Shari Moreau

124I Positron Emission Tomography Versus 131I Planar Imaging in the Identification of Residual Thyroid Tissue and/or Metastasis in Patients Who Have Well-Differentiated Thyroid Cancer

BACKGROUND AND OBJECTIVE (124)I emits a positron and can be imaged with a positron emission tomography (PET) scanner. The objective of this study was to compare the ability of diagnostic (124)I PET images versus (131)I planar whole-body imaging in detecting residual thyroid tissue and/or metastatic well-differentiated thyroid cancer (WDTC). METHODS Patients were recruited prospectively for this study who (i) had WDTC, (ii) were suspected of having metastatic WDTC, and (iii) were referred for (131)I whole-body dosimetry. The prescribed activity was 1-2 mCi (37-74 MBq) and 1.7 mCi (62.9 MBq) for (131)I and (124)I, respectively. For each image, one blinded reader (D.V.N.) categorized every focus of (131)I and (124)I radioiodine uptake as 1 = definite physiological uptake/artifact, 2 = most likely physiological uptake/artifact, 3 = indeterminate, 4 = residual thyroid tissue/metastases in the neck/bed, 5 = most likely metastases, or 6 = definite metastases. Foci categorized as 4, 5, or 6 were considered positive. When available, foci categorized as 4, 5, or 6 were correlated with other diagnostic studies. RESULTS Of the 25 patients, 8 patients (32%) had more positive foci on (124)I images than on (131)I, of which 3 patients to date have had metastases confirmed in one or more of the additional positive (124)I foci. (124)I demonstrated the same number of foci as on (131)I in 16 patients (14 with no positive foci, and 2 with two positive and five positive foci each). One patient had one additional positive focus on (131)I not seen on (124)I, which has not yet been confirmed as a metastasis. A total of 97 positive foci were identified on either (124)I or (131)I. (124)I identified 49 positive foci not seen with (131)I, and (131)I identified one positive focus not seen with (124)I. CONCLUSION Relative to (131)I planar whole-body imaging, (124)I PET identified as many as 50% more foci of radioiodine uptake suggestive of additional residual thyroid tissue and/or metastases in as many as 32% more patients who had WDTC.

The Utility of Radioiodine Scans Prior to Iodine 131 Ablation in Patients with Well-Differentiated Thyroid Cancer

BACKGROUND The utility of radioiodine (RAI) scans prior to (131)I ablation is controversial. The objective of this study was to evaluate the utility of RAI scans prior to (131)I ablation in patient with well-differentiated thyroid cancer. METHOD All RAI scans performed prior to (131)I ablation from July 2000 to November 2006 at Washington Hospital Center were reviewed retrospectively. Patients were excluded who were suspected of having 1) loco-regional disease, 2) distant metastases, and/or 3) physiological uptake that might alter management prior to the pre-ablation RAI scans. RAI scans were performed either 24 hours after dosing with 37-148 MBq of (123)I or 48 hours after dosing with 37-148 MBq of (131)I with imaging of the whole body, the thyroid bed/neck with a pinhole collimator, and the neck and chest with a parallel-hole collimator. One reviewer blindly evaluated each set of scans using six criteria, and for the purpose of this study, the thresholds for each criterion for which the patients management may have been altered prior to (131)I ablation are noted in parentheses: 1) the number of foci of RAI uptake in thyroid bed/neck (0 or > or =6), 2) the location(s) of these foci in the thyroid bed/neck (outside the thyroid bed), 3) the size of the largest foci in thyroid bed/neck (> or =1 lobe), 4) the percent uptake in the thyroid bed/neck (> or =15%), 5) uptake suggestive of distant metastases, and 6) significant altered biodistribution (e.g., any breast, marked salivary gland, or marked gastrointestinal uptake). RESULTS Of 355 sets of scans reviewed, 53% of patients had findings on the RAI scans that might have altered the patients management prior to their (131)I ablation. The data grouped by the criteria noted above were 1) 12% with six or more foci suggesting local metastases and 6% (22) with no focal uptake, 2) 14% with suggestion of lymph node metastases, 3) 1.1% with at least one focus > or =1 lobe, 4) 8% with > or =15% uptake, 5) 4% with distant metastases, 6) 16% demonstrating altered distribution with 6% breast, 3% salivary, 10% GI, and 0.3% urinary bladder. CONCLUSION Pre-ablation RAI scans demonstrate a significant number of findings that may alter the management of patients with well-differentiated thyroid cancer prior to (131)I ablation.

Utility of the Radioiodine Whole-Body Retention at 48 Hours for Modifying Empiric Activity of 131-Iodine for the Treatment of Metastatic Well-Differentiated Thyroid Carcinoma

BACKGROUND Dosimetry has been used to help identify when empiric dosages of 131-I treatment for suspected metastatic well-differentiated thyroid carcinoma (WDTC) may be increased or should be decreased, but dosimetry is complex, and easier approaches would be useful. The three objectives of this study were to assess the utility of the percent whole-body retention of 131-I at 48 hours (%WBR(48hr)) in identifying patients with WDTC in whom the therapeutic empiric prescribed activity of 131-I might be increased/decreased, to evaluate the thresholds proposed by Sisson et al. in 2003 for increasing or decreasing activity, and to determine the relationship between %WBR(48hr) and maximum tolerated activity (MTA). METHOD A retrospective review was conducted of patients who had WDTC, total thyroidectomy, suspected metastatic disease, thyroid hormone withdrawal, and 131-I dosimetry. The %WBR(48hr) was determined based on the Benua-Leeper dosimetry protocol, and the four thresholds and recommendations of Sisson et al., 2003 for the use of %WBR(48hr) were evaluated relative to an empiric activity (EA) of 7.4 GBq of 131-I. A biexponential equation was determined from the %WBR(48hr) data. RESULTS Of 142 patients, 47 patients had a %WBR(48hr) of <9%, and all could have received more than the EA of 7.4 GBq with an average of 21.0 GBq (incremental range of 6.8-23.2 GBq). Ten patients had a %WBR(48hr) < or = 5%, and all could have had their EA of 7.4 GBq safely increased by at least 250%. Conversely, if the %WBR(48hr) was >24.8%, then 7 of 14 of these patients would have exceeded the MTA by 0.37-3.18 GBq with an EA of 7.4 GBq. Finally, for patients with a %WBR(48hr) > 40%, five of six patients would have exceeded the MTA by 0.85-3.18 GBq. A biexponential regression equation is presented. CONCLUSION We conclude that, with respect to the treatment of metastatic epithelial cell thyroid cancer, the %WBR(48hr) of 131-I helps identify those patients in whom the empiric therapeutic prescribed activity of 131-I may be increased or should be decreased so as not to exceed the MTA and that Sisson et al.s thresholds published in 2003 are applicable. We favor a biexponential regression model using the %WBR(48hr) and a lower limit threshold as a potentially useful method for determining how much an empiric therapeutic prescribed activity of 131-I can be increased or decreased.

Salivary Gland Protection with Sialagogues: A Case Study

BACKGROUND To decrease the severity and frequency of radiation sialoadenitis, postponement of the use of sialagogues has been proposed for the first 24 hours after (131)I treatment for well-differentiated thyroid cancer. One proposed mechanism is that sialagogues increased salivation and salivary blood flow resulting in greater radioiodine uptake in the salivary glands-a rebound effect. This case study demonstrates no rebound effect. METHODS A 33-year-old woman with well-differentiated thyroid cancer desired to know whether she would have a rebound effect if she used sialagogues during the 24-hour period after her (131)I treatment. Salivary images of the parotid glands were initiated 2 hours after the administration of (131)I for her whole body scan. Lemon juice was administered. Background corrected time-activity curves were obtained for both parotid glands. The potential reduction in radiation absorbed dose to the parotid glands secondary to the administration of lemon juice was calculated. RESULTS The time-activity curves demonstrated that the (131)I in the right and left parotid glands decreased rapidly after lemon juice by 87% and 83%, respectively, with return to pre-lemon juice levels by 30 and 13 minutes in the right and left parotid glands, respectively. However, at no time during the 1 hour of imaging did the uptake in either parotid gland significantly exceed the pre-lemon juice levels of activity. The potential reduction of radiation absorbed dose to the parotid glands secondary to the use of lemon juice ranged from as much as 30% to 67%. CONCLUSION This case study demonstrates 1) an approach to assess whether an individual patient will have increased or decreased radioiodine uptake in the salivary glands after administration of sialagogues without the administration of any additional radioiodine, 2) a decrease of radioiodine uptake in the salivary glands after lemon juice without a rebound effect, and 3) a potential reduction of radiation absorbed dose with administration of sialagogues.

Doxorubicin-induced cardiac toxicity and cardiac rest gated blood pool imaging.

Anthracyclines are one of the most commonly used and potent chemotherapeutic agents. Doxorubicin (Adriamycin) is one common anthracycline used to treat many solid tumors including breast, sarcomas, gynecologic and hematological malignancies, such as leukemias and lymphomas. However, its use is often limited due to dose-dependent cardiotoxicity. As a result, patients receiving doxorubicin should have close monitoring of their left ventricular function. The gated cardiac blood pool (GBP) study is one of the most accurate and reproducible methods of assessing left ventricular function. This report presents an overview of (1) the incidence, clinical course, mechanisms, pathology, prevention, and monitoring of doxorubicin-induced cardiotoxicity (DIC), (2) the use of GBP studies in monitoring for DIC, and (3) 2 algorithms for the use of GBP studies in monitoring for DIC. This report concludes with a proposed algorithm for the use of GBP studies in DIC. With an understanding of DIC, GBP studies, and various algorithms, the interpreting physician may help the oncologist identify DIC earlier, more accurately, and before it becomes clinically apparent.