Menefee, Michael E.

3521 Background: Systemic therapies have had little impact on the outcomes of patients with advanced differentiated thyroid cancers. Methods: A three-outcome one-stage Phase II trial was conducted to assess the anti-tumor activity and toxicities of the orally bioavailable VEGF/tyrosine kinase inhibitor pazopanib (800 mg daily) in patients with advanced and progressive radioiodine-insensitive differentiated thyroid cancers. Up to 2 prior therapies were allowed, with measurable disease required. Design: at the 0.10 significance level, there would be a 90% chance of detecting a RECIST response rate of >20% given a true response rate of >5%; with the regimen considered promising if >4 confirmed responses observed. Results: From February to November 2008, 32 patients (53% male) aged 23–79 years (median: 63 years) were enrolled. Common sites of metastases were: lung (100%), nodes (52%), and bone (39%). Measurement data are available for 26 patients, with the median number of cycles administered thus far 4 (range: 1–8, total: 101). Overall, therapy has been well tolerated. Six patients (23%) required dose reduction due to: grade 2+ ALT (3 pts), grade 3 mucositis (1 pt); grade 3 diarrhea and dehydration (1 pt), and grade 3 abdominal pain (1 pt.). Other serious toxicities included grade 3 colon perforation and grade 3 chest pain (1 pt). No thyroglobulin antibody (TGA) negative patient has become TGA positive, and 11 of 16 patients (69%) with initially elevated thyroglobulin levels experienced a decline in thyroglobulin of >50%. Five RECIST partial responses have been confirmed to date (19%). Two patients are alive with disease progression and another has died from disease progression. Conclusions: Pazopanib appears to have both a favorable toxicity profile and promising clinical activity in patients with advanced and progressive differentiated thyroid cancers. Supported in part by NCI CA15083 and CM62205. No significant financial relationships to disclose.

Introduction: Multikinase inhibitors have clinical activity in radioactive iodine refractory (RAIR) differentiated thyroid cancers (DTCs) but are not curative; optimal management and salvage therapies remain unclear. This study assessed clinical effects of pazopanib therapy in RAIR-DTC patients with progressive disease, examining in parallel biomarker that might forecast/precede therapeutic response. Methods: Assessment of responses and toxicities and of any association between thyroglobulin (Tg) changes cycle 1 and RECIST (response evaluation criteria in solid tumors) response to pazopanib therapy were prospectively undertaken in Tg antibody negative RAIR-DTC patients. RECIST progressive metastatic disease <6 months preceding enrollment was required. With a sample size of 68 (assuming 23 attaining partial response [PR]), there would be 90% chance of detecting a difference of >30% when the proportion of patients attaining PR whose Tg values decrease by >50% is >50% cycle 1 (one-sided α = 0.10, two sample test of proportions). Mean corpuscular volume (MCV) change or mutational status or pretreatment were also explored as early correlates of eventual RECIST response. Results: From 2009 to 2011, 60 individuals were treated and evaluated; (one additional patient withdrew; another was found ineligible before therapy initiation); 91.7% had previous systemic therapy beyond RAI. Adverse events included one death (thromboembolic) deemed possibly pazopanib associated. Twenty-two confirmed RECIST PRs resulted (36.7%, confidence interval; CI [24.6–50.1]); mean administered 4-week cycles was 10. Among 44 fully accessible patients, the Tg nadir was greater among the 20 attaining PR (median: −86.8%; interquartile range [IQR]: −90.7% to −70.9%) compared with the 28 who did not (median: −69.0%; IQR: −78.1% to −27.7%, Wilcoxon rank-sum test: p = 0.002). However, the difference in the proportion of PRs among those whose Tg fell ≥50% after cycle 1 versus those that did not were not significantly correlated (−23.5% [CI: −55.3 to 8.3]; Fisher's exact test p -value = 0.27). RECIST response was also not correlated with/predicted by early MCV change, receipt of prior therapy, or tumor mutational status. Conclusions: This trial prospectively confirmed pazopanib to have clinical activity and manageable toxicities in patients with progressive RAIR-DTC. Response to pazopanib, however, was not robustly forecast by early associated changes in Tg or MCV, by prior therapy, or by tumor mutational status. ClinicalTrials.gov NCT00625846.

Abstract Context Clinical applications of genomic assessment of thyroid cancers are rapidly evolving. Objectives, Design, and Setting We studied tumor samples from patients with imminently threatening and rare thyroid cancers to identify genomic alterations that might correlate with outcomes and/or be productively therapeutically targetable. Patient Context Progressive and metastatic, and/or rare, thyroid cancers were studied, 2012 to 2016, at Mayo Clinic sites. Intervention The intervention was Foundation One tumor interrogation. Main Outcome Measures Main outcome measures included genomic alterations, patient characteristics, and overall survival. Results Samples from 55 patients were evaluated: 20 anaplastic thyroid cancers (ATCs) (36%), 25 radioactive iodine–refractory differentiated thyroid cancers (DTCs)/poorly differentiated thyroid cancers (PDTCs) (45%; 14 papillary thyroid cancer [PTCs], 6 PDTCs, 5 Hürthle cell cancers), 8 medullary thyroid cancers (MTCs) (15%), and 2 others (a spindle epithelial tumor with thymus-like differentiation, and a primary thyroid sarcoma). Overall, 72% of DTCs, 79% of ATCs, and 75% of MTCs were deemed to have potentially productively targetable alterations. The most commonly encountered mutation was of TERT promoter (56% of DTCs, 68% of ATCs)—but this is not presently targetable. Targetable BRAFV600E mutations were found in 40% of DTCs/PDTCs (83% of PTCs) and 32% of ATCs; of MTCs, 75% had targetable RET mutations, and 25% HRAS mutations. Of patient tumors with nonmutated BRAFV600E, 53% of DTC/PDTCs and 69% of ATCs had other potentially productively targetable mutations. Genomic alterations in our series of poor prognosis metastatic DTC/PDTCs also closely resembled those seen in ATC. Conclusions Whereas genomic interrogation of favorable prognosis thyroid cancer seems ill advised, potentially productively targetable mutations were demonstrated in the majority of tumors from patients with metastatic thyroid cancers requiring systemic therapy, suggesting a rationale for the selective application of this technology.

5544 Background: Pazopanib, an orally bioavailable multitargeted inhibitor of kinases including VEGF-R, demonstrated impressive activity in metastatic differentiated thyroid cancer (49% durable RECIST PRs) and promising preclinical activity in anaplastic thyroid cancer (ATC) models, prompting its evaluation also as a candidate therapeutic in advanced ATC. Methods: A multicenter single arm phase II trial of 800 mg pazopanib daily was undertaken with the primary endpoint of RECIST response rate. The trial was designed such that there would be a 90% chance of detecting a response rate of >20% at the 0.10 significance level when the true tumor response rate is >5%. A pre-specified stopping rule designated that enrollment would cease unless 1 or more RECIST PRs+CRs were observed in the first 14 of 33 potential patients. Eligibility required informed consent, >18 years of age, performance status ECOG 0-2, systolic blood pressure (BP) <140 mm Hg and diastolic BP <90 mm Hg at entry, QTc interval <480 msecs, and measurable disease by RECIST criteria. Anatomical imaging and toxicity evaluations were required every 4 weeks. Results: Sixteen patients were enrolled. One patient withdrew prior to therapy, leaving 15 evaluable patients – 33.3% were male, with a median age of 66 years (range 45-77); 11 of 15 patients had progressed through prior systemic therapy. Four patients required 1-2 dose reductions, with the most common severe toxicities (CTC-AE version 3.0 grades 3-5) hypertension (13%) and pharyngolaryngeal pain (13%). Reasons for treatment discontinuation included: disease progression (12 pts), death on study due to a vascular event possibly related to treatment (1 pt.), and intolerability (radiation recall tracheitis – 1 pt, and uncontrolled hypertension – 1 pt). Although transient disease regression was observed in several patients, there were no confirmed RECIST tumor responses, triggering study closure at time of interim analysis. Two patients are alive with disease 9.9 months and 2.9 years post-registration; the remaining 13 died of disease. The median time to progression was 62 days and the median survival time was 111 days. Conclusions: Pazopanib has poor single agent activity in advanced anaplastic thyroid cancer.

TPS2618 Background: MEDI-573 is an investigational dual-targeting human antibody that neutralizes IGF-I/-II ligands and inhibits IGF‑1R and insulin receptor-A (IR-A) signaling pathways. By sparing IR-B and its hybrid receptors, MEDI-573 may achieve antitumor activity without perturbing glucose homeostasis. Objectives of this phase 1 dose-escalation and expansion study are to evaluate safety and determine the maximum tolerated dose (MTD), optimal biologically effective dose, pharmacokinetics, pharmacodynamics, and immunogenicity of MEDI-573 in adult patients with solid tumors. Methods: Patients with advanced solid tumors, Karnofsky status ≥60, and adequate organ function were treated with escalating doses of MEDI-573 IV once weekly (0.5 to 15 mg/kg) or every 3 weeks (30 or 45 mg/kg q3w) using a 3+3 design. Three patients per dose level were evaluated for safety. A biomarker-rich dose-expansion arm tested weekly 5 or 15 mg/kg MEDI‑573 in patients with advanced bladder cancer. Results: Preliminary data are presented for 43 patients (25 M, 18 F), median age 64 years. No dose-limiting toxicities or serious toxicity patterns occurred at any dose level. Drug-related adverse events occurring in ≥10% of patients were fatigue (28%), decreased appetite (23%), nausea (16%), diarrhea (14%), and anemia (12%); the majority were ≤ grade 2. Perturbations in insulin and growth hormone were not observed. Clinically significant changes in serum glucose were rare. The MTD was not reached after completely enrolling patients through the highest dose, 45 mg/kg IV q3w. Serum exposure of MEDI-573 increased with increasing dose. Full suppression of IGF‑I/-II was achieved with weekly and q3w dosing. No neutralizing antibodies against MEDI‑573 were detected. Of 43 patients, 8 (19%) had stable disease ≥12 weeks. The longest exposure was 21 months in a patient with well-differentiated liposarcoma. Conclusions: MEDI-573 demonstrated an acceptable safety profile at all doses tested. No dose-limiting toxicity or serious toxicities, including those related to glucose homeostasis, were detected. These preliminary results support further clinical development.

Overview: Until only recently, few effective systemic therapies were available to treat patients with metastatic thyroid cancers. Recent advances in better understanding the pathogenesis and altered signaling pathways—especially in medullary and differentiated thyroid cancers (MTCs and DTCs)—have begun to change this situation substantially. Vandetanib, an orally bioavailable inhibitor of the RET kinase that is constitutively activated in MTC, has now been approved by the U.S. Food and Drug Administration (FDA) for use in progressive and symptomatic metastatic MTC; it has been shown to delay time to progression relative to placebo in a randomized phase III trial. Further, vascular endothelial growth factor receptor (VEGF-R) inhibitory agents including sorafenib, sunitinib, pazopanib, and axitinib that are already approved in the United States for use in advanced renal cell carcinoma have shown high response rates in treating advanced DTCs in multiple phase II trials, and have become commonly used in progressive radioiodine-refractory metastatic DTC. Yet additional agents are now in development, with several including XL184 (cabozantinib) also showing promise in DTC and MTC. In anaplastic thyroid cancer (ATC), progress has been slower, with the greatest apparent gains resulting more from the application of systemic therapies earlier in the disease course, especially when used in conjunction with initial surgical and radiation therapies. Despite recent progress, additional effective systemic therapeutic approaches remain sorely needed for treating metastatic MTC, DTC, and ATC.

122 Background: Mixed response (MR) to systemic therapy is common and associated with a poor prognosis. MR often represents a therapeutic dilemma resulting in the discontinuation of a therapy to which a portion of the tumor is still sensitive, due to the emergence of resistance in other metastatic deposits. We hypothesize that discordant responses in patients receiving immunotherapy may be associated with genomic variation within discordant tumors. Methods: We defined MR with the following criteria: 1) At least one tumor has increased in size while another tumor has decreased; 2) One or more tumors have remained stable while another has increased; 3) One or more tumors have remained stable while another has decreased. 4) A new tumor has developed while other tumors have decreased or remained stable. Between 2012 and 2017, we identified 112 patients with a MR. Two patients with metastatic lung cancer, treated with nivolumab underwent paired, simultaneous sampling of discordant tumors. Results: Both patients treated with nivolumab demonstrated genomic heterogeneity between discordant tumors on next-generation sequencing, including one patient with SCLC. Conclusions: MR remains a common and challenging therapeutic quandary. Genomic heterogeneity and differences in TMB of metastatic tumors demonstrating a MR, may be factors that contribute to this phenomenon. Further characterization of genomic discrepancies in MR may provide insights into mechanisms of emerging resistance, as well as, more rational and effective combinatorial therapies.[Table: see text]

Introduction: Individuals receiving systemic anticancer therapies for advanced solid tumors routinely undergo imaging studies to assess the efficacy of the treatment. Mixed response (MR) to cancer therapy is a common but poorly described phenomenon. There is a paucity of data regarding both the incidence and possible mechanisms of this clinical quandary. Potential etiologies include tumor heterogeneity, differences in tumor microenvironment, and discrepancies in drug delivery to different tumor deposits. It is also possible that MR simply reflects differences in the rate of resistance emerging. MR represents a therapeutic dilemma for the clinician. Methods: Mixed tumor response was defined as: One tumor decreasing in size; one tumor increasing in size (classified as RECIST response/progressions), One tumor stable; another tumor progressing, One tumor stable; another tumor responding, New tumor; another tumor responding or remaining stable. Between 2015 and 2017, 120 restaging CT scans were reviewed of patients who had received at least 1 line of therapy for advanced cancer diagnosis which showed MR; hematologic malignancies were excluded. Charts were reviewed to determine the clinical decision that was made at the time of the MR. Results: A total of 120 scans with MR were reviewed from various solid tumor diagnoses. 38 scans were excluded due to loss of follow-up or death. Of the remaining 82 scans, therapy was switched in 30, the same therapy was continued in 50, and an additional agent was added to the current treatment in 2 cases (Table). Of the patients in which treatment was switched, 20% (6/30) showed response to treatment on the following scan. Of the cases that were kept on current treatment, none showed response on the following restaging scan which was done 6–8 weeks later. There were 4 (10%) deaths prior to the next scan in the group that had treatment switched and similarly 5 deaths (10%) prior to the next scan in the group in which treatment remained the same. Conclusion: MR is associated with a poor prognosis, irrespective of treatment decisions. These data are retrospective and our sample size is small, so definitive conclusions cannot be drawn. However, changing therapy when a MR is observed may be of benefit to some patients. A prospective evaluation to more accurately describe and understand the MR phenomenon is warranted.