Irinotecan (CPT-11) in metastatic colorectal cancer patients resistant to 5-fluorouracil (5-FU): A phase II study

A Randomised Phase II Study of Irinotecan in Combination with 5-FU/FA Compared with Irinotecan Alone as Second-Line Treatment of Patients with Metastatic Colorectal Carcinoma

BACKGROUND

We conducted a randomised phase II study to compare irinotecan monotherapy with irinotecan in combination with infusional 5-fluorouracil/folinic acid (5-FU/FA) regarding efficacy and safety of these regimens in second-line therapy after failed fluoropyrimidine therapy in patients with metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

55 patients with mCRC after failure of a first-line therapy were randomised to receive either irinotecan 80 mg/m2 followed by FA 500 mg/m2 and 5-FU 2,000 mg/m2 24 h weekly for 6 weeks, with courses repeated on day 50 (arm A), or irinotecan 125 mg/m2 weekly for 4 weeks, with cycles repeated on day 43 (Arm B).

RESULTS

Both regimens yielded a partial response rate of 11% with identical progression-free survival (3.7 months for both regimens) and similar overall survival (9.5 months for the combination therapy vs. 10.7 months for the monotherapy). Both regimens were very well tolerated, and the combination of irinotecan with 5-FU/FA did not result in increased toxicity.

CONCLUSION

Our study confirms that irinotecan alone or in combination with infusional 5-FU/FA is an effective and safe regimen for CRC patients who failed first-line therapies. However, the role of 5-FU in addition to irinotecan for fluoropyrimidine failures remains unclear. Due to the small sample size, a decision cannot be made which therapy should be preferred, and a significant contribution to the efficacy of single-agent irinotecan is not obvious from this small randomised phase II trial.

Synthesis and antitumor activity of 5-bromo-1-mesyluracil

Large-scale preparation of 5-bromo-1-mesyluracil (BMsU) 4 has been optimized. BMsU was synthesized by condensation of silylated 5-bromouracil and MsCl in acetonitrile or by the reaction of 5-bromouracil with MsCl in pyridine. The same product was obtained by bromination of 1-mesyluracil. The purpose of this study was to elucidate the effects of BMsU on the biosynthetic activity of tumor cell enzymes involved in DNA, RNA and protein syntheses, and in de novo and salvage pyrimidine and purine syntheses. Investigations were performed in vitro on human cervix carcinoma cells (HeLa). BMsU displayed inhibitory effects on DNA and RNA syntheses in HeLa cells after 24 h of treatment. De nova biosynthesis of pyrimidine and purine was also affected. Antitumor activity of BMsU is closely associated with its inhibitory activity on the enzymes that play an important role in the metabolism of tumor cells. In vivo antitumor activity of BMsU was also investigated. The model used in investigations was a mouse anaplastic mammary carcinoma transplanted into the thigh of the right leg of CBA mice. Significant reduction in tumor growth time was achieved with BmsU administered at a dose of 50 mg/kg.

Phase II trial of fortnightly irinotecan (CPT-11) in the treatment of colorectal cancer patients resistant to previous fluoropyrimidine-based chemotherapy

INTRODUCTION

This phase II study investigated the anti-tumour activity and toxicity of CPT-11 (250 mg/m2 i.v. infusion over 60 minutes) administered every 2 weeks as second-line chemotherapy in patients with advanced colorectal cancer (CRC).

MATERIAL AND METHODS

Patients (n = 63) with histology diagnosis of advanced CRC and proven resistance to previous fluoropyrimidine therapy were enrolled.

RESULTS

A total of 510 CPT-11 cycles were administered, with a mean of 8 cycles per patient (range: 1-32). The median relative dose intensity was 93%. Partial response (PR) was obtained in 11 patients (17.5%; 95%CI: 8.1%-26.7%) and 29 patients (46.0%) showed stable disease (clinical benefit of 63.5%). The median duration of response was 6.8 months (95%CI: 6.1-7.5 months), median survival was 8.8 months (95%CI: 6.3-11.5 months) and median time to disease progression was 4.5 months (95%CI: 3.9-5.0 months). Overall, this schedule of CPT-11 chemotherapy was well tolerated by the patient. Neutropenia was the most frequent grade 3/4 haematological toxicity (20.6% of patients and 4.1% of cycles). Neutropenia with concurrent fever or infection occurred in 7 patients (11.1%). Late onset diarrhoea was the most frequent grade 3/4 non-haematological toxicity (19.0% of patients and 2.3% of cycles). Other, lower-incidence, toxicities were anaemia, fever, infection, mucositis, nausea and vomiting. There were no toxic deaths.

CONCLUSIONS

We found that CPT-11, administered as 250 mg/m2 i.v. infusion over 60 minutes every 2 weeks, was active and well tolerated schedule in the second-line chemotherapy of advanced CRC patients. This bi-weekly scheme could be used as an alternative to the weekly or the every-three-week schedule as well as in combined therapies with other chemotherapeutic agents for the treatment of advanced, metastatic, CRC.

Inhibitory effects of asiatic acid and CPT-11 on growth of HT-29 cells

Asiatic acid is a pentacyclic triterpene contained in medicinal plants. The cytotoxic effect of this compound and its augmentative effect on the anticancer drug irinotecan hydrochloride (CPT-11) were investigated in the human colon adenocarcinoma cell line HT-29. Asiatic acid dose-dependently showed cytotoxicity in HT-29 cells. DNA fragmentation, annexin-positive apoptotic cells, and caspase-3 activation were observed in a dose-dependent manner. A caspase-3 inhibitor suppressed the DNA ladder formation in a concentration-dependent manner. Bcl-2 and Bcl-XL proteins were decreased by asiatic acid treatment. These results indicate that asiatic acid induced apoptosis in HT-29 cells via caspase-3 activation. Cytotoxic effects of combined treatment with CPT-11 and asiatic acid on HT-29 cells were further examined. Simultaneous treatment or sequential exposure first to asiatic acid and then to CPT-11 showed an additive effect. Synergism was observed when cells were first exposed to CPT-11 and then to asiatic acid. These results suggest that asiatic acid can be used as an agent for increasing sensitivity of colon cancer cells to treatment with CPT-11 or as an agent for reducing adverse effects of CPT-11.