Phase II study of combination therapy with S-1 and irinotecan in patients with advanced colorectal cancer

Phase II trial of daily S-1 combined with weekly irinotecan in previously treated patients with advanced or recurrent squamous cell lung cancer: North Japan lung cancer group 1101

BACKGROUND

This phase II trial was designed to evaluate the efficacy and safety of S-1 combined with weekly irinotecan as a second- or third-line treatment for patients with advanced or recurrent squamous cell lung cancer.

METHODS

Patients with a body surface area <1.25, 1.25-1.50, and >1.50 m2 received oral S-1 on days 1-14 at 80, 100, and 120 mg/day, respectively, and irinotecan on days 1 and 8 at 70 mg/m2 every 3 weeks. The primary endpoint was the overall response rate, and the secondary endpoints were progression-free survival, overall survival, and the incidence and severity of adverse effects.

RESULTS

Between September 2011 and December 2014, 30 patients were enrolled in this study. The overall response rate was 6.7% (95% confidence interval [CI]: 0.8%-22.1%), and the disease control rate was 73.3%. The median progression-free survival was 3.0 months (95% CI: 2.5-3.4 months), and the median overall survival was 10.5 months (95% CI: 5.6-13.7 months). Grade 3/4 treatment-related adverse events were reported in ≥10% of the patients, including leukopenia (21%), neutropenia (21%), anemia (17%), anorexia (10%), and hypokalemia (10%).

CONCLUSIONS

Although the treatment-related adverse events were manageable, the combination of weekly irinotecan and S-1 did not have the expected effect.

Safety of apatinib plus S-1 for advanced solid tumor as palliative treatment

The aim of the present study was to explore the safety of apatinib plus S-1 in treating advanced solid tumors after failure of two or more lines of chemotherapy. A total of 33 patients with advanced cancer treated between April 2016 to March 2019 were retrospectively analyzed. Of these, 13 patients had non-small cell lung cancer (NSCLC), 13 patients had SCLC, 4 patients had esophageal cancer and 3 had cervical cancer. All patients were treated with apatinib 250 mg once daily combined with S-1 60 mg/m2 twice daily for 14 days, repeated every 3 weeks. Adverse reactions were observed until aggravation of adverse reactions beyond the tolerable range or disease progression, and the survival rate and clinical benefits were calculated. The results suggested that the incidence rate of adverse effects (grade 3-4) was 45.5% (15/33). The top three severe adverse effects were hypertension (15.2%), thrombocytopenia (12.1%) and proteinuria (9.1%). A total of 2 patients with lung squamous-cell carcinomas died of severe pulmonary hemorrhage. Other adverse reactions were tolerated in the cohort. A total of 10 patients achieved partial response and the objective response rate was 30.3%. Furthermore, 13 patients achieved stable disease and 10 patients had progressive disease, and accordingly, the disease control rate was 72.7%. In conclusion, apatinib plus S-1 for advanced solid tumor patients as palliative treatment have a certain efficacy and was relatively safe but should be used with caution in patients with squamous-cell lung carcinoma and the efficacy and safety requires further assessment.

A phase II study of irinotecan combined with S-1 in patients with advanced or recurrent cervical cancer previously treated with platinum based chemotherapy

OBJECTIVES

We conducted a phase II study to investigate the efficacy and toxicities of irinotecan plus oral S-1 in patients with advanced or recurrent uterine cervical cancer.

METHODS

Patients with advanced or recurrent cervical cancer previously treated with platinum based chemotherapy were enrolled. Irinotecan (150 mg/m²) was administered intravenously over the course of 90 min on day 1, and S-1 (80 mg/m²) was given orally in two divided doses from days 1 to 14 of a 21 day cycle. The primary endpoint of this phase II study was response rate. Secondary endpoints included safety, progression free survival, and overall survival.

RESULTS

A total of 19 patients were enrolled and treated. The response rate was 29.4%. Grade 3-4 hematologic toxicities were observed in three patients (15.7%). The only grade 3-4 non-hematologic toxicity observed was grade 3 diarrhea. The median progression free survival and overall survival were 3 months and 9 months, respectively.

CONCLUSION

S-1 plus irinotecan in a 3 weekly setting is safe and active in women with advanced or recurrent cervical cancer previously treated with platinum based chemotherapy. Future corroborative clinical studies are warranted.

Phase I Clinical Study of Irinotecan Plus S-1 in Patients With Advanced or Recurrent Cervical Cancer Previously Treated With Platinum-Based Chemotherapy

OBJECTIVES

This study aimed to determine the maximum tolerated dose and acute dose-limiting toxicities (DLTs) of intravenous irinotecan plus oral S-1 in patients with advanced or recurrent uterine cervical cancer.

METHODS

Irinotecan was administered intravenously over the course of 90 minutes on day 1, and S-1 was given orally in 2 divided doses from days 1 to 14 of a 21-day cycle. The dose of S-1 was escalated in a stepwise fashion from 40 (level 1) to 60 mg/m (level 2) and then 80 mg/m (level 3), whereas the dosage of irinotecan remained the same (150 mg/m). The primary end point for the escalation study was acute DLT that occurred within 2 cycles of chemotherapy.

RESULTS

Twelve patients were enrolled and treated over 3 dose levels. Their median age was 47 years (range, 28-48 years). At level 1, one episode of grade 3 anemia and a grade 3 fatigue were observed, but no DLT developed. At level 2, the first patient experienced febrile neutropenia, which was considered to be a DLT. To evaluate the toxicity of this dose level, 5 more patients were evaluated. However, no DLT developed in these patients. At level 3, although grade 1 to 2 hematological and nonhematological toxicities developed, no DLT occurred.

CONCLUSIONS

In women with advanced or recurrent cervical cancer previously treated with platinum-based chemotherapy, S-1 plus irinotecan in a triweekly setting is a reasonable treatment regimen with an acceptable toxicity profile. The recommended doses of S-1 and irinotecan for this regimen are 80 and 150 mg/m, respectively.

Real-world cost analysis of chemotherapy for colorectal cancer in Japan: detailed costs of various regimens during the entire course of chemotherapy

BACKGROUND

Various chemotherapy regimens for advanced colorectal cancer have been introduced to clinical practice in Japan over the past decade. The cost profiles of these regimens, however, remain unclear in Japan. To explore the detailed costs of different regimens used to treat advanced colorectal cancer during the entire course of chemotherapy in patients treated in a practical setting, we conducted a so-called "real-world" cost analysis.

METHOD

A detailed cost analysis was performed retrospectively. Patients with advanced colorectal cancer who had received chemotherapy in a practical healthcare setting from July 2004 through October 2010 were extracted from the ordering system database of Showa University Hospital. Direct medical costs of chemotherapy regimens were calculated from the hospital billing data of the patients. The analysis was conducted from a payer's perspective.

RESULTS

A total of 30 patients with advanced colorectal cancer were identified. Twenty patients received up to second-line treatment, and 8 received up to third-line treatment. The regimens identified from among all courses of treatment in all patients were 13 oxaliplatin-based regimens, 31 irinotecan-based regimens, and 11 regimens including molecular targeted agents. The average (95% confidence interval [95% CI]) monthly cost during the overall period from the beginning of treatment to the end of treatment was 308,363 (258,792 to 357,933) Japanese yen (JPY). According to the type of regimen, the average monthly cost was 418,463 (357,413 to 479,513) JPY for oxaliplatin-based regimens, 215,499 (188,359 to 242,639) JPY for irinotecan-based regimens, and 705,460 (586,733 to 824,187) JPY for regimens including molecular targeted agents. Anticancer drug costs and hospital fees accounted for 50 to 77% and 11 to 25% of the overall costs of chemotherapy, respectively.

CONCLUSION

The costs of irinotecan-based regimens were lower than those of oxaliplatin-based regimens and regimens including molecular targeted agents in Japan. Using a lower cost regimen for first-line treatment can potentially reduce the overall cost of chemotherapy. The main cost drivers were the anticancer drug costs and hospitalization costs.

Preventive effects of amino-acid-rich elemental diet Elental® on chemotherapy-induced oral mucositis in patients with colorectal cancer: a prospective pilot study

Purpose

The prospective pilot study was designed to evaluate the preventive effects of amino-acid-rich elemental diet (ED), Elental^®, on chemotherapy-induced oral mucositis in patients with colorectal cancer. The factors influencing its efficacy are also investigated.

Methods

A total of 22 eligible patients with colorectal cancer experiencing grade 1–3 oral mucositis during treatment with fluorouracil-based chemotherapy entered the current study. Their average age was 67 years. There were 10 male and 12 female. The PS was 0 in the majority of patients. Patients received two courses of the same chemotherapy regimen and Elental^® concurrently after recovery to grade 0 or 1 oral mucositis.

Results

FOLFOX6 + bevacizumab in 8 patients, FOLFIRI + bevacizumab in 8 patients, FOLFIRI + panitumumab in 1 patient, FOLFIRI in 1 patient, XELOX + bevacizumab in 2 patients, and S-1 + cetuximab in 2 patients were used as first-line (16 cases) or as second-line (6 cases) chemotherapy. Dose reduction of 5-fluorouracil (5-FU) or oral fluoropyrimidine was performed in the 2 patients achieving grade 3 oral mucositis and in the 3 patients achieving grade 2 oral mucositis. The maximum grade of oral mucositis decreased in 18 of the 22 patients during the first treatment course with Elental^® (p = 0.0002) and in 20 of the 22 patients in the second course (p < 0.0001). Multivariate analyses found that the dose reduction in 5-FU or oral fluoropyrimidine, ED intake, and the prior administration of ED were each a significant factor for the preventive efficacy on oral mucositis.

Conclusion

The amino-acid-rich elemental diet Elental^® may be useful as a countermeasure for 5-FU-based chemotherapy-induced oral mucositis in patients with colorectal cancer.

Chemotherapy for Late-Stage Cancer Patients: Meta-Analysis of Complete Response Rates

Complete response (CR) rates reported for cytotoxic chemotherapy for late-stage cancer patients are generally low, with few exceptions, regardless of the solid cancer type or drug regimen. We investigated CR rates reported in the literature for clinical trials using chemotherapy alone, across a wide range of tumour types and chemotherapeutic regimens, to determine an overall CR rate for late-stage cancers. A total of 141 reports were located using the PubMed database. A meta-analysis was performed of reported CR from 68 chemotherapy trials (total 2732 patients) using standard agents across late-stage solid cancers—a binomial model with random effects was adopted. Mean CR rates were compared for different cancer types, and for chemotherapeutic agents with different mechanisms of action, using a logistic regression. Our results showed that the CR rates for chemotherapy treatment of late-stage cancer were generally low at 7.4%, regardless of the cancer type or drug regimen used. We found no evidence that CR rates differed between different chemotherapy drug types, but amongst different cancer types small CR differences were evident, although none exceeded a mean CR rate of 11%. This remarkable concordance of CR rates regardless of cancer or therapy type remains currently unexplained, and motivates further investigation.

An internally and externally validated nomogram for predicting the risk of irinotecan-induced severe neutropenia in advanced colorectal cancer patients

Background:

In Asians, the risk of irinotecan-induced severe toxicities is related in part to UGT1A1*6 (UGT, UDP glucuronosyltransferase) and UGT1A1*28, variant alleles that reduce the elimination of SN-38, the active metabolite of irinotecan. We prospectively studied the relation between the UGT1A1 genotype and the safety of irinotecan-based regimens in Japanese patients with advanced colorectal cancer, and then constructed a nomogram for predicting the risk of severe neutropenia in the first treatment cycle.

Methods:

Safety data were obtained from 1312 patients monitored during the first 3 cycles of irinotecan-based regimen in a prospective observational study. In development of the nomogram, multivariable logistic regression analysis was used to test the associations of candidate factors to severe neutropenia in the first cycle. The final nomogram based on the results of multivariable analysis was constructed and validated internally using a bootstrapping technique and externally in an independent data set (n=350).

Results:

The UGT1A1 genotype was confirmed to be associated with increased risks of irinotecan-induced grade 3 or 4 neutropenia and diarrhoea. The final nomogram included type of regimen, administered dose of irinotecan, gender, age, UGT1A1 genotype, Eastern Cooperative Oncology Group performance status, pre-treatment absolute neutrophil count, and total bilirubin level. The model was validated both internally (bootstrap-adjusted concordance index, 0.69) and externally (concordance index, 0.70).

Conclusions:

Our nomogram can be used before treatment to accurately predict the probability of irinotecan-induced severe neutropenia in the first cycle of therapy. Additional studies should evaluate the effect of nomogram-guided dosing on efficacy in patients receiving irinotecan.

Efficacy of S-1 in colorectal cancer

INTRODUCTION

S-1 is an oral fluoropyrimidine that consists of tegafur, 5-chloro-2, 4-dihydroxypyridine and potassium oxonate. It has been developed as a prodrug of 5-fluorouracil with the goal of improving therapeutic efficacy and tolerability.

AREAS COVERED

This review aims to provide an evidence-based update of clinical trials that have investigated the clinical efficacy, adverse-event profile, dosage and administration of S-1, given alone or in combination with conventional chemotherapeutics and new target-oriented drugs, in the management of colorectal cancer (CRC). Additionally, differences in the tolerability and pharmacokinetics of S-1 between Caucasians and Asians have been described. Finally, the therapeutic efficacy of S-1 regarding metastatic CRC or postoperative CRC has been discussed. Available data have stimulated further research, including Phase III trials for the treatment of advanced CRC.

EXPERT OPINION

Treatment using S-1 combined with oxaliplatin (± bevacizumab) and irinotecan has achieved promising results in terms of feasibility, safety and effectiveness. Furthermore, S-1 is an acceptable treatment as adjuvant chemotherapy for colon cancer.

A phase 3 non-inferiority study of 5-FU/l-leucovorin/irinotecan (FOLFIRI) versus irinotecan/S-1 (IRIS) as second-line chemotherapy for metastatic colorectal cancer: updated results of the FIRIS study

PURPOSE

The FIRIS study previously demonstrated non-inferiority of IRIS (irinotecan plus S-1) to FOLFIRI (5-fluorouracil/leucovorin with irinotecan) for progression-free survival as the second-line chemotherapy for metastatic colorectal cancer (mCRC) as the primary endpoint. The overall survival (OS) data were immature at the time of the primary analysis.

METHODS

Between 30 January 2006 and 29 January 2008, 426 patients with mCRC who failed in first-line chemotherapy were randomly assigned to receive either FOLFIRI or IRIS. After the primary analysis, the follow-up survey was cut off on 29 July 2010, and the final OS data were analysed.

RESULTS

With a median follow-up of 39.2 months, the median OS was 17.4 months in the FOLFIRI group and 17.8 months in the IRIS group [hazard ratio (HR) 0.900; 95% confidence interval (CI) 0.728-1.112]. In the pre-planned subgroup of patients who received prior chemotherapy containing oxaliplatin, the median OS was 12.7 months in the FOLFIRI group and 15.3 months in the IRIS group (HR 0.755; 95% CI 0.580-0.983).

CONCLUSIONS

IRIS is non-inferior to FOLFIRI for OS as second-line chemotherapy for mCRC. IRIS can be an option for second-line chemotherapy of mCRC. (ClinicalTrials.gov Number: NCT00284258).

Irinotecan Plus S-1 Followed by Hepatectomy for a Patient with Initially Unresectable Colorectal Liver Metastases, Who Showed Severe Drug Rash with Oxaliplatin Plus 5-FU and Leucovorin (FOLFOX)

For unresectable colorectal liver metastases (CRLM), hepatic resection with or without chemotherapy is the only curative treatment that sufficiently achieves long-term survival. However, occasional severe allergic responses to anticancer drugs necessitate treatment discontinuation. A 45-year-old woman presented with metachronous unresectable colorectal liver metastases. Chemotherapy with oxaliplatin plus 5-FU and leucovorin (FOLFOX) was initiated, but severe allergic dermatitis developed after the second cycle. Although she reported no prior history of adverse reactions to tegafur-uracil, a drug lymphocyte stimulation test showed an allergic response to 5-FU. We subsequently replaced with Irinotecan plus S-1 (IRIS) chemotherapy which was well tolerated and resulted in a partial response after 3 cycles. As a result, right trisectionectomy was successfully performed and no recurrence was detected in the following 3 years. A severe allergic reaction to intravenous 5-FU-containing drug regimens can be successfully alleviated by switching to S-1-containing regimens such as IRIS or S-1 plus oxaliplatin (SOX).

Phase I/II trial of irinotecan and S-1 combination chemotherapy as a second-line treatment for advanced colorectal cancer

BACKGROUND

This study attempted to determine the therapeutic dosage of irinotecan and S-1 (IRIS) as a second-line treatment for colorectal cancer (CRC).

METHODS

S-1 was administered on days 1-14 of a 28-day cycle. Irinotecan was administered on days 1 and 15. The irinotecan dose was then escalated to determine the maximum-tolerated dose and the recommended dose at a fixed dosage of S-1 (80 or 65 mg·m(-2)·day(-1)). The S-1 dose was reduced to 65 mg·m(-2)·day(-1) when dose-limiting toxicities were observed at 80 mg·m(-2)· day(-1) and the irinotecan dose was increased.

RESULTS

The recommended dose was 65 mg/m(2) for S-1 and 75 mg/m(2) for irinotecan. Twenty-one patients were treated at the recommended dose. The overall response rate was 28.6%.

CONCLUSION

This modified IRIS regimen is considered effective with acceptable toxicities for advanced CRC resistant to treatment with 5-fluorouracil/leucovorin or uracil and tegafur/leucovorin.

Phase II clinical trial of metronomic chemotherapy with combined irinotecan and tegafur-gimeracil-oteracil potassium in metastatic and recurrent breast cancer

BACKGROUND

We investigated the efficacy and safety of metronomic chemotherapy with combined irinotecan and tegafur-gimeracil-oteracil potassium (TS-1) in patients with metastatic and recurrent breast cancer (MRBC), and the association between irinotecan metabolizing enzyme UDP-glucuronosyltransferase 1A1 (UGT1A1) gene polymorphisms and adverse events.

METHODS

The study group comprised 40 patients aged 35-79 years. Irinotecan (60 mg/m(2) in 5 % dextrose) was administered by 120-min infusion on days 1, 8, and 15 every 4 weeks. TS-1 (prescribed in a standard quantity) was administered at 80 mg/m(2)/day orally on days 3-7, 10-14, and 17-21 every 4 weeks.

RESULTS

Tumor response data were available for 34 patients. Median follow-up was 12 months (range 1-45 months). Response rate was 47 % (one complete and 15 partial responses). Stable disease was observed in 17 patients (50 %). One patient had disease progression (3 %). Median progression-free survival was 14 months [95 % confidence interval (CI), 10-26]. Median overall survival was 26 months (95 % CI not calculable owing to sample size), and 79.3 % of patients survived for 1 year. The most common grade 3 or 4 adverse events were neutropenia (15 %), leukopenia (12.5 %), diarrhea (7.5 %), and anemia (2.5 %). All other adverse events were grade 1 or 2. Treatment-related toxicity was generally modest and manageable. No significant correlation was observed between UGT1A1 polymorphisms and hematological or non-hematological toxicities.

CONCLUSIONS

Metronomic chemotherapy with combined irinotecan and TS-1 was effective in MRBC patients. Adverse effects were mild and the regimen was safely administered without identifying UGT1A1 polymorphisms.

Multicenter Phase II Study of a New Effective S-1 and Irinotecan Combination Schedule in Patients with Unresectable Metastatic or Recurrent Colorectal Cancer

INTRODUCTION

This multicenter phase II study determined the efficacy and safety of new daily oral S-1 and weekly irinotecan (CPT-11) combination schedule in patients with previously untreated advanced or recurrent colorectal cancer.

PATIENTS AND METHODS

Patients received first-line chemotherapy comprising S-1 80 mg/m(2)/day given on days 3 to 7, 10 to 14, and 17 to 21 and 60 mg/m(2) CPT-11 administered intravenously on days 1, 8, and 15 of a 28-day cycle.

RESULTS

A total of 45 eligible patients were enrolled in this study. The overall response rate was 48.9%. Median progression-free survival and median overall survival was 8.1 months and 20.9 months, respectively. The rates of grade 3 or 4 toxicity were as follows: neutropenia, 8.9%; anemia, 4.4%; anorexia, 6.7%; and diarrhea, 6.7%.

CONCLUSIONS

This new S-1 and irinotecan combination schedule appeared to be an effective, well-tolerated, and convenient regimen in patients with advanced colorectal cancer as compared with conventional regimens such as FOLFIRI and IRIS.

Phase I/II study of S-1 combined with biweekly irinotecan chemotherapy in previously treated advanced non-small cell lung cancer

PURPOSE

This phase I/II study was designed to evaluate a combination of irinotecan and S-1 a new regimen for salvage chemotherapy in patients with advanced or metastatic non-small cell lung cancer (NSCLC).

METHODS

The study group comprised patients with advanced or metastatic NSCLC who had previously received at least one platinum-containing chemotherapy. Patients received irinotecan on days 1, 15 and oral S-1 (40 mg/m(2) twice daily as a fixed dose) on day 1 to 14 of a 28-day cycle.

RESULTS

In the phase I part, irinotecan was given in escalating doses of 70 (Level 1), 80 (Level 2), and 90 mg/m(2) (Level 3). Three of the 5 patients given Level 3 had dose-limiting toxicity, and Level 2 (80 mg/m(2) of irinotecan) was designated as the recommended dose. In phase II, 38 patients received a median of 7.4 cycles of irinotecan at the recommended dose. The overall response rate was 15.8 % (90 % confidence interval (CI): 6.1-25.5 %), and the median progression-free and overall survival times were 4.5 months (95 % CI: 3.5-5.0) and 15.0 months (95 % CI: 9.5-20.6) months, respectively. Toxicity was generally mild. Grade 3 or higher toxicity included neutropenia in 17.9 % of the patients, thrombocytopenia in 5.1 % and nausea in 7.7 %.

CONCLUSION

Combination chemotherapy with S-1 and irinotecan was considered an effective salvage regimen in patients with advanced or metastatic NSCLC.

Phase II study of combined chemotherapy with irinotecan and S-1 (IRIS) plus bevacizumab in patients with inoperable recurrent or advanced colorectal cancer

BACKGROUND

In Japan, a study comparing the effectiveness and safety of irinotecan plus S-1 (IRIS) with those of a combination of 5-fluorouracil, leucovorin, and irinotecan (FOLFIRI) as second-line treatment in patients with advanced or recurrent colorectal cancer demonstrated that IRIS was non-inferior to FOLFIRI. We previously reported that IRIS is also effective as first-line treatment.

PATIENTS AND METHODS

Eligibility criteria included inoperable recurrent colorectal cancer with a confirmed diagnosis of adenocarcinoma, age ≥20 years, and no history of prior chemotherapy. S-1 (40-60 mg twice daily) was given orally on Days 1 to 14, and irinotecan (100 mg/m(2)) and bevacizumab (5 mg/kg) were given intravenously on Days 1 and 15 of a 28-day cycle. The primary endpoint was safety. The secondary endpoints included overall response (OR), progression-free survival (PFS), and overall survival (OS).

RESULTS

A total of 52 eligible patients were enrolled from October 2007 through March 2009. In safety analysis, the incidences of grade 3 or 4 adverse reactions were as follows: neutropenia, 27%; hypertension, 21%; and diarrhea, 17%. The overall response rate was 57.7%. Median progression-free survival was 16.7 months.

CONCLUSION

IRIS plus bevacizumab is a well-tolerated, highly effective chemotherapeutic regimen that is easy to administer.

S-1 for the treatment of gastrointestinal cancer

INTRODUCTION

5-Fluorouracil (5-FU)-based regimens are used worldwide as the standard treatment in chemotherapy for gastric cancer. S-1 , a fourth-generation oral fluoropyrimidine that combines tegafur and two biochemical modulators: gimeracil and oteracil potassium, is now attracting considerable interest.

AREAS COVERED

This review addresses the clinical evidence of S-1 in gastrointestinal malignancies, such as gastric, colorectal, pancreatic and biliary tract cancers. S-1 has demonstrated advantages over standard therapies, in both advanced and postoperative settings, in large Phase III studies. S-1 alone or S-1 plus cisplatin is recommended in the 2010 Gastric Cancer Treatment Guidelines, by the Japanese Gastric Cancer Association. Results from Phase III studies have demonstrated that S-1 in combination with chemotherapies, such as cisplatin in gastric cancer, and irinotecan and oxaliplatin in colorectal cancers, is non-inferior to conventional 5-FU-based standard regimens, with the benefit of convenience and reduced toxicity.

EXPERT OPINION

The excellent design of S-1 aimed to reduce toxicity by avoiding certain routes of degradation, and to enhance activity by reducing catabolism. This has provided not only a suitable alternative to 5-FU, but also higher efficacy.

A Phase II study of clinical outcomes of 3-week cycles of irinotecan and S-1 in patients with previously untreated metastatic colorectal cancer: influence of the UGT1A1 and CYP2A6 polymorphisms on clinical activity

OBJECTIVES

We investigated the efficacy and safety of the combination of irinotecan (CPT-11) and S-1 (IRIS regimen) as a first-line treatment in patients with metastatic colorectal cancer. We also evaluated the association between UGT1A1 and CYP2A6 polymorphisms and clinical phenotypes.

METHODS

The patients received CPT-11 (225 mg/m(2)) on day 1 and S-1 (80 mg/m(2)) on days 1-14 every 3 weeks. The association of the UGT1A1 (*6 and *28) and CYP2A6(*4, *7, *9, and *10) polymorphisms with toxicities and efficacy were analyzed.

RESULTS

Thirty patients were treated. The overall response rate was 66.7% (95% CI 48.7-84.6). The median time to progression was 7.6 months (95% CI 5.8-9.5). The most common grade 3/4 hematologic and non-hematologic toxicity were neutropenia (53.4%) and diarrhea (16.7%), respectively. The allele frequencies of UGT1A1*6 and *28 were 15.5 and 10.3%, respectively. The frequencies of CYP2A6*4, *7, *9, and *10 were 15.5, 8.6, 29.3, and 3.5%, respectively. Stratification of patients according to the number of UGT1A1*28 and *6 alleles showed a significant correlation between the number of defective alleles and the incidence of grade 3/4 neutropenia.

CONCLUSIONS

Our results indicate that IRIS is a promising first-line regimen in patients with metastatic colorectal cancer. Severe neutropenia may be associated with interindividual variations in UGT1A1 polymorphisms.

Phase II study of oral S-1 with irinotecan and bevacizumab (SIRB) as first-line therapy for patients with metastatic colorectal cancer

Fluorouracil (5-FU) plus irinotecan combined with bevacizumab has significant activity in metastatic colorectal cancer (mCRC), but S-1 has become a substitute for continuous infusion of 5-FU and has a very low incidence of hand-foot syndrome. With the S-1 plus irinotecan regimen (SIR), the response rate was 62.5%, and the progression-free survival was 8.0 months. We report here on an update of efficacy and safety of the SIR plus bevacizumab (SIRB) regimen as first line treatment for mCRC patients. Fifty-one eligible patients with histologically confirmed advanced or recurrent colorectal cancer received this treatment. S-1 was administered orally on days 1-14 of a 21-day cycle. Patients were assigned on the basis of body surface area (BSA) to receive one of the following oral doses twice daily: 40 mg, 50 mg, or 60 mg. Irinotecan (150 mg/m(2)) plus bevacizumab (7.5 mg/kg) were administered by intravenous infusion on day 1. Safety analysis identified a grade 3/4 neutropenia rate of 26%. Other grade 3/4 toxicities were diarrhea (8%), nausea (6%), vomiting (2%), and hypertension (8%). The response rate was 67% and the median progression-free survival time was 373 days. The SIRB regimen appears to be highly active and well tolerated as first-line treatment for mCRC.

Phase II study of combined treatment with irinotecan and S-1 (IRIS) in patients with inoperable or recurrent advanced colorectal cancer (HGCSG0302)

OBJECTIVES

This phase II study was designed to evaluate the efficacy and safety of oral fluoropyrimidine S-1 plus irinotecan (IRIS regimen) in patients with previously untreated metastatic colorectal cancer.

METHODS

The response rate was the primary endpoint. Safety, progression-free survival time, and median survival time were secondary endpoints. The subjects were untreated patients with inoperable advanced colorectal cancer. Irinotecan was administered at a dose of 100 mg/m² (on days 1 and 15). S-1 (40 mg/m²) was administered for 2 weeks (on days 1 to 14) and followed by a 2-week rest.

RESULTS

Forty patients were enrolled. Four patients had grade 4 neutropenia, and six patients had grade 3 diarrhea. No other serious hematologic or nonhematologic adverse reactions occurred, and all patients received IRIS safely on an outpatient basis. The response rate was 52.5% (95% confidence interval [CI], 36.1-68.5%). Median progression-free survival was 8.6 months (95% CI, 5.3-11.9), and median survival time was 23.4 months (95% CI, 15.9-30.8).

CONCLUSIONS

IRIS produced a high response rate and could be given safely. IRIS may become a first-line treatment for inoperable or recurrent advanced colorectal cancer.

Circulating endothelial progenitor cells in metronomic chemotherapy using irinotecan and/or bevacizumab for colon carcinoma: Study of their clinical significance

The aim of the present study was to clarify the antitumor efficacy of metronomic chemotherapy using irinotecan (CPT-11) combined with or without bevacizumab against colon cancer, and the significance of circulating endothelial cell (CECs) and endothelial progenitor cells (CEPs) as a surrogate marker for metronomic chemotherapy. KM12SM cells were implanted into the subcutis of nude mouse. After confirming that the implanted tumors had grown 5 mm in size, group A received an intraperitoneal injection of 40 mg/kg CPT-11 every two weeks for 4 weeks [conventional maximum-tolerated dose (MTD)], group B received 10 mg/kg twice weekly (metronomic), group C received 10 mg/kg twice weekly combined with 5 mg/kg bevacizumab twice weekly (metronomic + anti-angiogenic), and the control group received 0.2 ml of PBS every week. Serial changes of CECs and CEPs in peripheral blood and microvessel density (MVD) in the tumor tissues were evaluated. The results showed that the antitumor activity in group B and in group C was significantly higher than that in group A. A significant inhibition in CEPs on day 15 in the metronomic therapy groups B and C was noted when compared to that in the control group, while there was no significant difference in CECs and CEPs between the groups on days 4 and 8. The MVD on day 15 in metronomic groups was significantly lower than that in group A. In conclusion, metronomic chemotherapy of CPT-11 with or without bevacizumab for colon cancer was more effective than the MTD therapy via anti-angiogenic effects. Sequential measurement of CEPs may be a predictive factor for the efficacy and a decisive factor for the optimal dose of metronomic therapy in colon cancer.

A phase I study of S-1 and irinotecan combination therapy in previously treated advanced non-small cell lung cancer patients

BACKGROUND

This phase I study was conducted to evaluate the feasibility and to determine the recommended doses of the combination therapy of S-1 and irinotecan (CPT-11) in patients with advanced non-small cell lung cancer (NSCLC) as second-line treatment.

METHODS

Patients with NSCLC who were previously treated with one chemotherapy regimen and had a performance status of 0 or 1 were eligible. CPT-11 was administered at 60 mg/m² (level 1), 80 mg/m² (level 2) on days 1 and 8, and oral S-1 was administered at 80 mg/day for body surface area (BSA) less than 1.25 m², 100 mg/day for BSA 1.25-1.5 m², and 120 mg/day for BSA more than 1.5 m² on days 1-14 every 3 weeks. The dose-limiting toxicity (DLT) was defined as grade 4 leukocytopenia or neutropenia, grade ≥ 3 neutropenia with fever over 38°C, grade ≥ 3 thrombocytopenia, or grade ≥ 3 major nonhematological toxicities.

RESULTS

Nine patients were enrolled in the study. None of 3 patients enrolled in level 1 had any DLT. Of 6 patients in level 2, 2 patients had grade 3 diarrhea and one had grade 3 interstitial pneumonia. Level 1 was declared as the recommended dose.

CONCLUSION

The feasibility of the combination therapy of S-1 and CPT-11 was shown in the second-line setting for the treatment of advanced NSCLC. The recommended dose of CPT-11 was 60 mg/m² combined with standard dose of S-1 for phase II trials of pretreated advanced NSCLC patients.

Phase I/II study of a 3-week cycle of irinotecan and S-1 in patients with advanced colorectal cancer

The combination of an oral fluoropyrimidine derivative, S-1, and irinotecan is expected to be a promising regimen for advanced colorectal cancer. This study was performed to determine the maximum tolerated dose (MTD) and recommended dose (RD) of irinotecan combined with S-1 in a 3-week cycle regimen and to observe the safety and efficacy for patients with previously untreated advanced colorectal cancer. Eighty milligrams per m(2) of S-1 was given orally for 14 consecutive days and escalated doses of irinotecan were administered on days 1 and 8 every 3 weeks in the phase I trial. Forty patients were treated at the RD during the phase II trial. Forty-three patients were enrolled between February 2005 and March 2007. The dose-limiting toxicity was diarrhea and abdominal pain. The MTD of irinotecan was 100 mg/m(2) and the RD was determined to be 80 mg/m(2) of irinotecan combined with 80 mg/m(2) of S-1. The phase II trial showed that 22 of 40 patients achieved a complete or partial response and eight had stable disease. The overall response rate was 55.0%. The median progression-free survival time and median survival time were 6.7 and 21 months, respectively. There were no treatment-related deaths. The main toxicities were leukopenia, neutropenia, anorexia and diarrhea. This study suggests the combination of irinotecan and S-1 repeated every 3 weeks is tolerable and effective for patients with previously untreated advanced colorectal cancer.

Irinotecan plus S-1 (IRIS) versus fluorouracil and folinic acid plus irinotecan (FOLFIRI) as second-line chemotherapy for metastatic colorectal cancer: a randomised phase 2/3 non-inferiority study (FIRIS study)

BACKGROUND

Fluorouracil and folinic acid with either oxaliplatin (FOLFOX) or irinotecan (FOLFIRI) are widely used as first-line or second-line chemotherapy for metastatic colorectal cancer. However, infusional fluorouracil-based regimens, requiring continuous infusion and implantation of an intravenous port system, are inconvenient. We therefore planned an open-label randomised controlled trial to verify the non-inferiority of irinotecan plus oral S-1 (a combination of tegafur, 5-chloro-2,4-dihydroxypyridine, and potassium oxonate; IRIS) to FOLFIRI as second-line chemotherapy for metastatic colorectal cancer.

METHODS

Between Jan 30, 2006, and Jan 29, 2008, 426 patients with metastatic colorectal cancer needing second-line chemotherapy from 40 institutions in Japan were randomly assigned by a computer-based minimisation method to receive either FOLFIRI (n=213) or IRIS (n=213). In the FOLFIRI group, patients received folinic acid (200 mg/m(2)) and irinotecan (150 mg/m(2)) and then a bolus injection of fluorouracil (400 mg/m(2)) on day 1 and a continuous infusion of fluorouracil (2400 mg/m(2)) over 46 h, repeated every 2 weeks. In the IRIS group, patients received irinotecan (125 mg/m(2)) on days 1 and 15 and S-1 (40-60 mg according to body surface area) twice daily for 2 weeks, repeated every 4 weeks. The primary endpoint was progression-free survival, with a non-inferiority margin of 1.333. Statistical analysis was on the basis of initially randomised participants. This study is registered with ClinicalTrials.gov, number NCT00284258.

FINDINGS

All randomised patients were included in the primary analysis. After a median follow-up of 12.9 months (IQR 11.5-18.2), median progression-free survival was 5.1 months in the FOLFIRI group and 5.8 months in the IRIS group (hazard ratio 1.077, 95% CI 0.879-1.319, non-inferiority test p=0.039). The most common grade three or four adverse drug reactions were neutropenia (110 [52.1%] of 211 patients in the FOLFIRI group and 76 [36.2%] of 210 patients in the IRIS group; p=0.0012), leucopenia (33 [15.6%] in the FOLFIRI group and 38 [18.1%] in the IRIS group; p=0.5178), and diarrhoea (ten [4.7%] in the FOLFIRI group and 43 [20.5%] in the IRIS group; p<0.0001). One treatment-related death from hypotension due to shock was reported in the FOLFIRI group within 28 days after the end of treatment; no treatment-related deaths were reported in the IRIS group.

INTERPRETATION

Progression-free survival with IRIS is not inferior to that with FOLFIRI in patients receiving second-line chemotherapy for metastatic colorectal cancer. Treatment with IRIS could be an additional therapeutic option for second-line chemotherapy in metastatic colorectal cancer.

FUNDING

Taiho Pharmaceutical Co Ltd and Daiichi Sankyo Co Ltd.

A phase II study of combination therapy with irinotecan and S-1 (IRIS) in patients with advanced colorectal cancer

PURPOSE

A combination of irinotecan with continuous infusional 5-fluorouracil (5-FU) is the standard treatment for advanced colorectal cancer. The aim of this study was to determine the efficacy and safety of combining irinotecan and S-1 (IRIS) in patients with advanced colorectal cancer.

METHODS

Irinotecan was administered as an intravenous infusion at a dose of 120 mg/m(2) on day 1 and 15. And S-1 was administered orally on days 1-14 of a 28-day cycle. S-1 was given orally at a dose that did not exceed 40 mg/m(2) based BSA: BSA < 1.25 m(2), 40 mg twice daily; 1.25-1.5 m(2), 50 mg twice daily, and BSA > 1.5 m(2), 60 mg twice daily, for 14 consecutive days.

RESULTS

A total of 38 patients were enrolled. An intent-to-treat analysis showed a complete response and partial response to occur in 13.2% and 50.0%, respectively. The disease control rate was 84.2%. The median progression-free survival and overall survival were 10.0 months and 29.1 months, respectively. The rates of grade 3/4 toxicity over 4 cycles were the following: neutropenia, 15.8%; leucopenia, 7.9%; anorexia, 15.8%; diarrhea, 10.5%.

CONCLUSION

IRIS is an effective, well tolerated and convenient treatment regimen for patients with advanced colorectal cancer.

Dosage escalation study of S-1 and irinotecan in metronomic chemotherapy against advanced colorectal cancer

The anti-angiogenic efficacy of chemotherapy would seem to be optimized by administering comparatively lower doses of drugs on a more frequent (daily, several times a week, or weekly) or continuous schedule, with no extended interruptions - sometimes referred to as 'metronomic' chemotherapy. This phase I study was performed to determine the recommended dosage (RD) of metronomic chemotherapy using oral fluoropyrimidine S-1 plus weekly irinotecan (CPT-11) in patients with previously untreated advanced or recurrent colorectal cancer. Patients received first-line chemotherapy consisting of 80 mg/m(2) of S-1 given on days 3 to 7, 10 to 14, and 17 to 21 with escalating dosages of CPT-11 (from 40 mg/m(2)) administered intravenously on day 1, 8, and 15 of a 28-day cycle. Standard patient eligibility criteria were used. Based on the concept of metronomic chemotherapy, dose limiting toxicity (DLT) was defined any toxicity that resulted in skipping of CPT-11 administration, or more than 5 days suspension in S-1 administration, in addition to the conventional criteria. If the maximum tolerated dosage (MTD) was defined as the maximum dosage at which no suspension of CPT-11 or S-1 administration occurred, the RD was considered to be the dosage one rank lower than the MTD. On the other hand, in the present study the MTD was defined as the dosage at which at least one suspension of CPT-11 or S-1 administration occurred, the MTD was considered to be the RD. Two of the first 3 patients at level 4 received 60 mg/m(2) of CPT-11 and 80 mg/m(2) of S-1 experienced a suspension in CPT-11 administration, thus level 4 was defined as the MTD and RD. Sixty mg/m(2) of CPT-11 and 80 mg/m(2) of S-1 were the indicated RD for the following phase II study of metronomic chemotherapy.

VEGF hypersecretion as a plausible mechanism for pseudo-meigs' syndrome in advanced colorectal cancer

We present a case of pseudo-meigs' syndrome caused by a metastatic ovarian tumor of rectal cancer origin, and examine the possible involvement of vascular endothelial growth factor (VEGF) in the pathogenesis of refractory fluid retention. A 42-year-old woman with advanced rectal cancer underwent a laparoscopic anterior resection of the rectum. During systemic chemotherapy treatment, she complained of severe abdominal distension 16 months following the operation. We failed to improve massive ascites by diuretics and repeated abdominocenteses. Without any definite evidence of carcinomatous peritonitis, we chose to extirpate an enlarged ovarian tumor on the presumptive diagnosis of pseudo-meigs' syndrome. Ascites disappeared promptly after resecting the ovarian tumors and the subject resumed systemic chemotherapy. Preoperative high levels of serum VEGF were normalized promptly after the operation. Levels of VEGF expression in metastatic ovarian tumors were as weak as in the primary tumor upon immunohistochemical staining. In contrast, increased VEGF expression was evident in epithelial cells of oviducts. For patients with massive and refractory ascites, we need to keep in mind the disease entity of pseudo-meigs' syndrome, since surgical intervention possibly improves conditions. Furthermore, the hypersecretion of VEGF from oviducts may play a role in the pathogenesis of clinical manifestations of pseudo-meigs' syndrome.

S-1: a new oral fluoropyrimidine in the treatment of patients with advanced non-small-cell lung cancer

S-1 (also known as TS-1; Taiho Pharmaceutical Co. Ltd.; Tokyo, Japan) is a new oral fluoropyrimidine formulation that combines tegafur, 5-chloro-2,4-dihydroxypyridine (CDHP), and potassium oxonate in a molar ratio of 1:0.4:1. Single-agent S-1 has demonstrated marked activity against non-small-cell lung cancer (NSCLC) as well as a broad array of other solid tumors, including gastric, colorectal, breast, cervical, and pancreatic cancers. This comprehensive review summarizes the results of previous clinical studies and describes ongoing clinical trials of S-1 in advanced NSCLC. S-1 combined with platinum compounds, irinotecan, and gemcitabine has produced promising results in terms of feasibility, safety, and effectiveness. Available data have stimulated further research, including phase III trials for the first-line treatment of advanced NSCLC.

Efficacy of S-1 monotherapy for non-small cell lung cancer after the failure of two or more prior chemotherapy regimens

The efficacy and safety of S-1 monotherapy for patients with advanced or recurrent non-small cell lung cancer (NSCLC) after the failure of two or more prior chemotherapy regimens were investigated. Records of 36 patients with advanced or recurrent NSCLC who received S-1 monotherapy between January 2005 and December 2008, following the failure of previous chemotherapy, were reviewed retrospectively at two institutions. S-1 was given orally twice daily on days 1-28 every six weeks; the dose was based on body surface area. The median number of prior chemotherapy regimens was three (range 2-5), and that of courses given per patient was two (range 1-10). No patient achieved complete response, 4 patients (11.1%) achieved partial response, 10 patients (27%) had stable disease and 18 patients (50%) had progressive disease. The median progression-free survival was 3 months and the median overall survival was 15.2 months. No grade 4 hematological toxicity was noted. Grade ≥3 non-hematological toxicities were observed in 5 patients (13.9%). No deaths related to S-1 monotherapy occurred. S-1 monotherapy exhibits activity with acceptable toxicity as third-line or subsequent chemotherapy for advanced NSCLC.

Phase I/II study of sequential therapy with irinotecan and S-1 for metastatic colorectal cancer

Background:

Both irinotecan (CPT-11) and S-1 are active against colorectal cancer; however, as S-1 is a prodrug of 5-fluorouracil (5-FU), 5-FU and its metabolites might inhibit the antitumour effect of CPT-11. Therefore, we designed a sequential combination, in which CPT-11 infusion was given on day 1 and S-1 was given orally at 80 mg m⁻² per day on days 3–16 every 3 weeks.

Methods:

Twelve patients entered the phase I study, and the recommended doses were determined as a CPT-11 dose of 150 mg m⁻² and an S-1 dose of 80 mg m⁻².

Results:

In all, 36 patients entered the phase II study, of whom 4 and 16 had complete and partial responses. The overall response rate was 55.6% (95% confidence interval, 38.1–72.1%), and median progression-free survival was 7.7 months (95% confidence interval, 4.8–12.6 months). Grade 3 neutropenia was the most common haematological toxicity and occurred in 6.5% of 215 treatment courses. Grade 3 non-haematological toxicities included anorexia (1.4%) and diarrhoea (0.9%). There was no grade 4 toxicity of any kind.

Conclusion:

Our results suggest that this regimen is convenient, safe and promising, compared with conventional regimens for patients with metastatic colorectal cancer.

Effects of oral administration of S-1 on the pharmacokinetics of SN-38, irinotecan active metabolite, in patients with advanced colorectal cancer

Previous studies have assessed the efficacy and safety of combined treatment with irinotecan (7-ethyl-10-[4-[1-piperidino]-1-piperidino]carbonyloxycamptothecin, CPT-11) and S-1, containing tegafur, a prodrug of 5-fluorouracil, in the treatment of colorectal and gastric cancer. The objective of this study was to describe the interaction between CPT-11 and S-1 in 4 patients with colorectal cancer. Coadministration of S-1 changed the pharmacokinetic behavior of CPT-11 and its metabolites. In particular, maximum plasma concentration (Cmax) and area under the plasma concentration curve (AUC) of 7-ethyl-10-hydroxycampothecin (SN-38) was markedly decreased by coadministration of S-1. For SN-38, the median ratio of Cmax and AUC with S-1 to those without S-1 was median 0.34 (range 0.24-0.78) and 0.56 (range 0.23-0.68), respectively. A markedly difference in drug interaction among individual patients was observed. We conclude that the plasma concentration of SN-38 was decreased by oral administration of S-1 in patients with colorectal cancer. This observation might be important for clinical decisions regarding combination therapy.

Can inhibiting dihydropyrimidine dehydrogenase limit hand-foot syndrome caused by fluoropyrimidines?

Hand-foot syndrome (HFS) is a cutaneous adverse event that occurs in some patients treated with fluoropyrimidines. Although it is not life threatening, HFS can severely disrupt the daily lives of patients. HFS appears more frequently with 5-fluorouracil (5-FU) delivered by continuous infusion or with the 5-FU oral derivative capecitabine than with bolus 5-FU therapy. HFS is a leading cause of treatment interruption, dosage reduction, or, even, therapy discontinuation for patients on a capecitabine regimen. Interestingly, addition of a dihydropyrimidine dehydrogenase (DPD) inhibitor, such as uracil, 5-chloro-2,4-dihydroxypyridine, or eniluracil, to the fluoropyrimidine treatment regimen significantly diminishes the incidence of HFS. DPD inhibitors were initially combined with fluoropyrimidines to increase the efficacy of the drugs by impairing the DPD-mediated catabolism of 5-FU. However, with the accumulating findings from clinical trials that show the benefits of DPD inhibition on decreasing the risk of HFS, consideration should be given to changing the recommendations for the treatment of cancer patients with fluoropyrimidines to include DPD inhibitor components as standard therapy.

Phase I study of S-1 combined with irinotecan (CPT-11) in patients with advanced colorectal cancer

PURPOSE

To determine the maximum tolerated dose, recommended dose and dose-limiting toxicities of irinotecan plus S-1 in advanced colorectal cancer.

PATIENTS AND METHODS

S-1 was administered orally at 80 mg/m2/day for 21 consecutive days followed by a 2-week rest. CPT-11 was given intravenously on days 1 and 15 of each course, at an initial dose of 60 mg/m2/day, stepping up to 80, 100, 120 or 140 mg/m2/day. Courses were repeated every 5 weeks, unless disease progression or severe toxicities were observed.

RESULTS

A total of 20 patients were entered in this study. The maximum tolerated dose of CPT-11 was considered to be 100 mg/m2, because 2 of 3 patients developed dose-limiting toxicities, such as anorexia, fatigue and diarrhea. Therefore, the recommended dose of CPT-11 was set at 80 mg/m2. Tumor responses were seen in 8 of 14 patients with measurable lesions.

CONCLUSION

A combination of S-1 with CPT-11 is safe and can be recommended for further phase II studies in patients with advanced colorectal cancer.

Involvement of up-regulation of hepatic breast cancer resistance protein in decreased plasma concentration of 7-ethyl-10-hydroxycamptothecin (SN-38) by coadministration of S-1 in rats

The safety and efficacy of combination therapy with 7-ethyl-10-[4-[1-piperidino]-1-piperidino]carbonyloxycamptothecin (CPT-11, irinotecan) and S-1 composed of tegafur, a prodrug of 5-fluorouracil, gimeracil, and potassium oxonate, have been confirmed in patients with colorectal cancer. Previously, we showed that p.o. coadministration of S-1 decreased the plasma concentration of both CPT-11 and its metabolites in a patient with advanced colorectal cancer. The aim of this study was to clarify the mechanism of drug interaction using both in vivo and in vitro methods. Rats were administered S-1 p.o. (10 mg/kg) once a day for 7 consecutive days. On day 7, CPT-11 (10 mg/kg) was administered by i.v. injection. Coadministration of S-1 affected the pharmacokinetic behavior of CPT-11 and its metabolites, with a decrease in the C(max) and area under the plasma concentration curve (AUC) of the active metabolite 7-ethyl-10-hydroxycampothecin (SN-38) lactone form. Furthermore, the rate of biliary excretion of the SN-38 carboxylate form increased on coadministration of S-1. In the liver, the level of breast cancer resistance protein (BCRP), but not P-glycoprotein and multidrug resistance-associated protein 2, was elevated after administration of S-1. Enzymatic conversion of CPT-11 to SN-38 by carboxylesterase (CES) was unaffected by the liver microsomes of rats treated with S-1. In addition, components of S-1 did not inhibit the hydrolysis of p-nitrophenylacetate, a substrate of CES, in the S9 fraction of HepG2 cells. Therefore, the mechanism of drug interaction between CPT-11 and S-1 appears to involve up-regulation of BCRP in the liver, resulting in an increased rate of biliary excretion of SN-38 accompanied by a decrease in the C(max) and AUC of SN-38.