New directions in the treatment of colorectal cancer: a look to the future

Nonpeptidomimetic farnesyltransferase inhibitor RPR-115135 increases cytotoxicity of 5-fluorouracil: role of p53

A new nonpeptidic farnesyltransferase inhibitor, RPR-115135, in combination with 5-fluorouracil (5-FU) was studied in an isogenic cell line model system consisting of human colon cancer HCT-116 cells. HCT-116 cells were transfected with an empty control pCMV vector and with a dominant-negative mutated p53 transgene (248R/W). We found that, relative to control transfectants, there was a slight tendency for the p53 inactivated cells to be less sensitive to 5-FU after 6 days of continuous treatment. Simultaneous administration of RPR-115135 and 5-FU, at equitoxic concentrations, resulted in an enhancement of 5-FU cytotoxicity, especially in the CMV-2 clone. Growth inhibition could be accounted for on the basis of a specific cell cycle arrest phenotype (G(2)-M arrest in CMV-2 and S arrest in mutated clones), as assayed by flow cytometry. The combination RPR-115135 + 5-FU increases apoptotic events only in the CMV-2 clone.

Management of chemotherapy-induced adverse effects in the treatment of colorectal cancer

The anticancer agents fluorouracil, raltitrexed, irinotecan and oxaliplatin show limited efficacy in the treatment of colorectal cancer and may be associated with substantial toxicity. Therefore, the prevention and reduction of chemotherapy-induced adverse effects is of major significance, in accordance with the increasing concern for the quality of life of patients with cancer. Therapeutic drug monitoring of fluorouracil and chronomodulation of fluorouracil and oxaliplatin, have been effective in reducing the incidence and gravity of adverse effects in several clinical trials. However, these concepts have not been implemented in clinical practice yet. At the present time, dose adaptation and supportive measures are the main tools for toxicity control in the treatment of colorectal cancer. In this review, supportive measures for alleviation of the adverse effects of fluorouracil, raltitrexed, irinotecan and oxaliplatin, respectively, are described, based on study results. The main adverse effects of these agents are myelosuppression, oral mucositis, diarrhoea, acute cholinergic syndrome, nausea and emesis, neurotoxicity, hand-foot syndrome and other cutaneous adverse effects, ocular toxicity, cardiotoxicity, small bowel toxicity, asthenia, elevated liver transaminase levels and alopecia. The incidence and gravity of these adverse effects are more or less related to the agent and administration schedule involved. The supportive measures and recommendations include the use of specific drugs, alterations of administration schedule and several nonpharmacological methods. In addition, guidelines for dosage adjustments when toxicity occurs are presented. For optimal management of adverse effects, patients should be considered individually, while patients, nurses and physicians should cooperate to identify and treat adverse effects in an early stage of their development.

High-performance liquid chromatographic technique for the simultaneous determination of lactone and hydroxy acid forms of camptothecin and SN-38 in tissue culture media and cancer cells

Analysis of camptothecins in biologic media is hampered by chemical hydrolysis of the parent lactone (form I) to an inactive hydroxy acid (form II). A solid-phase extraction (SPE) method utilizing C2-bonded silica particles (100 mg, 1 ml) is presented for simultaneous determination of forms I and II of camptothecin (CPT) and SN-38 (active metabolite of clinically used CPT-11) in culture media and cell lysates. A new HPLC separation is described that efficiently resolves all four compounds employing gradient elution with 10 mM ammonium acetate, increasing methanol (20-80% over 15 min), and a 15-cm by 3-mm Symmetry Shield (RP8) column. Components were detected by fluorescence at an excitation wavelength of 380 nm and emission wavelength of 423 nm. Lactones were shown to be unstable at alkaline pH and hydroxy acids unstable at alkaline pH while the following conditions preserved the chemical equilibrium in specimens: samples kept on ice, final pH of eluates 7.4, autosampler temperature 4 degrees C, and analysis cycle <4 h. Quantitative recovery of lactones was achieved from RPMI culture medium over a wide concentration range (93.5-111.6% for 1-400 ng/ml) although greater variability was noted with the hydroxy acids (59.6-110.3%, 1-400 ng/ml). Limit of quantitation (precision and accuracy <20%) was 0.2 ng/ml for CPT lactone, 0.5 ng/ml for SN-38 lactone, and 2 ng/ml for the two hydroxy acids. The method was applied to quantitate the accumulation of SN-38 and CPT (form I and II) in HT29 and HCT116 human colon cancer cells.

Sequence effect of irinotecan and fluorouracil treatment on pharmacokinetics and toxicity in chemotherapy-naive metastatic colorectal cancer patients

PURPOSE

To investigate the sequence effect of irinotecan and a 48-hour infusion of fluorouracil (5-FU) modulated by leucovorin (LV) on the plasma pharmacokinetics of irinotecan and its metabolites, the toxicity profile of this combination, and irinotecan's maximum-tolerated dose (MTD).

PATIENTS AND METHODS

Thirty-three metastatic colorectal cancer patients were randomized to receive a 60-minute infusion of irinotecan before or after a 48-hour infusion of 5-FU modulated by LV. The reverse sequence was used after 21 days for the second cycle. 5-FU 3,500 mg/m2 was preceded by l-LV 250 mg/m2. Irinotecan 150 mg/m2 (starting dose) was administered to the first three patients. The dose was escalated by 50 mg/m2 in subsequent groups of three to six patients to determine the MTD for both sequences. Pharmacokinetic analysis of irinotecan and its metabolites was performed after each cycle.

RESULTS

Toxicities were affected by the sequence of administration of irinotecan and 5-FU, with an improved tolerability for irinotecan followed by 5-FU. The irinotecan MTD was reached at 300 mg/m2 when irinotecan followed 5-FU and at 450 mg/m2 when it preceded 5-FU. In seven of 23 patients who received both sequences at identical irinotecan doses, the dose-limiting toxicity was observed only when irinotecan followed 5-FU. Pharmacokinetic analysis revealed that the administration sequence significantly affected the SN-38 area under the concentration-versus-time curve (AUC), which was 40.1% lower (P <.05) when irinotecan preceded 5-FU.

CONCLUSION

The sequence of treatment with irinotecan and infusional 5-FU affects the tolerability of this combination. This can be explained in part by a reduced SN-38 AUC when irinotecan preceded infusional 5-FU. Well-defined 5-FU/irinotecan regimens are needed because the administration sequence or the interval between the agents might affect treatment tolerance and perhaps also activity.

Review of the role of CPT-11 in the treatment of colorectal cancer

Colorectal cancer (CRC) is the second leading cause of cancer death in Western countries, and although the treatment of advanced CRC has progressed substantially, the improvements in response rates have not always been translated into a significant survival benefit. Until recently, the standard therapy for advanced CRC was a variety of biomodulated 5-fluorouracil (5-FU) regimens. 5-FU was used as first- or second-line therapy, and a different 5-FU regimen was used second line if first-line 5-FU therapy failed. Typically, the survival times for these patients were short and their quality of life poor. In recent years, a variety of new agents have emerged that have demonstrated activity in the treatment of advanced CRC. Of these, irinotecan (CPT-11) and oxaliplatin in combination with 5-FU and folinic acid (FA) have yielded the most promising results. However, only CPT-11 combined with either bolus or high-dose infusional 5-FU/FA, in randomized phase III studies, has demonstrated an increased response rate and median time to progression, producing a significant and clinically relevant survival advantage. In 2 randomized phase III studies, oxaliplatin/5-FU/FA demonstrated a clear increase in response rate over 5-FU/FA alone but failed to demonstrate a survival advantage. CPT-11 was approved by the Food and Drug Administration in April 2000 for the first-line treatment of advanced CRC in combination with 5-FU/FA.

New chemotherapy approaches in colorectal cancer

Colorectal cancer is one of the leading causes of cancer deaths in the Western world, with approximately 50% of all patients dying from metastatic disease. Until recently, therapeutic options for advanced colorectal cancer were mainly confined to chemotherapy with 5-fluorouracil in various schedules, with or without biochemical modulation with leucovorin. The development of new cytotoxic drugs with substantial activity in this tumor during the past 2 years has dramatically changed treatment strategies and therapeutic goals in metastatic colorectal cancer and has introduced neoadjuvant chemotherapy followed by secondary surgery with the intent of long-term survival. Among these new drugs, oral fluoropyrimidines (tegafur/uracil and capecitabine), irinotecan, and oxaliplatin have already established themselves as part of various treatment approaches. Other novel therapeutics including agents designed to act on molecular targets already show promising activity and will become part of combination protocols with current standard chemotherapy.

Targeting cyclooxygenase 2 and HER-2/neu pathways inhibits colorectal carcinoma growth

BACKGROUND & AIMS

The cyclooxygenase 2 (COX-2) and ErbB/HER pathways are important modulators of cancer cell growth. We sought to determine the effects of treatment with a specific COX-2 inhibitor and/or a monoclonal antibody against the ErbB receptor subtype HER-2/neu on carcinoma cell growth.

METHODS

A cell-proliferation assay was used to determine the response of HCA-7 cells to the HER-3/HER-4 ligand heregulin beta-1 (HRGbeta-1). Both in vitro and in vivo assays were used to determine the effects of the selective COX-2 inhibitor, celecoxib, and/or an anti-HER-2/neu monoclonal antibody (either Herceptin [Genetech Inc., S. San Francisco, CA] or 2C4) on cell growth.

RESULTS

HCA-7 cells express HER-2/neu messenger RNA and protein, and exposure of these cells to HRGbeta-1 results in a significant stimulation of cell growth. Celecoxib or Herceptin inhibits HCA-7 cell growth in vitro and in vivo. Combination therapy with celecoxib plus Herceptin or celecoxib plus 2C4 resulted in additive effects that resulted in almost complete inhibition of tumor growth.

CONCLUSIONS

Combined treatment with COX-2 and HER-2/neu inhibitors more effectively reduces colorectal carcinoma growth than either agent alone. Therefore, targeting of both the COX-2 and ErbB signaling pathways may represent a novel approach for the treatment and/or prevention of colorectal cancer in humans.

Schedule specific biochemical modulation of 5-fluorouracil in advanced colorectal cancer: a randomized study. GISCAD, IOR and collaborating centers

BACKGROUND

We have recently suggested that bolus 5-fluorouracil (5-FU) may work via a RNA directed mechanism while continuous infusion 5-FU may kill cells via a thymidylate synthase related pathway. It may thus be possible to selectively modulate each schedule biochemically. We have compared an alternating regimen of bolus and continuous infusion 5-FU, selectively modulated for the schedule of administration, with modulated bolus 5-FU in advanced colorectal cancer patients.

PATIENTS AND METHODS

Two hundred fourteen patients from nineteen Italian centers were randomized to the control arm consisting of biweekly cycles of MTX, 200 mg/m2 on day 1, followed by bolus 5-FU 600 mg/m2 on day 2 and 6-S-leucovorin rescue, or to the experimental arm consisting of two biweekly cycles of the same regimen as in the control arm alternated to three weeks of continuous infusion 5-FU (200 mg/m2 day) + weekly bolus 6-S-leucovorin, 20 mg/m2.

RESULTS

Nine CR and twenty-seven PR were obtained on one hundred eleven evaluable patients treated in experimental arm (RR = 32%, 95% confidence interval (95% CI): 24%-42%), while two CR and eleven PR were observed among one hundred three evaluable patients in control arm (RR = 13%, 95% CI: 7%-21%). WHO grade 3-4 toxicity occurred in 13% of cycles of experimental arm and in 8% of cycles in control arm. The PFS was significantly longer in experimental arm (6.2 vs. 4.3 months, odds ratio 0.66, P = 0.003), while the overall survival was similar in both arms (14.8 months in experimental arm vs. 14.1 months in control arm); quality of life was similar as well. Eighty percent of patients receiving second-line chemotherapy in control arm were treated with continuous infusion 5-FU.

CONCLUSIONS

Alternating, schedule-specific biochemical modulation of FU is more active than MTX --> 5-FU as first-line treatment of advanced colorectal cancer. However, the overall survival was similar suggesting that alternating bolus and infusional 5-FU upfront may be as effective as giving them in sequence as first- and second-line treatment.