of the programme.

RESULTS

Evaluation of the programme given by the patients was very good. Knowledge and perceived quality of life had increased significantly at the end and 6 months after rehabilitation. Mental symptoms of anxiety and depressivity were reduced directly and also 6 months after rehabilitation.

CONCLUSION

Over the course of a multidimensional cardiac rehabilitation programme focusing on training of disease-directed competences, patients felt better and were better informed. However, special attention needs to be given to possible deterioration effects education programmes can have in patients with increased trait-anxiety or hypochondriac tendencies.

Blind source unmixing in multi-spectral optoacoustic tomography

Multispectral optoacoustic (photoacoustic) tomography (MSOT) is a hybrid modality that can image through several millimeters to centimeters of diffuse tissues, attaining resolutions typical of ultrasound imaging. The method can further identify tissue biomarkers by decomposing the spectral contributions of different photo-absorbing molecules of interest. In this work we investigate the performance of blind source unmixing methods and spectral fitting approaches in decomposing the contributions of fluorescent dyes from the tissue background, based on MSOT measurements in mice. We find blind unmixing as a promising method for accurate MSOT decomposition, suitable also for spectral unmixing in fluorescence imaging. We further demonstrate its capacity with temporal unmixing on real-time MSOT data obtained in-vivo for enhancing the visualization of absorber agent flow in the mouse vascular system.

Self-management of oral anticoagulation in nonvalvular atrial fibrillation (SMAAF study)

Most patients with atrial fibrillation are at risk of suffering thromboembolic events. This risk can be reduced by twothirds by efficient anticoagulation. This prospective multi-center trial investigated whether the quality of treatment can be improved by self-management in patients with atrial fibrillations (SMAAF Study) compared to conventional patient management by the family doctor.

METHODS

Two thousand patients suitable for self-management were to be randomized into the two arms of the study. In the period of investigation from December 1999 to July 2001, only 202 patients (64.3+/-9.2 years, 69.3% men) consented to participate. The study was discontinued prematurely since the number of patients was too low. As a consequence, the group comparison is confined to the evaluation of the INR values measured using the two-tailed t test.

RESULTS

Of the 202 patients included, 101 were assigned to the self-management group (64.6+/-9.6 years, 71.4% men) and 101 (64.1+/-8.9 years, 61.4% men, n.s.) were assigned to the group managed by the family doctor. The total number of INR measurements was 2 865. This comprised 2 072 measurements in patients under self-management and 793 in the family doctor group. The values were within the target range significantly more frequently (p=0.0061) in patients under self-management (67.8%) as compared to the family doctor group (58.5%). There was a trend with regard to the time within target range, but the difference was not significant (178.8+/-126 days as compared to 155.9+/-118.4 days). In the self-management group, there were two severe hemorrhages, and there was one thromboembolic event in the family doctor group.

CONCLUSION

Management of oral anticoagulation by INR self-management in patients with atrial fibrillation is not inferior to conventional care.

Combined intrauterine and extrauterine gestation. A rare cause of acute abdominal pain

This is the report of a patient, that had without using any assisted reproduction technology (ART) the rare event of a heterotopic pregnancy. After verifying the intrauterine pregnancy by ultrasound, the ectopic tubal pregnancy (EP) was detected at an emergency abdominal surgery as the cause of an intraabdominal hemorrhage. After removal the further pregnancy was uncomplicated.

[Background and evaluation plan of a study on self-management of anticoagulation in patients with non-valvular atrial fibrillation (SMAAF Study)]

The objective of this open, randomized, multicenter study is to investigate the benefits and economic efficiency of self-management of oral anticoagulation in patients with atrial fibrillation (SMAAF study) in comparison with a group of patients given conventional care by a general practitioner or specialist. Two thousand patients suitable for self-management will be assigned at random to either the self-management group or the control group. The numbers of thromboembolic and hemorrhagic complications requiring treatment during the 2-year follow-up period will be recorded as the primary end point. The secondary endpoint variables will be maintenance of the INR value in the individual target range, INR variance, the course of complications over time, and the cost efficiency of self-management compared with the routine procedures. The last of these parameters will include the diagnostic and/or therapeutic measures carried out, the duration of inpatient hospital treatment, and the social consequences (subsequent rehabilitation treatment, inability to work, forced retirement). The estimate of the required number of patients was based on the assumption that during long-term anticoagulant therapy within the framework of primary and secondary prevention 4% of patients with chronic non-valvular atrial fibrillation would have severe thromboembolic of hemorrhagic complications each year. Since this rate can be halved by self-management, a one-tailed chi 2-test of 80% power and a 5% significance threshold would require n = 997 patients per group. The results of the SMAAF study will establish the socioeconomic benefits of self-management in patients with non-valvular atrial fibrillation.

Combined hyperlipidemia is associated with increased exercise-induced muscle protein release which is improved by triglyceride-lowering intervention

Although myopathy is considered an adverse effect of treatment with 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors and fibrates in combined hyperlipidemia, the present study was performed to investigate whether combined hyperlipidemia itself is associated with skeletal muscle pathology and whether lipid-lowering intervention has beneficial effects. To investigate whether combined hyperlipidemia is associated with skeletal muscle pathology, 10 male patients and 15 normolipidemic controls underwent a 45-minute standardized bicycle ergometer test at a load of 2 W/kg lean body mass (parallel study). One- and 8-hour postexercise increments in the plasma level of the muscle proteins creatine kinase (CK), myoglobin (Mb), and fatty acid-binding protein (FABP) were assessed as parameters for (subclinical) skeletal muscle pathology. The 8-hour postexercise increments in CK and Mb and 1-hour postexercise increment in Mb were significantly higher in patients than in controls, thus indicating increased exercise-induced muscle membrane permeability in combined hyperlipidemia. To investigate the effects of lipid-lowering intervention on skeletal muscle in combined hyperlipidemia, 21 subjects with combined hyperlipidemia were randomized double-blindly to receive 6 weeks of treatment with fluvastatin 40 mg/d, gemfibrozil 600 mg twice daily, or combination therapy. All subjects underwent an ergometer test before and after treatment. Gemfibrozil treatment alone reduced the CK increments 8 hours postexercise by 47% and the FABP increments 1 and 8 hours postexercise by 83% and 101%, respectively (all P < .05). Combined treatment reduced Mb increments 1 hour postexercise by 54% and FABP increments 8 hours postexercise by 44% (all P < .05). A highly significant correlation existed between therapy-induced changes in plasma triglycerides and changes in postexercise increments of FABP and Mb. In conclusion, combined hyperlipidemia is associated with an increased exercise-induced release of muscle proteins, which is ameliorated by triglyceride-lowering intervention. As FABP is an indicator for ischemia-induced skeletal muscle pathology, a possible explanation is the impaired muscle blood flow during hypertriglyceridemia, which may be reversed by triglyceride-lowering intervention. The mechanism and clinical relevance of these findings remain to be investigated.

Functional differences in lipid metabolism in resting skeletal muscle of various fiber types

Intramuscular lipid pool turnover [triacylglycerols (TG), phospholipids (PL), mono- and diacylglycerols (MG, DG)] and the oxidation of endogenous and exogenous lipids were determined with pulse-chase studies in incubated muscles of varied oxidative potential [soleus strips (SOL)--> epitrochlearis --> flexor digitorum brevis]. Incorporation of palmitate into TG and PL pools and its oxidation were linearly related to time and exogenous palmitate concentration in all muscles. Total palmitate incorporation (deposition and oxidation) was greatest in SOL. However, palmitate incorporation into TG was similar in all muscles when expressed as a percentage of the total incorporation. In contrast, palmitate incorporation into PL was greatest in the least oxidative muscle. Palmitate oxidation, incorporation into TG, and citrate synthase activity were all strongly correlated with muscle cytosolic fatty acid-binding protein content (r = 0.96, 1.0, and 0.98, respectively). During the chase, reducing exogenous palmitate from 1.0 mM to 0.5 or 0 mM resulted in a significant (approximately 30%) loss of [(14)C]palmitate from the TG pool in SOL and a significant increase in (14)CO(2) production from endogenous stores. No significant loss of (14)C label from lipid pools occurred in the less oxidative muscles, suggesting a closely regulated interaction between energy provision from exogenous and endogenous lipid pools in oxidative muscle. Glucose oxidation increased significantly in all muscles in the absence of palmitate. The loss of (14)C label from TG in SOL during the chase without palmitate was not accompanied by a significant change in TG content. This suggests that, during rest, there is a small subpool of TG with a relatively rapid turnover.

Purification and characterization of recombinant human parathyroid hormone-related protein

Full-length human parathyroid hormone-related protein (PTHrP-(1-141] as well as a carboxyl-terminal shortened form (PTHrP-(1-108] have been expressed from recombinant DNA-derived clones. These proteins were expressed in Escherichia coli as fusion proteins so that cyanogen bromide cleavage yields the desired product. Both proteins were purified and then characterized by sodium dodecyl sulfate gel electrophoresis, amino-terminal amino acid sequencing, peptide mapping, and mass spectral analysis. Recombinant PTHrP-(1-141), PTHrP-(1-108), synthetic PTHrP-(1-34), and naturally derived PTHrP are all equipotent in the stimulation of cyclic AMP levels in the osteoblast-like cell line UMR 106-01. However, PTHrP-(1-141) and -(1-108) are two to four times more active than PTHrP-(1-34) in the stimulation of plasminogen activator activity from this cell line. PTHrP-(1-141) reacts equipotently with PTHrP-(1-34) in a radioimmunoassay using an antiserum prepared against PTHrP-(1-34). PTHrP-(1-141), -(1-108), and -(1-84) were used as PTHrP-specific mobility standards on sodium dodecyl sulfate gel electrophoresis to determine the approximate length of two forms of naturally derived PTHrP. The data show that PTHrP purified from the lung tumor cell line BEN contains a major form of about 108 amino acids and another form of about 141 amino acids.

Long-term follow-up using serial serum thyroglobulin determinations in patients with differentiated thyroid carcinoma

Although thyroglobulin is generally recognized as a useful marker for metastases in cases of differentiated thyroid carcinoma, there have been few reports of the use of thyroglobulin determination for long-term follow-up. This report presents the results of long-term follow-up studies carried out for periods of up to 4 years in 18 patients, including 4 patients with local and 14 with distant metastases. After successful treatment, thyroglobulin fell to unmeasurable levels in the four patients with local metastases and in four of six patients with distant metastases. In some patients treated successfully with 131I, the thyroglobulin level remained elevated for several months before falling to within the normal range. Thyroglobulin levels correlated with tumor growth in six of eight patients with tumor progression, remained high with a slight downward trend in one patient, and declined to unmeasurable levels in another case. Only one patient in this group showed radioiodine uptake in the metastases at the end of the observation period. The lack of 131I uptake in the other patients probably reflects the low degree of differentiation of the metastases. The following conclusions regarding the use of thyroglobulin measurement for the long-term follow-up of thyroid carcinoma can be made: (1) Following 131I therapy for metastatic thyroid carcinoma, return of thyroglobulin levels to within the normal range may take several months. The trend observed in serial thyroglobulin determinations is more meaningful than the absolute values for evaluating the success of therapy. (2) Thyroglobulin levels correlate with tumor growth in most cases of tumor progression, even when changes in differentiation may have led to a loss of radioiodine uptake by the metastases. It may be concluded that serial thyroglobulin determinations are therefore useful for the detection of metastases that do not accumulate radioiodine.