Sequential Therapeutic Response Modeling for Tumor Treatment Using Computational Hybrid Control Systems Approach

OBJECTIVE

Tumorigenesis is due to uncontrolled cell division arising from mutations and alterations in the proliferative controls of the cell population. The fight against tumor growth and development has often relied on combination therapy that has been acclaimed as one of the main standards of care in cancer therapeutics and prevention of drug-related resistances. The toxicity of the combinatorial drugs raises a significant concern whenever patients take two or more drugs concurrently at the maximum tolerated dose. A promising solution in tumor treatment involves the administration of the drugs in an alternating or sequential fashion rather than a simultaneous manner. In this paper, we investigate how feasible such an approach is from a mathematical perspective and propose a switched hybrid control systems framework.

METHODS

We explore the response of tumor cells dynamics to sequential drugs administration with the aid of a time-dependent switching strategy. A transit compartmentalized model is employed to describe the tumor cells progression to death.

RESULTS

The design of the time-based drug switching logic ensures the proliferating tumor cells are repressed.

CONCLUSIONS

Simulation results are provided using the tumor growth dynamics with sequential drugs intake to demonstrate the effectiveness of the proposed method in reducing the tumor size.

SIGNIFICANCE

This paper is the first attempt to provide a switched hybrid control systems framework on sequential drug administration to biomedical researchers and clinicians.

Time-Based Switching Control of Genetic Regulatory Networks: Toward Sequential Drug Intake for Cancer Therapy

As cancer growth and development typically involves multiple genes and pathways, combination therapy has been touted as the standard of care in the treatment of cancer. However, drug toxicity becomes a major concern whenever a patient takes 2 or more drugs simultaneously at the maximum tolerable dosage. A potential solution would be administering the drugs in a sequential or alternating manner rather than concurrently. This study therefore examines the feasibility of such an approach from a switched system control perspective. Particularly, we study how genetic regulatory systems respond to sequential (switched) drug inputs using the time-based switching mechanism. The design of the time-driven drug switching function guarantees the stability of the genetic regulatory system and the repression of the diseased genes. Simulation results using proof-of-concept models and the proliferation and survival pathways with sequential drug inputs show the effectiveness of the proposed approach.

The Wide Experience of the Sequential Therapy for Patients with Metastatic Renal Cell Carcinoma

Sequential targeted therapies are the standard of care for patients with metastatic renal cell carcinoma (mRCC). Several drugs are available for patients whose disease progresses while they receive initial tyrosine kinase inhibitor (TKI) therapy; these include nivolumab (an inhibitor of PD-1 receptor), everolimus (an inhibitor of the mechanistic target of rapamycin) or additional TKIs. Until now, there has been no clinical evidence to support the use of one strategy versus another, so investigators and physicians rely on experience, judgement and findings from molecular analyses to select the appropriate treatment. However, with the arrival of nivolumab and cabozantinib that provide an overall survival higher than other alternative treatments, therapeutic strategies may have changed. Here, we discuss findings from preclinical and clinical studies that might help clinicians to choose the optimal treatment approach for patients with mRCC who progress to initial therapy.

Pazopanib as a second-line treatment for non-cytokine-treated metastatic renal cell carcinoma: a meta-analysis of the effect of treatment

BACKGROUND

The currently recommended treatment algorithm for patients with advanced renal cell carcinoma who fail the first-line targeted therapy does not normally include pazopanib as a second-line treatment option. It would therefore be of interest to determine the efficiency of pazopanib in this setting in terms of the partial response rate (PRR), disease control rate (DCR), and progression-free survival (PFS).

METHODS

Peer-reviewed clinical reports without language restriction, both full papers and conference abstracts, which assessed the second-line use of pazopanib following failure of first-line non-cytokine-targeted therapy, were included. After the literature retrieval, we conducted a Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA)-compliant systematic review of the literature and meta-analysis of the size of the effect of each outcome measure (PRR, DCR, and PFS). The effect size and 95 % confidence interval (CI) were calculated using fixed-effect or random-effects models based on the heterogeneity represented by I(2) of selected studies. Meta-analysis forest plots with a fixed-effect model showing the PRR and DCR were created.

RESULTS

Our results show that there are no available comparative studies on pazopanib second-line treatment. Only phase II trials or retrospective analysis reports were retrievable. Six studies (comprising 217 patients) were included in the qualitative and quantitative analysis. Pazopanib as a second-line treatment resulted in a PRR of 23 % (95 % CI, 17-31 %; I(2) = 52.6 %) and a DCR of 73 % (95 % CI, 65-80 %; I(2) = 0.00 %). The meta-analysis with fixed-effect model revealed that PFS was 6.5 months (95 % CI, 5.6-7.5 months; I(2) = 86.2 %).

CONCLUSIONS

In conclusion, the effectiveness and indication of pazopanib for use in the second-line setting has not yet been examined in-depth; however, this meta-analysis has shown that the treatment effects in terms of PRR, DCR, and PFS may be similar to other well-studied second-line targeted therapies. Rigorous comparative phase III trials testing this hypothesis are required.

Optimizing clinical benefit with targeted treatment in mRCC: "Tumor growth rate" as an alternative clinical endpoint

Tumor growth rate (TGR), usually defined as the ratio between the slope of tumor growth before the initiation of treatment and the slope of tumor growth during treatment, between the nadir and disease progression, is a measure of the rate at which tumor volume increases over time. In patients with metastatic renal cell carcinoma (mRCC), TGR has emerged as a reliable alternative parameter to allow a quantitative and dynamic evaluation of tumor response. This review presents evidence on the correlation between TGR and treatment outcomes and discusses the potential role of this tool within the treatment scenario of mRCC. Current evidence, albeit of retrospective nature, suggests that TGR might represent a useful tool to assess whether treatment is altering the course of the disease, and has shown to be significantly associated with progression-free survival and overall survival. Therefore, TGR may represent a valuable endpoint for clinical trials evaluating new molecularly targeted therapies. Most importantly, incorporation of TGR in the assessment of individual patients undergoing targeted therapies may help clinicians decide if a given agent is no longer able to control disease growth and whether continuing therapy beyond RECIST progression may still produce clinical benefit.

Real-world dosing and drug costs with everolimus or axitinib as second targeted therapies for advanced renal cell carcinoma: a retrospective chart review in the US

OBJECTIVE

To describe dosing patterns and to compare the drug costs per month spent in progression-free survival (PFS) among patients with advanced renal cell carcinoma (aRCC) treated with everolimus or axitinib following a first tyrosine kinase inhibitor (TKI).

METHODS

A medical record retrospective review was conducted among medical oncologists and hematologists/oncologists in the US. Patient eligibility criteria included: (1) age ≥18 years; (2) discontinuation of first TKI (sunitinib, sorafenib, or pazopanib) for medical reasons; (3) initiation of axitinib or everolimus as a second targeted therapy during February 2012-January 2013. Real-world dosing patterns were summarized. Dose-specific drug costs (as of October 2014) were based on wholesale acquisition costs from RED BOOK Online. PFS was compared between everolimus and axitinib using a multivariable Cox proportion hazards model. Everolimus and axitinib drug costs per month of PFS were compared using multivariable gamma regression models.

RESULTS

A total of 325 patients received everolimus and 127 patients received axitinib as second targeted therapy. Higher proportions of patients treated with axitinib vs everolimus started on a higher than label-recommended starting dose (14% vs 2%) or experienced dose escalation (11% vs 1%) on second targeted therapy. The PFS did not differ significantly between patients receiving everolimus or axitinib (adjusted hazard ratio (HR) = 1.16; 95% confidence interval [CI] = 0.73-1.82). After baseline characteristics adjustment, axitinib was associated with 17% ($1830) higher drug costs per month of PFS compared to everolimus ($12,467 vs $10,637; p < 0.001).

LIMITATIONS

Retrospective observational study design and only drug acquisition costs considered in drug costs estimates.

CONCLUSIONS

Patients with aRCC receiving axitinib as second targeted therapy were more likely to initiate at a higher than label-recommended dose and were more likely to dose escalate than patients receiving everolimus. With similar observed durations of PFS, drug costs were significantly higher-by 17% per month of PFS-with axitinib than with everolimus.

Improving outcomes in metastatic clear cell renal cell carcinoma by sequencing therapy

Targeted agents have substantially improved outcomes in metastatic clear cell renal cell carcinoma. However, due to multiple mechanisms of evasive resistance, almost all patients progress at some point and may require subsequent therapies. Various agents have been explored after failure of first-line treatment in randomized clinical trials. However, so far few questions about the optimal sequence have been answered. Both everolimus and axitinib have been considered standard of care after failure of first-line VEGF-TKI; sorafenib has been proposed as an additional option. In clinical practice, several factors may influence the choice of subsequent treatment: these include considerations on appropriate drug exposure in first-line, gained insights on prognostic and predictive factors as well as mechanisms of resistance. Once the decision in second-line has been made and treatment has been initiated, treating physicians may already be challenged by the question of what to offer in third- and later lines. Treatment beyond second-line treatment isn't supported by strong evidence, and at this stage of disease, retrospective reports on rechallenge may help to guide decisions. In addition, local treatment approaches including metastasectomy and stereotactic radiosurgery may help to optimize outcomes in all treatment lines.

Comparative effectiveness of second-line targeted therapies for metastatic renal cell carcinoma: synthesis of findings from two multi-practice chart reviews in the United States

BACKGROUND

Second-line targeted therapies for metastatic renal cell carcinoma (mRCC) include mammalian target of rapamycin (mTOR) inhibitors and tyrosine kinase inhibitors (TKIs). This study compares the effectiveness of these therapies in a multi-practice chart review and synthesizes the findings with those of a similarly designed study.

METHODS

Medical oncologists/hematologists (N = 36) were recruited to review charts for patients aged ≥18 years, received a first-line TKI and initiated second-line targeted therapy in 2010 or later. The primary outcome was time from second-line initiation to treatment failure (TTF; discontinuation, physician-assessed progression, or death, whichever occurred first). TTF was compared among patients receiving second-line everolimus (EVE), temsirolimus (TEM), or TKI as a class, using a Cox proportional hazards model adjusting for type of initial TKI and response, histological subtype, performance status, and sites of metastasis. Hazard ratios (HRs) for TTF were pooled, in a meta-analysis, with previously reported HRs for progression-free survival from a chart review with a similar design.

RESULTS

A total of 138, 64 and 79 patients received second-line therapy with EVE, TEM or a TKI, respectively. Adjusting for baseline characteristics, EVE was associated with numerical, but not statistically significant, reductions of 28% (HR = 0.72; 95% CI [0.45-1.16]) and 26% (HR = 0.74; 95% CI [0.48-1.15]) in the hazard of TTF compared to TEM and TKI, respectively. After pooling the HRs from both studies, EVE was associated with significantly reduced hazards of TTF compared to TEM and TKI (HR = 0.73; 95% CI [0.57-0.93]; and HR = 0.75; 95% CI [0.57-0.98], respectively).

LIMITATIONS

LIMITATIONS include retrospective analyses with possible missing or erroneous chart data, confounding of unobserved factors due to non-randomization, and limited data for axitinib during the study period.

CONCLUSIONS

In pooled results from two independent multi-practice chart reviews of second-line mRCC treatment, EVE was associated with significantly reduced hazards of treatment failure compared to TEM and to TKIs as a class.

Management of metastatic renal cell carcinoma patients with poor-risk features: current status and future perspectives

With seven agents approved for renal cell carcinoma within the past few years, there has undoubtedly been progress in treating this disease. However, patients with poor-risk features remain a challenging and difficult-to-treat population, with the mTOR inhibitor, temsirolimus, the only agent approved in the first-line setting. Phase III trial data are still lacking VEGF-pathway inhibitors in patients with poor prognostic features. Poor-risk patients need to be considered as a heterogeneous population. Further understanding of biomarkers can lead to a better selection of patients who may benefit the most from treatment and improvements in prognosis. The presence of poor Karnofsky scores and liver or CNS disease may affect the outcome of these patients much more than other identified factors. This consideration may provide the rationale to further stratify poor-risk patients further subgroups destined to receive either cure or palliation.

Using cumulative toxicity to identify the optimal second-line targeted therapy in patients with metastatic renal cell carcinoma: what's new?

The life expectancy in metastatic renal cell carcinoma patients treated with targeted therapies can be influenced by the time spent on treatment, and the current focus of clinical research in this field appears to be on extending the time on treatment while limiting toxicities. It has been proposed that a strategy based on the sequential administration of two tyrosine kinase inhibitors could result in unacceptable cumulative toxicity for many metastatic renal cell carcinoma patients, while switching to a mTOR inhibitor does not. However, a definite consensus on this issue has not been reached. As very little information from head-to-head studies is available, clinicians have to base their treatment decisions on existing evidence, with an obvious preference for high-quality studies. Some recent studies have provided new insights into the issue of cumulative toxicity of second-line targeted therapies in metastatic renal cell carcinoma patients. In this article, we discuss the evidence emerging from the randomized AXIS and RECORD-3 trials.

Angiogenic and signalling proteins correlate with sensitivity to sequential treatment in renal cell cancer

BACKGROUND

We aimed to study key signalling proteins involved in angiogenesis and proliferation on the response to inhibitors of tyrosine kinases and mammalian target of rapamycin in first- and in second-line treatment of renal cell carcinoma (RCC).

METHODS

In a panel of human RCC tumours, in vitro and in nude mice, we evaluated the effect of sunitinib, sorafenib and everolimus, alone and in sequence, on tumour growth and expression of signalling proteins involved in proliferation and resistance to treatment.

RESULTS

We demonstrated that, as single agents, sunitinib, sorafenib and everolimus share similar activity in inhibiting cell proliferation, signal transduction and vascular endothelial growth factor (VEGF) secretion in different RCC models, both in vitro and in tumour xenografts. Pre-treatment with sunitinib reduced the response to subsequent sunitinib and sorafenib but not to everolimus. Inability by sunitinib to persistently inhibit HIF-1, VEGF and pMAPK anticipated treatment resistance in xenografted tumours. After first-line sunitinib, second-line treatment with everolimus was more effective than either sorafenib or rechallenge with sunitinib in interfering with signalling proteins, VEGF and interleukin-8, translating into a significant advantage in tumour growth inhibition and mice survival.

CONCLUSION

We demonstrated that a panel of angiogenic and signalling proteins can correlate with the onset of resistance to sunitinib and the activity of everolimus in second line.