Exceptional Response to Cabozantinib of Rapidly Evolving Brain Metastases of Renal Cell Carcinoma: A Case Report and Review of the Literature

An Overview of Systemic Targeted Therapy in Renal Cell Carcinoma, with a Focus on Metastatic Renal Cell Carcinoma and Brain Metastases

The most commonly diagnosed malignancy of the urinary system is represented by renal cell carcinoma. Various subvariants of RCC were described, with a clear-cell type prevailing in about 85% of all RCC tumors. Patients with metastases from renal cell carcinoma did not have many effective therapies until the end of the 1980s, as long as hormonal therapy and chemotherapy were the only options available. The outcomes were unsatisfactory due to the poor effectiveness of the available therapeutic options, but then interferon-alpha and interleukin-2 showed treatment effectiveness, providing benefits but only for less than half of the patients. However, it was not until 2004 that targeted therapies emerged, prolonging the survival rate. Currently, new technologies and strategies are being developed to improve the actual efficacy of available treatments and their prognostic aspects. This article summarizes the mechanisms of action, importance, benefits, adverse events of special interest, and efficacy of immunotherapy in metastatic renal cell carcinoma, with a focus on brain metastases.

An interdisciplinary consensus on the management of brain metastases in patients with renal cell carcinoma

Brain metastases are a challenging manifestation of renal cell carcinoma. We have a limited understanding of brain metastasis tumor and immune biology, drivers of resistance to systemic treatment, and their overall poor prognosis. Current data support a multimodal treatment strategy with radiation treatment and/or surgery. Nonetheless, the optimal approach for the management of brain metastases from renal cell carcinoma remains unclear. To improve patient care, the authors sought to standardize practical management strategies. They performed an unstructured literature review and elaborated on the current management strategies through an international group of experts from different disciplines assembled via the network of the International Kidney Cancer Coalition. Experts from different disciplines were administered a survey to answer questions related to current challenges and unmet patient needs. On the basis of the integrated approach of literature review and survey study results, the authors built algorithms for the management of single and multiple brain metastases in patients with renal cell carcinoma. The literature review, consensus statements, and algorithms presented in this report can serve as a framework guiding treatment decisions for patients. CA Cancer J Clin. 2022;72:454-489.

RET signaling pathway and RET inhibitors in human cancer

Rearranged during transfection (RET) receptor tyrosine kinase was first identified over thirty years ago as a novel transforming gene. Since its discovery and subsequent pathway characterization, RET alterations have been identified in numerous cancer types and are most prevalent in thyroid carcinomas and non-small cell lung cancer (NSCLC). In other tumor types such as breast cancer and salivary gland carcinomas, RET alterations can be found at lower frequencies. Aberrant RET activity is associated with poor prognosis of thyroid and lung carcinoma patients, and is strongly correlated with increased risk of distant metastases. RET aberrations encompass a variety of genomic or proteomic alterations, most of which confer constitutive activation of RET. Activating RET alterations, such as point mutations or gene fusions, enhance activity of signaling pathways downstream of RET, namely PI3K/AKT, RAS/RAF, MAPK, and PLCγ pathways, to promote cell proliferation, growth, and survival. Given the important role that mutant RET plays in metastatic cancers, significant efforts have been made in developing inhibitors against RET kinase activity. These efforts have led to FDA approval of Selpercatinib and Pralsetinib for NSCLC, as well as, additional selective RET inhibitors in preclinical and clinical testing. This review covers the current biological understanding of RET signaling, the impact of RET hyperactivity on tumor progression in multiple tumor types, and RET inhibitors with promising preclinical and clinical efficacy.

Clinical Activity and Safety of Cabozantinib for Brain Metastases in Patients With Renal Cell Carcinoma

Importance

Patients with brain metastases from renal cell carcinoma (RCC) have been underrepresented in clinical trials, and effective systemic therapy is lacking. Cabozantinib shows robust clinical activity in metastatic RCC, but its effect on brain metastases remains unclear.

Objective

To assess the clinical activity and toxic effects of cabozantinib to treat brain metastases in patients with metastatic RCC.

Design, Setting, and Participants

This retrospective cohort study included patients with metastatic RCC and brain metastases treated in 15 international institutions (US, Belgium, France, and Spain) between January 2014 and October 2020. Cohort A comprised patients with progressing brain metastases without concomitant brain-directed local therapy, and cohort B comprised patients with stable or progressing brain metastases concomitantly treated by brain-directed local therapy.

Exposures

Receipt of cabozantinib monotherapy at any line of treatment.

Main Outcomes and Measures

Intracranial radiological response rate by modified Response Evaluation Criteria in Solid Tumors, version 1.1, and toxic effects of cabozantinib.

Results

Of the 88 patients with brain metastases from RCC included in the study, 33 (38%) were in cohort A and 55 (62%) were in cohort B; the majority of patients were men (n = 69; 78%), and the median age at cabozantinib initiation was 61 years (range, 34-81 years). Median follow-up was 17 months (range, 2-74 months). The intracranial response rate was 55% (95% CI, 36%-73%) and 47% (95% CI, 33%-61%) in cohorts A and B, respectively. In cohort A, the extracranial response rate was 48% (95% CI, 31%-66%), median time to treatment failure was 8.9 months (95% CI, 5.9-12.3 months), and median overall survival was 15 months (95% CI, 9.0-30.0 months). In cohort B, the extracranial response rate was 38% (95% CI, 25%-52%), time to treatment failure was 9.7 months (95% CI, 6.0-13.2 months), and median overall survival was 16 months (95% CI, 12.0-21.9 months). Cabozantinib was well tolerated, with no unexpected toxic effects or neurological adverse events reported. No treatment-related deaths were observed.

Conclusions and Relevance

In this cohort study, cabozantinib showed considerable intracranial activity and an acceptable safety profile in patients with RCC and brain metastases. Support of prospective studies evaluating the efficacy of cabozantinib for brain metastases in patients with RCC is critical.

Dual immune check point blockade or immune check point-tyrosine kinase inhibitor combination: as a first-line treatment in metastatic renal cell carcinoma?

PURPOSE OF REVIEW

To discuss treatment decisions in the first-line setting of metastatic renal cell carcinoma (mRCC).

RECENT FINDINGS

Immune check point inhibitor (ICI) combinations have replaced sunitinib as the standard of care in the first-line treatment of mRCC. Dual ICI treatment with nivolumab and ipilimumab was shown to significantly improve overall survival and objective response rates. Similarly, the ICI-tyrosine kinase inhibitor combinations pembrolizumab and axitinib and nivolumab and cabozantinib have demonstrated superiority in terms of overall survival, objective response rates and progression-free survival versus sunitinib. The lack of both comparative trials and predictive markers impedes individualized treatment decisions. Clinicians are left to make treatment choices based on clinical and biological factors. These factors may include differences in toxicity profiles, the rate of complete remission, a clinical situation that requires urgent tumor shrinkage, the presence of inflammation, histological or immune-histochemical features and others.

SUMMARY

In the absence of comparative trials, clinical and biological factors may facilitate the choice between various treatment options in the first-line setting of mRCC. In addition, both the experience of the physician with a specific treatment together with patient's preferences and expectations of systemic therapy may be part of the decision-making process.

TRK xDFG Mutations Trigger a Sensitivity Switch from Type I to II Kinase Inhibitors

On-target resistance to next-generation TRK inhibitors in TRK fusion-positive cancers is largely uncharacterized. In patients with these tumors, we found that TRK xDFG mutations confer resistance to type I next-generation TRK inhibitors designed to maintain potency against several kinase domain mutations. Computational modeling and biochemical assays showed that TRKA^G667 and TRKC^G696 xDFG substitutions reduce drug binding by generating steric hindrance. Concurrently, these mutations stabilize the inactive (DFG-out) conformations of the kinases, thus sensitizing these kinases to type II TRK inhibitors. Consistently, type II inhibitors impede the growth and TRK-mediated signaling of xDFG-mutant isogenic and patient-derived models. Collectively, these data demonstrate that adaptive conformational resistance can be abrogated by shifting kinase engagement modes. Given the prior identification of paralogous xDFG resistance mutations in other oncogene-addicted cancers, these findings provide insights into rational type II drug design by leveraging inhibitor class affinity switching to address recalcitrant resistant alterations. SIGNIFICANCE: In TRK fusion-positive cancers, TRK xDFG substitutions represent a shared liability for type I TRK inhibitors. In contrast, they represent a potential biomarker of type II TRK inhibitor activity. As all currently available type II agents are multikinase inhibitors, rational drug design should focus on selective type II inhibitor creation.This article is highlighted in the In This Issue feature, p. 1.

Cabozantinib in Renal Cell Carcinoma With Brain Metastases: Safety and Efficacy in a Real-World Population

BACKGROUND

Cabozantinib showed efficacy and manageable toxicity in patients with metastatic renal cell carcinoma (mRCC). In this study we aimed to describe the safety and to collect evidence on the potential efficacy of cabozantinib in mRCC patients with brain metastases (BM) in a real-world experience.

MATERIALS AND METHODS

We retrospectively collected data of patients treated with cabozantinib within the Italian Managed Access Program. Patients were selected for the presence of BM before the start of treatment and for at least 1 previous tyrosine kinase inhibitor (TKI) treatment regimen for metastatic disease. Safety data were reported, and overall response rate (ORR), brain-specific response, progression-free survival (PFS), and median overall survival (OS) were analyzed.

RESULTS

Overall, 12 patients treated with cabozantinib were evaluated. Any grade adverse events (AEs) accounted for 92%, Grade 3/4 AEs rated at 36% with no major neurological side effects. The most common AEs included hypertension (33%), fatigue (24%), aminotransferase elevation (25%), hypothyroidism (16%), and gastrointestinal toxicity (16%). The ORR was 50% with a disease control rate of 75%. All 5 patients treated with a combined systemic and brain-directed approach obtained intracranial disease control, without increased toxicity. Median PFS and median OS were 5.8 and 8.8 months, respectively. Comparable safety and tolerability results for other TKI regimens were reported from the literature.

CONCLUSION

Cabozantinib showed safety, acceptable tolerability, and promising antitumor activity in a population of mRCC patients with BM from a real-world experience. A combined modality approach for renal cell carcinoma with BM, whenever feasible, could be recommended to improve oncological outcomes.

Brain Complete Response to Cabozantinib prior to Radiation Therapy in Metastatic Renal Cell Carcinoma

Cabozantinib represents an established vascular endothelial growth factor- (VEGF-) tyrosine kinase inhibitor (TKI) in the treatment paradigm of metastatic renal cell carcinoma (mRCC). Its activity in mRCC patients with brain metastases (BMs) has been largely underreported in prospective clinical trials. We present the unique case of a heavily pretreated mRCC patient with BMs who achieved a brain complete response to cabozantinib prior to receiving radiation therapy. We end with a literature review and discussion of the biologic rationale and growing evidence supporting the intracranial activity of cabozantinib.

Les métastases cérébrales de cancer du rein, un défi clinique

BRAIN METASTASES IN RENAL CELL CARCINOMA, AN UNMET NEED

Brain metastases from renal cell carcinomas are associated with dismal prognosis and might be present in up to 10 % of metastatic patients. Biologically, the blood brain barrier might be disrupted in brain metastases and thus do not exclusively account for treatment resistance. Brain metastases often acquire additional molecular alterations that might provide aggressive features. They are also associated with high lymphocytic infiltration and expression of immune checkpoints PD-1/PD-L1. In clinical routine, scores based on metastatic volume and patients' performance status might help better predict survival. The cornerstone of brain metastases treatment is stereotactic radiation therapy if patients are eligible, while systemic treatments such as antiangiogenics and immune checkpoint inhibitors only provide limited disease control. Early identification of patients with brain metastases from renal cell carcinomas and promotion of dedicated clinical trials will be important to try and improve current clinical management.

Activity of cabozantinib in radioresistant brain metastases from renal cell carcinoma: two case reports

Background

Renal cell carcinoma represents 3–5% of adult malignant tumors. Metastases are found in 30–40% of patients and brain metastases occurred in more than 10% of them. Despite significant progress in medical treatment, patients with brain metastases still have a limited survival. Cabozantinib, a tyrosine kinase inhibitor directed against vascular endothelial growth factor receptors, was recently registered for the treatment of metastatic renal cell carcinoma. Almost no data are, however, available on patients with brain metastases.

Case presentation

Case 1 is a 51-year-old man of North African origin; Case 2 is a 55-year-old European man. Case 1 and Case 2 had metastases of renal carcinoma at initial diagnosis and were treated with vascular endothelial growth factor receptors tyrosine kinase inhibitors. Case 1 had clear cell renal carcinoma and underwent nephrectomy; he then received several lines of tyrosine kinase inhibitor directed against vascular endothelial growth factor receptors and the mTor complex. During the second treatment a brain metastasis was diagnosed and treated with radiosurgery with rapid efficacy. Two years later he received nivolumab, an antibody directed against the programmed death-1 and programmed death-ligand 1 complex, but disease progression was observed with the reappearance of the brain metastasis together with neurologic symptoms. Cabozantinib was administered and induced a rapid clinical improvement as well as tumor regression in all sites including his brain. Sequencing of his tumor evidenced a mutation of the MET gene. Case 2 had a papillary renal carcinoma with brain metastases at time of diagnosis. After radiation of the brain tumors, a vascular endothelial growth factor receptor tyrosine kinase inhibitor was administered for 3 years. The disease was under control in all sites except in his brain; several new brain metastases requiring new radiation treatments developed. The disease finally progressed at all metastatic sites including his brain and he had several neurological symptoms. Cabozantinib was administered and rapidly induced a clinical improvement; a further computed tomography scan and brain magnetic resonance imaging showed significant tumor regressions. No MET gene mutation or amplification was observed in the tumor analysis.

Conclusions

These case reports indicate that cabozantinib was able, first, to reach brain tumors and second, to induce significant regressions in renal carcinoma brain metastases that were resistant to radiation as well as to previous systemic vascular endothelial growth factor receptor tyrosine kinase inhibitors.

Cabozantinib for the Management of Metastatic Clear Cell Renal Cell Carcinoma

Cabozantinib is a multi-tyrosine kinase inhibitor used for the treatment of various solid-organ tumours. It was recently approved as a first- and second-line therapeutic for the management of advanced/metastatic renal cell carcinoma based on the results of two randomised controlled trials. The phase III METEOR trial compared cabozantinib against everolimus as a second- or greater line therapy and found benefits in progression-free and overall survival, and the phase II CABOSUN trial compared cabozantinib against sunitinib as a first-line therapeutic and found benefits in terms of progression-free survival. This review briefly summarises how cabozantinib fits into current treatment paradigms for the management of advanced renal cell carcinoma.