Accelerated disease progression after discontinuation of sorafenib in a patient with metastatic papillary thyroid cancer

Resistance, rebound, and recurrence regrowth patterns in pediatric low-grade glioma treated by MAPK inhibition: A modified Delphi approach to build international consensus-based definitions-International Pediatric Low-Grade Glioma Coalition

Pediatric low-grade glioma (pLGG) is the most common childhood brain tumor group. The natural history, when curative resection is not possible, is one of a chronic disease with periods of tumor stability and episodes of tumor progression. While there is a high overall survival rate, many patients experience significant and potentially lifelong morbidities. The majority of pLGGs have an underlying activation of the RAS/MAPK pathway due to mutational events, leading to the use of molecularly targeted therapies in clinical trials, with recent regulatory approval for the combination of BRAF and MEK inhibition for BRAFV600E mutated pLGG. Despite encouraging activity, tumor regrowth can occur during therapy due to drug resistance, off treatment as tumor recurrence, or as reported in some patients as a rapid rebound growth within 3 months of discontinuing targeted therapy. Definitions of these patterns of regrowth have not been well described in pLGG. For this reason, the International Pediatric Low-Grade Glioma Coalition, a global group of physicians and scientists, formed the Resistance, Rebound, and Recurrence (R3) working group to study resistance, rebound, and recurrence. A modified Delphi approach was undertaken to produce consensus-based definitions and recommendations for regrowth patterns in pLGG with specific reference to targeted therapies.

Low Dose of Lenvatinib Treatment for Patients of Radioiodine-Refractory Differentiated Thyroid Carcinoma - A Real-World Experience

Background

Lenvatinib treatment of 24 mg/day for radioiodine-refractory differentiated thyroid carcinoma (RRDTC) patients was almost intolerable, with high rates of dose reduction, interruption and discontinuation. Balancing treatment safety with disease risks remains challenging, and the appropriate dosage remains unclear in Asia.

Patients and Methods

A total of 65 RRDTC patients treated with lenvatinib were retrospectively collected from Oct. 2015 to Jun. 2020 from two medical centers of South Taiwan. The drug tolerability, treatment efficacy and clinical outcomes were analyzed.

Results

Different doses of lenvatinib were initiated but ultimately maintained with a median dose of 10 mg/day within the first 3 months. The disease control rate reached 89.2%, including 24.6% partial response and 64.6% stable disease. Disease progression occurred in 10.8% of patients and increased to 40.0% at the end. Eventually, the treatment dose achieved a median progression-free survival (PFS) of 26.1 months (95% CI: 17.1-NA) with overall survival (OS) not reached yet (24.1~NA). Overall, the 48-month PFS rate was 35.6% (95% CI: 18.5–68.4) and 48-month OS was 54.3% (95% CI: 41.2–71.7). The dose was tolerable with a dose reduction rate of 44.6%, dose interruption rate of 40.0% and fewer high-graded adverse events. The drug discontinuation rate was only 3.1%. However, RRDTC patients with bone metastasis or maximal dose exposure to RAI (≥600 mCi) may have less efficacy to the low maintenance dose treatment.

Conclusion

Assessing treatment intensity, safety and efficacy, low-dose lenvatinib treatment was well tolerated by RRDTC patients and displayed acceptable drug efficacy and outcomes.

Lenvatinib: an investigational agent for the treatment of differentiated thyroid cancer

INTRODUCTION

Differentiated thyroid cancer (DTC; >90% of all TCs) derives from follicular cells. Surgery is the main therapeutic strategy, and radioiodine (RAI) is administered after thyroidectomy. When DTC progresses, it does not respond to RAI and thyroid-stimulating hormone (TSH)-suppressive thyroid hormone treatment, and other therapies (i.e. surgery, external beam radiation therapy and chemotherapy) do not lead to a better survival. Thanks to the understanding of the molecular pathways involved in TC progression, important advances have been done. Lenvatinib is a multitargeted tyrosine kinase inhibitor of VEGFR1-3, FGFR1-4, PDGFRα, RET, and KIT signaling networks implicated in tumor angiogenesis, approved in locally recurrent or metastatic, progressive, RAI-refractory DTC. Unmet needs regarding the patient clinical therapy responsiveness in aggressive RAI-refractory DTC still remain.

AREAS COVERED

We provide an overview from the literature of in vitro, in vivo and real-life studies regarding lenvatinib as an investigational agent for the treatment of aggressive TC.

EXPERT OPINION

According to the SELECT trial, the treatment should be initiated with a dosage of 24 mg/day, subsequently decreasing it in relation to the side effects. The decision making process in patients with aggressive RAI-refractory DTC should be personalized and the potential toxicity should be properly managed.

Hif-1α Inhibitors Could Successfully Inhibit the Progression of Differentiated Thyroid Cancer in Vitro

Hypoxia-inducible factor (HIF)-1α plays an important role in cancer progression. In various cancers, including thyroid cancer, overexpression of HIF-1α is related to poor prognosis or treatment response. However, few studies have investigated the role of HIF-1α inhibition in thyroid cancer progression. We evaluated the utility of the HIF-1α inhibitor IDF-11774 in vitro utilizing two thyroid cancer cell lines, K1 and BCPAP. Both cell lines were tested to elucidate the effects of IDF-11774 on cell proliferation and migration using soft agar and invasion assays. Here, we found that a reduction of HIF-1α expression in BCPAP cells was observed after treatment with IDF-11774 in a dose-dependent manner. Moreover, cell proliferation, migration, and anchorage-independent growth were effectively inhibited by IDF-11774 in BCPAP cells but not in K1 cells. Additionally, invasion of BCPAP but not K1 cells was controlled with IDF-11774 in a dose-dependent manner. Our findings suggest that promoting the degradation of HIF-1α could be a strategy to manage progression and that HIF-1α inhibitors are potent drugs for thyroid cancer treatment.

Papillary thyroid carcinoma with hyperthyroidism and multiple metastases: A case report

RATIONALE

Papillary thyroid carcinoma (PTC) is the most common type of primary thyroid cancer with a low incidence of distant metastases. PTC represents more than 70% to -90% of thyroid malignancies. Distant metastases have only been observed in only 1% to 15% of patients with PTC. In this article, we reported the case of a patient with PTC and hyperthyroidism as well as simultaneous multiple metastases.

PATIENT CONCERNS

A 47-year-old man was admitted to our hospital on February 22, 2019, with several neck masses that had been present for 12 months, low back pain for 9 months, and lower limb paraplegia for 3 months.

DIAGNOSES

According to the patient physical examination, adjuvant examination (e.g., ultrasound, computed tomography, magnetic resonance imaging, blood test, and biopsy) and medical history, the clinical diagnosis was as follows: thyroid papillary carcinoma; cervical lymph node metastasis; multisite bone metastasis (6th and 7th cervical vertebrae, left clavicle proximal, right scapula bone, thoracic vertebrae, lumbar vertebrae, sacral vertebrae, bilateral ilium, and left pubic bone); muscular metastasis (the right medial femoral muscle, the vastus lateralis muscle, left thigh muscle, and the flexor superficialis of the left forearm); possible mediastinal lymph node metastasis; and paraplegia due to the soft-tissue metastasis around the 9th thoracic vertebral spine; and hyperthyroidism (free thyroxine: 36.59 pmol/L, free triiodothyronine: 9.58 pmol/L, thyroid-stimulating hormone: 0.005 μIU/mL, thyroid autoantibody: 2.53 IU/L).

INTERVENTIONS AND OUTCOMES

The patient refused to undergo further intervention or follow-up.

LESSONS

In summary, this is the 1st case of in which a patient with PTC and hyperthyroidism, as well as simultaneous multiple skeletal muscles and bone metastases, lymph node metastasis, and paraplegia was observed. In practice, in cases where patients have PTC and hyperthyroidism, practitioners should perform further examinations to rule out the presence of distant metastases. We believe that the use of ultrasound has a unique advantage in the diagnosis of PTC and skeletal muscle metastasis.

Rapid disease progression after discontinuation of lenvatinib in thyroid cancer

Some thyroid cancer patients experience a rapid disease progression after the discontinuation of tyrosine kinase inhibitors (TKIs), which is called flare phenomenon. The incidence of the flare phenomenon of epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) ranged from 4% to 11.1% and the median time to occurrence of the flare phenomenon ranged from 7 to 12 days in previous reports. In this study, we investigate the timing and incidence of the flare phenomenon in thyroid cancer patients treated with lenvatinib.The records of patients treated with lenvatinib were retrospectively reviewed. The primary outcomes were the incidence rate and timing of the flare phenomenon after the discontinuation of lenvatinib. The flare phenomenon was defined as death, hospitalization attributable to tumor progression, or unexpected event (e.g., pleural drainage) within 1 month of lenvatinib cessation. We excluded patients with progression of underlying diseases other than thyroid cancer or infection, those in whom the disease progressed, or those who died without achieving a clinical response (stable disease, partial response, or complete response).In total, 8 (14.3%) of the 56 patients experienced the flare phenomenon. The median time from lenvatinib cessation to the flare phenomenon was 9 (range, 4-30) days. Three patients in the flare group died within 1 month of lenvatinib cessation without an imaging evaluation. The remaining 5 patients had dyspnea and pleural effusion, and pleural drainage was performed in 3 of the 5 patients. Lenvatinib was resumed in 4 of the 8 patients in the flare group. Median overall survival (OS) was 15.1 months in the flare group and 41.9 months in the non-flare group. The OS tended to be poor in the flare group than in the non-flare group; however, this difference was not statistically significant (P = .051).In lenvatinib treatment for thyroid cancer, the incidence and timing of the flare phenomenon were similar to those observed with other TKIs. OS tended to be poor in the flare group than in the non-flare group. Further studies are needed to determine the mechanism of the flare phenomenon and establish measures and treatment policies.

Efficacy and Limitations of Lenvatinib Therapy for Radioiodine-Refractory Differentiated Thyroid Cancer: Real-World Experiences

Background: The ultimate clinical goal of advanced cancer treatment is improvement of survival. Tyrosine kinase inhibitors (TKIs) were recently approved for radioiodine-refractory differentiated thyroid carcinoma (RR-DTC) that is resistant to conventional therapies since they have significant potential to improve survival in patients who previously had no more treatment strategies available. However, eligible patients are limited in clinical practice, making it difficult to accurately determine the efficacy of TKIs. Patients and Methods: We retrospectively analyzed the efficacy of lenvatinib at a single institution, enrolling 42 RR-DTC patients. Results: The best overall response was partial remission in 26 (62%) patients, stable disease in 10 (24%) patients, and progressive disease (PD) in 6 (14%) patients. The results indicated three-year overall survival (OS) and progression-free survival rates of 51.0% and 32.4%, respectively. Twenty-three (55%) patients had backgrounds that did not match the inclusion criteria of the Study of (E7080) Lenvatinib in Differentiated Cancer of the Thyroid (SELECT) trial. Furthermore, PD-experienced patients individually decided whether to continue lenvatinib, and 17 (41%) made the decision themselves; these patients had a three-year OS of 43.0% and postprogression survival (PPS) of 13.3 [95% confidence interval 6.1-not reached] months. Conclusions: Our real-world investigation revealed that patients have wide-ranging background characteristics, and the decision regarding continuation of therapy after PD is based on the patient's general condition. Our management protocol resulted in good PPS. Furthermore, our results indicated equivalent efficacy of lenvatinib as in the SELECT trial. In conclusion, lenvatinib proved effective for RR-DTC patients in a real-world setting.

Extended Real-World Observation of Patients Treated with Sorafenib for Radioactive Iodine-Refractory Differentiated Thyroid Carcinoma and Impact of Lenvatinib Salvage Treatment: A Korean Multicenter Study

Background: Treatment for patients with radioactive iodine (RAI)-refractory differentiated thyroid carcinoma (DTC) is challenging. Recently, two tyrosine kinase inhibitors (sorafenib and lenvatinib) have been approved and showed benefits for progression-free survival with tolerable adverse events. Methods: This is an extension study of a previous multicenter, retrospective cohort study of real-world experience in treating 98 patients with progressive RAI-refractory DTC with sorafenib. The primary endpoint was overall survival (OS). The efficacy of lenvatinib as salvage therapy after disease progression on first-line sorafenib was evaluated by comparing outcomes in 32 patients who were treated with lenvatinib with 41 patients who were not and therefore served as a no salvage treatment group. Results: The median OS of all 98 patients treated with sorafenib was 41.5 months, and the median progression-free survival was 13.5 months. Patients without disease-related symptoms before sorafenib treatment had better OS than those with symptoms (hazard ratio [HR] = 0.56 [95% confidence interval, CI 0.31-0.99], p = 0.048). Larger tumor size was associated with a minimally increased risk of death (HR = 1.02 [CI 1.00-1.03], p = 0.049). Best tumor response was not associated with OS (p = 0.490). Lenvatinib salvage treatment significantly improved OS in patients receiving it compared with those who did not (HR = 0.28 [CI 0.15-0.53], p < 0.001). The median OS from the time of disease progression after first-line sorafenib treatment was 4.9 months in no salvage treatment group, whereas it was not reached in the lenvatinib salvage group. Conclusions: The absence of disease-related symptoms and smaller tumor burden was associated with survival benefits of first-line sorafenib treatment in patients with progressive RAI-refractory DTC. Lenvatinib salvage therapy was effective in improving OS in patients with disease progression after first-line sorafenib.

Lenvatinib for thyroid cancer treatment: discovery, pre-clinical development and clinical application

Introduction: About one third of patients affected with thyroid cancer present with recurrent disease. Unresectability, advanced disease and radioiodine refractoriness are considered poor prognostic factors. Treatment with small molecules inhibiting molecular signaling can be considered for patients with progressive disease, when other therapeutic strategies cannot be applied. Lenvatinib is a tyrosine kinase inhibitor targeting multiple molecular factors involved in angiogenesis and tumor progression. Preclinical studies have demonstrated the utility of lenvatinib as a targeted therapy for different tumors, including both differentiated and anaplastic thyroid cancer.Areas covered: The authors provide an overview of the preclinical development of lenvatinib in the treatment of thyroid cancer and review its clinical application. They also provide their expert opinion on its development.Expert opinion: Preclinical studies have helped in the understanding of the mechanisms of thyroid carcinogenesis and in the development of a targeted therapy. These findings have represented the rationale for the use of lenvatinib in clinical trials, which have confirmed its utility but yet failed to prove a clear benefit in overall survival. The decision to start a systemic treatment with lenvatinib must be personalized for each patient evaluating the risk/benefits ratio. Treatment emergent adverse events must be considered and reasonably managed by a multidisciplinary approach.

Rapid pleural effusion after discontinuation of lenvatinib in a patient with pleural metastasis from thyroid cancer

We report a case of rapid pleural effusion after discontinuation of lenvatinib. A 73-year-old woman was diagnosed with poorly differentiated thyroid cancer with right pleural metastasis. Weekly paclitaxel treatment was performed for 18 weeks, but it was not effective. Oral administration of lenvatinib, a multi-target tyrosine kinase inhibitor, reduced the size of cervical and thoracic tumors and lowered serum thyroglobulin levels. Lenvatinib was discontinued on day 28 because of Grade 2 thrombocytopenia and Grade 3 petechiae. Seven days after discontinuation of lenvatinib, the patient was hospitalized because of dyspnea and right pleural effusion. Pleural effusion rapidly improved with drainage and re-initiation of lenvatinib and did not recur. Anorexia caused by lenvatinib led to undernutrition, which resulted in death 13 months after initiation of lenvatinib. Autopsy revealed extensive necrosis with primary and metastatic lesions, suggesting that the patient responded to lenvatinib. Physicians should be aware of the possibility of flare-up in patients with thyroid cancer treated with lenvatinib. Learning points: Autopsy findings revealed that lenvatinib was efficacious in treating poorly differentiated thyroid cancer without primary lesion resection. Flare-up phenomenon may occur in thyroid cancer treated with lenvatinib. Attention should be paid to flare-up phenomenon within a few days of discontinuing lenvatinib.

Treatment of refractory thyroid cancer

Distant metastases from thyroid cancer of follicular origin are uncommon. Treatment includes levothyroxine administration, focal treatment modalities with surgery, external radiation therapy and thermal ablation, and radioiodine in patients with uptake of ¹³¹I in their metastases. Two-thirds of distant metastases become refractory to radioiodine at some point, and when there is a significant tumor burden and documented progression on imaging, a treatment with a kinase inhibitor may provide benefits.

Clinical guidance for radioiodine refractory differentiated thyroid cancer

Prognosis from differentiated thyroid cancer is worse when the disease becomes refractory to radioiodine. Until recently, treatment options have been limited to local therapies such as surgery and radiotherapy, but the recent availability of systemic therapies now provides some potential for disease control. Multitargeted kinase inhibitors (TKIs) including lenvatinib and sorafenib have been shown to improve progression-free survival in phase III clinical trials, but are also associated with a spectrum of adverse effects. Other TKIs have been utilized as "redifferentiation" agents, increasing sodium iodide symporter expression in metastases and thus restoring radioiodine avidity. Some patients whose disease progresses on initial TKI therapy will still respond to a different TKI and clinical trials currently in progress will clarify the best options for such patients. As these drugs are not inexpensive, care needs to be taken to minimize not only biological but also financial toxicity. In this review, we examine the basic biology of radioiodine refractory disease and discuss optimal treatment approaches, with specific focus on choice and timing of TKI treatment. This clinical field remains fluid, and directions for future research include exploring biomarkers and considering adjuvant TKI use in certain patient groups.

Skeletal muscle metastases from papillary and follicular thyroid carcinomas: An extensive review of the literature

Skeletal muscle metastasis of papillary or follicular thyroid cancer (PTC/FTC) is a rare finding; only 11 cases of skeletal muscle PTC or FTC metastasis have been included in medical literature reviews. The aim of this study was to identify all published cases of PTC and FTC muscle metastases and derive the true incidence of this malignancy. The probability of detecting the skeletal muscle metastasis of PTC and FTC was calculated based on epidemiological data. Databases of scientific literature on the Internet were searched for articles using relevant key words. The analysis of epidemiological data calculated the probability of detecting skeletal muscle lesions of this type as approximately zero. The literature search revealed 44 published international papers, reporting 58 cases of PTC or FTC skeletal muscle metastasis in 45 patients over 110 years, from 1907 to 2017. The most frequent PTC/FTC metastatic muscle was the gluteus. The majority of cases of muscle metastasis were caused by PTC, and metastatic tumors in the skeletal muscle negatively impacted the survival of patients with PTC or FTC.

Intermittent Dosing of Dabrafenib and Trametinib in Metastatic BRAFV600E Mutated Papillary Thyroid Cancer: Two Case Reports

BACKGROUND

A multi-institutional, randomized phase II trial of continuous dosing of dabrafenib with or without trametinib is ongoing in metastatic thyroid cancer. Preclinical evidence and emerging clinical experience in other cancers support evaluating intermittent dosing of these two agents to achieve more durable response, while being better tolerated and more cost effective.

PATIENTS

Two consecutive patients with symptomatic, metastatic radioactive iodine-resistant BRAF^V600E mutated papillary thyroid cancer and poor performance status were treated initially with dabrafenib 150 mg twice daily plus trametinib 2 mg once daily, first in continuous daily dosing, then in a five-week-on and three-week-off schedule.

RESULTS

Both patients showed rapid clinical improvement upon starting the regimen. They also noted improved tolerance of treatment upon transitioning to the intermittent dosing schedule. They continue to show evidence of antitumor activity 27 and 18 months respectively from the start of treatment and 15 and 13 months respectively from the start of the first break using intermittent dosing.

CONCLUSIONS

Achieving durable palliation in these consecutive patients supports evaluating the intermittent dosing schedule of dabrafenib and trametinib in BRAF^V600E mutated papillary thyroid cancer. Results of the ongoing phase 3 trial of continuous daily dosing and a subsequent trial of intermittent dosing, as is being tested in other cancers, will be needed to confirm that an intermittent dosing strategy in thyroid cancer can forestall resistant disease, improve tolerability, and decrease the cost of care.

Aggressive differentiated thyroid cancer with multiple metastases and NRAS and TERT promoter mutations: A case report

Sorafenib, a tyrosine kinase inhibitor, is approved for the treatment of advanced differentiated thyroid carcinoma (DTC). Resistance to sorafenib may appear under treatment and may be associated with increased aggressiveness of the neoplasia. The present study reports the case of a 65-year-old male who underwent total thyroidectomy for a follicular thyroid carcinoma, Hürthle cell variant, in February 2005. Until January 2010, the patient received four consecutive ¹³¹I doses (total dose, 612 mCi) for increased serum thyroglobulin (Tg) and initial faint lung uptake (which eventually became undetectable). Subsequently, the patient developed several sequential bone (humerus, rib and skull), adrenal and lung metastases, the majority of which were surgically removed. Histological examination in all cases revealed evidence of DTC metastases that were strongly positive for Tg, as revealed by immunohistochemistry. In March 2014, sorafenib therapy was initiated, but it was discontinued 10 months later to allow an undelayable prostatectomy. Immediately upon surgery, the patient developed a large metastatic lesion in the right gluteal muscle, whose biopsy revealed undifferentiated neoplasia of epithelial origin, and the patient succumbed shortly afterwards. An extensive comparative search for biochemical and molecular markers was performed on all available tissues (primary tumor, and differentiated and undifferentiated metastases). The primary tumor and all the available metastases exhibited the same molecular oncogenic markers (namely, the RAS mutation p.Q61R and the telomerase promoter mutation C228T). In addition, the undifferentiated metastasis exhibited a p53 mutation. The present study reports a case of a sudden acceleration of DTC metastatic progression following sorafenib discontinuation, which could have been due to the emergence of sorafenib-resistant undifferentiated p53-positive tumor cell clones.

Tumors Sharply Increased after Ceasing Pazopanib Therapy for a Patient with Advanced Uterine Leiomyosarcoma: Experience of Tumor Flare

Pazopanib has activity in patients with soft-tissue sarcoma. We report an advanced uterine leiomyosarcoma case that suddenly worsened after cessation of pazopanib therapy. A 47-year-old woman had a primary uterine leiomyosarcoma tumor and multiple lung metastases, which progressed during her initial treatment. In subsequent treatment with pazopanib for 3 months, the sum of her tumor diameters after cessation sharply increased for two weeks. Symptoms such as dyspnea suddenly worsened also. She died of the disease one month after cessation of pazopanib therapy. Given the poor prognosis of recurrent uterine leiomyosarcoma and the rapid tumor enlargement after ending pazopanib therapy, control of this disease is especially important. Therefore, the decision to discontinue pazopanib therapy requires careful consideration.

Initial Size of Metastatic Lesions Is Best Prognostic Factor in Patients with Metastatic Differentiated Thyroid Carcinoma Confined to the Lung

BACKGROUND

For patients with lung metastases of differentiated thyroid carcinoma (DTC), there is no consensus on the maximal size of metastatic lesions to use when determining the intensity of follow-up and additional therapeutic options. This study evaluated the clinical outcomes and survival of patients with metastatic DTC confined to the lung, using the maximal diameter of lung lesions in the initial computed tomography.

METHODS

This retrospective cohort study included 112 DTC patients with metastases confined to the lung. The clinical responses were evaluated according to changes in the serum levels of stimulated thyroglobulin or antithyroglobulin antibody, disease status was evaluated according to radiological findings, progression-free survival (PFS), and cancer-specific survival (CSS).

RESULTS

Macronodular lung metastases (≥1 cm) were observed in 27 (24%) patients, and these patients had significantly poor biochemical responses and disease status (p < 0.001, and p < 0.001, respectively), irrespective of radioactive iodine (RAI) avidity. After adjusting for age, sex, primary tumor size, extrathyroidal invasion, cervical lymph node metastasis, time of lung metastasis, and RAI avidity, the macronodular group also had shorter PFS and CSS (p = 0.009 and p = 0.03, respectively) than the micronodular group. From the multivariate analyses, RAI avidity was not an independent prognostic factor predicting PFS and CSS. In the subgroup analyses, RAI avidity was a significant prognostic factor associated with better PFS and CSS (p = 0.013 and p = 0.021, respectively) in the micronodular group only.

CONCLUSIONS

The initial largest diameter of metastatic lesions is the most important prognostic factor for predicting poor clinical outcomes and survival in patients with metastatic DTC confined to the lung.

Pharmacodynamic study of axitinib in patients with advanced malignancies assessed with (18)F-3'deoxy-3'fluoro-L-thymidine positron emission tomography/computed tomography

PURPOSE

Rapid disease progression associated with increased tumor proliferation has been observed during withdrawal of anti-angiogenic therapy. We characterize the dynamics of withdrawal flare for axitinib.

METHODS

Thirty patients with metastatic solid malignancies received axitinib for 2 weeks, followed by a 1-week drug holiday. Twenty patients suitable for PET imaging received scans with (18)F-3'deoxy-3'fluoro-L-thymidine (FLT), a marker of proliferation. Plasma VEGF and axitinib pharmacokinetic levels were also assessed at specified time points.

RESULTS

During axitinib withdrawal, significant increases in both SUVmax (+22 %; p = 0.006) and SUVmean (+20 %; p = 0.001) were observed. Significant increases relative to peak axitinib concentration were observed at day 2 withdrawal for SUVmax and SUVmean, with no further significant increase from day 2 to day 7 of withdrawal. No significant change in SUVmax or SUVmean was observed during the treatment period, relative to baseline. VEGF concentration significantly increased when on drug (p < 0.001) and decreased back to a level indistinguishable from baseline by day 7 of drug washout (p = 0.448). No correlation between change in VEGF and change in imaging metrics was observed.

CONCLUSIONS

A significant increase in tumor proliferation was observed during withdrawal of axitinib therapy, and this flare occurred within 2 days of axitinib withdrawal. An exploratory analysis indicated that this flare may be associated with poor clinical outcome.

Treatment of distant metastases from follicular cell-derived thyroid cancer

Distant metastases from thyroid cancer of follicular origin are uncommon. Treatment includes levothyroxine administration at suppressive doses, focal treatment modalities with surgery, external radiation therapy and thermal ablation, and radioiodine in patients with uptake of ¹³¹I in their metastases. Two thirds of distant metastases will become refractory to radioiodine at some point, and when there is a significant tumor burden and documented progression on imaging, a treatment with a kinase inhibitor may provide benefits.