Raltitrexed (Tomudex) in combination with 5-fluorouracil for the treatment of patients with advanced colorectal cancer: preliminary results from phase I clinical trials

Can carcinoembryonic antigen replace computed tomography in response evaluation of metastatic colorectal cancer?

INTRODUCTION

Response Evaluation Criteria in Solid Tumours (RECISTs 1.1) define computed tomography (CT) as the gold standard in response evaluation of patients with metastatic colorectal cancer (mCRC) who are undergoing chemotherapy. The aim of this study was to evaluate whether carcinoembryonic antigen (CEA), which is cheaper and easier to perform, can replace repeated CT.

MATERIAL AND METHODS

The study included 66 patients with non-resectable mCRC participating in a phase I-II study. CEA values were determined, and CT images were taken every 2 months. CT images were externally and retrospectively reviewed according to the RECIST 1.1 criteria. Different cut-off values for CEA change in percent (DeltaCEA%) compared with baseline or nadir value underwent testing to find patients with disease control (that is stable disease, partial or complete response) at 2, 4, 6 and 8 months, in order to identify those who could have continued with chemotherapy based on CEA values alone. CT verification is needed in progressive disease (PD), and therefore identifying PD patients was our secondary endpoint.

RESULTS

The results showed that by using a cut-off value of 0 for DeltaCEA%, disease control was seen in all patients at all measuring points (negative predictive value (NPV) = 1.0). Secondarily, increasing CEA was able to identify all PD patients (sensitivity (Se) = 1.0) and in 50-74% of the patients increasing CEA provided a lead time to PD on upcoming CT. It was possible to replace CT with CEA in all patients with decreasing CEA, meaning that 23-47% of CT scans could have been avoided at any given time point.

CONCLUSION

When the CEA level at a certain measuring point is the same or lower than CEA at baseline or at nadir (the measuring point with the lowest CEA value) during treatment, CEA can replace CT.

Inside the biochemical pathways of thymidylate synthase perturbed by anticancer drugs: Novel strategies to overcome cancer chemoresistance

Our current understanding of the mechanisms of action of antitumor agents and the precise mechanisms underlying drug resistance is that these two processes are directly linked. Moreover, it is often possible to delineate chemoresistance mechanisms based on the specific mechanism of action of a given anticancer drug. A more holistic approach to the chemoresistance problem suggests that entire metabolic pathways, rather than single enzyme targets may better explain and educate us about the complexity of the cellular responses upon cytotoxic drug administration. Drugs, which target thymidylate synthase and folate-dependent enzymes, represent an important therapeutic arm in the treatment of various human malignancies. However, prolonged patient treatment often provokes drug resistance phenomena that render the chemotherapeutic treatment highly ineffective. Hence, strategies to overcome drug resistance are primarily designed to achieve either enhanced intracellular drug accumulation, to avoid the upregulation of folate-dependent enzymes, and to circumvent the impairment of DNA repair enzymes which are also responsible for cross-resistance to various anticancer drugs. The current clinical practice based on drug combination therapeutic regimens represents the most effective approach to counteract drug resistance. In the current paper, we review the molecular aspects of the activity of TS-targeting drugs and describe how such mechanisms are related to the emergence of clinical drug resistance. We also discuss the current possibilities to overcome drug resistance by using a molecular mechanistic approach based on medicinal chemistry methods focusing on rational structural modifications of novel antitumor agents. This paper also focuses on the importance of the modulation of metabolic pathways upon drug administration, their analysis and the assessment of their putative roles in the networks involved using a meta-analysis approach. The present review describes the main pathways that are modulated by TS-targeting anticancer drugs starting from the description of the normal functioning of the folate metabolic pathway, through the protein modulation occurring upon drug delivery to cultured tumor cells as well as cancer patients, finally describing how the pathways are modulated by drug resistance development. The data collected are then analyzed using network/netwire connecting methods in order to provide a wider view of the pathways involved and of the importance of such information in identifying additional proteins that could serve as novel druggable targets for efficacious cancer therapy.

Raltitrexed-based chemotherapy for advanced colorectal cancer

AIMS

To evaluate the efficiency and safety profile of raltitrexed-based chemotherapy in the treatment of advanced colorectal cancer.

METHODS

An electronic search was undertaken to identify randomized controlled trials comparing raltitrexed-based regimen to 5-fluorouracil-based regimen in patients with advanced colorectal cancer. The outcomes included overall survival, overall response rate and toxicities.

RESULTS

This meta-analysis included 11 studies with 4622 patients. Overall, there were no significant differences between the two regimens in terms of overall survival (HR=1.06, 95% CI: 0.96-1.17, P=0.23) or overall response rate (RR=1.09, 95% CI: 0.86-1.38, P=0.47). In subgroup analysis, patients in raltitrexed/oxaliplatin group had significantly higher partial response (RR=1.53, 95% CI: 1.17-2.00, P=0.002), overall response rate (RR=1.42, 95% CI: 1.10-1.82, P=0.006), disease control rate (RR=1.16, 95% CI: 1.04-1.29, P=0.009) and lower progressive disease (RR=0.61, 95% CI: 0.45-0.84, P=0.002) when compared to 5-fluorouracil/leucovorin/oxaliplatin group. Occurrence of severe anemia (RR=2.23, 95% CI: 1.38-3.59, P=0.0001), asthenia (RR=2.29, 95% CI: 1.36-3.84, P=0.002), hepatic disorders (RR=7.51, 95% CI: 1.30-43.56, P=0.02), and nausea/vomit (RR=1.70, 95% CI: 1.03-2.81, P=0.04) were significantly higher with the raltitrexed arm treatment, while frequencies of grade 3/4 alopecia (RR=0.36, 95% CI: 0.26-0.50, P<0.00001) and stomatitis/mucositis (RR=0.14, 95% CI: 0.07-0.31, P<0.00001) were increased in the 5-fluorouracil group.

CONCLUSIONS

Raltitrexed-based chemotherapy regimen leads to an equivalent overall survival and response rates with acceptable toxicities compared to traditional 5-fluorouracil-based regimen in patients with advanced colorectal cancer. Raltitrexed can be a treatment option for these patients when 5-fluorouracil-based regimens are not tolerated or inappropriate.

Irinotecan, oxaliplatin and raltitrexed for the treatment of advanced colorectal cancer

Out of every 17-18 individuals in the US, one develops colorectal cancer (CRC) in their lifetime. Of individuals diagnosed with CRC, > 50% present or develop metastatic disease, which, if untreated, is associated with 6-9 months median survival. Although surgical resection is the primary treatment modality for CRC, chemotherapy is the mainstay of treatment for metastatic or unresectable disease. For nearly three decades, 5-fluorouracil (5-FU) has been the chemotherapy of choice for treatment of CRC. However, the response rates to single 5-FU therapy have been suboptimal with an objective tumour response of 10-20%. Attempts have been made to improve the efficacy of 5-FU by either schedule alteration (protracted infusion versus intravenous push) or biochemical modulation with leucovorin (LV). Continuous infusion induced more tumour regression and prolonged the time-to-disease progression with some significant impact on survival (11.3 versus 12.1 months; p < 0.04). 5-FU/LV resulted in a significant increase in overall response rates and in the prolongation of disease-free survival in the adjuvant setting, although severe toxicities represent a major clinical problem. The last 10 years have seen the addition of several new agents such as irinotecan, oxaliplatin, raltitrexed, bevacizumab and cetuximab. The prognosis has significantly improved with the addition of these agents, with median survivals now > 20 months. This review paper focuses on irinotecan, oxaliplatin and raltitrexed when used alone and in combination.

Phase I trial of sequential raltitrexed followed by bolus 5-fluorouracil in patients with advanced colorectal cancer

Our objective was to determine the maximum tolerated dose (MTD) of sequential raltitrexed (Tomudex) and 5-fluorouracil (5-FU) by bolus administration every 3 weeks in patients with advanced colorectal cancer (aCRC) and appendiceal adenocarcinoma. This phase I dose-escalation study was carried out in three stages: (1) 5-FU fixed at 900 mg/m, raltitrexed escalated from 0.5 to 3.0 mg/m, (2) raltitrexed fixed at 3.0 mg/m, 5-FU escalated from 900 mg/m until dose-limiting toxicity (DLT) and (3) 5-FU fixed at the dose level below DLT, raltitrexed escalated from 3.0 mg/m until MTD. Seventy-one patients with measurable disease were enrolled. No DLTs were observed during stage 1 of treatment. At a fixed dose of raltitrexed 3.0 mg/m, DLT developed when 5-FU was increased to 1350 mg/m (stage 2). When 5-FU was fixed at 1200 mg/m and raltitrexed was increased to 6.0 mg/m (stage 3), DLT was dose limiting. The recommended doses for further study are 5.5 mg/m ralitrexed and 1200 mg/m 5-FU. Of the 69 patients evaluated for efficacy, one had a complete response (8.0 months) and five had partial responses (5.1-11.6 months). Thirty patients had stable disease for 5 or more cycles of therapy (mean time to progression: 3.6 months). Median survival was 11.7 months. We conclude that raltitrexed can be combined with bolus 5-FU, at raltitrexed doses that are higher than the recommended single-agent dose of 3.0 mg/m, with manageable toxicity. This combination shows encouraging activity, and survival appears promising in the pre-treated aCRC patient population. Further clinical trials are warranted.

Effects of antifolates on the binding of 5-fluoro-2'-deoxyuridine monophosphate to thymidylate synthase

Folate based inhibitors of thymidylate synthase (TS) might facilitate binding of 5-fluoro-2'-deoxyuridine-5'-monophosphate (FdUMP) to TS similar to the natural reduced folate 5,10-methylenetetrahydrofolate (CH(2)-H(4)-folate). We studied the lipophilic, non-polyglutamatable antifolates Nolatrexed (NTX) and AG331 and antifolates, that can have a polyglutamate side chain like the natural folate CH(2)-H(4)-folate; GW1843U89, Raltitrexed (RTX) and Multi-targetted antifolate (MTA) and pentaglutamates (RTX-Glu(5) and MTA-Glu(5)). The capacity of these compounds to facilitate the binding of [(3)H]FdUMP to Lactobacillus casei TS and an ammoniumsulphate precipitate of human TS was investigated. Only NTX, RTX-Glu(5) and MTA-Glu(5) facilitated FdUMP binding to L. casei TS and their dissociation constant K(d) (0.2-0.7 microM) was low compared to CH(2)-H(4)-folate (2.0 microM). The small lipophilic molecule NTX was favorable to the larger AG331. Polyglutamylation, as indicated by the difference in effect of RTX vs. RTX-Glu(5) and MTA vs. MTA-Glu(5), seems to be important for a classical antifolate to facilitate binding of FdUMP to bacterial TS. Effects of antifolates on FdUMP binding to human TS were different. At a low concentration (0.05 microM) NTX, RTX-Glu(5) and MTA-Glu(5) facilitated 3-5 times higher binding of [(3)H]FdUMP to TS than CH(2)-H(4)-folate. At higher concentrations (0.3-5 microM) of NTX, RTX-Glu(5) and MTA-Glu(5) the FdUMP binding decreased. The complex remained stable in the absence of (anti)folate for at least 24hr. The K(d) values of the antifolates for human TS varied from 19 to 387 nM, while the K(d) of CH(2)-H(4)-folate for human TS was 351 nM. The Hill coefficients, which indicated the type of cooperativity of the antifolates in the binding of FdUMP to TS were positive (0.58-0.99) at low concentrations (<0.3 microM) and negative (-0.35 to -0.81) at concentrations >0.3 microM except for GW1843U89, which only showed negative cooperativity (-1.70). It was shown with [(14)C]NTX that when the binding of FdUMP decreased at high NTX concentrations, the binding of NTX to TS still increased. This also held for the natural substrate dUMP. The negative cooperativity of the antifolates was clearly concentration dependent. The difference between human and L. casei TS in the FdUMP binding assays with antifolates can possibly be explained by interaction of the two subunits of human TS, which was absent in L. casei TS. The binding of antifolates to one of the two subunits induced a conformational change of the other subunit. This change no longer allowed the binding of FdUMP or dUMP at the active site. In conclusion this study showed that antifolates enhanced the binding of FdUMP to TS, especially at low antifolate concentrations, that are also clinically achievable, e.g. in human plasma.

A phase II study of epirubicin, cisplatin and raltitrexed combination chemotherapy (ECT) in patients with advanced oesophageal and gastric adenocarcinoma

BACKGROUND

The aim of this study was to evaluate the efficacy of the combination of epirubicin, cisplatin and ralitrexed (Tomudex). ECT, in patients with advanced oesophageal or gastric adenocarcinoma. Efficacy was assessed primarily as response rate and secondarily in terms of toxicity, time to progression and survival.

PATIENTS AND METHODS

Twenty-one patients with histologically and/or cytologically proven unresectable (7) or metastatic (14) gastro-oesophageal adenocarcinoma, who had bi-dimensionally measurable disease, with ECOG performance status < or = 2. with adequate haematological, hepatic and renal function received first-line chemotherapy with epirubicin (50 mg/m2). cisplatin (60 mg/m2) and Tomudex (2.5 mg/m2), ECT, at three-weekly intervals. Treatment consisted of three cycles of chemotherapy, with a further three cycles if there was disease response or stabilisation.

RESULTS

ECT is an active regimen in the treatment of advanced gastro-oesophageal adenocarcinoma with an overall intention-to-treat response rate of 29% (95% confidence intervals (CI): 11%-52%). In addition, 4 (19%) patients had stable disease. Median time to progression was 19 weeks (95% CI: 7-31 weeks). Median overall survival was 18 weeks (95% CI: 11-24 weeks). Seventeen patients failed to complete the six cycles of treatment due to disease progression (5). toxicity (3), non-toxic death (1 pulmonary embolism, 1 cardiac), severe allergy to epirubicin (1), patient decision (1) and five patients after the study was discontinued early due to toxicity. There were three toxic deaths: two due to sepsis complicating neutropaenia and one due to cardiorespiratory failure following drug induced enteritis. Nine patients experienced grade 3 or 4 neutropaenia, two patients experienced grade 3 or 4 nausea and vomiting and one patient had grade 4 diarrhoea.

CONCLUSIONS

The combination of epirubicin, cisplatin and tomudex is active against advanced gastro-oesophageal adenocarcinoma but the toxicity suggests that further evaluation in a randomised comparison to ECF is not appropriate.

Chemotherapeutic strategies for treatment of colorectal cancer: present and future developments

Colorectal cancer is one of the most common malignancies in Western nations. Treatment with 5-fluorouracil and leucovorin resulting in inhibition of DNA synthesis after inhibition of thymidylate synthase is the most common strategy for adjuvant and systemic chemotherapy in this disease. However, the majority of patients still fail to respond to this combination; therefore, new chemotherapeutic strategies have been developed. This process has proceeded rapidly due to a more proper translation of preclinical results to the clinic. Knowledge of proximal parameters (drug activation, drug-target interaction) and distal parameters (cell growth inhibitory parameters and cell death parameters) in drug response should offer the opportunity to discriminate between sensitivity and resistance to chemotherapy and therapeutic selectivity. This clinical commentary presents a review of a symposium held at the Vrije Universiteit Medical Center, Amsterdam, The Netherlands, which focused on both the preclinical and clinical aspects relating to the treatment of colorectal cancer.

New therapies, new directions: advances in the systemic treatment of metastatic colorectal cancer

Colorectal cancer is the second leading cause of cancer death and it is clear that patients with metastatic disease have better quality of life and survival when given treatment. Despite four decades of experience of treating patients with fluorouracil, there remains considerable controversy about the optimum dose and scheduling, as well as biomodulation with leucovorin and methotrexate. However, irrespective of the dose and schedule, overall survival times are poor--about 1 year. Disappointingly, oral agents with similar mechanisms to fluorouracil do not improve survival rates in comparison with fluorouracil and leucovorin treatment. Irinotecan and oxaliplatin are newer agents that have improved the response rates for patients with metastatic disease when they are added to flurouracil and leucovorin. The combination of irinotecan, fluorouracil, and leucovorin has also improved overall survival. These are small advances in the fight against colorectal cancer, and further drug development is necessary.

The relevance of drug sequence in combination chemotherapy

The concept of combining chemotherapeutic agents to increase the cytotoxic efficacy has evolved greatly over the past several years. In the past, the rationale for combination chemotherapy centered on attacking different biochemical targets, overcoming drug resistance in heterogenous tumors, and increasing the dose-density of combination chemotherapy to take advantage of tumor growth kinetics. The overall goal was to improve clinical efficacy with acceptable clinical toxicity. It is now apparent that the sequence of drug administration can significantly enhance the therapeutic effect of chemotherapy. These sequence-dependent effects can be explained by chemotherapy-induced cell cycle perturbations, or by pharmacodynamic interactions between the agents in combination. In this review, we focus on drug combinations with taxanes and camptothecins, which we believe best illustrate the importance of the cell cycle and pharmacologic interactions in the sequential administration of chemotherapy. As our understanding of the cell cycle grows, our ability to appropriately sequence chemotherapy can have a great impact on the treatment of human cancers. Copyright 2000 Harcourt Publishers Ltd.

Oxaliplatin. A review of its pharmacological properties and clinical efficacy in metastatic colorectal cancer and its potential in other malignancies

Oxaliplatin is a platinum compound that inhibits DNA synthesis, primarily by causing intrastrand cross-links in DNA. Oxaliplatin has a broad spectrum of antineoplastic activity and has demonstrated a lack of cross-resistance with other platinum compounds. In patients with metastatic colorectal cancer, intravenous oxaliplatin has been trialled as a monotherapy and in combination with other agents. The highest response rates were achieved when oxaliplatin was used in combination with fluorouracil/folinic acid (leucovorin; calcium folinate), typically > or = 50% in the first-line setting and 13 to 45% as a second-line therapy. First-line triple therapy with oxaliplatin and fuorouracil/folinic acid achieved significantly higher response rates and longer median progression-free survival than fluorouracil/folinic acid therapy alone. However, no significant difference in the median duration of overall survival was found. This may be a consequence of the subsequent use of oxaliplatin and/or surgery after disease progression in patients who relapsed after fluorouracil/folinic acid therapy alone. Neoadjuvant therapy with oxaliplatin/fluorouracil/folinic acid has proven beneficial in enabling surgical removal of previously unresectable liver metastases. In 2 studies, surgery with curative intent was performed in 16 and 51% of patients with initially unresectable liver metastases following oxaliplatin/fluorouracil/folinic acid therapy; the 5-year survival rates were 40 and 50%, respectively. In patients with advanced ovarian cancer, first-line therapy with oxaliplatin/cyclophosphamide achieved an objective response rate which did not differ significantly from that of cisplatin/cyclophosphamide (33 vs 42%). In addition, oxaliplatin has shown efficacy in patients with platinum-pretreated ovarian cancer and achieved objective response rates similar to paclitaxel in this setting (16 vs 17%). Promising results have also been found with oxaliplatin in patients with non-Hodgkin's lymphoma, breast cancer, mesothelioma and non-small cell lung cancer. Reversible, cumulative, peripheral sensory neuropathy is the principle dose-limiting factor of oxaliplatin therapy. Haematological and gastrointestinal toxicities occur frequently but are generally mild to moderate in intensity.

CONCLUSION

Oxaliplatin in combination with fluorouracil/folinic acid is an effective treatment option for patients with metastatic colorectal cancer, both as a first-line therapy and in patients refractory to previous chemotherapy. Although preliminary results failed to show any overall survival advantage of this regimen over fluorouracil/folinic acid alone, this may be a consequence of trial design and requires further examination. Additional clinical investigation of oxaliplatin in patients with other cancers is warranted given the promising results achieved in early trials, most notably in patients with platinum-pretreated ovarian cancer.

Raltitrexed ('Tomudex') and radiotherapy can be combined as postoperative treatment for rectal cancer

BACKGROUND

The optimal adjuvant therapy for operable rectal cancer is likely to be a combination of radiotherapy and chemotherapy. Raltitrexed ('Tomudex') is a specific thymidylate synthase inhibitor with a convenient administration schedule, acceptable and manageable toxicity, radiosensitising properties, and proven efficacy in the treatment of advanced colorectal cancer. It may, therefore, offer advantages compared with standard 5-FU chemotherapy regimens used in colorectal cancer. The aim of this phase I, dose-escalation study was to determine the recommended dose of raltitrexed for use with postoperative pelvic radiotherapy in patients with rectal cancer.

PATIENTS AND METHODS

Patients with resected Dukes' stage B or C rectal cancer were treated with a combination of raltitrexed and radiotherapy (50.4 Gy at 1.8 Gy per fraction over five to six weeks). At least three patients were treated at each of three escalating raltitrexed dose levels (2.0, 2.6 and 3.0 mg/m2) once every three weeks. Toxicity was assessed by the recording of WHO adverse events and biochemistry and haematology determinations.

RESULTS

A total of 22 patients entered the study, 17 of whom had Dukes' stage C disease. All three patients entered at a dose level of 3.0 mg/m2 experienced dose-limiting toxicity (DLT) (2 patients had grade 3 leucopenia and 1 patient had grade 2 leucopenia and grade 3 diarrhoea); however, only 2 of 1 patients entered at a dose level of 2.6 mg/m2 experienced DLT (1 patient had grade 4 neutropenia and 1 patient died probably due to aspiration pneumonia unrelated to treatment). The most common haematological toxic events were leucopenia (8 patients) and anaemia (6 patients). Only four haematological or biochemical toxic events were of grade 3 or 4. Other common toxicities were diarrhoea and nausea, which occurred in 15 and 9 patients, respectively.

CONCLUSIONS

This study demonstrates that raltitrexed can be combined with postoperative radiotherapy for treatment of patients with Dukes' stage B or C rectal cancer. The recommended dose of raltitrexed in this setting is 2.6 mg/m2, which is close to the full monotherapy dose.