Patient-based strategy for systemic treatment of metastatic renal cell carcinoma

Adverse events risk associated with regorafenib in the treatment of advanced solid tumors: meta-analysis of randomized controlled trials

Background

Regorafenib is a novel multikinase inhibitor (MKI) approved for use in the treatment of metastatic colorectal cancer (CRC), treatment-refractory gastrointestinal stromal tumors, and other solid tumor malignancies. However, the adverse events (AEs) associated with regorafenib have not been systematically investigated. Hence, we performed a meta-analysis to identify AEs associated with regorafenib in patients with advanced solid tumors.

Methods

The databases of PubMed, MEDLINE, and Embase and abstracts presented in American Society of Clinical Oncology annual meetings were searched for relevant publications from January 2004 to September 2017. Eligible studies were limited to prospective randomized controlled trials (RCTs) that evaluate the use of regorafenib in patients with advanced solid tumors. Incidence, relative risk (RR), and 95% CIs were calculated using a random or fixed effects model on the basis of the heterogeneity of the included studies.

Results

A total of 2,065 patients from six RCTs were included, and 1,340 of them received regorafenib and 725 received a placebo. Sixteen all-grade AEs and 15 high-grade AEs were investigated for their association with regorafenib. Results showed that hand-foot skin reaction (HFSR; 54%), diarrhea (33%), fatigue (32%), hypertension (31%), oral mucositis (28%), and anorexia (23%) were the most frequent clinical AEs. The most common high-grade (grade, ≥3) AEs were HFSR (16%), hypertension (13%), fatigue (6%), increased aspartate aminotransferase (AST; 6%), and hypophosphatemia (6%). Pooled RR showed that the use of regorafenib was associated with an increased risk of developing AEs. Subgroup analysis based on the prior MKI treatment showed that prior MKI treatment was associated with an increased incidence of all-grade anorexia (P=0.03) and a reduced incidence of high-grade increased AST (P=0.04). However, subgroup analysis based on the tumor type showed that no significant differences were found when comparing the RR of all-grade and high-grade AEs in patients with CRC or non-CRC.

Conclusion

The meta-analysis systematically investigated regorafenib-associated AEs. Knowledge of these AEs is essential for minimizing treatment-related toxicities and improving clinical outcomes.

Real-World Treatment Patterns and Costs for Patients with Renal Cell Carcinoma Initiating Treatment with Sunitinib and Pazopanib

BACKGROUND

Sunitinib and pazopanib are among the most prescribed targeted therapies for the systemic management of advanced renal cell carcinoma (RCC), but published cost comparisons between the 2 agents are few and limited by methodological and population differences. Also, sunitinib is administered on a 4-week on/2-week off cycle, and pazopanib is taken continuously. Thus, appropriate use and cost comparisons between the 2 drugs require methodological approaches to account for these differences. One way to accomplish this is to substitute expected for observed days supply. Recognizing the effects of nonrepresentative days supply values is important for assessing real-world treatment patterns and costs.

OBJECTIVES

To (a) characterize demographic and clinical characteristics among patients with RCC newly initiating sunitinib or pazopanib, using a large administrative claims dataset; (b) characterize treatment patterns, persistence, and costs for each treatment group; and (c) assess the effect on treatment patterns and costs for sunitinib by substituting 42 days for prescriptions with 28- or 30-day supplies to account for sunitinib's 4-week on/2-week off dosing schedule.

METHODS

This was a retrospective cohort study using health care claims data from the Truven MarketScan Research Databases, which include enrollment information and medical and pharmacy claims. Baseline patient demographic and clinical characteristics and treatment patterns (continuation, discontinuation, switching, or interruption; days supply; and persistence) were compared. Health care costs were calculated as mean daily index medication costs and as total, medical, and medication (all-cause and RCC-related) costs over the 12 months post-index period. Inclusion criteria were continuous health plan enrollment between 6 months pre-index and 12 months post-index; no RCC medications 6 months pre-index; ≥ 2 RCC diagnoses within ±180 days of index; and age ≥ 20 years. For demographic and clinical characteristics, treatment patterns, and costs, means (± standard deviations) for continuous data and relative frequencies for categorical data were reported. Chi-square tests or Student t-tests were used to evaluate differences other than costs. A generalized linear model with gamma distribution and log link was used for evaluating costs, controlling for patient demographic and pre-index clinical characteristics, persistence days, and index medication. All statistical tests were 2-tailed with significance set at P < 0.05 for all comparisons except for interactions with significance set at P < 0.10. The effects of substituting 42 days supply for sunitinib prescription records with 28 or 30 days supply were determined.

RESULTS

In total, 609 (15.1% of the sunitinib overall sample) sunitinib patients and 183 (8.3% of the pazopanib overall sample) pazopanib patients were included. Demographic and clinical characteristics were similar for each treatment cohort. The persistence periods and number of prescriptions filled were also similar. Without substitution, significant differences were observed between treatment groups in patterns of index medication use (overall P = 0.0409), with fewer patients taking sunitinib continuing treatment than patients taking pazopanib. However, with substitution, treatment patterns differed significantly (overall P = 0.0026), but with more sunitinib patients than pazopanib patients continuing treatment. Without substitution, unadjusted daily mean index medication costs were significantly different for sunitinib ($216) versus pazopanib ($177, P < 0.0001). Substitution of sunitinib days supply eliminated the significant differences in daily index medication costs between treatment groups. The 1-year RCC-related and all-cause medication, medical, and total unadjusted costs were not significantly different between treatment groups, and substitution had no effect on these costs. After adjustment for possible confounding factors, these cost results were similar to those found with unadjusted analyses.

CONCLUSIONS

In this study, patients with RCC who were initiating sunitinib and pazopanib had similar demographic and clinical characteristics and drug persistence patterns. The effect of substituting days supply values was demonstrated as an approach to considering differences in dosing cycles. Substitution significantly reduced sunitinib mean daily index medication costs and eliminated or reversed the direction of significant differences in costs between drugs during the persistence period. No significant differences were observed in unadjusted or adjusted 1-year costs.

DISCLOSURES

This study was funded and conducted fully by Pfizer. All authors are employees of Pfizer. This work was presented in part as posters at the 2015 Genitourinary Cancers Symposium, of the American Society of Clinical Oncology; Rosen Shingle Creek, Orlando, FL; February 26-28, 2015, and the 20th Annual International Meeting of the International Society for Pharmacoeconomics and Outcomes Research; Philadelphia, PA; May 16-20, 2015. All authors contributed to study concept and design and to data interpretation. Mardekian was primarily responsible for data collection, along with Harnett. MacLean and Harnett worked on the manuscript, which was revised by MacLean and Mardekian.

Survival of Patients With Advanced or Metastatic Renal Cell Carcinoma in Routine Practice Differs From That in Clinical Trials-Analyses From the German Clinical RCC Registry

INTRODUCTION

Because "real-life" patients often do not meet the strict eligibility criteria of clinical trials, we assessed the trial eligibility of patients with advanced or metastatic renal cell carcinoma (mRCC) in routine practice and compared the survival of "trial-ineligible" and potentially "trial-eligible" patients.

PATIENTS AND METHODS

The present prospective, multicenter German cohort study is recruiting patients from 110 oncology/urology outpatient centers and hospitals at initiation of systemic first-line treatment. The demographic, clinical, treatment, and survival data were collected. We defined patients as "trial-ineligible" when ≥ 1 exclusion criterion (Karnofsky performance status < 80%, hemoglobin less than the lower limit of normal, non-clear cell carcinoma histology) was documented. Otherwise, the patients were considered "trial-eligible".

RESULTS

Of 732 patients included, 57% were classified as "trial-ineligible". Overall, the median first-line progression-free survival (PFS) was 7.9 months (95% confidence interval [CI], 6.9-8.9 months). The median first-line PFS of "trial-eligible" and "trial-ineligible" patients was 11.0 months (95% CI, 9.6-13.1 months) and 5.3 months (95% CI, 4.6-6.5 months), respectively. The median OS of the "trial-eligible" and "trial-ineligible" patients was 26.0 months (95% CI, 22.1-29.7 months) and 12.6 months (95% CI, 10.6-15.8 months), respectively.

CONCLUSION

Our data suggest that patients in routine practice differ from patients treated in clinical trials and that almost 60% of mRCC patients in German routine practice would be ineligible for participation in clinical trials. While their first-line PFS and OS were shorter than those of "trial-eligible" patients, the PFS and OS of "trial-eligible" patients were comparable with the results from clinical trials. Physicians should be aware of these differences when discussing treatment options and outcome expectations with patients.

Adverse reactions in mRCC patients documented in routine practice by German office-based oncologists and uro-oncologists

Background Signal transduction inhibitors (STIs) have considerably improved treatment of advanced/metastasized renal cell carcinoma (mRCC). Most safety data for these drugs are derived from clinical trials. The purpose of this study was to evaluate which adverse drug reactions are documented during first-line treatments in routine clinical practice. Patients and methods The ongoing prospective German mRCC clinical registry is recruiting patients in 110 oncology and urology outpatient centers. Data from the first 250 patients who had completed first-line treatment were analyzed regarding adverse drug reactions (ADRs) documented in patients' medical records. Results Patients were older than in clinical trials and had comorbidities. Patients were treated with the STIs sunitinib (61%), temsirolimus (14%), sorafenib (10%), or bevacizumab combined with interferon (6%). About 520 ADRs were documented, of which 29% resulted in treatment modifications. The most frequently affected organ system was the gastrointestinal system. The most frequently documented ADRs were mucositis/stomatitis (14%), fatigue (14%), diarrhea (12%), and nausea (12%). Conclusions In routine practice, mRCC first-line treatments using STIs frequently lead to ADRs partly necessitating treatment modifications. The pattern of reported ADRs is similar to that reported in clinical trials, but frequencies of events differ, especially for symptoms of multifactorial origin that are not immediately associated with the treatment. These results indicate that perception and documentation of adverse reactions is different between clinical trials and routine practice, and that reviews of patients' medical records might not be the best method to assess safety in routine practice.

The anti-tumor effect of a polypeptide extracted from Tegillarca granosa Linnaeus on renal metastatic tumor OS-RC-2 cells

INTRODUCTION

Renal cell carcinoma is a type of malignant tumor often diagnosed in the urinary system. The aim of this study is to evaluate the anti-tumor effects and mechanisms of a polypeptide, Haishengsu (TG-1), with different concentrations (125, 250, 500 mg/kg) on renal metastatic tumor OS-RC-2 cells.

MATERIAL AND METHODS

We first established the renal metastatic tumor model. After being administered with TG-1, the weight of tumors was measured and the microstructural changes of renal carcinoma OS-RC-2 cells were compared using transmission electron microscopy before and after the therapy. The Ki67 expression in renal carcinoma OS-RC-2 cells was analyzed by RT-PCR and downstream signal molecule caspase-3 was measured by Western blot assay.

RESULTS

After treatment with different doses of TG-1, the tumor weights in the positive control group and experimental groups were smaller than those in the untreated control group, suggesting that TG-1 could effectively inhibit tumor growth in mice. The transmission electron microscopy and flow cytometry results indicated that TG-1 induces tumor cell apoptosis (p < 0.05). The tumor cells exhibited polymorphism changes and chromatin edge clustering. TG-1 also inhibited Ki67 expression and promoted caspase-3 expression in the tumor significantly (p < 0.05).

CONCLUSIONS

TG-1 inhibits the growth of the tumor and induces apoptosis of the tumor cells by inducing caspase-3 expression. The results provide a basis for clinical application of TG-1 in the future.

Aortic dissection during antiangiogenic therapy with sunitinib. A case report

CONTEXT

Sunitinib is an antiangiogenic drug that has been approved for treating metastatic renal cancer. Its action as a tyrosine kinase inhibitor of vascular endothelial growth factor receptors (VEGFRs) and other angiogenesis receptors may lead to adverse effects such as hypertension and heart failure. However, reports in the literature on an association between sunitinib therapy and acute aortic dissection are rare.

CASE REPORT

We report the case of a 68-year-old man with metastatic renal carcinoma who developed acute aortic dissection during sunitinib therapy. He had no history of hypertension or any other risk factor for aortic dissection. After aortic dissection had been diagnosed, sunitinib was withdrawn and an aortic endoprosthesis was placed. Afterwards, the patient was treated clinically with antihypertensive drugs and new therapy for renal cancer consisting of temsirolimus, an inhibitor of the mammalian target of rapamycin (mTOR) pathway.

CONCLUSION

Hypertension is a common event when antiangiogenic drugs are used in oncology. However, knowledge of other severe cardiovascular events that may occur in these patients, such as acute aortic dissection, is important. Adequate control over arterial pressure and frequent monitoring of patients during the first days of antiangiogenic therapy is essential for early diagnosis of possible adverse events.

Gramicidin A: A New Mission for an Old Antibiotic

Gramicidin A (GA) is a channel-forming ionophore that renders biological membranes permeable to specific cations which disrupts cellular ionic homeostasis. It is a well-known antibiotic, however it’s potential as a therapeutic agent for cancer has not been widely evaluated. In two recently published studies, we showed that GA treatment is toxic to cell lines and tumor xenografts derived from renal cell carcinoma (RCC), a devastating disease that is highly resistant to conventional therapy. GA was found to possess the qualities of both a cytotoxic drug and a targeted angiogenesis inhibitor, and this combination significantly compromised RCC growth in vitro and in vivo. In this review, we summarize our recent research on GA, discuss the possible mechanisms whereby it exerts its anti-tumor effects, and share our perspectives on the future opportunities and challenges to the use of GA as a new anticancer agent.

Efficacy of targeted treatment beyond third-line therapy in metastatic kidney cancer: retrospective analysis from a large-volume cancer center

INTRODUCTION/BACKGROUND

Currently, 7 agents are approved for the first- and second-line therapy for metastatic renal cell carcinoma. In contrast, data supporting their use beyond second line are limited. Here we summarize our experience in patients treated with more than 4 lines of therapy.

METHODS

We retrospectively assessed the outcome of 24 patients treated at our institution with at least 4 lines of therapy. Progression-free survival (PFS) and overall survival (OS) were calculated using Kaplan-Meier estimates.

RESULTS

Median OS from the initiation of first-line therapy for the whole cohort is 64.7 months. Up to 96% of the patients received a tyrosine kinase inhibitor (TKI) and mammalian target of rapamycin (mTOR) inhibitor (mTOR-I) within the first 3 lines of treatment. In the fourth or following lines, patients were treated with TKI, mTOR-I, bevacizumab/interferon, or experimental drugs. Seven patients continued treatment with a sixth-line agent; one has been treated up to the ninth line. Sixteen percent of the patients receiving fourth-line therapy and 13% receiving fifth-line therapy experienced a partial remission, which was independent from response to previous therapies. Median OS from fourth and fifth line was 30.8 and 26.2 months, respectively. Median PFS for fourth-line therapy was 5.8 months. No significant difference in PFS was observed for patients with disease that responded or did not respond to first-line therapy.

CONCLUSION

Despite the limitations of a retrospective analysis, our study suggests that selected patients benefit from multiple lines of treatment, independent of response to first-line therapy. However, the optimal sequence of treatment with regard to later lines remains to be determined.

First-, second-, third-line therapy for mRCC: benchmarks for trial design from the IMDC

BACKGROUND

Limited data exist on outcomes for metastatic renal cell carcinoma (mRCC) patients treated with multiple lines of therapy. Benchmarks for survival are required for patient counselling and clinical trial design.

METHODS

Outcomes of mRCC patients from the International mRCC Database Consortium database treated with 1, 2, or 3+ lines of targeted therapy (TT) were compared by proportional hazards regression. Overall survival (OS) and progression-free survival (PFS) were calculated using different population inclusion criteria.

RESULTS

In total, 2705 patients were treated with TT of which 57% received only first-line TT, 27% received two lines of TT, and 16% received 3+ lines of TT. Overall survival of patients who received 1, 2, or 3+ lines of TT were 14.9, 21.0, and 39.2 months, respectively, from first-line TT (P<0.0001). On multivariable analysis, 2 lines and 3+ lines of therapy were each associated with better OS (HR=0.738 and 0.626, P<0.0001). Survival outcomes for the subgroups were as follows: for all patients, OS 20.9 months and PFS 7.2 months; for those similar to eligible patients in the first-line ADAPT trial, OS 14.7 months and PFS 5.6 months; for those similar to patients in first-line TIVO-1 trial, OS 24.8 months and PFS 8.2 months; for those similar to patients in second-line INTORSECT trial, OS 13.0 months and PFS 3.9 months; and for those similar to patients in the third-line GOLD trial, OS 18.0 months and PFS 4.4 months.

CONCLUSIONS

Patients who are able to receive more lines of TT live longer. Survival benchmarks provide context and perspective when interpreting and designing clinical trials.

Retrospective claims analysis of best supportive care costs and survival in a US metastatic renal cell population

Introduction

Survival and best supportive care (BSC) costs for patients with metastatic renal cell carcinoma (mRCC), after stopping therapy, are poorly characterized yet an important aspect of patient care. This study examined survival and costs associated with BSC after one or two lines of therapy (LOTs) for mRCC.

Methods

A retrospective cohort analysis used claims data from commercially insured or Medicare Advantage Prescription Drug (MAPD) plan enrollees of a large United States health plan with an index RCC diagnosis (ICD-9-CM 189.0) between January 1, 2007 and June 30, 2010; initiating any of the following therapies 30 days pre-index date through disenrollment from plan: sunitinib, temsirolimus, sorafenib, bevacizumab, everolimus, pazopanib, cytokines. LOT was identified using prescription fill and administration dates. Health care costs represent health plan- plus patient-paid amounts.

Results

The cohort (n = 274) was 73% male, with a mean age of 63.3 years (SD 11.1), with 80% commercially insured (20% MAPD), and 68% starting BSC following one LOT. Mean BSC duration was longer following one than two LOTs (223 [SD 260], 176 [SD 163] days). Median survival from the start of BSC was similar following one and two LOTs (126 and 118 days). Total BSC costs following one and two LOTs averaged US$50,188 (SD $96,984) and $37,295 (SD $51,102). Monthly costs for BSC following one and two LOTs ($10,151 and $10,566) were not substantially lower than costs while on treatment ($14,621 and $16,957). Inpatient hospital costs represented 47% and 49% following one and two LOTs, with ambulatory costs of approximately 36% following each LOT.

Conclusion

Our study found similar survival and monthly costs for BSC following either one or two LOTs, with almost half of the cost reflecting inpatient care. Compared to costs on treatment ($14,621 to $16,957), BSC costs can be considerable ($10,151 to $10,566).

Experience with sorafenib in the treatment of advanced renal cell carcinoma

The molecular-targeted agent sorafenib is the first anticancer agent able to slow the progression of advanced/metastatic renal cell carcinoma, a tumor that was formerly refractory to conventional therapy. Experience from everyday clinical practice and investigations exploring the suitability of this agent for patients with harmful pathological conditions has extended the use of sorafenib to other settings of renal cell carcinoma and to particular risk populations. The aim of this review is to provide evidence on the most effective and safe use of sorafenib. The review pays particular attention to patients who have several comorbidities, such as impaired renal and cardiac function, and older patients whose frailty due to impaired organ function necessitates the most careful administration of targeted antineoplastic agents.

Prolonged survival after sequential multimodal treatment in metastatic renal cell carcinoma: two case reports and a review of the literature

INTRODUCTION

In this case series and short review of the literature, we underline the impact of nephrectomy combined with sequential therapy based on cytokines, antiangiogenic factors, and mammalian target of rapamycin inhibitors along with metastasectomy on overall survival and quality of life in patients with metastatic clear cell renal carcinoma.

CASE PRESENTATION

In the first of two cases reported here, a 53-year-old Caucasian man underwent a radical left nephrectomy for renal cell cancer and relapsed with a bone metastasis in his right humerus. He was treated with closed nailing and cytokine-based chemotherapy. For 5 years, the disease was stable and he had great improvement in quality of life. Subsequently, the disease relapsed in his lymph nodes, lung, and thorax soft tissue. He was then treated with antiangiogenic factors and mammalian target of rapamycin inhibitors. The disease progressed until September 2009, when he died of allergic shock during a blood transfusion, 9 years after the initial diagnosis of renal cell cancer.In the second case, a 54-year-old Caucasian man underwent a radical left nephrectomy for renal cell cancer. A year later, the disease progressed to his neck lymph nodes, and cytokine-based chemotherapy was initiated. While he was on cytokines, a solitary pulmonary nodule appeared and he underwent a metastasectomy. Nine months later, magnetic resonance imaging of his brain revealed a focal right occipitoparietal lesion, which was resected. After two years of active surveillance, the disease relapsed as a pulmonary metastasis and he was treated with an antiangiogenic factor. Further progressions presenting as enlarged axillary lymph nodes, chest soft tissue lesions, and thoracic spine bone metastases were sequentially observed. He then received a first-generation mammalian target of rapamycin inhibitor, an antiangiogenic factor, and later a second-generation mammalian target of rapamycin inhibitor and palliative radiotherapy. Ten years after the initial diagnosis of renal cell cancer, his disease is stable and he is on a third antiangiogenic factor and leads an active life.

CONCLUSIONS

One multidisciplinary approach to patients with metastatic renal cell cancer combines nephrectomy, metastasectomy, and radiotherapy (when feasible) with medical therapy based on cytokines and targeted treatment employing agents inhibiting angiogenesis, other receptor tyrosine kinases, and mammalian target of rapamycin. This approach could prolong survival and improve quality of life.

Current status of targeted therapy for advanced renal cell carcinoma

The treatment of metastatic renal cell carcinoma (mRCC) has recently evolved from being predominantly cytokine-based treatment to the use of targeted agents, which include sorafenib, sunitinib, bevacizumab (plus interferon alpha [IFN-α]), temsirolimus, everolimus, pazopanib, and most recently, axitinib. Improved understanding of the molecular pathways implicated in the pathogenesis of RCC has led to the development of specific targeted therapies for treating the disease. In Korea, it has been 5 years since targeted therapy became available for mRCC. Thus, we now have broader and better therapeutic options at hand, leading to a significantly improved prognosis for patients with mRCC. However, the treatment of mRCC remains a challenge and a major health problem. Many questions remain on the efficacy of combination treatments and on the best methods for achieving complete remission. Additional studies are needed to optimize the use of these agents by identifying those patients who would most benefit and by elucidating the best means of delivering these agents, either in combination or as sequential single agents. Furthermore, numerous ongoing research activities aim at improving the benefits of the new compounds in the metastatic situation or their application in the early phase of the disease. This review introduces what is currently known regarding the fundamental biology that underlies clear cell RCC, summarizes the clinical evidence supporting the benefits of targeted agents in mRCC treatment, discusses survival endpoints used in pivotal clinical trials, and outlines future research directions.

Treatment-related optimism protects quality of life in a phase II clinical trial for metastatic renal cell carcinoma

BACKGROUND

Patients on clinical trials often experience declining quality of life (QOL). Little is known about the psychosocial variables that buffer against decline.

PURPOSE

This study aims to examine correlations between psychosocial variables and QOL over the course of a clinical trial in patients with metastatic renal cell cancer.

METHODS

At baseline, 114 participants completed measures of treatment-related optimism, social support, and QOL (Functional Assessment of Cancer Therapy-General). QOL was also assessed 2, 4, and 8 weeks after the start of treatment with low-dose or intermediate-dose interferon.

RESULTS

QOL decreased significantly in the intermediate-dose group but not in the low-dose group (p < .01). The decline was less severe for patients who had high rather than low treatment optimism (p = .03). A higher level of social support was significantly associated with higher baseline QOL (p < .05) but a more rapid decline in QOL over time (p < .01).

CONCLUSION

Treatment optimism was favorably associated with QOL.

Metformin inhibits renal cell carcinoma in vitro and in vivo xenograft

OBJECTIVE

To evaluate the effects of metformin on renal cell carcinoma (RCC) and its underlying mechanisms.

MATERIALS AND METHODS

We used 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and colony formation assays to investigate the effects of metformin on RCC cell growth. Flow cytometry was used to evaluate the cell cycle changes after metformin treatment. We further determined the possible signaling molecules involved in this process by immunoblot analysis of various proteins. Furthermore, a xenograft model was used to study the effects of metformin on RCC tumor growth.

RESULTS

We demonstrated that metformin effectively inhibits cell proliferation in 786-O and OS-RC-2 RCC cell lines. Moreover, metformin down-regulated cyclin D1 expression and induced G0/G1 cell cycle arrest in these cells. Further study revealed metformin induced the activation of AMP-activated protein kinase (AMPK), and inhibited mammalian target of rapamycin (mTOR), which is a central regulator of protein synthesis and cell growth, and negatively regulated by AMPK. Most importantly, daily treatment of mice with metformin prevented RCC tumor growth in a xenograft model.

CONCLUSIONS

Metformin was able to induce G0/G1 cell cycle arrest and inhibit RCC growth in vitro and in vivo. These results suggest that metformin may be a potential therapeutic agent for the treatment of RCC.