New insights into metronomic chemotherapy-induced immunoregulation

A phase II study of a doublet metronomic chemotherapy regimen consisting of oral vinorelbine and capecitabine in Chinese women with HER2-negative metastatic breast cancer

BACKGROUND

This single-arm prospective phase II trial was performed to assess the efficacy and safety of the dual oral metronomic vinorelbine and capecitabine (mNC) regimen in women with HER2-negative metastatic breast cancer (MBC) in China.

METHODS

The mNC regimen was administered to the enrolled cases, including oral vinorelbine (VNR) 40 mg three times weekly (on days 1, 3 and 5 every week) and capecitabine (CAP) 500 mg three times a day, until disease progression or intolerable toxicity. The primary endpoint was the 1-year progression-free survival (PFS) rate. Secondary endpoints included objective response rate (ORR), disease control rate (DCR), clinical benefit rate (CBR) and treatment-related adverse events (TRAEs). Stratified factors included treatment lines and hormone receptor (HR) status.

RESULTS

Between June 2018 and March 2023, 29 patients were enrolled into the study. The median follow-up time was 25.4 months (range, 2.0-53.8). In the entire group, the 1-year PFS rate was 54.1%. ORR, DCR and CBR were 31.0%, 96.6% and 62.1%, respectively. The mPFS was 12.5 months (range, 1.1-28.1). Subgroup analysis revealed that ORRs were 29.4% and 33.3% in first- and ≥second-line chemotherapy, respectively. ORRs were 29.2% (7/24) and 40.0% (2/5) for HR-positive MBC and metastatic triple-negative breast cancer (mTNBC), respectively. Grade 3/4 TRAEs were neutropenia (10.3%) and nausea/vomiting (6.9%).

CONCLUSIONS

The dual oral mNC regimen showed very good safety features and improved compliance without loss of efficacy in both first- and second-line treatments. The regimen also reached an excellent ORR in the mTNBC subgroup.

Establishing the applicability of cancer vaccines in combination with chemotherapeutic entities: current aspect and achievable prospects

Cancer immunotherapy is one of the recently developed cancer treatment modalities. When compared with conventional anticancer drug regimens, immunotherapy has shown significantly better outcomes in terms of quality of life and overall survival. It incorporates a wide range of immunomodulatory modalities that channel the effects of the immune system either by broadly modulating the host immune system or by accurately targeting distinct tumor antigens. One such treatment modality that has gained interest is cancer vaccine therapy which acts by developing antibodies against tumor cells. Cancer vaccines target individual peptides or groups of antigens that are released by tumor cells and presented by the APCs. This also initiates an effective process to activate the host immune responses. Studies on various types of cancer vaccines are conducted, out of which only few are approved by FDA for clinical uses. Despite of documented safety and efficacy of conventional chemotherapy and cancer vaccines, individually they did not produce substantial results in eradication of the cancer as a monotherapy. Hence, the combination approach holds the extensive potential to provide significant improvement in disease outcomes. Certain chemotherapy has immunomodulatory effects and is proven to synergize with cancer vaccines thereby enhancing their anti-tumor activities. Chemotherapeutic agents are known to have immunostimulatory mechanisms apart from its cytotoxic effect and intensify the anti-tumor activities of vaccines by various mechanisms. This review highlights various cancer vaccines, their mechanism, and how their activity gets affected by chemotherapeutic agents. It also aims at summarizing the evidence-based outcome of the combination approach of a cancer vaccine with chemotherapy and a brief on future aspects.

Retrospective National "Real Life" Experience of the SFCE with the Metronomic MEMMAT and MEMMAT-like Protocol

BACKGROUND

Relapses in pediatric high-risk brain tumors remain unmet medical needs. Over the last 15 years, metronomic chemotherapy has gradually emerged as an alternative therapeutic approach.

PATIENTS AND METHODS

This is a national retrospective study of patients with relapsing pediatric brain tumors treated according to the MEMMAT or MEMMAT-like regimen from 2010 to 2022. Treatment consisted of daily oral thalidomide, fenofibrate, and celecoxib, and alternating 21-day cycles of metronomic etoposide and cyclophosphamide associated with bevacizumab and intraventricular chemotherapy.

RESULTS

Forty-one patients were included. The most frequent malignancies were medulloblastoma (22) and ATRT (8). Overall, the best responses were CR in eight patients (20%), PR in three patients (7%), and SD in three patients (7%), for a clinical benefit rate of 34%. The median overall survival was 26 months (IC95% = 12.4-42.7), and median EFS was 9.7 months (IC95% = 6.0-18.6). The most frequent grade ¾ toxicities were hematological. Dose had to be adjusted in 27% of the cases. There was no statistical difference in outcome between full or modified MEMMAT. The best setting seems to be when MEMMAT is used as a maintenance and at first relapse.

CONCLUSIONS

The metronomic MEMMAT combination can lead to sustained control of relapsed high-risk pediatric brain tumors.

125I Radiotherapy combined with metronomic chemotherapy may boost the abscopal effect, leading to complete regression of liver metastasis in an SCLC patient with a 58.5-month OS: a case report

The liver is the most common and lethal metastatic site in patients with extensive-stage small-cell lung cancer (ES-SCLC), and median survival with current standard treatment is only 9-10 months from diagnosis. Clinical observations show that a complete response (CR) is extremely rare in ES-SCLC patients with liver metastasis. Moreover, to the best of our knowledge, complete regression of liver metastasis induced by the abscopal effect, boosted primarily by permanent radioactive iodine-125 seeds implantation (PRISI), combined with a low-dose metronomic temozolomide (TMZ) regimen, has not been recorded. Here, we present the case of a 54-year-old male patient who developed multiple liver metastases from ES-SCLC after multiple lines of chemotherapy. The patient was given partial PRISI therapy (two out of six tumor lesions; 38 iodine-125 seeds in one dorsal lesion and 26 seeds in one ventral lesion), which was combined with TMZ metronomic chemotherapy (50 mg/m²/day, days 1-21, every 28 days). The abscopal effect was observed for 1 month after PRISI treatment. After about 1 year, all the liver metastases had completely disappeared, and the patient experienced no relapse. The patient eventually died of malnutrition caused by a non-tumor intestinal obstruction and had an overall survival of 58.5 months after diagnosis. PRISI combined with TMZ metronomic chemotherapy might be considered a potential therapy to trigger the abscopal effect in patients with liver metastases.

Metronomic chemotherapy in patients with advanced neuroendocrine tumors: A single-center retrospective analysis

Neuroendocrine tumors (NETs) are more commonly slow-growing, therefore patients often receive chronic systemic therapies for tumor growth control and preservation of quality of life. Metronomic chemotherapy (mCT) is in line with this goal as it leads to stabilization of tumor growth over time without severe systemic toxicity. This is a retrospective analysis of patients with metastatic NETs receiving metronomic capecitabine (mCAP) or temozolomide (mTEM), at a NET-referral center. The aims of the study were to explore activity and safety of mCT and relationships between some characteristics of the patient population and clinical outcomes. Among a total of 67 patients with metastatic well or moderately differentiated (W/M-D) NETs, mostly gastroenteropancreatic (GEP) and nonfunctioning, 1.2 years (95% CI: 0.8-1.8) median progression-free survival (mPFS), and 3.0 years (95% CI: 2.3-4.9) median overall survival (mOS) were observed. Disease control rate was 85%. Grade 3 adverse events occurred in 15% of patients in mCAP and 13% in mTEM, and were mostly hematological and gastrointestinal. At univariate and multivariate analysis none of the variables analyzed (treatment regimen, sex, age at diagnosis, site of primary tumor and metastases, number of previous mCT lines, baseline tumor status before mCT, Ki67 value) were significantly correlated to OS and PFS. Our retrospective study suggested that mCAP and mTEM can be active and well tolerated in patients with metastatic W/M-D NETs, irrespective of the primary site, site of metastases, line of treatment and baseline tumor status.

Immunomodulatory effects of metronomic vinorelbine (mVRL), with or without metronomic capecitabine (mCAPE), in hormone receptor positive (HR+)/HER2-negative metastatic breast cancer (MBC) patients: final results of the exploratory phase 2 Victor-5 study

Tregs are able of suppressing tumor-specific effector cells, such as lymphocytes CD8+, CD4+ and Natural Killer cells. Different drugs, especially different schedules of administration, like metronomic chemotherapy (mCHT), seem to be able to increase anticancer immunity, by acting on downregulation of Tregs. Most of the data available regarding the immunomodulating effect of mCHT have been obtained with Cyclophosphamide (CTX). Aim of the present study was to explore the effects of mVRL and mCAPE administration, alone or in combination, on T cells. Observation of 13 metastatic breast cancer patients lasted controlling for 56 days, where Treg frequencies and function, spontaneous anti-tumor T-cell responses were monitored, as well as the clinical outcome. No depletion in Treg absolute numbers, or percentage of T lymphocytes, was observed. Only in 5 patients, a modest and transient depletion of Tregs was observed during the first 14 days of treatment. To better describe the effect on Tregs, we subsequently looked at the variations in Memory, Naïve and Activated Treg subpopulations: we observed a trend in reduction for memory Treg (Treg MEM) and an increase for Treg Naïve (Treg NAIVE) and Treg Activated (Treg ACT) components. We finally analyzed the average trend of Treg in the Treg depleted patients and non-depleted ones, without fiding any significant differences. The trend of the Treg MEM appeared different, showing a reduction during the first 14 days, followed by an increase at the levels before treatment at Day 56 in the group of depleted patients and a progressive substantial reduction in the group of non-depleted patients along the entire course of treatment. Opposed to the data known, treatment with mVRL w/o mCAPE did not show any effect on Tregs.

Metronomic delivery of orally available pemetrexed-incorporated colloidal dispersions for boosting tumor-specific immunity

In this study, we developed oral pemetrexed (PMX) for metronomic dosing to enhance antitumor immunity. PMX was electrostatically complexed with positively charged lysine-linked deoxycholic acid (DL) as an intestinal permeation enhancer, forming PMX/DL, to enhance its intestinal permeability. PMX/DL was also incorporated into a colloidal dispersion (CD) comprised of the block copolymer of poly(ethylene oxide) and poly(propylene oxide), and caprylocaproyl macrogol-8 glycerides (PMX/DL-CD). CD-containing PMX/DL complex in a 1:1 molar ratio [PMX/DL(1:1)-CD] showed 4.66- and 7.19-fold greater permeability than free PMX through the Caco-2 cell monolayer and rat intestine, respectively. This resulted in a 282% improvement in oral bioavailability in rats. In addition, low-dose metronomic PMX led to more immunogenic cell death in CT26.CL25 cells compared to high PMX concentrations at the maximum tolerated dose. In CT26.CL25 tumor-bearing mice, oral metronomic PMX/DL-CD elicited greater antitumor immunity not only by enhancing the number of tumor-infiltrating lymphocytes but also by suppressing T cell functions. Oral PMX/DL-CD substantially increased programmed cell death protein ligand-1 (PD-L1) expression on tumor cells compared to the control and PMX-IV groups. This increased antitumor efficacy in combination with anti-programmed cell death protein-1 (aPD-1) antibody in terms of tumor rejection and immunological memory compared to the combination of PMX-IV and aPD-1. These results suggest that oral metronomic scheduling of PMX/DL-CD in combination with immunotherapy has synergistic antitumor effects.

Minimal PK/PD model for simultaneous description of the maximal tolerated dose and metronomic treatment outcomes in mouse tumor models

PURPOSE

Metronomic chemotherapy (MC) is a promising approach where, in contrast to the conventional maximal tolerated dose (MTD) strategy, regular fractionated doses of the drug are used. This approach has proven its efficacy, although drug dosing and scheduling are often chosen empirically. Pharmacokinetic/pharmacodynamic (PK/PD) models provide a way to choose optimal protocols with computational methods. Existing models are usually too complicated and are valid for only a subset of drug schedules. To address this issue, we propose herein a simple model that can describe MC and MTD regimens simultaneously.

METHODS

The minimal model comprises tumor suppression due to antiangiogenic drug effect together with a cell-kill term, responsible for its cytotoxicity. The model was tested on data obtained on tumor-bearing mice treated with gemcitabine in ether MTD, MC, or combined (MTD + MC) regimens.

RESULTS

We conducted a number of tests in which data were divided in various ways into training and validation sets. The model successfully described different trends in the MTD and MC regimens. With parameters obtained by fitting the model to MTD data, the simulations correctly predicted trends in both the MC and combined therapy groups.

CONCLUSION

Our results demonstrate that the proposed model presents a minimal yet efficient tool for modeling outcomes in different treatment regimens in mice. We hope that this model has the potential for use in clinical practice in the development of patient-specific chemotherapy scheduling protocols based on observed treatment response.

KLHL22 maintains PD-1 homeostasis and prevents excessive T cell suppression

Aberrant programmed cell death protein 1 (PD-1) expression on the surface of T cells is known to inhibit T cell effector activity and to play a pivotal role in tumor immune escape; thus, maintaining an appropriate level of PD-1 expression is of great significance. We identified KLHL22, an adaptor of the Cul3-based E3 ligase, as a major PD-1-associated protein that mediates the degradation of PD-1 before its transport to the cell surface. KLHL22 deficiency leads to overaccumulation of PD-1, which represses the antitumor response of T cells and promotes tumor progression. Importantly, KLHL22 was markedly decreased in tumor-infiltrating T cells from colorectal cancer patients. Meanwhile, treatment with 5-fluorouracil (5-FU) could increase PD-1 expression by inhibiting the transcription of KLHL22. These findings reveal that KLHL22 plays a crucial role in preventing excessive T cell suppression by maintaining PD-1 expression homeostasis and suggest the therapeutic potential of 5-FU in combination with anti-PD-1 in colorectal cancer patients.

Metronomic chemotherapy in non-small cell lung cancer

Metronomic chemotherapy (MCT) is defined as the rhythmic chemotherapy of low-dose cytotoxic drugs with short or no drug-free breaks over prolonged periods. MCT affects tumor cells and the tumor microenvironment. Particularly, the low-dose schedule impairs the repair process of endothelial cells, resulting in an anti-angiogenesis effect. By stimulating the immune system to eliminate tumor cells, MCT induces immunological activation. Furthermore, combined with targeted therapy, anti-angiogenic drugs enhance the efficacy of MCT. The present review is an overview of phase I, II and III clinical trials focusing on the efficacy, toxicity and mechanism of MCT in patients with non-small cell lung cancer (NSCLC). Furthermore, the prospects of MCT in NSCLC have been discussed. The present review indicated that MCT is an efficacious treatment for selected patients with NSCLC, with acceptable systemic side effects and economic viability for public health.

Impact of Cisplatin Dosing Regimens on Mammary Tumor Growth in an Animal Model

Background

We have recently introduced a modification of the seminal Simeoni model for tumor growth, the modification entailing the incorporation of delay differential equations into its formulation. We found that the modification was competitive with the Simeoni construct in modeling mammary tumor growth under cisplatin treatment in an animal model.

Methods

In our original study, we had two cohorts of animals: untreated, and treatment with bolus injection of cisplatin on day 0. We here explore how modifications in the cisplatin dosing scheme affect tumor growth in our model.

Results

We found that modest fractionation dosing schemes have little ultimate impact on tumor growth. In contrast, metronomic dosing schemes seem quite efficacious, and might yield effective control over tumor progression.

Conclusions

With regard to cisplatin as single agent chemotherapy, a minimum level of drug for a prolonged period of time seems more critical than rapid achievement of a very high dose for a shorter time frame for deterring tumor growth or progression. Exploration of tumor dose schedules with mathematical models can provide valuable insights into potentially effective therapeutic regimens.

Low-dose metronomic chemotherapy as an efficient treatment option in metastatic breast cancer-results of an exploratory case-control study

Purpose

There is growing interest in low-dose metronomic chemotherapy (LDMC) in metastatic breast cancer (MBC). In this retrospective case–control analysis, we compared the efficacy of LDMC and conventional chemotherapy (CCT) in MBC.

Methods

Each LDMC patient receiving oral cyclophosphamide (CTX) (50 mg daily) and methotrexate (MTX) (2.5 mg every other day) was matched with two controls who received CCT. Age, number of chemotherapy lines and metastatic sites as well as hormone receptor (HR) status were considered as matching criteria. Primary endpoint was disease control rate longer than 24 weeks (DCR). Secondary endpoints were progression-free survival (PFS), duration of response (DoR) and subgroup analyses using the matching criteria.

Results

40 cases and 80 controls entered the study. 30.0% patients with LDMC and 22.5% patients with CCT showed DCR (p = 0.380). The median PFS was 12.0 weeks in both groups (p = 0.218) and the median DoR was 31.0 vs. 20.5 weeks (p = 0.383), respectively. Among younger patients, DCR was 40.0% in LDMC vs. 25.0% in the CCT group (p = 0.249). DCR was achieved in 33.3% vs. 26.2% non-heavily pretreated patients (p = 0.568) and in 36.0% vs. 18.0% patients without multiple metastases (p = 0.096), respectively. In the HR-positive group, 30.0% LDMC vs. 28.3% CCT patients showed DCR (p = 1.000). Among triple-negative patients, DCR was achieved in 30.0% LDMC and 5.0% CCT patients (p = 0.095).

Conclusions

We demonstrated a similar efficacy of LDMC compared to CCT in the treatment of MBC. Thus, LDMC may be a valuable treatment option in selected MBC patients.

Stimulus-responsive tea polyphenols as nanocarrier for selective intracellular drug delivery

Nanodrug delivery systems have been widely researched to achieve efficient antitumor drug delivery. However, the controlled drug delivery at tumor cells remains the main challenge for antitumor therapy. Herein, a pH and reduction-responsive nanocarrier based on green tea polyphenols was employed as a smart excipient for chemotherapy drug delivery. Paclitaxel, as a chemotherapy drug, was loaded in the nanocarrier, noted as green tea polyphenol/paclitaxel. The green tea polyphenol/paclitaxel kept constant diameter at physiological condition (i.e. pH 7.4), while gradually enlarged at acid environment (pH = 5.5) and the reductive environment. The in vitro paclitaxel release results indicated that the release of paclitaxel from the green tea polyphenol/paclitaxel at pH 7.4 was slow, whereas obviously accelerated at the acid environment (pH = 5.5) and the reductive environment. The in vitro antitumor assay showed more efficient tumor cells inhibition of green tea polyphenol/paclitaxel than free paclitaxel. Meanwhile, due to the proper size (∼100 nm), green tea polyphenol/paclitaxel could effectively accumulate at tumor sites. In the in vivo mice bearing A549 xenograft mouse models, green tea polyphenol/paclitaxel exhibited satisfactory antitumor effect and depressed system toxicity when compared with free paclitaxel, owing to the enhanced paclitaxel accumulation and controlled paclitaxel release in the tumor cells. With simple compositions and satisfactory antitumor effects, this green tea polyphenol-based nanocarrier can be a promising nanodrug delivery system for the therapy of cancers.

Case report of long-term survival with metastatic triple-negative breast carcinoma: Treatment possibilities for metastatic disease

RATIONALE

Breast cancer is the most common as well as one of the most devastating cancers among women in the United States. Prognosis is poor for patients with metastatic breast cancer, especially for patients with so-called "triple-negative" disease. The lack of effective therapies for metastatic triple-negative breast cancer outlines the need for novel and innovative treatment strategies.

PATIENT CONCERNS

A 58-year-old underwent a mastectomy which revealed a recurrent triple-negative breast carcinoma. Afterward, she presented with a growing mass in her left axilla and chest wall. A computed tomography scan showed axillary and supraclavicular adenopathy, nodules in the left upper and lower lobe of the lungs, and 2 areas of disease in the liver. A bone scan showed lesions in the ribs.

DIAGNOSIS

The patient was diagnosed with a recurrent metastatic triple-negative breast carcinoma that spread to the lung, liver, and bones.

INTERVENTIONS

The patient was treated with metronomic chemotherapy, sequential chemotherapy regimens, and immunotherapy.

OUTCOMES

The patient is now over 15 years out from her diagnosis of metastatic disease without any evidence of recurrent disease, likely due to the patient's treatment strategy which included sequential metronomic chemotherapy regimens and immunotherapy.

LESSONS

Sequential metronomic chemotherapy regimens in combination with immunotherapy might be an effective treatment option for patients with metastatic triple-negative breast cancer. We hope that this case can provide some guidance for the treatment of metastatic triple-negative breast cancer and motivate research that can potentially lead to more cases of long-term survival for patients who develop this dismal disease.

Pan-European Expert Meeting on the Use of Metronomic Chemotherapy in Advanced Breast Cancer Patients: The PENELOPE Project

INTRODUCTION

Metronomic chemotherapy (mCHT) is a treatment regimen in which drugs are administered frequently or continuously and that maintains low, prolonged, and pharmacologically active plasma concentrations of drugs to avoid toxicity associated with traditional chemotherapy regimens, while achieving tumor response. Despite the increasing use of mCHT in patients with metastatic breast cancer (MBC) and the endorsement of mCHT in guidelines, no consensus exists about which patients may substantially benefit from mCHT, which agents can be recommended, and in which treatment setting mCHT is most appropriate.

METHODS

In October 2017, ten international experts in the management of breast cancer convened to develop a report describing the current status of the use of mCHT for the treatment of advanced breast cancer, based not only on current literature but also on their opinion. The Delphi method was used to reach consensus.

RESULTS

A full consensus was reached concerning the acknowledgement that mCHT is not simply a different way of administering chemotherapy but a truly new treatment option. The best-known effect of mCHT is on angiogenesis inhibition, but exciting new data are on the way regarding potential activity on immune system activation. The experts strongly suggest that the ideal patients for mCHT are those with hormone receptor (HR)-positive tumors or those with triple-negative disease. Independently of HR status, mCHT could be an advantageous option for elderly patients, who are often under-treated simply because of their age.

CONCLUSION

Current data support the use of mCHT in selected patients with MBC.

FUNDING

Pierre Fabre.

Successful Second-Line Metronomic Temozolomide in Metastatic Paraganglioma: Case Reports and Review of the Literature

Metastatic pheochromocytoma and paraganglioma (mPHEO/PGL) are frequently associated with succinate dehydrogenase B (SDHB) mutations. Cyclophosphamide-dacarbazine-vincristine (CVD) regimen is recommended as standard chemotherapy for advanced mPHEO/PGL. There is limited evidence to support the role of metronomic schemes (MS) of chemotherapy in mPHEO/PGL treatment. We report 2 patients with SDHB-related mPGL who received a regimen consisting of MS temozolomide (TMZ) and high-dose lanreotide after progression on both CVD chemotherapy and high-dose lanreotide. Molecular profiling of the tumor tissue from both patients revealed hypermethylation of the O6-methylguanine-DNA-methyltransferase (MGMT) promoter. In one patient, progression-free survival was 13 months and the second patient remained under treatment after 27 months of stabilization of metabolic response of his disease. Treatment was well tolerated, and adverse effects were virtually absent. A modification in the scheme of TMZ from standard schemes to MS is safe and feasible and can be considered in patients with progressive mPHEO/PGL refractory to dacarbazine in standard doses.

MUC1- and Survivin-based DNA Vaccine Combining Immunoadjuvants CpG and interleukin-2 in a Bicistronic Expression Plasmid Generates Specific Immune Responses and Antitumour Effects in a Murine Colorectal Carcinoma Model

DNA vaccination is a promising cancer treatment due to its safety, but poor immunogenicity limits its application. However, immunoadjuvants, heterogeneous prime-boost strategies and combination with conventional treatments can be used to improve the antitumour immune effects. A CpG motif and interleukin-2 (IL-2) cytokine are often used as adjuvants. In this study, a DNA vaccine containing a CpG motif was constructed to evaluate its adjuvant effect. The results show that the cytotoxicity of the DNA vaccine was increased fivefold, and survival lifetime was prolonged twofold by the CpG motif adjuvant. To simplify the industrial production process, a bicistronic plasmid was constructed to carry the fusion genes of survivin/MUC1 (MS) and IL-2 and with a CpG motif in its backbone. The results showed that the antitumour effect of the bicistronic vaccine was the same as that of the two vaccine co-injected regime. Furthermore, the vaccine could suppress metastatic tumour foci by 69.1% in colorectal carcinoma-bearing mice. Moreover, the vaccine induced survivin- and MUC1-specific immune responses in splenocytes and induced the immune promoting factor CCL-19 and GM-CSF upregulated, while metastatic-associated factor MMP-9 and immunosuppressing factor PD-L1 downregulated in tumour tissue. When combining the vaccine with the chemotherapy drug oxaliplatin, the survival was prolonged by about 2.5-fold. In conclusion, the DNA vaccine containing a CpG motif in bicistronic form showed good effects on colorectal cancer by inhibiting both tumour growth and metastasis, and combination with oxaliplatin could improve its antitumour effects.

Application of mathematical models to metronomic chemotherapy: What can be inferred from minimal parameterized models?

Metronomic chemotherapy refers to the frequent administration of chemotherapy at relatively low, minimally toxic doses without prolonged treatment interruptions. Different from conventional or maximum-tolerated-dose chemotherapy which aims at an eradication of all malignant cells, in a metronomic dosing the goal often lies in the long-term management of the disease when eradication proves elusive. Mathematical modeling and subsequent analysis (theoretical as well as numerical) have become an increasingly more valuable tool (in silico) both for determining conditions under which specific treatment strategies should be preferred and for numerically optimizing treatment regimens. While elaborate, computationally-driven patient specific schemes that would optimize the timing and drug dose levels are still a part of the future, such procedures may become instrumental in making chemotherapy effective in situations where it currently fails. Ideally, mathematical modeling and analysis will develop into an additional decision making tool in the complicated process that is the determination of efficient chemotherapy regimens. In this article, we review some of the results that have been obtained about metronomic chemotherapy from mathematical models and what they infer about the structure of optimal treatment regimens.

Resistance to metronomic chemotherapy and ways to overcome it

Therapeutic resistance is amongst the major determinants of cancer mortality. Contrary to initial expectations, antivascular therapies are equally prone to inherent or acquired resistance as other cancer treatment modalities. However, studies into resistance to vascular endothelial growth factor pathway inhibitors revealed distinct mechanisms of resistance compared to conventional cytotoxic therapy. While some of these novel mechanisms of resistance also appear to be functional regarding metronomic chemotherapy, herein we summarize available evidence for mechanisms of resistance specifically described in the context of metronomic chemotherapy. Numerous preclinically identified molecular targets and pathways represent promising avenues to overcome resistance and enhance the benefits achieved with metronomic chemotherapy eventually. However, there are considerable challenges to clinically translate the preclinical findings.

Tackling pancreatic cancer with metronomic chemotherapy

Pancreatic tumours, the majority of which arise from the exocrine pancreas, have recently shown an increasing incidence in western countries. Over the past few years more and more new selective molecules directed against specific cellular targets have become available for cancer therapy, leading to significant improvements. However, despite such advances in therapy, prognosis of pancreatic cancer remains disappointing. Metronomic chemotherapy (MCT), which consists in the administration of continuous, low-dose anticancer drugs, has demonstrated the ability to suppress tumour growth. Thus, it may provide an additional therapeutic opportunity for counteracting the progression of the tumour. Here we discuss evidence arising from preclinical and clinical studies regarding the use of MCT in pancreatic cancer. Good results have generally been achieved in preclinical studies, particularly when MCT was combined with standard dose chemotherapy or antinflammatory, antiangiogenic and immunostimolatory agents. The few available clinical experiences, which mainly refer to retrospective data, have reported good tolerability though mild activity of metronomic schedules. Further studies are therefore awaited to confirm both preclinical findings and the preliminary clinical data.

On drug resistance and metronomic chemotherapy: A mathematical modeling and optimal control approach

Effects that tumor heterogeneity and drug resistance have on the structure of chemotherapy protocols are discussed from a mathematical modeling and optimal control point of view. In the case when two compartments consisting of sensitive and resistant cells are considered, optimal protocols consist of full dose chemotherapy as long as the relative proportion of sensitive cells is high. When resistant cells become more dominant, optimal controls switch to lower dose regimens defined by so-called singular controls. The role that singular controls play in the structure of optimal therapy protocols for cell populations with a large number of traits is explored in mathematical models.

Metronomic chemotherapy: A potent macerator of cancer by inducing angiogenesis suppression and antitumor immune activation

Metronomic chemotherapy is a low dosing treatment strategy that attracts growing scientific and clinical interest. It refers to dense and uninterrupted administration of low doses of chemotherapeutic agents (without prolonged drug free intervals) over extended periods of time. Cancer chemotherapy is conventionally given in cycles of maximum tolerated doses (MTD) with the aim of inducing maximum cancer cell apoptosis. In contrast, the primary target of metronomic chemotherapy is the tumor's neovasculature. This is relevant to the emerging concept that tumors exist in a complex microenvironment of cancer cells, stromal cells and supporting vessels. In addition to its anti-angiogenetic properties, metronomic chemotherapy halts tumor growth by activating anti-tumor immunity, thus decreasing the acquired resistance to conventional chemotherapy. Herein, we present a review of the literature that provides a scientific basis for the merits of chemotherapy when administered on a metronomic schedule.

Metronomic chemotherapy: A relook at its basis and rationale

Metronomic administration of chemotherapy has long been recognized as having a different biological effect from maximal tolerated dose (MTD) administration. Preclinical studies have demonstrated these differences quite elegantly and many clinical trials have also demonstrated reproducible activity albeit small, in varied solid malignancies even in patients who were heavily pretreated. However, the concept of metronomic chemotherapy has been plagued by lack of a clear definition resulting in the published literature that is rather varied and confusing. There is a need for a definition that is mechanism(s)-based allowing metronomics to be distinguished from standard MTD concept. With significant advances made in understanding cancer biology and biotechnology, it is now possible to attain that goal. What is needed is both a concerted effort and adequate funding to work towards it. This is the only way for the oncology community to determine how metronomic chemotherapy fits in the overall cancer management schema.

Metronomic chemotherapy and nanocarrier platforms

The therapeutic concept of administering chemotherapeutic agents continuously at lower doses, relative to the maximum tolerated dose (MTD) without drug-free breaks over extended periods -known as "metronomic chemotherapy"- is a promising approach for anti-angiogenic cancer therapy. In comparison with MTD chemotherapy regimens, metronomic chemotherapy has demonstrated reduced toxicity. However, as a monotherapy, metronomic chemotherapy has failed to provide convincing results in clinical trials. Therapeutic approaches including combining the anti-angiogenic "metronomic" therapy with conventional radio-/chemo-therapy and/or targeted delivery of chemotherapeutic agents to tumor tissues via their encapsulation with nanocarrier-based platforms have proven to potentiate the overall therapeutic outcomes. In this review, therefore, we focused on the mutual contribution made by nanoscale drug delivery platforms to the therapeutic efficacy of metronomic-based chemotherapy. In addition, the influence that the dosing schedule has on the overall therapeutic efficacy of metronomic chemotherapy is discussed.

Next generation metronomic chemotherapy-report from the Fifth Biennial International Metronomic and Anti-angiogenic Therapy Meeting, 6-8 May 2016, Mumbai

The 5^th Biennial Metronomic and Anti-angiogenic Therapy Meeting was held on 6^th – 8^th May in the Indian city of Mumbai. The meeting brought together a wide range of clinicians and researchers interested in metronomic chemotherapy, anti-angiogenics, drug repurposing and combinations thereof. Clinical experiences, including many from India, were reported and discussed in three symposia covering breast cancer, head and neck cancers and paediatrics. On the pre-clinical side research into putative mechanisms of action, and the interactions between low dose metronomic chemotherapy and angiogenesis and immune responses, were discussed in a number of presentations. Drug repurposing was discussed both in terms of clinical results, particularly with respect to angiosarcoma and high-risk neuroblastoma, and in pre-clinical settings, particularly the potential for peri-operative interventions. However, it was clear that there remain a number of key areas of challenge, particularly in terms of definitions, perceptions in the wider oncological community, mechanisms of action and predictive biomarkers. While the potential for metronomics and drug repurposing in low and middle income countries remains a key theme, it is clear that there is also considerable potential for clinically relevant improvements in patient outcomes even in high income economies.

Highlights from the 1st Latin American meeting on metronomic chemotherapy and drug repositioning in oncology, 27-28 May, 2016, Rosario, Argentina

Following previous metronomic meetings in Marseille (2011), Milano (2014), and Mumbai (2016), the first Latin American metronomic meeting was held in the School of Medical Sciences, National University of Rosario, Rosario, Argentina on 27 and 28 of May, 2016. For the first time, clinicians and researchers with experience in the field of metronomics, coming from different countries in Latin America, had the opportunity of presenting and discussing their work. The talks were organised in three main sessions related to experience in the pre-clinical, and clinical (paediatric and adult) areas. The different presentations demonstrated that the fields of metronomic chemotherapy and repurposing drugs in oncology, known as metronomics, constitute a branch of cancer therapy in permanent evolution, which have strong groups working in Latin

America, both in the preclinical and the clinical settings including large, adequately designed randomised studies. It was shown that metronomics offers treatments, which, whether they are combined or not with the standard therapeutic approaches, are not only effective but also minimally toxic, with the consequent improvement of the patient’s quality of life, and inexpensive, a feature very important in low resource clinical settings. The potential use of metronomic chemotherapy was proposed as a cost/effective treatment in low-/middle-income countries, for adjuvant therapy in selected tumours. The fundamental role of the governmental agencies and non-governmental alliances, as the Metronomic Global Health Initiative, in supporting this research with public interest was underlined.

Chemically enhanced radiotherapy: visions for the future

Radiotherapy (RT) is an important part of cancer management, with more than a third of all cancer cures being attributable to RT. Despite the advances in RT over the past century, the overall outcomes in a majority of malignancies are still unsatisfactory. There has been a constant endeavor to enhance the outcome of RT, and this has been in the form of altered fractionation, oxymimetic radiosensitizers, the use of concurrent chemotherapy, anti-angiogenic therapy and anti-growth factor receptor targeted therapies. This article presents a vision for the future, with emphasis upon emerging prospects which could enhance RT outcomes. Positive speculations regarding the use of immunological aspects, the use of nanoscale technology and the adoption of metronomic concurrent chemotherapy have been presented. Also, the potential with the use of low dose hyperradiosensitivity in enhancing chemotherapy outcomes too has been discussed. In this era of evidence based clinical practise, there exists a strong obsession towards the 'present' with 'contempt towards the future'. Accepting the shortcomings of the existing modalities, there must be a strong zeal towards discovering better methodologies to enhance radiotherapeutic outcomes for the sake of a better future.

Optimizing Chemotherapeutic Anti-cancer Treatment and the Tumor Microenvironment: An Analysis of Mathematical Models

We review results about the structure of administration of chemotherapeutic anti-cancer treatment that we have obtained from an analysis of minimally parameterized mathematical models using methods of optimal control. This is a branch of continuous-time optimization that studies the minimization of a performance criterion imposed on an underlying dynamical system subject to constraints. The scheduling of anti-cancer treatments has all the features of such a problem: treatments are administered in time and the interactions of the drugs with the tumor and its microenvironment determine the efficacy of therapy. At the same time, constraints on the toxicity of the treatments need to be taken into account. The models we consider are low-dimensional and do not include more refined details, but they capture the essence of the underlying biology and our results give robust and rather conclusive qualitative information about the administration of optimal treatment protocols that strongly correlate with approaches taken in medical practice. We describe the changes that arise in optimal administration schedules as the mathematical models are increasingly refined to progress from models that only consider the cancerous cells to models that include the major components of the tumor microenvironment, namely the tumor vasculature and tumor-immune system interactions.

The results with the addition of metronomic cyclophosphamide to palliative radiotherapy for the treatment of non-small cell lung carcinoma

BACKGROUND

A considerable proportion of non-small cell lung carcinoma (NSCLC) patients are ineligible for radical therapies. Many are frail not to tolerate intravenous palliative chemotherapy either. These patients often receive palliative radiotherapy (RT), or supportive care alone. We intend to compare outcomes with palliative RT alone, versus palliative RT plus oral low dose metronomic cyclophosphamide.

METHODS

Data was mined from 139 eligible NSCLC patient records. Comparisons were made between 65 patients treated from January 2011 to March 2013 with palliative RT (20-30 Gray in 5-10 fractions) alone, versus 74 patients treated from April 2013 to December 2014 with palliative RT plus oral metronomic cyclophosphamide (50 mg once daily from day of initiation of RT until at least the day of disease progression). Response was assessed after 1-month post-RT by computed tomography. Patients with complete or partial response were recorded as responders. For the determination of progression free survival (PFS), progression would be declared in case of increase in size of lesions, development of new lesions, or development of effusions. The proportions of responders were compared with the Fisher exact test, and the PFS curves were compared with the log-rank test.

RESULTS

Differences in response rates were statistically insignificant. The PFS was significantly higher when metronomic chemotherapy was added to RT in comparison to treatment with RT alone (mean PFS 3.1 vs. 2.55 months; P=0.0501). Further histological sub-group analysis revealed that the enhanced outcomes with addition of metronomic cyclophosphamide to RT were limited to patients with adenocarcinoma histology (3.5 vs. 2.4 months; P=0.0053), while there was no benefit for those with squamous cell histology (2.6 vs. 2.6 months; P=1). At the dose of oral cyclophosphamide used, there was no recorded instance of any measurable hematological toxicity.

CONCLUSIONS

For pulmonary adenocarcinoma patients, the treatment with palliative RT plus oral metronomic cyclophosphamide is better than that with palliative RT alone. However, for pulmonary squamous cell carcinoma the addition of oral metronomic cyclophosphamide to palliative RT offered no benefit. Further studies with similar and different metronomic chemotherapy agents are justifiable.

CpG-1826 immunotherapy potentiates chemotherapeutic and anti-tumor immune responses to metronomic cyclophosphamide in a preclinical glioma model

Cyclophosphamide administered on an intermittent metronomic schedule induces strong immune-dependent regression in several glioma models. Here we investigate whether this immunogenic chemotherapy can be potentiated by combination with the immune stimulatory TLR9 agonist CpG-1826. CpG-1826 treatment of GL261 gliomas implanted in immune competent mice induced tumor growth delay associated with increased tumor recruitment of macrophages and B cells. Anti-tumor responses varied between individuals, with CpG-1826 inducing robust tumor growth delay in ~50% of treated mice. Both high and low CpG-1826-responsive mice showed striking improvements when CpG-1826 was combined with cyclophosphamide treatment. Tumor-associated macrophages, B cells, dendritic cells, and cytotoxic T cells were increased, T regulatory cells were not induced, and long-term GL261 glioma regression with immune memory was achieved when CpG-1826 was combined with either single cyclophosphamide dosing (90 mg/kg) or metronomic cyclophosphamide treatment (two cycles at 45 mg/kg, spaced 12-days apart). B16F10 melanoma, a low immunogenic tumor model, also showed enhanced immune and anti-tumor responses to cyclophosphamide/CpG-1826 chemoimmunotherapy, but unlike GL261 tumors, did not regress. TLR9-based immunotherapy can thus be effectively combined with immunogenic cyclophosphamide treatment to enhance immune-based anti-tumor responses, even in poorly immunogenic cancer models.

Dynamics and control of a mathematical model for metronomic chemotherapy

A 3-compartment model for metronomic chemotherapy that takes into account cancerous cells, the tumor vasculature and tumor immune-system interactions is considered as an optimal control problem. Metronomic chemo-therapy is the regular, almost continuous administration of chemotherapeutic agents at low dose, possibly with small interruptions to increase the efficacy of the drugs. There exists medical evidence that such administrations of specific cytotoxic agents (e.g., cyclophosphamide) have both antiangiogenic and immune stimulatory effects. A mathematical model for angiogenic signaling formulated by Hahnfeldt et al. is combined with the classical equations for tumor immune system interactions by Stepanova to form a minimally parameterized model to capture these effects of low dose chemotherapy. The model exhibits bistable behavior with the existence of both benign and malignant locally asymptotically stable equilibrium points. In this paper, the transfer of states from the malignant into the benign regions is used as a motivation for the construction of an objective functional that induces this process and the analysis of the corresponding optimal control problem is initiated.

[Metronomic Chemotherapy--A New Path to Treat Advanced Non-small Cell Lung Cancer]

节拍化疗是近年来兴起的一种新的化疗策略。与传统化疗不同，节拍化疗通过相对低剂量的、频繁的应用细胞毒性药物，没有较长的治疗间歇，发挥抗肿瘤作用。最初认为节拍化疗直接作用于肿瘤血管内皮细胞，发挥抗血管生成作用。近年来发现节拍化疗还有调节机体免疫功能，影响肿瘤干细胞，诱导细胞休眠的作用。晚期非小细胞肺癌（non-small cell lung cancer, NSCLC）的治疗已经从彻底的清除肿瘤细胞转向改善疗效、降低毒性和提高生活质量。节拍化疗可以避免传统化疗毒性大，作用不持久的缺点，目前一些临床研究正在探索节拍化疗对晚期NSCLC的作用，并且初见疗效，有望成为晚期NSCLC一种新的治疗模式。

Antitumor activity of mHSP65-TTL enhanced by administration of low dose cyclophosphamide in pancreatic cancer-bearing mice

Pancreatic cancer remains a lethal malignancy. Despite chemotherapy or/and radiotherapy after the surgery, the improvement on the overall survival of the patients has still been minimal. To develop novel therapeutic approaches, we tried to prepare mHSP65-TTL, a candidate vaccine prepared by mixing the recombinant mycobacterial heat shock protein 65 (mHSP65) with tumor tissue lysate (TTL) of Panc02 pancreatic cancer tissue. The mHSP65-TTL were used to immune the C57BL/6 mice implanted with the Panc02 cancer cells, in combination with or without low dose cyclophosphamide (CY). The results showed that mHSP65-TTL significantly prolonged the survival of the pancreatic cancer bearing mice and low dose CY enhanced the efficacy of the mHSP65-TTL. In addition, we detected mRNA expression of RORγt and IL-17A in spleen cells of mice received mHSP65-TTL or mHSP65-TTL plus CY, and found that mHSP65-TTL up-regulated mRNA expressions of RORγt and IL-17A, CY alone or mHSP65-TTL plus CY up-regulated mRNA expressions of RORγt. The work could provide an insight into a combinational approach for the immunotherapy of pancreatic cancer.

Cholesterol-Enhanced Polylactide-Based Stereocomplex Micelle for Effective Delivery of Doxorubicin

Nanoscale micelles as an effective drug delivery system have attracted increasing interest in malignancy therapy. The present study reported the construction of the cholesterol-enhanced doxorubicin (DOX)-loaded poly(D-lactide)-based micelle (CDM/DOX), poly(L-lactide)-based micelle (CLM/DOX), and stereocomplex micelle (CSCM/DOX) from the equimolar enantiomeric 4-armed poly(ethylene glycol)-polylactide copolymers in aqueous condition. Compared with CDM/DOX and CLM/DOX, CSCM/DOX showed the smallest hydrodynamic size of 96 ± 4.8 nm and the slowest DOX release. The DOX-loaded micelles exhibited a weaker DOX fluorescence inside mouse renal carcinoma cells (i.e., RenCa cells) compared to free DOX·HCl, probably because of a slower DOX release. More importantly, all the DOX-loaded micelles, especially CSCM/DOX, exhibited the excellent antiproliferative efficacy that was equal to or even better than free DOX·HCl toward RenCa cells attributed to their successful internalization. Furthermore, all of the DOX-loaded micelles exhibited the satisfactory hemocompatibility compared to free DOX·HCl, indicating the great potential for systemic chemotherapy through intravenous injection.