Successful Localization Using 68Ga-DOTATOC PET/CT of a Phosphaturic Mesenchymal Tumor Causing Osteomalacia in a Patient with Concurrent Follicular Lymphoma.

Diagnosing tumor-induced osteomalacia is often challenging because conventional imaging modalities may fail to locate the responsible tumor. This report describes the ability of 68Ga-DOTATOC PET/CT to successfully distinguish between the responsible phosphaturic mesenchymal tumor and concurrent lymphoma lesions. A 52-year-old man with bone pain for several years was diagnosed with a vitamin D-resistant hypophosphatemic osteomalacia. Whole body 18F-FDG PET/CT revealed multiple enlarged hypermetabolic lymph nodes in his bilateral cervical, axillary, mediastinal, abdominal, pelvic, and inguinal regions. Core needle biopsy of the right cervical lymph node confirmed the diagnosis of follicular lymphoma. However, lymphoma was not considered the cause of osteomalacia. 68Ga-DOTATOC PET/CT before chemotherapy showed a small nodule with intensely increased uptake in the right inguinal region, which was distinguished from the other enlarged lymph nodes. The nodule was surgically removed and histopathologically consistent with phosphaturic mesenchymal tumor. After surgery, the patient's serum phosphorus and alkaline phosphatase levels normalized without nutritional supplement.

Altered Biodistribution of 99mTc-DPD on Bone Scan After Intravenous Iron Supplement.

We report a case with altered biodistribution of 99mTc-dicarboxypropane diphosphonate (99mTc-DPD) on whole body bone scan after intravenous iron supplement therapy. A 47-year-old male patient who had recently been detected with a hepatic mass suggestive of hepatocellular carcinoma underwent bone scan as staging work-up before surgery. Bone scan images at 3 h after injection of 99mTc-DPD demonstrated unusually increased blood pool activities in the heart, liver, and spleen with usual skeletal uptakes. The patient had been treated for severe anemia from hemorrhoid with two intravenous administration of ferric hydroxide carboxymaltose complex at approximately 22 h and 2 h prior to the 99mTc-DPD injection, which we consider as the most probable cause of altered biodistribution of 99mTc-DPD.

Lack of Efficacy of Radioiodine Remnant Ablation for Papillary Thyroid Microcarcinoma: Verification Using Inverse Probability of Treatment Weighting.

BACKGROUND: Most of the increase in thyroid cancer in recent decades has been due to papillary thyroid microcarcinoma (PTMC). We evaluated the efficacy of radioiodine remnant ablation (RRA) in patients with PTMC. METHODS: This historical cohort study included 1932 PTMC patients without lateral cervical lymph node (LN) or distant metastasis who underwent total thyroidectomy (TT) during the median 8.3 years of follow-up. The clinical outcomes of patients with or without RRA were compared using weighted logistic regression models with the inverse probability of treatment weighting (IPTW) method and considering risk factors, including age, sex, primary tumor size, extrathyroidal extension, multifocality, and central cervical LN metastasis. RESULTS: The median primary tumor size of the RRA group was significantly larger than that of the no-RRA group (0.7 vs. 0.5 cm, P < 0.001). There were significantly more patients with multifocality, extrathyroidal extension, and cervical LN metastasis in the RRA group compared with the no-RRA group. There was no significant difference in recurrence-free survival between the two groups (P = 0.11). Cox proportional-hazard analysis with IPTW by adjusting for clinicopathological risk factors demonstrated no significant difference in recurrence of PTMC according to RRA treatment (hazard ratio [HR] 2.02; 95% confidence interval [CI] 0.65-6.25; P = 0.2). CONCLUSIONS: RRA had no therapeutic effect on the clinical outcomes of patients with PTMC who underwent TT. Surgical treatment without RRA could be applicable for patients with PTMC if there is no evidence of lateral cervical LN metastasis or distant metastasis.

Changes in the pulmonary function test after radioactive iodine treatment in patients with pulmonary metastases of differentiated thyroid cancer.

OBJECTIVE: Pulmonary function test (PFT) is a useful tool for an objective assessment of respiratory function. Impaired pulmonary function is critical for the survival and quality of life in patients with pulmonary metastases of solid cancers including thyroid cancer. This study aimed to evaluate clinical factors associated with severely impaired pulmonary function by serial assessment with PFT in patients with pulmonary metastasis of differentiated thyroid cancer (DTC) who received radioactive iodine treatment (RAIT). PATIENTS: This retrospective study enrolled 31 patients who underwent serial PFTs before and after RAIT for pulmonary metastasis of DTC. We evaluated the risk factors for severe impairment of pulmonary function. RESULTS: The median age of the patients was 44.1 years and 18 of them were female patients. Severe impairment of pulmonary function was observed in five patients (16%) after a median of three RAITs (cumulative I-131 activity = 20.4 GBq). These patients were older and more frequently had mild impairment of baseline pulmonary function, respiratory symptoms, or progressive disease compared with patients with stable pulmonary function. Neither cumulative dose nor number of RAIT was associated with decreased pulmonary function. Coexisting pulmonary diseases, presence of respiratory symptoms, and metastatic disease progression were significantly associated with severe decrease in forced vital capacity during follow-up (p =.047, p =.011, and p =.021, respectively). CONCLUSIONS: Pulmonary function was severely impaired during follow-up in some patients with pulmonary metastasis of DTC after a high-dose RAITs. Neither the number of RAIT nor the cumulative I-131 activity was associated with decreased pulmonary function. Serial PFT might be considered for some high-risk patients during follow-up.

Modified dynamic risk stratification for predicting recurrence using the response to initial therapy in patients with differentiated thyroid carcinoma.

OBJECTIVE: A new risk stratification system was proposed to estimate the risk of recurrence in patients with differentiated thyroid carcinoma (DTC) using the response to initial therapy. Here, we describe the modified dynamic risk stratification system, which takes into consideration the status of serum anti-Tg antibody (TgAb), and validate this system for assessing the risk of recurrence in patients with DTC. PATIENTS AND METHODS: Patients who underwent total thyroidectomy with radioiodine remnant ablation due to DTC between 2000 and 2005 were included. We classified patients into four groups based on the response to the initial therapy ('excellent', 'acceptable', 'biochemical incomplete', and 'structural incomplete' response). RESULTS: The median follow-up period of 715 patients with DTC was 8 years. The response to initial therapy was an important risk predictor for recurrent/persistent DTC. The relative risks (95% CI) of recurrence were 16.5 (6.3-43.0) in the 'acceptable response' group, 41.3 (15.4-110.8) in the 'biochemical incomplete response' group, and 281.2 (112.9-700.5) in the 'structural incomplete response' group compared with the 'excellent response' group (P<0.001, P<0.001, and P<0.001 respectively). The disease-free survival rate of the 'excellent response' group to initial therapy was 98.3% whereas that of the 'structural incomplete response' group was only 6.8%. CONCLUSIONS: Our study validates the usefulness of the modified dynamic risk stratification system including the status of serum TgAb for predicting recurrent/persistent disease in patients with DTC. Personalized risk assessment using the response to initial therapy could be useful for the follow-up and management of patients with DTC.

Effects of low-dose and high-dose postoperative radioiodine therapy on the clinical outcome in patients with small differentiated thyroid cancer having microscopic extrathyroidal extension.

BACKGROUND: It is unclear whether differentiated thyroid cancer (DTC) patients classified as intermediate risk based on the presence of microscopic extrathyroidal extension (ETE) should be treated with low or high doses of radioiodine (RAI) after surgery. We evaluated success rates and long-term clinical outcomes of patients with DTC of small tumor size, microscopic ETE, and no cervical lymph node (LN) metastasis treated either with a low (1.1 GBq) or high RAI dose (5.5 GBq). METHODS: This is a retrospective analysis of a historical cohort from 2000 to 2010 in a tertiary referral hospital. A total of 176 patients with small (≤2 cm) DTC, microscopic ETE, and no cervical LN metastasis were included. Ninety-six patients were treated with 1.1 GBq (LO group) and 80 patients with 5.5 GBq (HI group). Successful RAI therapy was defined as (i) negative stimulated thyroglobulin (Tg) in the absence of Tg antibodies, and (ii) absence of remnant thyroid tissue and of abnormal cervical LNs on ultrasonography. Clinical recurrence was defined as the reappearance of disease after ablation, which was confirmed by cytologically or pathologically proven malignant tissue or of distant metastatic lesions. RESULTS: There was no significant difference in the rate of successful RAI therapy between the LO and HI groups (p=0.75). In a subgroup analysis based on tumor size, success rates were not different between the LO group (34/35, 97%) and the HI group (50/56, 89%) in patients with a tumor size of 1-2 cm (p=0.24). In patients with smaller tumor size (≤1 cm), there was no significant difference in success rates between the LO (59/61, 97%) and HI groups (22/24, 92%; p=0.30). No patient had clinical recurrences in either group during the median 7.2 years of follow-up. CONCLUSIONS: Low-dose RAI therapy is sufficient to treat DTC patients classified as intermediate risk just by the presence of microscopic ETE.

Adjuvant radioactive therapy after reoperation for locoregionally recurrent papillary thyroid cancer in patients who initially underwent total thyroidectomy and high-dose remnant ablation.

CONTEXT: Some patients have elevated stimulated thyroglobulin (sTg) concentrations after reoperation for locoregionally recurrent/persistent papillary thyroid cancer (PTC). Little is known, however, about the efficacy of adjuvant radioactive iodine (RAI) therapy in these patients. OBJECTIVE: The objective of the study was to evaluate the efficacy of adjuvant RAI therapy in patients with elevated sTg after reoperation for locally recurrent/persistent PTC. DESIGN AND SETTINGS: This was a retrospective observational cohort study in a tertiary referral hospital. PATIENTS: We evaluated 45 consecutive patients with sTg greater than 2 ng/ml after reoperation for locoregionally recurrent PTC, all of whom had previously undergone initial total thyroidectomy followed by high-dose RAI remnant ablation. Of these 45 patients, 23 received adjuvant RAI therapy (adjuvant group) and 22 did not (control group). MAIN OUTCOME MEASURES: Main outcome measures included changes in sTg concentration after reoperation and disease-free survival. RESULTS: Over time, there were no significant differences in mean sTg concentration in the adjuvant (P = 0.35) and control (P = 0.74) groups. Only 15% of patients in the adjuvant group and 33% in the control group showed a greater than 50% decrease in sTg level from baseline. There were no between-group differences in changes (P = 0.83) or percent decrease (P = 0.97) in sTg concentration and no difference in clinical recurrence-free survival (P = 0.20). CONCLUSION: In patients who still have elevated sTg after reoperation for locally recurrent/persistent PTC, adjuvant RAI therapy compared with no additional RAI therapy resulted in no significant differences in the subsequent sTg changes or the recurrence-free survival.

Evaluation of metabolic characteristics and viability of lipiodolized hepatocellular carcinomas using 18F-FDG PET/CT.

UNLABELLED: This study aimed to evaluate the metabolic characteristics of lipiodolized hepatocellular carcinomas (HCCs) and the diagnostic accuracy of (18)F-FDG PET/CT in assessing the viability of lipiodolized HCCs. METHODS: Thirty-six patients (age range, 32-73 y) with 38 lipiodolized HCCs who had undergone transcatheter arterial chemoembolization (TACE) with lipiodol before (18)F-FDG PET/CT (2-434 d) and 55 patients (age range, 36-77 y) with 57 treatment-naïve HCCs who had not been treated with TACE were retrospectively studied. All patients underwent hepatic lobectomy or transplantation within 1 mo after PET/CT and multiphasic contrast-enhanced CT. (18)F-FDG uptake by lipiodolized and naïve HCCs was compared and correlated with tumor size, pathologic grade, serum α-fetoprotein (AFP) concentration, and time interval between TACE and PET/CT. The diagnostic accuracy of PET/CT and contrast-enhanced CT in evaluating the viability of lipiodolized HCC was compared. RESULTS: Histologic examination showed 30 viable and 8 nonviable lipiodolized HCCs. Of the 30 viable tumors, 19 showed increased, 10 similar, and 1 decreased (18)F-FDG uptake. Of the 8 nonviable HCCs, 3 showed increased and 5 decreased (18)F-FDG uptake. Uptake by viable lipiodolized HCCs was correlated with tumor size (P < 0.05) but not correlated with pathologic grade, AFP concentration, or interval between TACE and PET/CT. In contrast, (18)F-FDG uptake by naïve HCCs was significantly correlated with tumor size and pathologic grade (P < 0.05 for each comparison). When lipiodolized HCCs with (18)F-FDG uptake that was greater than or similar to that in the surrounding normal liver were considered viable, the diagnostic sensitivity of PET/CT and contrast-enhanced CT in the early postembolic period (<3 mo) was 100% and 94%, respectively, and that in the late postembolic period was 93% and 79%, respectively. The specificity of (18)F-FDG PET/CT and contrast-enhanced CT was 63% and 100%, respectively, in the acute period. Three viable lipiodolized HCCs with high AFP concentration were true-positives on PET/CT but false-negatives on contrast-enhanced CT images. CONCLUSION: After TACE, (18)F-FDG uptake in lipiodolized HCCs was not correlated with pathologic grade, in contrast to uptake in treatment-naïve HCCs. (18)F-FDG PET/CT showed a high diagnostic sensitivity in assessing the viability of lipiodolized HCCs, with moderate specificity. This method may be useful in determining the viability of lipiodolized HCCs in patients with increased serum AFP concentration or normal results on contrast-enhanced CT images.

Clinical outcomes of persistent radioiodine uptake in the neck shown by diagnostic whole body scan in patients with differentiated thyroid carcinoma after initial surgery and remnant ablation.

OBJECTIVES: To evaluate the clinical outcomes of persistent radioiodine uptake (RAIU) in the neck by diagnostic whole body scan (DxWBS) after initial therapy and the efficacy of the second ablation in patients with differentiated thyroid carcinoma (DTC). DESIGN: Patients with DTC who underwent bilateral surgery and high-dose remnant ablation between 2000 and 2004 were included. Patients with elevated serum stimulated thyroglobulin (sTg) or extensive lateral neck lymph node involvement at initial surgery underwent a second ablation, and patients with undetectable sTg or in very low-risk groups were observed. RESULTS: Among 572 patients, 25 had persistent RAIU in the neck at first DxWBS. After a median 65.7 months of follow-up, five of these patients (20%) had persistent disease, whereas another 20 patients had no abnormal findings by ultrasonography (US) or other imaging modalities. Seven of 20 patients underwent second ablation and 13 were observed. RAIU disappeared spontaneously in about half of the patients in the observation group. There were no significant between-group differences in change of RAIU at follow-up DxWBS (P = 0.62). Serum sTg decreased and eventually disappeared over a few years in both groups. Ablation failure was not an independent risk factor for recurrence (P = 0.169). CONCLUSIONS: Neck US and serum sTg, but not DxWBS, were useful diagnostic tools during follow-up of patients with persistent uptake in the neck at DxWBS. A second ablation was not necessary when neck US showed no evidence of disease, especially in patients with very low sTg concentration.

Empiric high-dose 131-iodine therapy lacks efficacy for treated papillary thyroid cancer patients with detectable serum thyroglobulin, but negative cervical sonography and 18F-fluorodeoxyglucose positron emission tomography scan.

CONTEXT: Some patients with elevated serum thyroglobulin (Tg) but a negative diagnostic whole body scan (WBS) after initial therapy for differentiated thyroid carcinoma may benefit from empirical radioactive iodine (RAI) therapy. However, previous studies enrolled patients with negative diagnostic WBS, regardless of neck ultrasonography (USG) and/or (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET), which have become the preferred diagnostic procedures in such patients. OBJECTIVE: The aim of this study was to evaluate the usefulness of empirical RAI therapy in patients with elevated stimulated Tg level and negative USG/FDG-PET findings after initial therapy for papillary thyroid carcinoma (PTC). DESIGN: This comparative study enrolled 39 patients with elevated stimulated Tg, negative diagnostic WBS, and negative USG/FDG-PET 1 yr after initial treatment. Empirical RAI therapy was performed in 14 patients (treatment group), whereas 25 patients were followed up without therapy (control group). RESULTS: There was no significant between-group difference in basal clinicopathological parameters. None of the 14 patients in the treatment group showed iodine uptake on posttreatment WBS. Five of 14 patients (36%) in the treatment group and eight of 25 (32%) in the control group had recurrence during the median 37 months of follow-up (P = 0.99). Changes in serum stimulated Tg concentrations did not differ between the two groups. CONCLUSION: Empirical RAI therapy and posttreatment WBS were not useful diagnostically or therapeutically in patients with positive serum stimulated Tg if such patients had negative USG and negative FDG-PET findings after initial treatment of PTC.

Redifferentiation therapy with 13-cis retinoic acids in radioiodine-resistant thyroid cancer.

Radioiodine (I-131) therapy is of proven efficacy for treatment of differentiated thyroid carcinoma (DTC). However, loss of differentiation in recurrent or metastatic DTC which decrease I-131 uptake may decrease the efficacy of I-131 therapy. Therefore, strategies to improve I-131 uptake are mandatory. This study is an open label clinical study to evaluate the effectiveness of 13-cis retinoic acid (13-cis RA) for improving I-131 uptake in recurrent or metastatic of DTC with defective I-131 uptake. Eleven patients (Age 27-66 years, M : F=4 : 7) were given 13-cis RA (1.5 mg/kg daily for 5 weeks), followed by 200 mCi (7.4 GBq) I-131 treatment. The differences of serum thyroglobulin (Tg) level and I-131 uptake on the post-treatment whole body scan (RxWBS) were compared before and after 13-cis RA therapy. Six out of 11 patients showed significantly increased (above 50%) Tg levels just after RA therapy. However, Tg levels a year after I-131 therapy were increased, stable and decreased in 7, 2 and 1 patients, respectively. Iodine uptake on RxWBS showed marginal improvement in only 2 patients and their Tg levels after one year follow-up increased. Most frequent adverse events were dry skin and lips. 13-cis RA partially restores I-131 uptake in few patients with recurrent or metastatic DTC. The use of 13-cis RA in current protocol has only limited usefulness and is not routinely recommended as currently used protocol.

Capecitabine and cisplatin chemotherapy (XP) alone or sequentially combined chemoradiotherapy containing XP regimen in patients with three different settings of stage IV esophageal cancer.

BACKGROUND: The 1997 staging system for esophageal carcinoma subdivided distant metastatic disease (M1) into nonregional lymph node metastases (M1a) and other metastases (M1b). To determine the relevance of this classification system, we investigated the efficacy and toxicity of capecitabine/cisplatin (XP) chemotherapy alone or in combination with radiotherapy. METHODS: We identified 74 patients with M1 disease treated at Asan Medical Center from January 2003 to December 2005. Of these patients, 19 (25.7%) were classified as M1a, 29 (39.2%) as M1b (nonvisceral lymph node metastases), and 26 (35.1%) as M1b (visceral metastases). All patients were treated with first two cycles of XP induction chemotherapy, consisting of capecitabine 1000 mg/m(2) twice daily on days 1-14, and i.v. cisplatin 60 mg/m(2) on day 1, every 3 weeks. Patients classified as M1a and M1b (nonvisceral lymph node metastases) were treated with 54 Gy of radiotherapy, concurrently with weekly capecitabine 800 mg/m(2) twice daily on days 1-5 and i.v. cisplatin 30 mg/m(2) on day 1 during radiation. Patients classified as M1b (visceral metastases) were treated with chemotherapy only until disease progression or intolerance to chemotherapy. RESULTS: In response to the first two cycles of chemotherapy, 3/18 (16.7%) M1a nonregional lymph node (LN), 4/27 (14.8%) M1b nonvisceral LN metastases and 5/25 (20%) M1b visceral metastases patients attained partial responses. After definitive chemoradiation in the setting of M1a, M1b nonvisceral LN metastases and maximum cycles of chemotherapy in the M1b visceral metastases setting, the response rates were 77.8, 62.9 and 36.0% respectively. With median follow-up of 12.5 months (range 0.5-22.8), 50 of 74 patients (67.5%) died. The median time to progression (TTP) was 7.8 months (95% CI, 6.0-9.5 months) and the median overall survival (OS) was 12.0 months (95% CI, 9.0-15.0 months). Median TTP in the M1a, M1b nonvisceral LN metastases and M1b visceral metastases were 10.3, 6.5 and 5.9 months, respectively (P = 0.087), whereas median OS in these groups was 13.8, 13.8, and 8.2 months, respectively (P = 0.134). Median TTP was 8.4 months (95% CI, 5.5-11.3 months) in the 48 patients with M1a and M1b nonvisceral LN metastases and 5.9 months (95% CI, 2.7-9.0 months) in the 26 patients with M1b visceral metastases (P = 0.03), and median OS in these two groups was 13.8 months (95% CI, 10.4-17.3 months) and 8.2 months (95% CI, 5.7-10.7 months), respectively (P = 0.04). CONCLUSION: The similar OS in patients with M1a and M1b nonvisceral LN metastases suggests that concurrent chemoradiotherapy might contribute in the latter. Our findings indicate that sequentially combined chemoradiotherapy containing XP regimen was active and well tolerated as first-line treatment for M1a as well as M1b esophageal cancer.

Fully automated synthesis of [18F]fluoromisonidazole using a conventional [18F]FDG module.

We developed a new fully automated method for the synthesis of [18F]fluoromisonidazole ([18F]FMISO) by modifying a commercial FDG synthesizer and its disposable fluid pathway. A three-step procedure was used to prepare the tosylate precursor, 1-(2'-nitro-1'-imidazolyl)-2-O-tetrahydrofuranyl-3-O-toluenesulfonylpropanediol. Using glycerol as the starting material, the precursor was synthesized with a yield of 21%. The optimal labeling conditions for the automated synthesis of [18F]FMISO was 10 mg of precursor in acetonitrile (2 ml heated at 105 degrees C for 360 s, followed by heating at 75 degrees C for 280 s and hydrolysis with 1 N HCl at 105 degrees C for 300 s. Using 3.7 GBq of [18F]F- as a starting activity, [18F]FMISO was obtained with high end-of-synthesis (EOS) radiochemical yields of 58.5+/-3.5% for 60.0+/-5.2 min with high-performance liquid chromatography (HPLC) purification. When solid-phase purification steps were added, the EOS radiochemical yields were 54.5+/-2.8% (337+/-25 GBq/micromol) for 70.0+/-3.8 min (n=10 for each group, decay-corrected). With a high starting radioactivity of 37.0 GBq, we obtained radiochemical yields of 54.4+/-2.9% and 52.8+/-4.2%, respectively (n=3). The solid-phase purification removed unreacted [18F]fluoride and polar impurities before the HPLC procedure. Long-term tests showed a good stability of 98.2+/-1.5%. This new automated synthesis procedure combines high and reproducible yields with the advantage of using a disposable cassette system.

Serum thyroglobulin levels at the time of 131I remnant ablation just after thyroidectomy are useful for early prediction of clinical recurrence in low-risk patients with differentiated thyroid carcinoma.

We investigated whether serum thyroglobulin (Tg) measured at the time of remnant ablation (ablation-Tg) could be a prognostic indicator complementary to serum Tg levels at the time of the first diagnostic whole-body scan (WBS) after thyroid hormone withdrawal (control-Tg; approximately 6-12 months after ablation-Tg) and whether ablation-Tg could predict the persistence or recurrence of disease in low-risk patients with differentiated thyroid carcinoma. Patients with differentiated thyroid carcinoma (n = 268) treated with total or near-total thyroidectomy followed by immediate (131)I remnant ablation were studied. Patients with anti-Tg autoantibodies and those showing evidence of extracervical metastases were excluded. Two patients showing remnant uptake on follow-up diagnostic WBS received a second ablation. We found significant correlation between ablation-Tg and control-Tg levels; 114 of 143 patients (80%) with ablation-Tg greater than 2 microg/liter showed detectable (>/=1 microg/liter) control-Tg, and 70 of 125 (56%) patients with ablation-Tg 2 microg/liter or less showed undetectable (<1 microg/liter) control-Tg [odds ratio 5.1, 95% confidence interval (CI) 3.0-8.9, P < 0.001]. When the 268 patients were followed up for a mean period of 5.7 +/- 1.4 yr (range 2.8-8.3 yr), 35 (13%) had recurrences; 73 (27%) were classified as "Tg positive, no evidence of disease"; and 160 (60%) showed complete remission. Of 143 patients with ablation-Tg greater than 2 microg/liter, recurrence was observed in 33 cases (23%); "Tg positive, no evidence of disease," was observed in 52 cases (36%); and complete remission was observed in 58 cases (41%). Of 125 patients with ablation-Tg 2 microg/liter or less, two patients (2%) showed recurrence during the follow-up; 21 patients (17%) were regarded as "Tg positive, no evidence of disease"; and 102 patients (81%) showed complete remission. The positive predictive value for recurrence in patients having ablation-Tg greater than 2 microg/liter was found to be 23.1% (33 of 143 patients, 95% CI 16.4-30.8%). The negative predictive value for recurrence in patients having ablation-Tg 2 microg/liter or less was found to be 98.4% (123 of 125 patients, 95% CI 94.4-99.8%). These data indicate that serum Tg levels measured at the time of immediate postoperative (131)I remnant ablation correlated well with serum Tg levels at the time of the initial diagnostic WBS and had a complementary role for predicting persistence or recurrence of disease in the earliest postoperative period.