Irinotecan in metastatic colorectal cancer: dose intensification and combination with new agents, including biological response modifiers

Impact of follow-up on generalized pairwise comparisons for estimating the irinotecan benefit in advanced/metastatic gastric cancer

BACKGROUND AND OBJECTIVES

The net treatment effect (∆) is a new method to assess the treatment benefit that combines multiple time-to-event, binary and continuous endpoints according to a pre-specified sequence. It represents the net probability for a random patient treated in the experimental arm to have a better overall outcome than a random patient from the control arm does. We aimed at characterizing the impact of follow-up on ∆ estimated from both time-to-event and binary toxicity endpoints, in randomized controlled trials (RCTs) of irinotecan-based regimen in advanced/metastatic gastric cancer (AGC).

STUDY DESIGN

Three RCTs are reanalysed. The net treatment effect using from one to three outcomes (i.e. overall survival, time to progression and toxicity in this order) and the hazard ratio (HR) were estimated after various cut-off dates and compared to the values obtained after complete follow-up were reported.

RESULTS

In all three RCTs (897 patients), the irinotecan-based regimen was superior to the non-irinotecan containing regimen in terms of HR and ∆. This superiority was lower when the net treatment effect also accounted for toxicity. The HR was slightly less influenced by an incomplete follow-up than ∆ was, but correction proposed by Péron to account for censored observations showed quite robust results.

CONCLUSIONS

The net treatment effect using Péron's correction can be used in case of interim analyses or high censoring rates. In addition to relative measures such as the hazard ratio, it provides a simple mean to evaluate the net treatment effect with and without toxicity outcomes.

Pharmacological principles of intraperitoneal and bidirectional chemotherapy

Intraperitoneal chemotherapy is associated with a significant pharmacokinetic and pharmacodynamic benefit and can, alone or in combination with systemic chemotherapy (bidirectional chemotherapy), be used for treating primary and secondary peritoneal surface malignancies. Due to the peritoneal-plasma barrier, high intraperitoneal drug concentration can be achieved by intraperitoneal chemotherapy, whereas systemic concentration remains low. Bidirectional chemotherapy may provide in addition adequate drug concentrations from the side of the subperitoneal space to the peritoneal tumour nodules. Major pharmacological problems of intraperitoneal chemotherapy are limited tissue penetration and poor homogeneity of drug distribution to the entire seroperitoneal surface. Significant pharmacological determinants of intraperitoneal chemotherapy are choice of drug, drug dosage, solution volume, carrier solution, intra-abdominal pressure, temperature, duration, mode of administration, extent of peritonectomy and interindividual variability. Drugs most commonly applied for intraperitoneal chemotherapy include mitomycin C, cisplatin, carboplatin, oxaliplatin, irinotecan, 5-fluoruracil, gemcitabine, paclitaxel, docetaxel, doxorubicin, premetrexed and melphalan. The drugs and their doses that are used vary widely among centres. While the adequate drug choice for intraperitoneal and bidirectional chemotherapy is essential, randomized clinical trials to determine the most optimal drug or drug combination are lacking, and only eight retrospective comparative clinical studies are available. Further clinical pharmacological studies are required to determine the most effective drug regimen for intraperitoneal and bidirectional chemotherapy in various indications. In the future, reliable drug sensitivity testing and genetic profiling of peritoneal metastases will be needed for enabling patient-specific therapy.

Molecular insights into microbial β-glucuronidase inhibition to abrogate CPT-11 toxicity

Bacterial β-glucuronidases expressed by the symbiotic intestinal microbiota appear to play important roles in drug-induced epithelial cell toxicity in the gastrointestinal (GI) tract. For the anticancer drug CPT-11 (irinotecan) and the nonsteroidal anti-inflammatory drug diclofenac, it has been shown that removal of the glucuronide moieties from drug metabolites by bacterial β-glucuronidases in the GI lumen can significantly damage the intestinal epithelium. Furthermore, selective disruption of bacterial β-glucuronidases by small molecule inhibitors alleviates these side effects, which, for CPT-11 {7-ethyl-10-[4-(1-piperidino)-1-piperidino]}, can be dose limiting. Here we characterize novel microbial β-glucuronidase inhibitors that inhibit Escherichia coli β-glucuronidase in vitro with Ki values between 180 nM and 2 μM, and disrupt the enzyme in E. coli cells, with EC50 values as low as 300 nM. All compounds are selective for E. coli β-glucuronidase without inhibiting purified mammalian β-glucuronidase, and they do not impact the survival of either bacterial or mammalian cells. The 2.8 Å resolution crystal structure of one inhibitor bound to E. coli β-glucuronidase demonstrates that it contacts and orders only a portion of the "bacterial loop" present in microbial, but not mammalian, β-glucuronidases. The most potent compound examined in this group was found to protect mice against CPT-11-induced diarrhea. Taken together, these data advance our understanding of the chemical and structural basis of selective microbial β-glucuronidase inhibition, which may improve human drug efficacy and toxicity.

[Prognostic factors and survival of metastatic colorectal cancer in the Sousse University Hospital (Tunisia): comparative study of two treatment period of 200 patients]

Between 1994 and 2005, 200 patients with metastatic colo-rectal cancers were treated in the Sousse CHU (Tunisia), we analysed two groups of patients, the group 1 was treated in the period after 1999 (N = 64), the group 2 was treated in the period between 1999 and 2005 (N = 136).

PATIENTS AND METHODS

Mean age of the patients was 50 years, localisation of metastases was liver in 67.3% of cases, 23% of patients had multiple metastases, 44% of cases developed metastases after a median period of 11.4 months. All patients had received first line of chemotherapy, the regimen of chemotherapy was in the group 1, Fufol in the majority of cases (76%), the regimen of chemotherapy was in the group 2, simplified LV5FU2 associated to irinotecan in the majority of cases (83%), 28% of all patients received second line of chemotherapy.

RESULTS

The median survival was 13.8 months in the group 1 and 19 months in the group 2. Overall survival rates at 2 years were 35% and 42% (p = 0.02) in group 1 and 2, respectively. Prognostic factors for a better survival using univariate analysis were: normal ACE (P < 0.01), normal liver analysis (P < 0.001), response after 3 cycles of chemotherapy (P < 0.0005), resection of liver metastases (P < 0.05). The multivariate analysis (cox model) revealed only one independent factor: radiologic response after 3 cycles of chemotherapy (P < 0.03).

CONCLUSION

The prognostic of patients with metastatic disease is poor, although palliative chemotherapy after the recent advances and the use of new drugs have been shown to be able to prolong survival and to improve the quality of life over best supportive care. This study report amelioration of prognostic and survival of metastatic colorectal cancers in Tunisia.

Current place of high-dose irinotecan chemotherapy in patients with metastatic colorectal cancer

INTRODUCTION

Irinotecan has an important place in the treatment of metastatic colorectal cancer. It was initially administered as monotherapy, but is now generally used in combination with 5-fluorouracil or targeted therapies (cetuximab or bevacizumab), with various doses.

METHODS

We here review the main studies assessing irinotecan doses escalation, and discuss the potent advantages of this escalation.

RESULTS

Several studies have demonstrated a dose-intensity relationship for irinotecan, and high doses (up to 600 mg/m2 as monotherapy, 260 mg/m2 in combination therapy) have been used with satisfactory safety and higher objective response rates. It is possible that, in practice, some patients receive insufficient doses of irinotecan. Dose escalation could be considered in carefully selected patients: young patients with a good performance status and normal liver function. This approach could be useful in patients with liver metastases, which may become resectable in the case of a major tumour response. It is wise to perform UGT1A1 genotyping prior to dose escalation to detect patients at high risk of toxicity (genotype 7/7). The role of another laboratory parameter, which needs to be evaluated is the KRAS status of the tumour. A KRAS mutation confers resistance to cetuximab, which reduces treatment options, especially in first-line. However, in the CRYSTAL trial comparing FOLFIRI to FOLFIRI-cetuximab as first-line therapy, the presence of a KRAS mutation did not appear to influence the efficacy of FOLFIRI. The value of irinotecan dose escalation needs to be determined in this setting.

CONCLUSION

Irinotecan dose escalation is potentially of interest in highly selected patients, but this concept is only based on phase I or II trials and must be validated by a randomized trial. Its value regarding other regimens such as FOLFIRINOX or combinations with targeted therapies also needs to be determined.

Developing Strategies for Liver Metastases From Colorectal Cancer

Five-year survival rates of patients with liver metastases from colorectal cancer range from 30% to 40% for those who undergo successful resection procedures, and is almost nil among those unable to have surgery. However, improved chemotherapy strategies for nonoperable patients (specifically, the use of neoadjuvant oxaliplatin- and irinotecan-based regimens) have increased response rates and tumor downstaging such that 15% to 30% of initially nonoperable patients are able to have secondary, or rescue, surgery. Preliminary data also indicate that new targeted therapies should further increase response rates and thus resection rates. Operative techniques such as portal vein embolization and two-stage procedures for patients with multiple or large tumors, as well as use of cryosurgery and radiofrequency ablation, are also contributing to more effective removal of liver metastases from colorectal cancer. This brief report describes data supporting the expanding application of hepatectomy for patients with colorectal liver metastases.

The epidermal growth factor receptor gene family as a target for therapeutic intervention in numerous cancers: what's genetics got to do with it?

Over the past 30 years, a relatively simple growth factor and its cognate receptor have provided seminal insights into the understanding of the genetic basis of cancer, as well as growth factor signalling. The epidermal growth factor (EGF), its cognate receptor (EGFR) and related family members have been shown to be important in normal, as well as the malignant growth of many cell types including: glioblastomata, astrocytomas, medulloblastomata, non-small cell lung carcinoma (NSCLC) and breast cancer. This review summarises the history of the EGFR gene and the v-ErbB oncogene, as well as diverse approaches developed to inhibit EGFR activity. The two most advanced therapies use either small-molecule cell membrane permeable kinase inhibitors or antibodies which prevent receptor activation. Recent clinical trials indicate that certain NSCLC patients have mutations in the EGFR gene which makes them more responsive to kinase inhibitors. These mutations appear to enhance the ability of the ligand to activate EGFR activity and also prolong the binding of the EGFR inhibitor to the kinase domain. Evidence to date suggests that these EGFR mutations in NSCLC occur more frequently in Japan than in the western hemisphere. Although these mutations are correlated with enhanced efficacy to the inhibitors in NSCLC, they can not explain or predict the sensitivity of many other cancer patients to the beneficial effects of the EGFR kinase inhibitors or antibody mediated therapy. As with as other small-molecule kinase inhibitors and susceptible diseases (e.g., imatinib and chronic myeloid leukaemia), resistance to EGFR inhibitors has been reported recently, documenting the requirement for development of multi-pronged therapeutic approaches. EGFR kinase inhibitors are also being evaluated as adjuvants in hormonal therapy of breast cancer - especially those which overexpress EGFR. Genetically engineered antibodies specific for the EGFR family member ErbB2 have been developed which show efficacy in the treatment of primary, and prevent the relapse of, breast cancer. Clearly, the EGF/EGFR signalling cascade has, and continues to play, an important role in the development of novel anticancer targeted therapies.

Cyclooxygenase-2 (COX-2)-independent anticarcinogenic effects of selective COX-2 inhibitors

Nonsteroidal antiinflammatory drugs (NSAIDs) appear to reduce the risk of developing cancer. One mechanism through which NSAIDs act to reduce carcinogenesis is to inhibit the activity of cyclooxygenase-2 (COX-2), an enzyme that is overexpressed in various cancer tissues. Overexpression of COX-2 increases cell proliferation and inhibits apoptosis. However, selective COX-2 inhibitors can also act through COX-independent mechanisms. In this review, we describe the COX-2-independent molecular targets of these COX-2 inhibitors and discuss how these targets may be involved in the anticarcinogenic activities of these selective COX-2 inhibitors. We also compare the concentrations of these inhibitors used in in vitro and in vivo experiments and discuss the implications of the in vitro studies for clinical management of cancer with these drugs.

Efficacy and Safety of Cetuximab/Irinotecan in Chemotherapy-Refractory Metastatic Colorectal Adenocarcinomas: A Clinical Practice Setting, Multicenter Experience

BACKGROUND

This study was designed to evaluate the efficacy and safety of irinotecan/cetuximab administered as third- or fourth-line therapy in a retrospective series of patients with metastatic colorectal cancer refractory to oxaliplatin and irinotecan.

PATIENTS AND METHODS

Most patients (90%) had been previously treated with adjuvant 5-fluorouracil/leucovorin, and all had received oxaliplatin-based regimens before receiving irinotecan-based second-line treatment. Sixty patients with irinotecan-refractory colorectal cancer received a regimen comprising weekly irinotecan 120 mg/m2 as a 1-hour intravenous infusion and cetuximab 400 mg/m2 infused over 2 hours as the initial dose and 250 mg/m2 infused over 1 hour for the subsequent administrations. A single treatment cycle comprised 4 weekly infusions followed by 2 weeks of rest.

RESULTS

According to an intent-to-treat analysis, a partial response was exhibited in 12 of 60 enrolled patients (20%; 95% confidence interval, 11%-32%) with a median duration of 5.1 months (range, 3-7.4 months). The tumor growth control rate was 50% (95% confidence interval, 37%-63%). Objective responses did not correlate with performance status, number of sites of disease, and pretreatments or epidermal growth factor receptor status. The median progression-free survival was 3.1 months (range, 1.2-9 months), whereas median overall survival was 6 months (range, 2-13 months). Both survival parameters correlated with performance status at the beginning of treatment. The main grade 3/4 toxicities were nausea (33%), diarrhea (27%), leukopenia (18%), asthenia (13%), and acne-like reaction (13%).

CONCLUSION

Our data suggest that the weekly irinotecan/cetuximab regimen is feasible in an outpatient setting and tolerated by most patients. At present, combinations of chemotherapy with cetuximab are being evaluated in patients with earlier-stage disease in a number of ongoing studies.

Equivalent effect of DNA damage-induced apoptotic cell death or long-term cell cycle arrest on colon carcinoma cell proliferation and tumour growth

Knowledge of the type of biological reaction to chemotherapy is a prerequisite for its rational enhancement. We previously showed that irinotecan-induced DNA damage triggers in the HCT116p53(wt) colon carcinoma cell line a long-term cell cycle arrest and in HCT116p53(-/-) cells apoptosis (Magrini et al., 2002). To compare the contribution of long-term cell cycle arrest and that of apoptosis to inhibition of cell proliferation after irinotecan-induced DNA damage, we used this isogenic system as well as the cell lines LS174T (p53(wt)) and HT-29 (p53(mut)). Both p53(wt) cell lines responded to damage by undergoing a long-term tetraploid G1 arrest, whereas the p53(mut) cell lines underwent apoptosis. Cell cycle arrest as well as apoptosis caused a similar delay in cell proliferation. Irinotecan treatment also induced in mouse tumours derived from the p53(wt) cell lines a tetraploid G1 arrest and in those derived from the p53-deficient cell lines a transient G2/M arrest and apoptosis. The delay of tumour growth was in the same range in both groups, that is, arrest- and apoptosis-mediated tumour growth inhibition was comparable. In conclusion, cell cycle arrest as well as apoptosis may be equipotent mechanisms mediating the chemotherapeutic effects of irinotecan.

Weekly irinotecan plus UFT and leucovorin as first-line chemotherapy of patients with advanced colorectal cancer

We evaluated the antitumoral efficacy and safety of CPT-11 125 mg/m2 (weekly 90 min i.v. infusion; days 1, 8 and 15) combined with UFT (oral combination of tegafur and uracil) 200 mg/m2/day plus leucovorin (LV) 45 mg/m2/day (both divided into three separate oral doses every 8 h, days 1-21) every 4 weeks as first-line chemotherapy of metastatic colorectal cancer (CRC). Fifty-three patients > or =18 years old with histologically confirmed diagnosis of advanced CRC and bidimensionally measurable disease were enrolled. Three patients (6%) showed CR and 8 patients (15%) showed PR (ORR = 21% (95% CI, 10-32). Stable disease was reported in 19 patients (36%) [tumor control rate = 57% (95% CI, 43-70)]. The median time to progression and overall survival were 7.9 and 18.2 months, respectively (1-year rate = 74%; 2-years rate = 26%). CPT-11/UFT/LV treatment was well tolerated: the most reported grade 3/4 toxicities were neutropenia (11% of patients) and delayed diarrhea (28% of patients). No significant differences in response rate, survival or toxicity were found between younger (< or =65 years) and older patients (> 65 years). Weekly CPT-11 plus UFT/LV was found effective and safe as first-line chemotherapy for metastatic CRC. The addition of CPT-11 to UFT/LV doubled the response rate compared to the results previously reported with UFT/LV, while myelosuppression remained low.

Dual inhibition of epidermal growth factor receptor and vascular endothelial growth factor receptor phosphorylation by AEE788 reduces growth and metastasis of human colon carcinoma in an orthotopic nude mouse model

We studied growth factors and their receptors in tumor cells and tumor-associated endothelial cells as the therapeutic targets in colon cancer. Immunohistochemical analysis of 13 surgical specimens of human colon adenocarcinoma revealed that both tumor cells and tumor-associated endothelial cells in 11 of the 13 specimens expressed the epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha), EGF receptor (EGFR), phosphorylated EGFR (pEGFR), vascular endothelial growth factor (VEGF), VEGF receptor (VEGFR), and phosphorylated VEGFR (pVEGFR). HT29 human colon cancer cells growing orthotopically in the cecum of nude mice expressed a high level of EGF, EGFR, pEGFR, VEGF, VEGFR, and pVEGFR. Double-immunofluorescence staining found that tumor-associated mouse endothelial cells also expressed pEGFR and pVEGFR. Tumors in mice treated for 5 weeks with oral AEE788 (an inhibitor of EGFR and VEGFR tyrosine kinase) as a single agent or with CPT-11 alone were smaller (>50%) than those in control mice. Mice treated with the combination of AEE788 and CPT-11 had significantly smaller tumors (P < 0.01) and complete inhibition of lymph node metastasis. AEE788 alone or in combination with CPT-11 inhibited pEGFR, pVEGFR, and phosphorylated Akt expression on tumor-associated endothelial cells as well as on tumor cells. The combination therapy also significantly decreased microvessel density and tumor cell proliferation and increased the level of apoptosis in both tumor cells and tumor-associated endothelial cells. Collectively, these data suggest that the dual inhibition of EGFR and VEGFR signaling pathways in tumor cells and tumor-associated endothelial cells in combination with chemotherapy can provide a new approach to the treatment of colon cancer.

The irinotecan/5-fluorouracil combination induces apoptosis and enhances manganese superoxide dismutase activity in HT-29 human colon carcinoma cells

BACKGROUND

We examined whether induction of apoptosis and Mn-superoxide dismutase (Mn-SOD) and Cu,Zn-superoxide dismutase (Cu,Zn-SOD) activities were involved in the greater cytotoxicity of the irinotecan (CPT-11)/5-fluorouracil (5-FU) combination for human colon cancer cells when compared to both drugs alone.

METHODS

HT-29 and SNU-C4 human colon carcinoma cell lines were treated with 5-FU and CPT-11, then apoptosis was evaluated by flow cytometry and SOD activities were determined by polyacrylamide gel electrophoresis.

RESULTS

Enhanced apoptosis of HT-29 cells was observed with all treatments containing 5-FU in SNU-C4 cells; however, in HT-29 cells, apoptosis was enhanced only with the CPT-11/5-FU combination. In the SNU-C4 cell line, none of the treatments exerted a significant effect on Cu,Zn-SOD or Mn-SOD activity. However, in HT-29 cells, the CPT-11/5-FU combination enhanced Mn-SOD activity when compared to cells treated with CPT-11 alone. Nevertheless, the combined treatment did not interfere with Cu,Zn-SOD activity.

CONCLUSION

Treatment with the CPT-11/5-FU combination may promote in HT-29 cell apoptosis by enhancing Mn-SOD activity.