Angiogenesis is a vital process in the formation and progression of thyroid cancer, where overexpression of vascular endothelial growth (VEGF) and vascular endothelial growth factor (VEGFR) is commonly observed in cancerous thyroid cells. Consequently, mTKIs are utilized for clinically targeted therapy of thyroid cancer. The China NMPA has approved sorafenib and lenvatinib for use as first-line systemic treatments in patients with progressive RAIR-DTC. However, adverse drug reactions and drug resistance restrict their clinical utility to some extent. In our case, we presented a woman with RAIR-DTC who initially received sorafenib treatment upon diagnosis. The initial course of sorafenib therapy led to disease stabilization, however, the patient experienced progressive lung metastases several months post-treatment initiation. Previous studies have indicated that anlotinib exhibits stronger anti-angiogenic activity compared to sorafenib[17]. After a multidisciplinary team discussion, the patient was enrolled in an anlotinib treatment regimen on February 23, 2022.
Anlotinib can inhibit tumor angiogenesis, growth, invasion, lymphangiogenesis, and spread of lymphatic metastasis[18-20], and has been shown to be effective against a variety of solid tumors[21-26]. In 2018, it was approved by the China NMPA as a new third-line treatment option for advanced non-small cell lung cancer [27]. In addition, the selectivity of anlotinib for inhibiting the VEGF receptor-2 is over twenty times that of other anti-VEGF medications[27], making it more effective in anti-tumor activity at the same concentration compared to other anti-VEGF receptor TKIs. In April 2022, the Chinese NMPA officially approved anlotinib for the treatment of inoperable, iodine-refractory, locally advanced or metastatic DTC.
Preclinical research indicates that anlotinib significantly suppresses the viability of PTC and anaplastic thyroid cancer (ATC) cells, primarily by inducing G2/M cell cycle arrest and upregulating TP53 expression. It suppresses thyroid cancer cell migration in vitro and restrains the growth of xenograft thyroid tumors in mice, thus exerting an anti-tumor effect[28]. Clinical studies have indicated that anlotinib can induce objective responses and prolong PFS of advanced thyroid cancer. A Phase II trial has confirmed anlotinib's sustained anti-tumor effect in patients with locally advanced or metastatic medullary thyroid cancer, with a PFS rate of 85.5% at 48-week [12]. In a multicenter Phase IIB trial [29], anlotinib demonstrated efficacy and safety in 91 Asian patients with unresectable medullary thyroid carcinoma, achieving an objective response rate (ORR) of 48.4% and significantly extending PFS (20.7 vs. 11.1 months, P = 0.029). Additionally, anlotinib in combination with the PD-1 inhibitor sintilimab has shown promising results in ATC patients, with significant tumor reduction and a sustained remission period of 18.3 months[30]. In RAIR-DTC, a Phase II trial [13] revealed a substantial PFS extension for the anlotinib group (40.5 vs. 8.4 months, p < 0.001) and an ORR of 59.21%. Notably, a patient with recurrent and metastatic RAIR-DTC exhibited over 37 months of PFS, carrying both TERT promoter C228T and BRAF V600E mutations[31]. Anlotinib's potential in neoadjuvant settings was also explored, with a Phase II trial [32] reporting an ORR of 76.9% in the neoadjuvant treatment of locally advanced thyroid cancer.
Targeted therapies have significantly enhanced the treatment outcomes for thyroid cancer, yet challenges such as "off-target effects", intolerance to toxic side effects, and resistance remain. Research indicates that anti-angiogenic agents can induce normalization of tumor vasculature, thereby enhancing blood perfusion and drug delivery, and subsequently augmenting the efficacy of chemotherapy[33-35]. In the treatment of other tumor types, the addition of chemotherapy drugs has been shown to enhance the effects of targeted therapies. Specifically, in the treatment of Her-2-positive advanced breast cancer, the combination of paclitaxel with anti-Her-2 targeted drugs has emerged as a standard therapeutic approach. Thyroid cancer, traditionally insensitive to chemotherapy alone, has shown improved outcomes with the concurrent use of chemotherapy and targeted therapy, which also allows for reduced chemotherapy dosages and diminished toxic side effects. Anlotinib-based chemotherapy regimens have exhibited promising efficacy and tolerability in locally advanced or metastatic ATC[36]. Adopting a 'targeted therapy plus chemotherapy' approach for the case. The initial six months of combination therapy with anlotinib and albumin-bound paclitaxel effectively controlled the disease, stabilizing structural lesions and biochemical thyroglobulin levels. At the 12-month evaluation, a partial response was achieved per RECIST 1.1 criteria. Ongoing treatment indicates lesion size reduction, suggesting anlotinib's efficacy in stabilizing RAIR-DTC, particularly in patients with suboptimal responses to sorafenib.
For combination treatment regimens, safety and therapeutic tolerance are paramount. A comprehensive systematic review of clinical studies evaluating the safety and adverse event management of anlotinib in oncology treatment concluded that anlotinib's toxicity is acceptable or manageable, both in clinical trials and in real-world cases involving advanced cancer patients[37]. Furthermore, research indicates that maintenance therapy with anlotinib following chemotherapy and anlotinib combination treatment yields favorable outcomes for patients with advanced or metastatic soft tissue sarcoma, extending survival and demonstrating good tolerability[38]. In the present case, the primary adverse reactions observed were mild myelosuppression associated with chemotherapy and hypertension related to anti-angiogenic therapy. However, through appropriate management, the patient's myelosuppression was mitigated, and hypertension was effectively controlled. This indicate that the combination of anlotinib with albumin-bound paclitaxel does not elevate the risk of serious toxicity, and the treatment's safety profile is manageable. Nevertheless, there is a dearth of randomized, prospective clinical trials exploring the combination of anlotinib with chemotherapy for RAIR-DTC. The findings of this case report require further validation in a larger cohort of patients, with particular emphasis on the safety of the combined treatment approach.