Definitive Radiotherapy for Oligometastatic and Oligoprogressive Thyroid Cancer

PURPOSE/OBJECTIVE(S)

Local consolidative radiotherapy (LCT) for oligometastatic disease is a promising paradigm improving outcomes for various malignancies but has been underexplored for metastatic thyroid cancer. We hypothesize that LCT to distant sites with definitive RT doses can yield favorable outcomes and defer systemic therapy escalation for these patients.

MATERIALS/METHODS

We reviewed 96 thyroid cancer patients who received 175 LCT courses from 2010-2022 to 228 metastatic sites, including: thorax (45%), bone (40%), brain (6%), head/neck (5%), and abdomen (3%). Common prescriptions were 50-55Gy/4-5fxs or 56-70Gy/8-10fxs for lung; 52.5-60Gy/15fxs for mediastinum; and 18-24Gy/1fx or 27-30Gy/3fxs for bone. RECIST v1.1 and CTCAE v5.0 were used to define progression and toxicities, respectively. Outcomes were evaluated via Kaplan-Meier and associations examined via Cox proportional hazards modeling.

RESULTS

Median age was 63 years (range: 26-92), with 62 oligometastatic cases (total 1-5 sites) and 34 oligoprogressive (with 1-5 growing sites). Primary disease was controlled in all patients, with 39% receiving post-op RT and 66% prior RAI. Histologies included papillary (40%), anaplastic (25%), follicular (12%), medullary (9%), Hurthle (7%), and poorly-differentiated (7%). Median time from initial diagnosis to LCT was 3 yrs (IQR 1-8), and median follow-up from 1st LCT was 21 mos (IQR 9-51). Patients received an average 2 LCT courses (range 1-8) treating 1-4 sites. Median survival (OS) from 1st LCT was 9 yrs (95% CI = 5-14). On multivariable analysis (MVA), worse OS was associated with anaplastic histology (HR 4.6, p<.01), but longer OS was associated with prior RAI (HR 0.33, p = .02) and oligometastatic disease (HR 0.3, p = .01). For anaplastic histology, median OS was 1.2 years vs. 9.3 years for non-anaplastic; 3-yr OS was 36% vs. 88% (log-rank, p<.01). Five-year OS for oligometastatic cases was 75% vs 53% for oligoprogressive (log-rank, p = .04). Median progression free survival (PFS) from 1st LCT was 15.5 mos (95% C I = 11-20). On MVA for all LCT courses, time to any progression (TTP) was negatively associated with anaplastic histology (HR 1.7, p = .02) and 2nd or higher LCT course (HR 1.45, p = .05), but favorably associated with thoracic site (HR 0.49, p<.01). Following later LCT courses, median TTP was 11 mos vs 17 mos for initial LCT course (log-rank, p = .03). After LCT to lung/chest, TTP was 18.6 mos vs 9.5 mos for non-thoracic sites (log-rank, p<.01). Only 6% of failures occurred at previously treated lesions. Most LCT courses (67%) were without ongoing chemotherapy, while 25% entailed continuing the same regimen and 9% had planned treatment post-RT. There were 2 Grade 3 toxicities (pneumonitis and esophagitis) and no Grade 4-5 events.

CONCLUSION

With high local control rates and minimal toxicity, LCT can be a feasible strategy to defer systemic therapy escalation for oligometastatic and oligoprogressive thyroid cancer.

Dabrafenib plus trametinib in patients with BRAF V600E–mutant anaplastic thyroid cancer: updated analysis from the phase II ROAR basket study

Background:

Combined therapy with dabrafenib plus trametinib was approved in several countries for treatment of BRAF V600E-mutant anaplastic thyroid cancer (ATC) based on an earlier interim analysis of 23 response-assessable patients in the ATC cohort of the phase II Rare Oncology Agnostic Research (ROAR) basket study. We report an updated analysis describing the efficacy and safety of dabrafenib plus trametinib in the full ROAR ATC cohort of 36 patients with ~4 years of additional study follow-up.

Patients and methods:

ROAR (NCT02034110) is an open-label, nonrandomized, phase II basket study evaluating dabrafenib plus trametinib in BRAF V600E-mutant rare cancers. The ATC cohort comprised 36 patients with unresectable or metastatic ATC who received dabrafenib 150 mg twice daily plus trametinib 2 mg once daily orally until disease progression, unacceptable toxicity, or death. The primary endpoint was investigator-assessed overall response rate (ORR) per Response Evaluation Criteria in Solid Tumors version 1.1. Secondary endpoints were duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety.

Results:

At data cutoff (14 September 2020), median follow-up was 11.1 months (range, 0.9–76.6 months). The investigator-assessed ORR was 56% (95% confidence interval, 38.1% to 72.1%), including three complete responses; the 12-month DOR rate was 50%. Median PFS and OS were 6.7 and 14.5 months, respectively. The respective 12-month PFS and OS rates were 43.2% and 51.7%, and the 24-month OS rate was 31.5%. No new safety signals were identified with additional follow-up, and adverse events were consistent with the established tolerability of dabrafenib plus trametinib.

Conclusions:

These updated results confirm the substantial clinical benefit and manageable toxicity of dabrafenib plus trametinib in BRAF V600E-mutant ATC. Dabrafenib plus trametinib notably improved long-term survival and represents a meaningful treatment option for this rare, aggressive cancer.

Distinguishing Recurrent Thyroid Cancer from Residual Nonmalignant Thyroid Tissue Using Multiphasic Multidetector CT

BACKGROUND AND PURPOSE

During thyroidectomy incomplete resection of the thyroid gland may occur. This complicates the imaging surveillance of these patients as residual thyroid needs to be distinguished from local recurrence. Therefore, the purpose of this study was to determine if multiphasic multi-detector computed tomography (4D-MDCT) can differentiate residual nonmalignant thyroid tissue and recurrent thyroid carcinoma after thyroidectomy.

MATERIALS AND METHODS

In this retrospective study, Hounsfield unit values on multiphasic multidetector CT in precontrast, arterial (25 seconds), venous (55 seconds), and delayed (85 seconds) phases were compared in 29 lesions of recurrent thyroid cancer, 29 with normal thyroid, and 29 with diseased thyroid (thyroiditis/multinodular thyroid). The comparison of Hounsfield unit values among lesion types by phase was performed using ANOVA. The performance of Hounsfield unit values to predict recurrence was evaluated by logistic regression and receiver operating characteristic analysis.

RESULTS

All 3 tissue types had near-parallel enhancement characteristics, with a wash-in-washout pattern. Statistically different Hounsfield unit density was noted between the recurrence (lowest Hounsfield unit), diseased (intermediate Hounsfield unit), and normal (highest Hounsfield unit) thyroid groups throughout all 4 phases (P < .001 for each group and in each phase). Dichotomized recurrence-versus-diseased/normal thyroid tissue with univariate logistic regression analysis demonstrated that the area under the receiver operating characteristic curve for differentiating benign from malignant thyroid for the various phases of enhancement was greatest in the precontrast phase at 0.983 (95% CI, 0.954-1), with a cutoff value of ≤62 (sensitivity/specificity, 0.966/0.983) followed by the arterial phase.

CONCLUSIONS

Recurrent thyroid carcinoma can be distinguished from residual nonmalignant thyroid tissue using multiphasic multidetector CT with high accuracy. The maximum information for discrimination is in the precontrast images, then the arterial phase. An optimal clinical protocol could be built from any number of phases but should include a precontrast phase.

Selective RET kinase inhibition for patients with RET-altered cancers

Background

Alterations involving the RET kinase are implicated in the pathogenesis of lung, thyroid and other cancers. However, the clinical activity of multikinase inhibitors (MKIs) with anti-RET activity in RET-altered patients appears limited, calling into question the therapeutic potential of targeting RET. LOXO-292 is a selective RET inhibitor designed to inhibit diverse RET fusions, activating mutations and acquired resistance mutations.

Patients and methods

Potent anti-RET activity, high selectivity, and central nervous system coverage were confirmed preclinically using a variety of in vitro and in vivo RET-dependent tumor models. Due to clinical urgency, two patients with RET-altered, MKI-resistant cancers were treated with LOXO-292, utilizing rapid dose-titration guided by real-time pharmacokinetic assessments to achieve meaningful clinical exposures safely and rapidly.

Results

LOXO-292 demonstrated potent and selective anti-RET activity preclinically against human cancer cell lines harboring endogenous RET gene alterations; cells engineered to express a KIF5B-RET fusion protein -/+ the RET V804M gatekeeper resistance mutation or the common RET activating mutation M918T; and RET-altered human cancer cell line and patient-derived xenografts, including a patient-derived RET fusion-positive xenograft injected orthotopically into the brain. A patient with RET M918T-mutant medullary thyroid cancer metastatic to the liver and an acquired RET V804M gatekeeper resistance mutation, previously treated with six MKI regimens, experienced rapid reductions in tumor calcitonin, CEA and cell-free DNA, resolution of painful hepatomegaly and tumor-related diarrhea and a confirmed tumor response. A second patient with KIF5B-RET fusion-positive lung cancer, acquired resistance to alectinib and symptomatic brain metastases experienced a dramatic response in the brain, and her symptoms resolved.

Conclusions

These results provide proof-of-concept of the clinical actionability of RET alterations, and identify selective RET inhibition by LOXO-292 as a promising treatment in heavily pretreated, multikinase inhibitor-experienced patients with diverse RET-altered tumors.

Imaging of Anaplastic Thyroid Carcinoma

Anaplastic thyroid carcinoma is fatal if unresectable. However, improved survival has been reported after gross total resection and multimodality therapy. In this report, we describe the contrast-enhanced high-resolution CT characteristics of anaplastic thyroid carcinoma in 57 patients. Anaplastic thyroid carcinoma presented as a large neck mass with necrosis in 82% of cases. The tumors demonstrated common extrathyroidal extension (91%). Sixty-two percent of tumors demonstrated calcification. Visceral space invasion involved the esophagus (62%), trachea (57%), and larynx (29%). Carotid artery encasement was present in 42%, and 43% involved the internal jugular vein. Sixty-three percent had lateral compartment lymphadenopathy; 58% of these nodes were necrotic, and 11% were cystic. No metastatic nodes had calcification. Central compartment lymphadenopathy was seen in 56% of cases, and lateral retropharyngeal lymphadenopathy was detected in 12%. Knowledge of these imaging features aids in guiding the approach to the initial tissue diagnosis with either fine-needle aspiration or core biopsy, assessing the feasibility of surgical resection, and determining prognosis.

Treatment (tx) with tyrosine kinase inhibitors (TKIs) for patients (pts) with differentiated thyroid cancer (DTC): The M. D. Anderson Cancer Center (MDACC) experience

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Background: DTC is a relatively common tumor and about 20% will develop distant metastases (mets) of which at least 50% will not respond to standard tx. Until recently, tx for pts with progressive, RAI negative disease was limited. However, the identification of biologic targets in DTC has led to several trials with TKIs. Objectives: We sought to describe the MDACC experience with off-label use of TKIs to determine which pts benefit the most. Methods: Adult pts with a diagnosis of DTC treated with single agent sorafenib (SOR) or sunitinib (SUN), and who had a baseline and at least 1 follow-up (f/u) scan after 3 months (mos) of therapy, were included. All imaging data, as well as the TSH-suppressed thyroglobulin (TG) levels corresponding to each scan date were collected. RECIST was used to determine response. Results: We identified 33 pts from our clinical database. 15 pts met inclusion criteria: 9 women, 6 men. No pts were excluded due to progression or death before 3 mos. Median age 61 years (range, 38–83). 7 patients had papillary, 6 follicular (including 2 insular subtypes), 2 Hurthle cell. Most patients had RAI negative disease. SOR was used in 13, SUN in 2. Both SUN pts had been on SOR; 1 failed and 1 had intolerable side effects to SOR. Median time on tx was 42 weeks. All pts had evidence of PD prior to start of tx. Best response was 3 (20%) PR, 9 (60%) SD, 3 (20%) PD. Clinical benefit (PR+SD) = 80%. The SUN pt who was refractory to SOR had a 38% reduction in tumor size. The most noticeable activity occurred in lung (median change: -16%), whereas lymph nodes had PD or SD (median change: +3%). The 2 pts with pleural mets had PD. Four pts had bone mets: 2 had XRT and had SD in bone, while the other 2 did not have XRT and had PD in bone. At 12 mos PFS was 65% and OS was 85%. Median f/u time was 16 mos. All histologic types had similar responses. Log (TG) correlated with response (p = 0.0005). Conclusions: SOR and SUN are effective in pts with widely metastatic, progressive DTC, with most pts achieving SD or PR. The most noticeable responses occurred in the lungs in contrast with minimal changes in nodal mets, suggesting a tissue-specific response to tx. Log (TG) significantly correlated with response to tx and therefore may have value as a surrogate marker of response.

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Epoetin-alpha compared to standard of care decreases number of packed red blood cell transfusions in patients receiving hyper-CVAD for acute lymphocytic leukemia, lymphoblastic lymphoma, and Burkitt’s lymphoma

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Background: Anemia is common in patients with acute lymphocytic leukemia (ALL), lymphoblastic lymphoma (LL), and Burkitt’s lymphoma (BL) treated with chemotherapy and is associated with poor cancer control. Studies have shown that mild correction of anemia is associated with a significant improvement in quality of life. The current standard of care (SOC) for treatment of anemia in ALL, LL, BL is packed red blood cell (PRBC) transfusions. Objectives: To evaluate if EPO 1)decreases number/frequency of transfusions, and 2) adversely influences the complete remission (CR) rate. Methods: Patients with newly diagnosed ALL, LL, or BL receiving hyper-CVAD were randomized to EPO vs SOC within 14 days of starting chemotherapy. EPO dose was 40,000 units SQ weekly and escalated to 60,000 units after 4 weeks if indicated. Both arms received PRBC transfusions as per guidelines. Patients were considered evaluable if they had been on the study for at least 5 weeks. Results: 46 of 70 patients were evaluable: 16 ALL, 4 BL, and 3 LL on EPO (total 23) and 20 ALL, 1 BL, 2 LL in the SOC arm (total 23). The 2 groups were comparable in baseline hemoglobin and number of courses of chemotherapy completed. Median baseline erythroepoietin level was 299 (r 12–10,532) in the EPO arm vs. 104 (r 7–491; p=0.02) in the SOC arm. Time to neutrophil and platelet recovery was comparable in both arms. All patients with ALL (both arms) achieved a CR. One patient with LL on the EPO arm had no response to chemotherapy while all patients with BL and LL on the SOC arm achieved a CR. Conclusions: 1) EPO significantly decreased the frequency and number of PRBC transfusions in patients with ALL, LL, and BL on hyper-CVAD. 2) EPO does not affect recovery of other cell lines. 3) Use of EPO does not appear to have an adverse impact on CR rates in patients with ALL.

No significant financial relationships to disclose.

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