Repeat Redifferentiation of Radioiodine Refractory BRAFV600E Mutated Thyroid Cancer With Dabrafenib

N/A (Letter to the Editor).

Redifferentiation of Differentiated Thyroid Cancer: Clinical Insights from a Narrative Review of Literature

Background: Patients who have metastatic differentiated thyroid cancer (mDTC) frequently have negative diagnostic and/or post-therapy radioiodine scans. As a result, ¹³¹I therapy is frequently no longer considered a therapeutic option for these patients. However, with the knowledge of genomic alterations of patients with mDTC, the use of selected agents in specific patient groups may be used with the intention to re-establish ¹³¹I uptake (i.e., redifferentiation) and additional ¹³¹I therapy. The objectives of this narrative review are to present definitions of related terminology, a brief overview of the molecular mechanisms of redifferentiating agents, and a narrative review of the literature for redifferentiation in patients who have radioiodine refractory mDTC. Summary: We searched multiple electronic databases and reviewed the relevant English-language literature reported after 2010. Fourteen articles were included in this narrative review. Conclusions: Preliminary data suggest that select agents may offer potential for re-establishing ¹³¹I uptake in selected patients with radioiodine refractory mDTC (e.g., negative diagnostic and/or post-therapy radioiodine scans). These agents may also enhance uptake (e.g., uptake enhancement) in patients who have ¹³¹I uptake in mDTC on a diagnostic and/or post-therapy radioiodine scan. As a result, this may facilitate higher absorbed dose delivered (Gy (rad]) per ¹³¹I activity administered [GBq (mCi)]. This in turn may increase the likelihood of a better therapeutic effect for the planned administered ¹³¹I activity or a reduction in the originally planned administered ¹³¹I activity, while achieving the same intended therapeutic effect with potentially less untoward effects. Further studies are warranted to confirm these preliminary observations and to confirm acceptable subsequent ¹³¹I therapy responses after redifferentiation and/or uptake enhancement.

Metastatic Differentiated Thyroid Cancer Survival Is Unaffected by Mode of Preparation for 131I Administration

Context

Recombinant human thyrotropin (rhTSH) is currently not Food and Drug Administration approved for the treatment of high-risk patients with differentiated thyroid cancer (DTC).

Objective

The goal of our study was to compare the outcomes in higher-risk patients with metastatic DTC prepared for radioiodine (RAI) therapy with rhTSH vs thyroid hormone withdrawal (THW).

Methods

A retrospective chart review was performed of patients with metastatic DTC in follow-up at MedStar Washington Hospital Center and MedStar Georgetown University Hospital from 2009 to 2017. Patients were divided according to their preparation for RAI therapy, with assessment of progression-free survival (PFS) and overall survival (OS).

Results

Fifty-five patients with distant metastases (16 men, 39 women) were prepared for RAI therapy exclusively either with rhTSH (n = 27) or with THW (n = 28). There were no statistically significant differences between the groups regarding clinicopathological features and history of RAI therapies. The median follow-up time for patients with rhTSH-aided therapies was 4.2 years (range, 3.3-5.5 years) and for patients with THW-aided therapies was 6.8 years (range, 4.2-11.6 years) (P = .002). Multivariate analysis showed that the method of thyrotropin stimulation was not associated with a difference in PFS or OS.

Conclusion

As has been shown previously for low-risk DTC, this study indicates that the mode of preparation for RAI therapy does not appear to influence the outcomes of patients with metastatic DTC. PFS and OS were similar for patients with THW-aided or rhTSH-aided RAI therapies.

Optimal Time for 124I PET/CT Imaging in Metastatic Differentiated Thyroid Cancer

BACKGROUND

The objective of this study was to determine the optimal time for 124I PET/CT imaging to maximize the detection of locoregional and/or distant metastases of differentiated thyroid cancer.

METHODS

Differentiated thyroid cancer patients suspected of having metastatic disease were prepared with low-iodine diet and appropriate thyroid-stimulating hormone stimulation. 124I PET and low-dose localization CT were performed over 4 days after oral administration of 31.5 or 62.9 MBq (0.85 or 1.7 mCi) of 124I. Each scan was independently reviewed by 2 nuclear medicine physicians. All foci of activity were categorized, and the visual intensity of uptake was scored by a semiquantitative 3-point grading system (1: mild uptake, 2: moderate uptake, 3: intense uptake). Lesion volumes were determined on the CT image or on the PET images. Background (bkg) was also measured for each lesion and on each individual PET image. For each lesion, the mean activity concentration rate per unit administered activity (ACRmean/AA) and lesion-to-bkg ratios were compared across the 5 different time points. The semiquantitative grade and the quantitative measurements were compared.

RESULTS

A total of 45 124I PET/CT scans were reviewed for 9 patients. In the visual assessment, a total of 31 foci suggestive for or highly suggestive of metastasis were identified on 124I PET/CT. Of these, 6 were seen on the 2-h, 18 on the 24-h, 27 on the 48-h, 24 on the 72-h, and 20 on the 96-h scan. There was a significant difference between the 24- and 48-h scans in the total number of foci (ie, locoregional and distant metastasis) (P < 0.05) and in the number of distant metastases (P < 0.05). The 24-, 48-, and 72-h scans identified the same number of locoregional foci. The 48-h scan visualized more of the distant metastases than any other time point. 124I PET/CT with dual-time-point imaging was superior to single-time-point imaging (97% vs 87%). In the quantitative analysis, the median ACRmean/AA was highest at 24 and 48 h, and the median lesion-to-bkg ratio was variable for different lesion locations. For lung metastases, the highest median lesion-to-bkg ratio was at 72 and 96 h.

CONCLUSIONS

124I PET/CT with dual-time-point imaging was superior to any single-time-point imaging (P < 0.10). Based on the visual assessment, dual time points at 48 + 72 h or 48 + 96 h yielded the highest lesion detection rate, whereas for single-time-point imaging, the 48-h images had the highest lesion detection rate. If the 48-h scan is completely negative or has negative 124I uptake in the region of interest, then a 72- or 96-h scan may be valuable. If lung metastases are suspected, then one should consider additional imaging at 72 or 96 h.

30 mCi exploratory scan for two-step dosimetric 131I therapy in differentiated thyroid cancer patients: A novel approach and case report

Differentiated thyroid cancer patients with significantly elevated or rapidly rising serum thyroglobulin (Tg) levels and negative diagnostic radioiodine scans (DxScan) often present a therapeutic dilemma in deciding whether or not to administer an ¹³¹I treatment. In this report, we describe a novel two-step approach of a 30 mCi ¹³¹I exploratory scan before a dosimetric ¹³¹I therapy to help “un-blind” the treating physician of the benefit/risk ratio of a further “blind” ¹³¹I treatment. A 51-year-old man presented with rising Tg levels, a negative DxScan, and a history of widely metastatic follicular thyroid cancer. He had undergone total thyroidectomy, remnant ablation with 3.8 GBq (103.5 mCi) of ¹³¹I, Gammaknife^®, and treatment with 12.1 GBq (326 mCi) of ¹³¹I for multiple metastases. However, at 19 months after the treatments, his Tg levels continued to rise, and scans demonstrated no evidence of radioiodine-avid metastatic disease. In anticipation of a “blind” ¹³¹I treatment, the medical team and the patient opted for a 30 mCi exploratory scan. The total dosimetrically guided prescribed activity (DGPA) was decided based on the whole-body dosimetry. The patient was first given 30 mCi of ¹³¹I, and the exploratory scan was performed 22 h later, which demonstrated ¹³¹I uptake in the left lung, left humeral head, T10, and right proximal thigh muscle. Based on the positive exploratory scan, the remainder of the DGPA was administered within several hours after the scan. On the post-DGPA treatment scan performed at 5–7 days, the lesions seen on the ~ 22 h exploratory scan were confirmed, and an additional lesion was observed in the left kidney. The 30 mCi exploratory scan suggested the potential for a response in the radioiodine-avid lesions despite a negative diagnostic scan. This method allows ¹³¹I treatment to be administered to patients who may have a greater potential for a therapeutic response while avoiding unwarranted side effects in those patients with nonavid disease.

124I Positron Emission Tomography/Computed Tomography Versus Conventional Radioiodine Imaging in Differentiated Thyroid Cancer: A Review

Background: Studies report a wide spectrum of ¹²⁴I positron emission tomography (PET)/computed tomography (CT) sensitivity and specificity in the detection of differentiated thyroid cancer (DTC) lesions. This study reviews the lesion detection rate of pretherapy ¹²⁴I PET/CT in different patient populations and further analyzes the factors necessary for a better detection on ¹²⁴I PET/CT. Methods: A literature search was performed using multiple different databases (MEDLINE, EMBASE, Northern Lights, and handsearching) covering 1996 to April 2018. Two reviewers reviewed and extracted study data for ¹²⁴I, ¹²³I, and ¹³¹I scans in DTC. Results: This review includes 4 retrospective and 10 prospective studies in which 495 DTC patients underwent ¹²⁴I and ¹³¹I imaging; no studies made comparisons with ¹²³I. In the reports that compared ¹²⁴I PET/CT with diagnostic ¹³¹I scans, there were a total of 72 patients in whom 120 lesions were detected on ¹²⁴I imaging, whereas only 52 were detected on diagnostic ¹³¹I scans. In publications that compared ¹²⁴I with post-therapy ¹³¹I scans in 266 patients, 410 lesions were detected with ¹²⁴I PET, whereas 390 were detected on post-therapy ¹³¹I scans. Based on ¹²⁴I PET/CT in six studies, TNM staging was revised in 15-21% of patients, and disease management was altered in 5-29% of patients. Conclusions:¹²⁴I PET/CT is able to identify a greater number of foci compared with diagnostic ¹³¹I scans. ¹²⁴I PET may have better detection compared with post-therapy ¹³¹I scans in patients who are ¹³¹I therapy naive, have less aggressive pathology, or do not have disseminated lung metastases. Additional metastatic lesion detection by ¹²⁴I PET may have a significant clinical impact in the management of patients before ¹³¹I therapy in some patients.

Nationwide Survey on Implementation of 2011 Nuclear Regulatory Commission Policy on Release of Patients After 131I Therapy for Thyroid Cancer

The objective of this nationwide survey was to evaluate whether there has been a change in the practice regarding hospital release of differentiated thyroid cancer patients treated with ¹³¹I since the publication of Nuclear Regulatory Commission Regulatory Issue Summary 2011-01 addressing patient release. Methods: A survey was emailed to approximately 25,000 members of ThyCa: Thyroid Cancer Survivors' Association, Inc., and was available online from March to August 2018. Responses were included from adult patients regarding their most recent ¹³¹I therapy received between 2011 and 2018 ("after 2011"). Responses to this survey were compared with those of a similar previous survey for ¹³¹I therapies received between 1997 and 2009 ("before 2009"). Results: Of the 2,136 responses, 1,111 met the inclusion criteria. A similar percentage (∼98%) of patients were given oral or written radiation safety instructions (RSIs) after 2011 and before 2009, with a shift away from nuclear medicine physicians providing instructions after 2011 (43%) in comparison with before 2009 (54%; P < 0.001). More patients were able to discuss and individualize the RSIs after 2011 (67%) than before 2009 (29%; P < 0.001). However, 2% of patients do not recall ever receiving RSIs after 2011. After 2011, more patients were treated as outpatients (87%) than before 2009 (66%; P < 0.001). For outpatients, more patients were discharged within 30 min after receiving ¹³¹I therapy after 2011 (78%) than before 2009 (72%; P = 0.002). The same percentage (0.6%) of patients traveled more than 2 h with at least 2 occupants in the vehicle within approximately 1 m of the patient after 2011 and before 2009. Immediately after therapy, a similar percentage of patients stayed in a nonprivate residence after 2011 (4%) and before 2009 (5%; P = 0.28). Of the 27 outpatients released within 30 min to nonprivate residences, 2 patients received 5.55-11.1 GBq (150-299 mCi) of ¹³¹I. Conclusion: This survey suggests that since publication of the Nuclear Regulatory Commission Regulatory Issue Summary 2011-01 on patient release after radioiodine therapy, there have been improvements in some radiation safety practices on release of outpatients, as well as improvements in patient compliance on travel and lodging.

Radioiodine Imaging for Differentiated Thyroid Cancer: Not All Radioiodine Images Are Performed Equally

Background: Radioiodine scanning may help risk stratify patients with differentiated thyroid carcinoma (DTC) during initial and subsequent restaging. To maximize the information obtained from radioiodine scanning, image quality and interpretation should be optimized. However, not all radioiodine scans are performed equally. This illustrated article reviews seven techniques that may significantly improve the information obtained from a radioiodine scan in patients with DTC, which in turn may alter management such as showing regional or distant metastases that were otherwise unknown and/or help classify whether a metastasis is radioiodine avid. Summary: The first of the techniques is spot imaging of anatomical areas of interest using a gamma camera with a parallel-hole collimator. Spot images typically provide superior spatial resolution and enhanced lesion detection compared with whole-body scans using the same equipment. The second technique is spot imaging of the thyroid bed and neck with a pin-hole collimator, further improving spatial resolution. Two other techniques, delayed image acquisition and longer acquisition time, may clarify the nature of indeterminate foci of uptake or areas with negative initial findings. Delayed image acquisition may increase tumor-to-background ratio and thus improves lesion detectability. Longer acquisition times also increase contrast resolution between lesions and background activity, again increasing the detectability of malignant lesions. The fifth technique, adjustment of image brightness/contrast on film or on the computer screen, may reveal previously unobserved subtle differences in counts. The sixth technique, focus-specific history, comprises additional patient information that is specific to a focus of radioiodine uptake and elicited by the nuclear medicine physician or technologist. The goal is to help determine if the focus represents a metastasis or an artifact, which in turn decreases false positives and increases specificity. The seventh technique, single-photon emission computed tomography/computed tomography, improves contrast resolution and helps localize foci of uptake to anatomical structures. Conclusions: Technique is important to maximize information obtained from radioiodine scans in patients with DTC. With the greater usage and understanding of these seven techniques, physicians will significantly improve the information obtained from a radioiodine scan in patients with DTC, which in turn may alter management and potentially outcomes.

Improved Survival After Multimodal Approach with 131I Treatment in Patients with Bone Metastases Secondary to Differentiated Thyroid Cancer

Background: The objective of this study was to evaluate the overall survival (OS) of radioiodine (¹³¹I) treatments alone or combined with non-¹³¹I treatments in patients with bone metastases (BM) of differentiated thyroid cancer (DTC). Methods: This was a retrospective study of patients who were evaluated between 2001 and 2018 at MedStar Washington Hospital Center and who had DTC, BM, and at least one ¹³¹I treatment after the diagnosis of BM. The OS was analyzed by Kaplan-Meier survival curves and was compared by log-rank test between two groups: patients who received ¹³¹I treatments alone and those who received treatments combining ¹³¹I with non-¹³¹I treatments (CombTx). Non-¹³¹I treatments include surgery, radiofrequency ablation, cryotherapy, arterial embolization, external beam radiation, Cyberknife, systemic targeted therapy, and anti-resorptive medication. Results: A total of 77 patients met the above criteria and were followed up to 41 years. Thirty percent (23/77) of patients received ¹³¹I treatment alone, and 70% (54/77) received CombTx. For ¹³¹I treatment alone, the median survival was 3.9 years, and the 1-, 2-, 3-, 5-, and 10-year OS rates were 86%, 81%, 61%, 35%, and 23%, respectively. For CombTx, the median survival was 7.7 years, and the 1-, 2-, 3-, 5-, and 10-year OS rates were 96%, 92%, 86%, 69%, and 30%, respectively. Patients who had undergone initial ¹³¹I therapy within six months post thyroidectomy demonstrated a better median survival after BM diagnosis than those whose initial ¹³¹I therapy was six months or more after thyroidectomy (6.5 vs. 0.5 years; p < 0.001). Patients who received external beam radiation therapy demonstrated a better median survival than those who did not (7.8 vs. 4.4 years; p = 0.016). Patients who received denosumab demonstrated a better median survival than those who did not (7.7 vs. 5.2 years; p = 0.03). Patients who were <55 years of age at the initial diagnosis of DTC or at the initial diagnosis of BM had a better median OS than those diagnosed at ≥55 years of age (both p = 0.01). In the multivariate analysis, only age at initial diagnosis of DTC and initial ¹³¹I therapy within six months post thyroidectomy, and multiple ¹³¹I treatments were independent prognostic factors. Conclusions: In patients with DTC with BM, ¹³¹I treatment in combination with one or more non-¹³¹I direct and systemic treatments was associated with a significant increase in OS compared with those patients who were treated by ¹³¹I treatment alone.

Controversies, Consensus, and Collaboration in the Use of 131I Therapy in Differentiated Thyroid Cancer: A Joint Statement from the American Thyroid Association, the European Association of Nuclear Medicine, the Society of Nuclear Medicine and Molecular Imaging, and the European Thyroid Association

BACKGROUND

Publication of the 2015 American Thyroid Association (ATA) management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer was met with disagreement by the extended nuclear medicine community with regard to some of the recommendations related to the diagnostic and therapeutic use of radioiodine (¹³¹I). Because of these concerns, the European Association of Nuclear Medicine and the Society of Nuclear Medicine and Molecular Imaging declined to endorse the ATA guidelines. As a result of these differences in opinion, patients and clinicians risk receiving conflicting advice with regard to several key thyroid cancer management issues.

SUMMARY

To address some of the differences in opinion and controversies associated with the therapeutic uses of ¹³¹I in differentiated thyroid cancer constructively, the ATA, the European Association of Nuclear Medicine, the Society of Nuclear Medicine and Molecular Imaging, and the European Thyroid Association each sent senior leadership and subject-matter experts to a two-day interactive meeting. The goals of this first meeting were to (i) formalize the dialogue and activities between the four societies; (ii) discuss indications for ¹³¹I adjuvant treatment; (iii) define the optimal prescribed activity of ¹³¹I for adjuvant treatment; and (iv) clarify the definition and classification of ¹³¹I-refractory thyroid cancer.

CONCLUSION

By fostering an open, productive, and evidence-based discussion, the Martinique meeting restored trust, confidence, and a sense of collegiality between individuals and organizations that are committed to optimal thyroid disease management. The result of this first meeting is a set of nine principles (The Martinique Principles) that (i) describe a commitment to proactive, purposeful, and inclusive interdisciplinary cooperation; (ii) define the goals of ¹³¹I therapy as remnant ablation, adjuvant treatment, or treatment of known disease; (iii) describe the importance of evaluating postoperative disease status and multiple other factors beyond clinicopathologic staging in ¹³¹I therapy decision making; (iv) recognize that the optimal administered activity of ¹³¹I adjuvant treatment cannot be definitely determined from the published literature; and (v) acknowledge that current definitions of ¹³¹I-refractory disease are suboptimal and do not represent definitive criteria to mandate whether ¹³¹I therapy should be recommended.

Conventional Radioiodine Therapy for Differentiated Thyroid Cancer

This article presents an overview of the use of radioactive iodine (131-I) in the treatment of patients with differentiated thyroid cancer. Topics reviewed include definitions; staging; the 2 principal methods for selection of 131-I dosage; the indications for ablation, adjuvant treatment, and treatment; the recommendations for the use of 131-I contained in the guidelines of the American Thyroid Association and the Society of Nuclear Medicine and Molecular Imaging; the dosage recommendations and selection of dosage approach for 131-I by these organizations; the use of recombinant human thyrotropin for radioiodine ablation, adjuvant therapy, or treatment; and the MedStar Washington Hospital Center approach.

Brain Metastases From Differentiated Thyroid Carcinoma: Prevalence, Current Therapies, and Outcomes

BACKGROUND AND OBJECTIVE

The brain is an unusual site for distant metastases of differentiated thyroid carcinoma (DTC). The aim of this study was to document the prevalence of brain metastases from DTC at our institutions and to analyze the current therapies and the outcomes of these patients.

METHODS

We performed a retrospective chart review of patients with DTC and secondary neoplasia of the brain.

RESULTS

From 2002 to 2016, 9514 cases of thyroid cancer were evaluated across our institutions and 24 patients met our inclusion criteria, corresponding to a prevalence of 0.3% of patients with DTC. Fourteen (58.3%) were female and 10 (41.7%) were male. Fifteen patients had papillary thyroid cancer (PTC) (62.5%). Brain metastases were diagnosed 0 to 37 years (mean ± SD, 10.6 ± 10.4 years) after the initial diagnosis of thyroid cancer. Patients undergoing surgery had a median survival time longer than those that did not undergo surgery (27.3 months vs 6.8 months; P = 0.15). Patients who underwent stereotactic radiosurgery (SRS) had a median survival time longer than those that did not receive SRS (52.5 months vs 6.7 months; P = 0.11). Twelve patients (50%) were treated with tyrosine kinase inhibitors (TKIs), and they had a better survival than those who have not used a TKI (median survival time, 27.2 months vs 4.7 months; P < 0.05).

CONCLUSION

The prevalence of brain metastases of DTC in our institutions was 0.3% over 15 years. The median survival time after diagnosis of brain metastases was 19 months. In our study population, the use of TKI improved the survival rates.

Detection at Public Facilities of 131I in Patients Treated for Differentiated Thyroid Cancer: Frequency, Sites, Management by Security Agents, and Physician Documentation Recommended for Patients

Patients treated with ¹³¹I may be identified at security checkpoints at various public facilities. The objective of this survey was to determine the frequency of detection, the spectrum of public facilities, the various methods of management of the situation by security agents, and the spectrum of physician documentation for patients regarding their ¹³¹I therapy. Methods: Data were tabulated from a Thyroid Cancer Survivors' Association, Inc., survey emailed to approximately 15,000 associates and available online from December 2013 to December 2014. Responses were tabulated from respondents who reported that they were 18 y old or older, had received at least 1 ¹³¹I treatment for differentiated thyroid cancer, and were responding regarding their last ¹³¹I treatment. Results: Of 621 respondents, 595 reported an attempt to pass through a public facility security checkpoint. Of these 595 patients, approximately 10% (57) were identified as being radioactive. The facility reported by 43 respondents was an airport for 35% (15), border crossing for 33% (14), government building for 19% (8), shopping mall for 7% (3), train station for 5% (2), and steel recycling plant for 2% (1). The security agent's management of the situation reported by 47 respondents included questioning for 81% (38), allowing them to proceed without a change in travel plans for 57% (27), requesting documentation of the therapy for 55% (26), rescanning for 55% (26), calling a member of the treating team for validation for 17% (8), "strip" searching for 4% (2), detaining such that a change in travel plans was required for 6% (3), and prohibiting continued travel for 4% (2). The period of detainment reported by these 47 respondents was less than 30 min for 57% (27), 30 to less than 60 min for 21% (10), 1 to less than 1.5 h for 15% (7), 1.5 to less than 2 h for 2% (1), 2-4 h for 0% (0), and greater than 4 h for 4% (2). Data regarding physician documentation are presented. Conclusion: The detection of radioactivity at a variety of security checkpoints at public facilities after¹³¹I therapy occurred in approximately 10% of respondents. Travel inconvenience is not infrequent and may require alteration of travel plans. Physicians should take steps to ensure that patients not only have appropriate documentation of their ¹³¹I therapy with them but also have instructions regarding how security agents may verify their ¹³¹I therapy.

Use of 99mTc-sestamibi SPECT/CT when conventional imaging studies are negative for localizing suspected recurrence in differentiated thyroid cancer: a method and a lesson for clinical management

PURPOSE

The detection of recurrent disease in differentiated thyroid cancer (DTC) patients with elevated or rising serum thyroglobulin (Tg) levels and multiple negative conventional imaging studies can be challenging, especially when ¹⁸F-FDG PET/CT scan is also negative. We report a patient and review the literature on the diagnostic use of ^99mTc-sestamibi scans to identify the source of elevated or rising Tg in patients with negative conventional imaging including negative ¹⁸F-FDG PET/CT scans.

PATIENT AND METHODS

A 73-year-old woman was referred for widely-invasive metastatic follicular thyroid cancer with bone metastasis to her left mandible. She had a total thyroidectomy, left mandibular resection, and ¹³¹I therapy of 145 mCi (5.4 GBq) and her subsequent unstimulated serum Tg level was 29 ng/ml (TgAb negative). At six months' follow-up, her stimulated Tg was 527 ng/ml (TSH 188 mIU/L, TgAb negative). All imaging studies performed within the prior 12 months were reported as negative for recurrence or metastasis; this included neck ultrasound, diagnostic radioiodine scan, chest CT and, ¹⁸F-FDG PET/CT. The patient was injected with 24.6 mCi (910 MBq) of ^99mTc-sestamibi intravenously, and whole-body and SPECT/CT images were acquired.

RESULTS

The ^99mTc-sestamibi whole-body posterior image demonstrated abnormal focal uptake in the right posterior calvarium and corresponded to an occipital lytic bone lesion on the SPECT/CT. The patient underwent surgical resection of the skull metastasis, and pathology confirmed metastatic follicular thyroid cancer. Five months post-surgery, the suppressed Tg was markedly reduced and remained stable at ~3.2 ng/ml. With the knowledge of the DTC recurrence location, the two sets of ¹⁸F-FDG images were re-evaluated. The more thorough and targeted interpretation underscored the importance of structured image reporting. The current literature on the utility of ^99mTc-sestamibi scans when radioiodine, ¹⁸F-FDG PET/CT, and other imaging studies are negative is sparse and inconsistent.

CONCLUSIONS

^99mTc-sestamibi may have a role in thyroid cancer localization when physical exam, neck ultrasound, radioiodine scan, chest/abdomen CT, and ¹⁸F-FDG PET/CT does not identify the source of elevated Tg levels in DTC.

Radioiodine Refractory Differentiated Thyroid Cancer: Time to Update the Classifications

BACKGROUND

The management of aggressive and progressing metastatic differentiated thyroid cancer (DTC) is very difficult, and the determination as to when such patients are refractory to ¹³¹I therapy (e.g., radioiodine refractory) is problematic and controversial.

OBJECTIVE

The objective of this review is to discuss (i) the present major classifications of radioiodine refractory disease in DTC, (ii) factors that should be considered before designating a patient's DTC as radioiodine refractory, (iii) potential approaches and caveats to help manage and minimize a patient's exclusion from an ¹³¹I therapy that may have potential benefit in patients with aggressive and progressing metastatic DTC, (iv) next steps for revision of the classifications of radioiodine refractory DTC, and (v) areas for future research.

SUMMARY

To date, the classifications of radioiodine refractory DTC, although very useful, are not sacrosanct especially in the context of individualized patient management, and merely because a patient meets one or more of the various classifications, one should not consider by definition, fiat, or de facto that that a patient's DTC is radioiodine refractory. Rather, each patient should be individually managed with a good understanding of the limitations of the various classifications and potential approaches to help manage that patient. With awareness of the suggestions and caveats discussed herein and with assessment of the many other factors that affect the patient's specific clinical situation, the managing physician can deliver appropriate individualized patient care. A multi-organizational committee should be established as a standing committee to supervise and assist in the update of the classifications of radioiodine refractory DTC, including discussions of their limitations.

CONCLUSION

Classifications to help determine radioiodine refractory disease will continue to evolve as (i) more studies are published, (ii) managing physicians better understand the limitations and confounding factors of present classifications, and (iii) new agents either increase or reestablish ¹³¹I uptake.

Poor patient compliance with instructions for continuous sialogogues after 131 I therapy

OBJECTIVES

To analyze the role of patient compliance as a factor in evaluating the effectiveness of continuous sialogogues to prevent salivary side effects from ¹³¹ I therapy in differentiated thyroid cancer patients.

METHODS

Differentiated thyroid cancer patients who were clinically scheduled for an ¹³¹ I therapy at MedStar Washington Hospital Center between 2012 and 2013 were given instructions for continuous sialogogues per standard clinical protocol. The prospective survey was given at multiple time points.

RESULTS

Ninety-nine patients consented to participate of whom 94 participants had complete data. The mean prescribed ¹³¹ I activity was 121 ± 50 mCi (4.5 ± 1.9 GBq), range 27.5-288 mCi (1.0-10.7 GBq ). Overall, only 10% (9/94) of patients were compliant with continuous sialogogues. Even though all patients took sialogogues on the first day of post-therapy, 17% of participants did not continuously take sialogogues during the first day, 60% during the first night, and 72% on the second day despite rigorous instructions to continue for two days.

CONCLUSION

Despite repetitive instructions to use sialogogues continuously, most patients (90%) were not compliant. In future studies, strict monitoring and evaluation of patient compliance will be crucial when assessing the effect of continuous versus intermittent or delayed initiation of sialogogues.

Eliminating the Age Cutoff in Staging of Differentiated Thyroid Cancer: The Safest Road?

BACKGROUND

Unlike virtually all other cancer types, thyroid cancer is unique in that patient age is a key component in its staging. Pathologists and clinicians worldwide have accepted an age cutoff of 45 years for staging; in 2018, this advances to age 55 years in the eighth edition of the American Joint Commission on Cancer staging system.

EVIDENCE ACQUISITION

Clinical and basic research studies, reviews, and previous editions of consensus statements regarding thyroid cancer staging were reviewed, with particular focus on the influence of age in thyroid cancer prognosis.

PURPOSE

This perspective briefly reviews the basis for this practice and challenges it as no more appropriate than for other malignancies.

EVIDENCE SYNTHESIS

The majority of findings report an association of age with thyroid cancer survival but do not support a specific age cutoff; rather, they suggest that outcome is affected by age as a continuous variable. Conceivably, other factors interact with age on a continuous basis over time, affecting prognosis. When identified, these factors could alter our current concept of the importance of an age cutoff in staging.

CONCLUSIONS

Among all cancers, age has an important role in only thyroid cancer staging. The consideration of age as a continuous variable and the search for age-associated prognostic variables could elucidate a more accurate staging system.

Radioiodine refractory differentiated thyroid cancer

Differentiated thyroid cancer (DTC) is usually curable with surgery, radioactive iodine (RAI), and thyroid-stimulating hormone (TSH) suppression. However, local recurrence and/or distant metastases occur in approximately 15% of cases during follow-up, and nearly two-thirds of these patients will become RAI-refractory (RR-DTC) with a poor prognosis. This review focuses on the most challenging and rapidly evolving aspects of RR-DTC, and we discuss the considerable improvement in more accurately defining RR-DTC, more effective therapeutic strategies, and describe the diagnosis, pathogenesis, and future prospects of RR-DTC. Along with the detection of serum thyroglobulin and anatomic imaging modalities, such as ultrasound and computer tomography, radionuclide molecular imaging plays a vital role in the evaluation of RR-DTC. In addition, continual progress has been made in the management of RR-DTC, including watchful waiting under appropriate TSH suppression, local treatment approaches, and systemic therapies (molecular targeted therapy, redifferentiation therapy, gene therapy, and cancer immunotherapy). These all hold promise to change the natural history of RR-DTC.

The BEIR VII Estimates of Low-Dose Radiation Health Risks Are Based on Faulty Assumptions and Data Analyses: A Call for Reassessment

The 2006 National Academy of Sciences Biologic Effects of Ionizing Radiation (BEIR) VII report is a well-recognized and frequently cited source on the legitimacy of the linear no-threshold (LNT) model-a model entailing a linear and causal relationship between ionizing radiation and human cancer risk. Linearity means that all radiation causes cancer and explicitly excludes a threshold below which radiogenic cancer risk disappears. However, the BEIR VII committee has erred in the interpretation of its selected literature; specifically, the in vitro data quoted fail to support LNT. Moreover, in vitro data cannot be considered as definitive proof of cancer development in intact organisms. This review is presented to stimulate a critical reevaluation by a BEIR VIII committee to reassess the validity, and use, of LNT and its derived policies.

Selected Radiation Safety Aspects Including Transportation and Lodging After Outpatient 131I Therapy for Differentiated Thyroid Cancer

BACKGROUND

Whether radioactive iodine (¹³¹I) treatments for differentiated thyroid cancer should be performed as an outpatient or inpatient remains controversial. The objective of this study was to survey selected aspects of radiation safety of patients treated with ¹³¹I for differentiated thyroid cancer as an outpatient.

METHODS

An e-mail invitation was sent to over 15,000 members of ThyCa: Thyroid Cancer Survivors' Association, Inc. to complete a web-based survey on selected aspects of radiation safety regarding their last outpatient ¹³¹I treatment.

RESULTS

A total of 1549 patients completed the survey. Forty-five percent (699/1541) of the respondents reported no discussion on the choice of an inpatient or outpatient treatment. Moreover, 5% (79/1541) of the respondents reported that their insurance company made the decision. Survey respondents recalled receiving oral and written radiation safety instructions 97% (1459/1504) and 93% (1351/1447) of the time, respectively. Nuclear medicine physicians delivered oral and written instructions to 54% (807/1504) and 41% (602/1462) of the respondents, respectively. Eighty-eight percent (1208/1370) of the respondents were discharged within 1 hour after receiving their ¹³¹I treatment, and 97% (1334/1373) traveled in their own car after being released from the treating facility. Immediately post-therapy, 94% (1398/1488) of the respondents stayed at their own home or a relative's home, while 5% (76/1488) resided in a public lodging. The specific recommendations received by patients about radiation precautions varied widely among the respondents. Ninety-nine percent (1451/1467) of the respondents believed they were compliant with the instructions.

CONCLUSION

This is the largest, patient-based survey published regarding selected radiation safety aspects of outpatient ¹³¹I treatment. This survey suggests several concerns about radiation safety, such as the decision process regarding inpatient versus outpatient treatment, instructions about radiation safety, transportation, and lodging after radioiodine therapy. These concerns warrant further discussion, guidelines, and/or policies.

Amifostine does not protect thyroid cancer cells in DNA damaging in vitro models

BACKGROUND

Amifostine is a potent scavenger of reactive oxygen species that is used for the salivary gland protection during therapy with radioactive iodine for thyroid cancer. There are no data on the potential effect of amifostine on thyroid cancer cells.

METHODS

We investigated the effects of the active form of amifostine (WR-1065) on the response of thyroid cancer cells to treatment with DNA-damaging agents. WR-1065 was examined in human thyroid cancer cell lines (FTC133, TPC1, BCPAP and C643) and embryonic fibroblast cells NIH3T3. DNA damage was induced by exposure to H₂O₂ (0.1 mM), by treatment with the radiomimetic neocarzinostatin (NCS 250 ng/mL) and by γ-radiation (6 Gy). DNA damage, cell viability and apoptosis were examined.

RESULTS

We demonstrated the selective action of WR-1065 (0.1 mM), which prevented oxidative stress-induced DNA damage in fibroblasts, but did not protect thyroid cancer cells from DNA damage and apoptosis documented by caspase-3 and PARP cleavage after exposure to H₂O₂, NCS and γ-radiation. Prolonged exposure to WR-1065 (0.1 mM for 24 h) was toxic for thyroid cancer cells; this treatment decreased the number of viable cells by 8% in C643 cells, 47% in TPC cells, 92% in BCPAP cells and 82% in FTC 133 cells. The cytotoxic effects of WR-1065 were not associated with induction of apoptosis.

CONCLUSIONS

Our data show that amifostine has no protective effect on thyroid cancer cells against DNA-damaging agents in vitro and suggest that amifostine will not attenuate the efficacy of radioiodine treatment in patients with thyroid cancer.

Selected Controversies of Radioiodine Imaging and Therapy in Differentiated Thyroid Cancer

This article discusses the more controversial areas of the management of differentiated thyroid cancer, namely, the utility of pretherapy staging radioiodine scans; the prescribed activity for iodine-131 remnant ablation, adjuvant treatment, and distant metastases; preparation with thyroid hormone withdrawal versus recombinant human thyroid-stimulating hormone; and the classification of radioiodine refractory differentiated thyroid cancer. The author reviews various aspects of the controversies, such as the recommendations of the 2015 guidelines of the American Thyroid Association, arguments for and against the various controversies, and selected references.

Number of Foci of Functioning Thyroid Tissue Remaining after Thyroidectomy for Differentiated Thyroid Cancer: Institutional Experience

Radioiodine imaging of the neck with a pinhole collimator (PinC) is frequently performed in differentiated thyroid cancer (DTC) patients for visualizing individual, and a total number of foci (NOF) of functioning residual thyroid tissue (FRTT) within the thyroid bed in postthyroidectomy patients. The objective of this study was to determine our experience regarding the NOF of FRTT visualized on pretherapy radioiodine PinC images. We performed a retrospective review of radioiodine PinC images of the neck of patients with very low-risk DTC and who had thyroidectomy performed by selected surgeons at MedStar Washington Hospital Center. For each patient's image, the NOF of FRTT was determined by two blind readers. Statistical analysis was performed. One hundred and twenty-six patients met the criteria. Surgeon (S1, S2, S3, and S4) performed 17, 10, 86, and 13 thyroidectomies, respectively. The analysis (mean, range, and standard deviation) of NOF of FRTT was: S1: (2.2, 0-5, 1.3); S2: (1.6, 1–3, 0.8); S3: (2.6, 0–7, 1.5); S4: (3.3, 1–5, 1.3). The percentages of < 2, ≤3, ≤4, and <5 foci remaining were 4.9%, 21.5%, 77.0%, and 91.3%, respectively. For the selected surgeons, the NOF of FRTT in the thyroid bed or neck in postthyroidectomy patients never exceeded 7, rarely exceeded 5 (2.4%), and infrequently exceeded 4 (8.7%). Based on these data, our thresholds of the NOF for which we perform further workup for possible locoregional disease are ≥5. Each facility is encouraged to establish their own criteria for their facility and preferably for each of their surgeons.

Recombinant Human Thyroid-Stimulating Hormone Versus Thyroid Hormone Withdrawal in 124I PET/CT-Based Dosimetry for 131I Therapy of Metastatic Differentiated Thyroid Cancer

Patients with metastatic differentiated thyroid cancer (DTC) may be prepared using either thyroid-stimulating hormone withdrawal (THW) or recombinant human thyroid-stimulating hormone (rhTSH) injections before ¹³¹I administration for treatment. The objective of this study was to compare the absorbed dose to the critical organs and tumors determined by ¹²⁴I PET/CT-based dosimetry for ¹³¹I therapy of metastatic DTC when the same patient was prepared with and imaged after both THW and rhTSH injections. Methods: Four DTC patients at MedStar Washington Hospital Center were first prepared using the rhTSH method and imaged by ¹²⁴I PET/CT at 2, 24, 48, 72, and 96 h after administration of approximately 30-63 MBq of ¹²⁴I. After 5-8 wk, the same patients were prepared using the THW method and imaged as before. The ¹²⁴I PET/CT images acquired as part of a prospective study were used to perform retrospective dosimetric calculations for ¹³¹I therapy for the normal organs with the dosimetry package 3D-RD. The absorbed doses from ¹³¹I for the lungs, liver, heart, kidneys, and bone marrow were obtained for each study (rhTSH and THW). Twenty-two lesions in 3 patients were identified. The contours were drawn on each PET image of each study. Time-integrated activity coefficients were calculated and used as input in OLINDA/EXM sphere dose calculator to obtain the absorbed dose to tumors. Results: The THW-to-rhTSH organ absorbed dose ratio averaged over 5 organs for the first 3 patients was 1.5, 2.5, and 0.64, respectively, and averaged over 3 organs for the fourth patient was 1.1. The absorbed dose per unit administered activity to the bone marrow was 0.13, 0.086, 0.33, and 0.068 mGy/MBq after rhTSH and 0.11, 0.14, 0.22, and 0.080 mGy/MBq after THW for each patient, respectively. With the exception of 3 lesions of 1 patient, the absorbed dose per unit administered activity of ¹³¹I was higher in the THW study than in the rhTSH study. The ratio of the average tumor absorbed dose after stimulation by THW compared with stimulation by rhTSH injections was 3.9, 27, and 1.4 for patient 1, patient 2, and patient 3, respectively. The ratio of mean tumor to bone marrow absorbed dose per unit administered activity of ¹³¹I, after THW and rhTSH, was 232 and 62 (patient 1), 12 and 0.78 (patient 2), and 22 and 11 (patient 3), respectively. Conclusion: The results suggest a high patient variability in the overall absorbed dose to the normal organs per MBq of ¹³¹I administered, between the 2 TSH stimulation methods. The tumor-to-dose-limiting-organ (bone marrow) absorbed dose ratio, that is, the therapeutic index, was higher in the THW-aided than rhTSH-aided administrations. Additional comparison for tumor and normal organ absorbed dose in patients prepared using both methods is needed before definitive conclusions may be drawn regarding rhTSH versus THW patient preparation methods for ¹³¹I therapy of metastatic DTC.

Effects of Dosimetrically Guided I-131 Therapy on Hematopoiesis in Patients With Differentiated Thyroid Cancer

OBJECTIVE

The objective of the study was to evaluate the effects of dosimetrically guided I-131 prescribed activities on hematopoiesis reflected by changes in complete blood counts (CBCs).

DESIGN

This was a retrospective analysis.

SETTING

The study was conducted at an academic center.

PATIENTS

A total of 152 patients with differentiated thyroid cancer who had 185 dosimetrically guided I-131 treatments.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

Repeated-measure ANOVA was used for the analysis of the differences in the averages of CBCs that were documented at baseline and 1, 6, 12, 24–36, and 48–60 months after I-131 treatment.

RESULTS

All parameters decreased to their respective nadir at 1 month and then gradually returned toward baseline values. White blood cells (WBCs) and platelets (PLTs) were the most significantly affected cells. At 1 month, the decrease was 29.6% (P < .0001) for WBCs and 25% (P < .0001) for PLTs, whereas at 12 months, the decrease was 15.5% (P < .0001) and 13% (P < .0001), respectively. Lymphocytes appeared to be more susceptible to I-131 than neutrophils (ANCs). The decreases were small in absolute numbers for red blood cells, hematocrit and hemoglobin not surpassing 10%. Multivariate analysis demonstrated that the ratio of administered prescribed activity-to-maximum tolerated activity was associated with the decreases in WBCs (P = .0038), ANCs (P = .0063), and red blood cells (P = .029), with borderline significance for PLTs (P = .057) and hemoglobin (P = .057).

CONCLUSIONS

Dosimetrically guided I-131 resulted in statistically significant decreases in CBC parameters, which were more prominent in WBCs and PLTs. Lymphocytes were more severely affected than ANCs, whereas all parameters reached a nadir at 1 month and then gradually returned toward baseline values over the 5-year follow-up of our study.

Metformin Attenuates 131I-Induced Decrease in Peripheral Blood Cells in Patients with Differentiated Thyroid Cancer

BACKGROUND

131I treatment (tx) of differentiated thyroid cancer (DTC) is associated with hematopoietic toxicity. It was hypothesized that metformin could have radioprotective effects on bone-marrow function. The objective was to determine whether metformin prevents 131I-induced changes in complete blood counts (CBC) in patients with DTC.

METHODS

A retrospective analysis was performed of CBC values in DTC patients who were (40 patients: metformin group) or were not taking metformin (39 patients: control group) at the time of administration of 131I. Repeated measures analysis of variance was used for the analysis of the differences in the averages of CBC that were documented at baseline and at 1, 6, and 12 months post 131I tx.

RESULTS

The groups were comparable in terms of age, sex, stage of DTC, 131I dose administered, and baseline CBC values. In the control group, the decrease in white blood cells (WBC) was 35.8% (p < 0.0001) at one month, 21.8% (p < 0.0001) at six months, and 19.4% (p < 0.0001) at 12 months. In the metformin group, the decrease in WBC was 17.1% (p < 0.0001) at one month, and 8.6% at six months (p = 0.01), while at 12 months WBC had returned to baseline values (p = 0.9). Differences between the two groups were highly statistically significant at all time points (p < 0.0001, p = 0.0027, and p < 0.0001, respectively). Lymphocytes were more sensitive to 131I, but metformin's radioprotective properties were more prominent in neutrophils. At 12 months, the decrease in platelets in the control group was 15.5% (p < 0.0001) versus 5.6% (p = 0.056) in the metformin group, while at one and six months the reductions in the two groups were comparable. No statistically significant differences were observed between the two groups in the change from baseline values for hemoglobin.

CONCLUSIONS

Metformin attenuated the 131I-induced decrease in CBC parameters, and its radioprotective properties were more prominent in WBC. Patients who were taking metformin during 131I tx also experienced a faster recovery in their blood counts, when compared to the control group. Further study is warranted in order to examine if the radioprotective properties of metformin observed in the current study for 131I tx can also apply to other forms of therapeutic chemo- and radiotherapy.

Validation of a Simple Thyroid Cancer Dosimetry Model Based on the Fractional Whole-Body Retention at 48 Hours Post-Administration of (131)I

BACKGROUND

Standard dosimetric methods to determine the maximum tolerated activity (MTA) of (131)I for the treatment of metastatic, well-differentiated thyroid cancer (DTC) are time-consuming and require complex analysis. As a result, reliable, accurate, and simplified methods are desirable. The objective of this study was to evaluate the validity of a simple regression dosimetry model.

METHOD

Previously, the authors reported a bi-exponential model for estimating the MTA of (131)I for the treatment of metastatic DTC based on a limit of 2 Gy to the blood. This model uses the patient's body surface area (BSA) along with the fractional whole-body retention (WBR) at 48 hours following oral administration of a diagnostic dosage of (131)I. A bi-exponential regression model was developed between the MTA normalized to the patient's BSA and the percent retention value at the 48-hour time point (R): MTA (GBq)/BSA (m(2)) = (13.91 · e(-0.0387R) + 42.33 · e(-0.8522R)). In this study, the same model was applied to a different set of adult patients referred for dosimetry and possible (131)I treatment of DTC under conditions of thyroid hormone withdrawal or recombinant human thyrotropin (rhTSH) stimulation. All patients (n = 170; 96 female) referred to the authors' clinic for dosimetry and possible (131)I treatment for metastatic DTC during the collection period were included in this study, apart from those undergoing renal dialysis. The MTA predicted (MTAp) using the model described above was compared to the measured MTA (MTAm), with statistical analysis performed using ProStat v4.5.

RESULTS

In this group, the MTAm ranged from 2.3 to 41.1 GBq. The linear correlation between the MTAp and MTAm was excellent (r = 0.96), with an average deviation of only ± 1.2%. However, to avoid overdosing a patient on the basis of the MTAp, a weighting factor (<1.0) should be applied (e.g., using a value of 0.7 would result in only one patient receiving a prescribed activity of (131)I that exceeded the MTAm [<3%]).

CONCLUSIONS

The % 48-hour WBR as determined by the bi-exponential function noted herein with reasonable restrictions has been validated as a reliable simplified dosimetry model.

Spinal metastases due to thyroid carcinoma: an analysis of 202 patients

BACKGROUND

Spinal metastases (SMs) due to thyroid cancer (TC) are associated with significantly reduced quality of life. The goal of this study is to analyze the clinical manifestations, presentation, and treatments of TC SMs, and to describe specific features of SMs associated with different TC types.

PATIENTS AND METHODS

A retrospective analysis of 202 TC SM patients treated at Medstar Washington Hospital Center (37) and collected from the literature (165) was performed.

RESULTS

The mean age of patients with SMs was 56.9±14.7 years, and the female-to-male ratio was 2.1:1. Of all patients, 29% (28% of follicular thyroid cancer [FTC] and 37% of papillary thyroid cancer [PTC]) had SMs only. Twenty-nine percent of all patients and 54% of patients with single-site SMs had neither bone non-SMs nor solid organ metastases at the time of presentation. Thirty-five percent of patients had SMs as an initial presentation of TC. TC patients presenting with SMs had a lower rate of other bone and visceral involvement compared with patients whose SMs were diagnosed at the time of thyroid surgery or during follow-up (p<0.05). SMs were more often the initial manifestation of FTC (41% vs. 24%), while PTC SMs were more commonly diagnosed after TC diagnosis (76% vs. 59%; p<0.05). PTC SMs were more frequently diagnosed as synchronous (63% vs. 36% in FTC) versus FTC SMs that developed as metachronous metastases (64% vs. 37% in PTC; p<0.01). All FTC SMs developed within 82 (0-372) months and all PTC SMs within 35 (0-144) months (p<0.01). In FTC SMs as TC manifestation, solid organ metastases involvement was less common than in FTC SMs that were found after TC diagnosis (34% vs. 67%; p<0.01); multisite FTC SMs compared to solitary FTC SMs were associated with the development of other bone nonspinal metastases (82% vs. 30%; p<0.01) and solitary organ metastases (65% vs. 41%; p<0.01). These correlations were not observed in PTC SMs. FTC patients often had neural structure compression (myelopathy/radiculopathy; 72% vs. 36% in PTC), while PTC patients frequently were asymptomatic (38% vs. 5% in FTC; p<0.01). FTC SMs more commonly were (131)I-avid (p<0.01). FTC patients required surgery more frequently (72% vs. 55% in PTC; p<0.05).

CONCLUSIONS

Our study reveals that a significant part of TC SMs patients have solitary spinal involvement at the time of presentation and may be considered for aggressive treatment with the intention to improve quality of life and survival. FTC SMs and PTC SMs appear to have distinct presentations, behavior, and treatment modalities, and should be categorized separately for treatment and follow-up planning.

Current treatment modalities for spinal metastases secondary to thyroid carcinoma

BACKGROUND

The spine is the most common site of bone metastases due to thyroid cancer, which develop in more than 3% of patients with well-differentiated thyroid cancer. Nearly half of patients with bone metastases from thyroid cancer develop vertebral metastases. Spinal metastases are associated with significantly reduced quality of life due to pain, neurological deficit, and increased mortality.

SUMMARY

Treatment options for patients with thyroid spinal metastases include radioiodine therapy, pharmacologic therapy, and surgical treatments, with recent advances in radiosurgery and minimally invasive spinal surgery as well. Therapeutic interventions require a multidisciplinary approach and aim to control pain, preserve or improve neurologic function, optimize local tumor control, and improve quality of life. We have proposed a three-tiered approach to the management and practical algorithms for patients with spinal metastases from thyroid carcinoma.

CONCLUSIONS

The introduction of novel and improved techniques for the treatment of spinal metastases has created the opportunity to significantly improve control of metastatic tumor growth and the quality of life for the patients with spinal metastases from thyroid cancer. In order for these options to be effectively used, a multidisciplinary approach must be applied in the management of the patients with thyroid spinal metastases.

Do negative 124I pretherapy positron emission tomography scans in patients with elevated serum thyroglobulin levels predict negative 131I posttherapy scans?

BACKGROUND

The management of patients with differentiated thyroid cancer (DTC) who have elevated serum thyroglobulin (Tg) levels and negative (131)I or (123)I scans is problematic, and the decision regarding whether or not to administer (131)I therapy (a "blind" therapy) is also problematic. While (124)I positron emission tomography (PET) imaging has been shown to detect more foci of residual thyroid tissue and/or metastases secondary to DTC than planar (131)I images, the utility of a negative (124)I PET scan in deciding whether or not to consider performing blind (131)I therapy is unknown. The objective of this study was to determine whether a negative (124)I pretherapy PET scan in patients with elevated serum Tg levels and negative (131)I or (123)I scans predicts a negative (131)I posttherapy scan.

METHODS

Several prospective studies have been performed to compare the radiopharmacokinetics of (124)I PET versus (131)I planar imaging in patients who 1) had histologically proven DTC, 2) were suspected to have metastatic DTC (e.g., elevated Tg, positive recent fine-needle aspiration cytology, suspicious enlarging mass), and 3) had (131)I planar and (124)I PET imaging performed. Using these criteria, we retrospectively identified patients who had an elevated Tg, a negative diagnostic (131)I/(123)I scan, a negative diagnostic (124)I PET scan, therapy with (131)I, a post-therapy (131)I scan, and a prior (131)I therapy with a subsequent positive post-(131)I therapy scan. For each scan, two readers categorized every focus of (131)I and (124)I uptake as positive for thyroid tissue/metastases or physiological.

RESULTS

Twelve patients met the above criteria. Ten of these 12 patients (83%) had positive foci on (131)I posttherapy scan.

CONCLUSION

In our selected patient population, (131)I posttherapy scans are frequently positive in patients with elevated serum Tg levels, a negative diagnostic (131)I or (123)I scan, and a negative (124)I PET scan. Thus, for a patient with elevated serum Tg level, negative diagnostic (131)I planar scan, and a prior post-(131)I therapy scan that was positive, a negative (124)I PET scan will have a low predictive value for a negative post-(131)I therapy scan and should not be used to exclude the option of blind (131)I therapy.

Potential use of recombinant human thyrotropin in the treatment of distant metastases in patients with differentiated thyroid cancer

OBJECTIVE

In order to effectively treat differentiated thyroid cancer (DTC) with radioiodine (RAI) it is necessary to raise serum TSH levels either endogenously by thyroid hormone withdrawal (THW) or exogenously by administration of recombinant human TSH (rhTSH). The goal of this review is to present current data on the relative efficacy and side effects profile of rhTSH-aided versus THW-aided RAI therapy for the treatment of patients with distant metastases of DTC.

METHODS

We have searched the PubMed database for articles including the keywords "rhTSH", "thyroid cancer", and "distant metastases" published between January 1, 1996 and January 7, 2012. As references, we used clinical case series, case reports, review articles, and practical guidelines.

RESULTS

Exogenous stimulation of TSH is associated with better quality of life because it obviates signs and symptoms of hypothyroidism resulting from endogenous TSH stimulation. The rate of neurological complications after rhTSH and THW-aided RAI therapy for brain and spine metastases is similar. The rate of leukopenia, thrombocytopenia, xerostomia, and pulmonary fibrosis is similar after preparation for RAI treatment with rhTSH and THW. There is currently a controversy regarding RAI uptake in metastatic lesions after preparation with rhTSH versus THW, with some studies suggesting equal and some superior uptake after preparation with THW. Analysis of available retrospective studies comparing survival rates, progression free survival, and biochemical and structural response to a dosimetrically-determined dose of RAI shows similar efficacy after preparation for therapy with rhTSH and THW.

CONCLUSION

The rhTSH stimulation is not presently approved by the FDA as a method of preparation for adjunctive therapy with RAI in patients with metastatic DTC. Data on rhTSH compassionate use suggest that rhTSH stimulation is as equally effective as THW as a method of preparation for dosimetry-based RAI treatment in patients with RAI-avid metastatic DTC.

Radioiodine treatment of metastatic thyroid cancer: relative efficacy and side effect profile of preparation by thyroid hormone withdrawal versus recombinant human thyrotropin

BACKGROUND

To effectively treat differentiated thyroid cancer (DTC) with radioiodine (RAI) it is necessary to raise serum thyrotropin (TSH) levels either endogenously by thyroid hormone withdrawal (THW) or exogenously by administration of recombinant human TSH (rhTSH). The aim of our study was to compare the relative efficacy and side effect profile of rhTSH versus THW preparation for RAI therapy of metastatic DTC.

METHODS

Fifty-six patients (31 women and 25 men) with RAI-avid distant metastases of DTC treated with either rhTSH-aided (n=15) or THW-aided RAI (n=41) and followed for 72±36.2 months were retrospectively analyzed. The groups were comparable in regard to mean size of target lesions (rhTSH vs. THW 6.4 vs. 4.8 cm, p=0.41), mean baseline thyroglobulin level (6995 vs. 5544 ng/mL, p=0.83), distribution of micronodular and macronodular pulmonary metastases (67% vs. 63%, p=0.54, 13% vs. 15% p=0.64, respectively), osseous (53% vs. 29%, p=0.09), brain (0% vs. 2%, p=0.73), and liver/kidney metastases (13% vs. 2%, p=0.61). Patients in the rhTSH group were older (rhTSH vs. THW mean 62 vs. 49 years, p=0.01), and received lower cumulative RAI dose (256 vs. 416 mCi, p=0.03), which was more frequently based on dosimetric calculations (80% vs. 46%, p=0.024). Responses to treatment were based on RECIST 1.1 criteria.

RESULTS

Adjusted by age rates of complete response (CR), stable disease (SD), progressive disease (PD), and progression free survival (PFS) were not different between the groups (rhTSH vs. THW CR hazard ratio [HR] 0.97, 95% CI 0.08-11.42, p=0.982; SD HR 3.22, 95% CI 0.79-13.18, p=0.104, PD HR 0.26, 95% CI 0.52-1.26, p=0.094; PFS HR 0.41, 95% CI 0.14-1.23, p=0.112). The only independent risk factor for nonresponding to treatment and presentation with PD was age (HR 1.06, 95% CI 1.02-1.11, p=0.008). Age was also an independent factor affecting PFS (HR 1.04 for each year, 95% CI 1.02-1.07, p=0.001). Rates of leukopenia, thrombocytopenia, xerostomia, and restrictive pulmonary disease after RAI were not significantly different (rhTSH vs. THW 30% vs. 28%, p=0.61, 10% vs. 0%, p=0.37, 0% vs. 12%, p=0.20, 0% vs. 2%, p=0.73, respectively).

CONCLUSIONS

Patients with metastatic DTC prepared with rhTSH achieve comparable benefit of RAI therapy as those treated after THW.

Efficacy of dosimetric versus empiric prescribed activity of 131I for therapy of differentiated thyroid cancer

BACKGROUND

The optimal management of high-risk patients with differentiated thyroid cancer (DTC) consists of thyroidectomy followed by radioiodine ((131)I) therapy. The prescribed activity of (131)I can be determined using two approaches: 1) empiric prescribed activity of (131)I (E-Rx); and 2) dosimetry-based prescribed activity of (131)I (D-Rx).

AIM

The aim of the study was to compare the relative treatment efficacy and side effects of D-Rx vs. E-Rx.

METHODS

A retrospective analysis was performed of patients with distant metastases and/or locoregionally advanced radioiodine-avid DTC who were treated with either D-Rx or E-Rx. Response to treatment was based on RECIST (Response Evaluation Criteria in Solid Tumors) 1.1 criteria.

RESULTS

The study group consisted of 87 patients followed for 51 ± 35 months, of whom 43 were treated with D-Rx and 44 with E-Rx. Multivariate analysis, controlling for age, gender, and status of metastases revealed that the D-Rx group tended to be 70% less likely to progress (odds ratio, 0.29; 95% confidence interval, 0.087-1.02; P = 0.052) and more likely to obtain complete response (CR) compared to the E-Rx group (odds ratio, 8.2; 95% confidence interval, 1.2-53.5; P = 0.029). There was an association in the D-Rx group between the observed CR and percentage of maximum tolerable activity given as a first treatment of (131)I (P = 0.030). The advantage of D-Rx was specifically apparent in the locoregionally advanced group because CR was significantly higher in D-Rx vs. E-Rx in this group of patients (35.7 vs. 3.3%; P = 0.009). The rates of partial response, stable disease, and progression-free survival, as well as the frequency of side effects, were not significantly different between the two groups.

CONCLUSION

Higher efficacy of D-Rx with a similar safety profile compared to E-Rx supports the rationale for employing individually prescribed activity in high-risk patients with DTC.

Levothyroxine treatment in pregnancy: indications, efficacy, and therapeutic regimen

The prevalence of overt and subclinical hypothyroidism during pregnancy is estimated to be 0.3–0.5% and 2–3%, respectively. Thyroid autoantibodies are found in 5–18% of women in the childbearing age. The aim of this review is to underscore the clinical significance of these findings on the health of both the mother and her offspring. Methods of evaluation of thyroid function tests (TFTs) during pregnancy are described as are the threshold values for the diagnosis of overt and subclinical hypothyroidism or hypothyroxinemia. Anticipated differences in TFTs in iodine-sufficient and iodine-deficient areas are discussed and data are provided on potential complications of hypothyroidism/hypothyroxinemia and autoimmune thyroid disease during pregnancy and adverse effects for the offspring. The beneficial effects of levothyroxine therapy on pregnancy outcomes and offspring development are discussed with a proposed treatment regimen and follow up strategy.