Final results from a randomized phase 3 study of FOLFIRI {+/-} panitumumab for second-line treatment of metastatic colorectal cancer.

BACKGROUND: The study 20050181 demonstrated significant improvements in progression-free survival (PFS), objective response, and a nonsignificant trend toward increased overall survival (OS) with panitumumab-FOLFIRI versus FOLFIRI alone for second-line wild-type (WT) KRAS metastatic colorectal cancer (mCRC). Updated long-term data from a prespecified descriptive analysis are reported. PATIENTS AND METHODS: Patients receiving one prior mCRC treatment were randomly assigned (1:1) to panitumumab (6.0 mg/kg)-FOLFIRI versus FOLFIRI every 2 weeks. Co-primary end points (PFS and OS) were prospectively analyzed by tumor KRAS status. RESULTS: One thousand one hundred and eighty-six patients were randomly assigned. In patients with WT KRAS tumors, panitumumab-FOLFIRI significantly improved PFS versus FOLFIRI [median 6.7 versus 4.9 months; hazard ratio (HR) 0.82 [95% confidence interval (CI) 0.69, 0.97]; P = 0.023]. A trend toward longer OS was observed (median 14.5 versus 12.5 months; HR 0.92 [95% CI 0.78, 1.10]; P = 0.37). Response rates improved from 10% to 36% (P < 0.0001). From post hoc analyses in patients receiving prior oxaliplatin-bevacizumab, panitumumab-FOLFIRI improved PFS (median 6.4 versus 3.7 months; HR 0.58 [95% CI 0.37, 0.90]; P = 0.014). PFS and OS appeared longer for worst-grade skin toxicity of 2-4, versus 0-1 or FOLFIRI. Safety results were as previously reported and consistent with the known toxicities with anti-epidermal growth factor receptor therapy. CONCLUSIONS: These data confirm the primary efficacy and safety findings of this trial and support panitumumab-FOLFIRI as a second-line treatment of WT KRAS mCRC.

Two doses of NGR-hTNF in combination with capecitabine plus oxaliplatin in colorectal cancer patients failing standard therapies.

BACKGROUND: asparagine-glycine-arginine-human tumour necrosis factor (NGR-hTNF), an agent selectively damaging the tumour vasculature, showed a biphasic dose-response curve in preclinical models. Previous phase I trials of NGR-hTNF indicated 0.8 and 45 µg/m(2) as optimal biological and maximum-tolerated dose, respectively. PATIENTS AND METHODS: Two sequential cohorts of 12 colorectal cancer (CRC) patients who had failed standard therapies received NGR-hTNF 0.8 or 45 µg/m(2) in combination with capecitabine-oxaliplatin (XELOX). RESULTS: Median number of prior treatment lines was 3 in the low-dose and 2 in the high-dose cohort. Overall, 21 patients had been pretreated with oxaliplatin-based regimens. No grade 3-4 NGR-hTNF-related toxicities were observed. Grade 1-2 chills were reported in 43% and 40% of cycles in the low-dose and high-dose cohorts, respectively. In the low-dose cohort, one patient achieved a partial response and five had stable disease for a median of 4.6 months. In the high-dose cohort, six patients had stable disease for a median of 3.6 months. Three-month progression-free survival (PFS) rates were 50% and 33% in the low-dose and high-dose cohort, respectively. Three patients in low-dose cohort experienced PFS longer than PFS on last prior therapy. CONCLUSIONS: Both NGR-hTNF doses were safely combined with XELOX in pretreated CRC patients. Hint of activity was apparent only with low-dose NGR-hTNF.

Taxane-induced nail changes: incidence, clinical presentation and outcome.

The clinical characteristics of nail changes in seven patients receiving taxane-containing chemotherapy are described. They include nail pigmentation, subungual hematoma, Beau's lines and onycholysis and subungual suppuration. The incidence of such changes (ranging from 0% to 44%) is reviewed from a Medline search of the literature.

Schedule-dependent synergism between raltitrexed and irinotecan in human colon cancer cells in vitro.

The quinazoline folate analogue raltitrexed (ZD1694; Tomudex) and the camptothecin derivative irinotecan are two new agents showing clinical activity against colorectal cancer. To identify the optimal conditions to achieve synergistic cytotoxicity before the clinical development of their combination, we explored the interactions between ZD1694 and the active metabolite of irinotecan, 7-ethyl-10-hydroxycamptothecin (SN-38), in vitro. Cytotoxicity was evaluated with a clonogenic assay using the human colon cancer cell line HCT-8. Different schedules of administration and different dose ratios of the two agents were compared and evaluated for synergism, additivity, or antagonism with a quantitative method based on the median-effect principle of Chou and Talalay (T. C. Chou and P. Talalay, Adv. Enzyme Regul., 22: 27-55, 1984). Sequential short-term (1 and 4-h) exposures to SN-38 followed by ZD1694 resulted in synergistic cytotoxicity at broad dose-effect ranges. At a high level of cell kill, the synergism was greater when either equiactive doses of the two agents or higher relative doses of ZD1694 were used. A 24-h interval between exposure to SN-38 and ZD1694 significantly enhanced the magnitude of the synergy (P = 0.001). The opposite sequence or simultaneous exposures produced significantly less potentiation or nearly additive interactions (P = 0.0006 and P < 0.0001). The synergism was completely lost under conditions of more prolonged drug exposure (24-h continuous exposure). In conclusion, in this in vitro model of human colon cancer, ZD1694 and SN-38 produced synergistic cytotoxicity. Our findings support the clinical use of this combination and provide a rationale for a clinical trial using sequential short-term exposures to equiactive doses of SN-38 and ZD1694 administered sequentially with a 24-h interval.

The potential role of Tomudex in the treatment of advanced colorectal cancer.

AIMS AND BACKGROUND: The quinazoline folate analog thymidylate synthase inhibitor, Tomudex, is about to enter the Italian pharmaceutical market. Its place among the therapeutic options for advanced colorectal cancer is discussed. METHODS: The pros and cons of currently available chemotherapeutic regimens are briefly described with special attention to patient's and tumor's determinants of treatment outcome. The mechanism of action and the results of phase I, II and III studies of Tomudex are reviewed. RESULTS: Not all patients need to be treated. Guidelines are given in this respect. Tomudex at the dose of 3 mg/m2 given i.v. every three weeks has antitumor activity similar to that of currently available regimens, with a favorable toxicity profile. CONCLUSIONS: Current research approaches are unlikely to dramatically improve the treatment outcome of this disease in the near future. What can reasonably be expected is less toxicity and more convenient routes and schedules of drug administration that may translate into better quality of life for our patients. Tomudex has been devised along these lines.

Fluorouracil in colorectal cancer--a tale of two drugs: implications for biochemical modulation.

PURPOSE: To determine if fluorouracil (FUra) has different mechanisms of action as a function of the dose schedule used. DESIGN: The preclinical and clinical literature relating toxicity and antitumor effects of FUra as a function of its dose schedule, with and without modulating agents, was reviewed. RESULTS: The data support the hypothesis that FUra may be considered to be two different drugs, depending on its dose schedule (bolus v continuous infusion [CI]). CONCLUSION: These results suggest that additional therapeutic benefit may be obtained from FUra regimens by (1) appropriate schedule-dependent modulation, (2) the sequential or alternating use of cycles of bolus followed by cycles of CI FUra appropriately modulated, or (3) hybrid regimens, ie, those that contain both pulse and CI schedules.

Schedule-selective biochemical modulation of 5-fluorouracil: a phase II study in advanced colorectal cancer.

Based on experimental findings suggesting that 5-fluorouracil (FUra) may have different mechanisms of action depending on the schedule of administration, we generated the hypothesis that biochemical modulation of this fluoropyrimidine should be schedule specific. We thus tested the activity of a hybrid regimen consisting of two biweekly cycles of FUra bolus (600 mg/m2) modulated by pretreatment (24-h interval) with methotrexate (200 mg/m2), alternating with a 3-week continuous infusion of FUra (200 mg/m2/day) modulated by low-dose (6S)leucovorin (20 mg/m2 bolus weekly). Thirty-three consecutive patients with advanced measurable colorectal cancer and no prior therapy for metastatic disease entered the study from February 1992 to August 1993. They were treated with two biweekly cycles of FUra bolus (600 mg/m2) preceded by (24-h interval) methotrexate (200 mg/m2), alternating with a 3-week continuous infusion of FUra (200 mg/m2/day) modulated by low-dose (6S)leucovorin (20 mg/m2 bolus weekly). The median Eastern Cooperative Oncology Group performance status was 1; the liver was the only metastatic site in 17 patients. Treatment outcome was evaluated by computed tomographic scan in all patients, except for two. Three complete and 13 partial responses were obtained among these 33 patients (response rate, 48%; 95% confidence limits, 31-66%). Performance status (Eastern Cooperative Oncology Group) influenced clinical response. The combined complete response and partial response rate was 69%, 33%, and 25% in patients with an Eastern Cooperative Oncology Group performance status of 0, 1, and 2, respectively (chi2, 4.6, P = 0.032, two-tailed Mantel test for trend). After a median follow-up time of 26 months, 10 patients are still alive. The median progression-free survival and overall survival were 9.5 and 20.2 months, respectively. No toxic deaths or grade 4 toxicity occurred. The incidence of grade 3 toxicity per patient in any cycle was: mucositis 6%, diarrhea 3%, and vomiting 3% for the bolus part and 21%, 3%, and 6%, respectively, for the continuous infusion part of the regimen. Hand-foot syndrome occurred in 27% of the patients treated with the continuous infusion regimen.

Synergism and lack of cross-resistance between short-term and continuous exposure to fluorouracil in human colon adenocarcinoma cells.

BACKGROUND: Our recent findings in vitro in the human colon adenocarcinoma cell line HCT-8 suggest that resistance to fluorouracil (5-FU) in patients with advanced colorectal cancer might be overcome by use of a different treatment schedule. PURPOSE: We tested the hypothesis that HCT-8 cells resistant to short-term 5-FU exposure retain sensitivity to continuous exposure and studied interactions between the two schedules. METHODS: HCT-8 cell lines resistant to short-term (pulse) treatment with 5-FU or to continuous exposure were obtained by six exposures to different concentrations of 5-FU for 4 hours or 7 days. We used a monolayer clonogenic assay to determine 5-FU-induced cell kill in resistant HCT-8 cells and sensitive parent cells. Parent cells were exposed to different concentrations of 5-FU for 1, 4, or 24 hours (short term), for 7 days (continuous exposure), or in a combination of both types of schedules. In a study of the mechanism of interaction between short-term and continuous exposure in parent cells, we performed flow cytometric DNA analysis to determine the percentage of cells in S phase and assays of thymidylate synthase inhibition in intact cells and of incorporation of [6-3H)]5-FU nucleotides into nucleic acids. RESULTS: Sensitive HCT-8 cells became fully resistant to 5-FU within five or six treatments, and low-dose continuous exposure almost immediately produced resistant clones. HCT-8 cells resistant to 5-FU given every 4 hours retained full sensitivity to continuous exposure, suggesting lack of cross-resistance between the two schedules, but cells resistant to continuous exposure were cross-resistant to short-term treatment. Parent cells showed a statistically significant (synergistic) enhancement of the cytotoxic activity for 5-FU exposure for 1 hour (100, 300, or 500 microM) followed by continuous exposure (0.5, 1, or 2 microM) or 4 hours (10, 30, or 60 microM) followed by continuous exposure (1 or 2 microM). Short-term plus continuous exposure produced a marked increase in percentage of S-phase cells, compared with the percentage for each schedule alone. The combination of 1-hour exposure and continuous exposure (1000 and 2 microM, respectively) produced a marked accumulation of cells in S phase at 24 hours (59%), which lasted up to 96 hours (53%). The combination of the two schedules produced only additive enhancement of thymidylate synthase inhibition as well as incorporation of [6-3H]5-FU nucleotides into nucleic acids of HCT-8 cells. CONCLUSIONS: Our findings provide a rationale for the use of bolus 5-FU and continuous infusion 5-FU in sequence. IMPLICATION: We are conducting a clinical trial of bolus methotrexate followed by continuous-infusion 5-FU plus leucovorin.

Enhancement of trimetrexate cytotoxicity in vitro and in vivo by carboxypeptidase G2.

Carboxypeptidase G2 (CPG2), an enzyme produced by Pseudomonas strain RS-16, hydrolyzes the glutamate residue from methotrexate and other folates. The possibility of enhancing trimetrexate cytotoxicity by CPG2 induced folate depletion was investigated in vitro in a human leukemia cell line, CCRF-CEM, and in three sublines of these cells each with a different methotrexate resistance phenotype. The cytotoxic effect in vitro was detected using a colorimetric assay with a tetrazolium salt, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Dose-effect relationships of drugs alone and in combination were analyzed by the median effect principle and by the combination indices for quantitation of synergy or antagonism with the aid of a computer program. Trimetrexate alone was cytotoxic against the parent and all the resistant cell lines with the drug concentrations required to decrease the cell count to 50% of control in the nanomolar range (1.4, 1.6, 1.5, and 0.7 nM in CCRF-CEM, CCRF-CEM/E, CCRF-CEM/P, and CCRF-CEM/T, respectively) following 5 days of exposure. The concentration of CPG2 required to decrease the cell count to 50% control for these cell lines was 3.5, 2.6, 26.6, and 7.9 x 10(-5) units/ml for CCRF-CEM, CCRF-CEM/E, CCRF-CEM/P, and CCRF-CEM/T, respectively. A synergistic cytotoxic effect of trimetrexate after simultaneous continuous exposure with CPG2 was observed with CCRF-CEM cells and with the three resistant cell lines. This drug combination given to BALB/c x DBA/2 F1 mice bearing L1210 cells also produced synergy over a narrow range of drug doses. The activity of this combination in both methotrexate sensitive and methotrexate resistant cell lines indicates that clinical trials of this combination should be undertaken.

Uptake and metabolism of 5,8-dideazaisofolic acid in human colon carcinoma cells.

The uptake and metabolism of radiolabeled 5,8-dideazaisofolic acid (IAHQ) (N-[p- ([(2-amino-4-hydroxy-6-quinazolinyl)amino]methyl)benzoyl]-L-glutamic acid), a new antifol targeted to thymidylate synthase, has been investigated in the human colon adenocarcinoma cell line HCT-8. [3H]IAHQ uptake was very slow, requiring days to achieve the intracellular level achieved in minutes by [3H]methotrexate. This slow transport of IAHQ was consistent with the long exposures required to achieve cytotoxicity. Intracellular [3H]IAHQ was converted in a concentration-dependent manner to poly-gamma-glutamate derivatives containing between two and four additional glutamate residues. These results are consistent with our hypothesis that IAHQ is a "pro-drug" which must be converted to polyglutamate derivatives before it is a sufficiently potent inhibitor of thymidylate synthase to induce a pyrimidineless state and cell death.

Mechanism of action of 5,8-dideazaisofolic acid and other quinazoline antifols in human colon carcinoma cells.

The clonal cytotoxic effects and mechanism of action of a new series of 2-amino-4-hydroxyquinazoline folate analogues (5,8-dideazafolates) have been assessed using the human colon tumor cell line HCT-8. Of these compounds only 5-methyl-5,8-dideazafolate was potentially more effective than a compound previously identified, 5,8-dideazaisofolate (H-338, NSC 289517). HCT-8 sublines resistant to methotrexate, 5-fluorodeoxyuridine, and H-338 were either minimally or not cross-resistant to the other agents. The cytotoxicity of H-338 was strongly dependent on the time of exposure; at exposure times shorter than 8 h it was essentially nontoxic. Thymidine alone, as well as leucovorin or folic acid, protected against the cytotoxic effects of H-338. This is consistent with thymidylate synthase (TS) as its only locus of action. Studies with dihydrofolate reductase and TS isolated from HCT-8 cells indicated that these quinazolines were weaker inhibitors of dihydrofolate reductase than was methotrexate, but they were not particularly potent TS inhibitors. However, synthetic poly-gamma-glutamate derivatives of quinazolines showed dramatically increased TS, but not dihydrofolate reductase, inhibition. TS inhibition increased as the polyglutamate chain length increased. Using isolated HCT-8 folylpolyglutamate synthetase, all the parent quinazolines containing L-glutamate were found to be substrates. With H-338, the results indicated that tetraglutamate or longer derivatives could be synthesized intracellularly. These results are consistent with our hypothesis that cytotoxicity by such quinazolines necessarily involves "lethal synthesis" from a prodrug; i.e., the nontoxic parent drug must be converted to polyglutamates before TS inhibition and subsequent cytotoxicity can occur.

Endogenous thymidine and hypoxanthine are a source of error in evaluating methotrexate cytotoxicity by clonogenic assays using undialyzed fetal bovine serum.

None of 13 fresh human tumor samples of various histology cloned in a two-layer agar culture system with 20% undialyzed fetal bovine serum (FBS) showed sensitivity to three antifolates, methotrexate (MTX), trimetrexate and 5,8-dideazaisofolic acid (IAHQ), even after continuous exposure to the highest concentrations (100 microM) for 21 days. In order to investigate this lack of antifolate drug effect, we compared the toxicity of continuous MTX exposure in the human colon carcinoma cell line HCT-8, cloned in a thymidineless medium (RPMI 1640) supplemented with 10% horse serum (HS), 10% fetal bovine serum (FBS), 20% FBS or 20% dialyzed FBS. In the presence of native FBS, when the minimum clone size was set at 30 cells/colony, the survival of HCT-8 cells reached a plateau at approximately 60% of untreated control after exposure to MTX concentrations between 0.1 microM and 100 microM. Only when the minimum clone size was set at 2 X 10(3) cells/colony was the sensitivity of HCT-8 cells to the antimetabolite comparable to that obtained in HS or dialyzed FBS (ED50 values in the range of 0.01 microM). MTX protection experiments indicated that even very small concentrations of thymidine and hypoxanthine together were sufficient to reproduce the pattern of sensitivity to MTX observed under culture conditions with undialyzed FBS. We conclude that for a proper evaluation of MTX cytotoxicity in clonogenic assays, dialyzed FBS and thymidine-less media should be employed; if native FBS is an absolute requirement for growth, only very large colonies (at least 10 cell divisions) should be scored.

Defective facilitated diffusion of nucleosides, a primary mechanism of resistance to 5-fluoro-2'-deoxyuridine in the HCT-8 human carcinoma line.

In vitro resistance of HCT-8 cells to 5-fluoro-2'-deoxyuridine (FdUrd) has been obtained after a stepwise increase (up to 1 microM) in the concentration of the nucleoside in the culture medium over a period of 6 months. With a clonogenic assay, the toxicities of 17 antineoplastic agents on HCT-8-sensitive and -resistant cells were compared. Resistant cells were 700-fold resistant to FdUrd and showed different degrees of cross-resistance to several purine and pyrimidine nucleoside analogues; no cross-resistance was noted to base analogues and other cytotoxic drugs. The activities of FdUrd phosphorylase, 5'-fluorouridine kinase, 5-fluorouridine phosphorylase, 5-fluorouracil phosphoribosyltransferase, and thymidylate synthase were not significantly different in the sensitive and resistant cell lines. Mixing experiments indirectly excluded the possible elevation of the level of cytoplasmic phosphatases. The activity of FdUrd kinase in sensitive cell extracts was no more than twice that of resistant cells, and the affinities of this enzyme for FdUrd and thymidine at 0.1 to 50 microM were similar in both cell lines. However, cultures of this line failed to accumulate 5-fluoro-2'-deoxyuridylate at concentrations of FdUrd that resulted in substantial accumulation of the nucleotide in the sensitive line. These contrasting data suggested a defect in the facilitated diffusion of the analogue. The entrance of free nucleoside and its subsequent phosphorylation were compared in the two lines over short (2 to 40 s) and longer time periods at 25 degrees C and at 4 degrees C over a range of extracellular FdUrd concentrations (0.1 to 10 microM). Rapid entrance of the nucleoside into sensitive cells was observed, but entry was not detectable in resistant cells. Dipyridamole and nitrobenzylthioinosine inhibition as well as high-performance liquid chromatography analysis confirmed that data obtained from the sensitive cell line during the first 40 s primarily reflected facilitated diffusion of free nucleoside.

Highly selective drug combinations for human colon cancer cells resistant in vitro to 5-fluoro-2'-deoxyuridine.

In the preceding companion paper, we describe a human colon carcinoma cell line that is resistant in vitro to 5-fluoro-2'-deoxyuridine by virtue of impaired nucleoside transport. Two drug combinations, methotrexate: hypoxanthine: thymidine (dThd) and 5,8-dideazaisofolic acid: dThd, selectively kill these resistant cells with no effect on the sensitive cell population. As little as 0.3 microM dThd was sufficient to completely protect sensitive cells from 5-fluoro-2'-deoxyuridine, and 5,8-dideazaisofolic acid at concentrations that produced over 80% lethality in unprotected cells and the same concentration of dThd in combination with 100 microM hypoxanthine fully protected sensitive cells from greater than 99% methotrexate-induced cell lethality. In contrast, when resistant cells were exposed to these drugs, they were not protected by dThd, or by the combination dThd: hypoxanthine, in concentrations up to 300 times higher than those necessary to prevent sensitive cell kill. Thus, it may be possible to protect normal renewal tissues while obtaining selective tumor cell kill with these two drug combinations in patients whose colon carcinoma cells are resistant to 5-fluoro-2'-deoxyuridine by virtue of defective transport.

Sequence-dependent synergism between dichloromethotrexate and cisplatin in a human colon carcinoma cell line.

We studied the cell killing effects of cisplatin (CDDP), 3',5'-dichloromethotrexate (DCM), and different combinations of these drugs in a human colon carcinoma line (HCT-8). Using a clonogenic assay, the ED50 values for DCM were 3, 0.3, and 0.05 microM after 4-, 24-, and 48-hour exposure, respectively, while cell kill induced by CDDP was less time-dependent (ED50 values: 16, 7.8, 3.3, and 2.8 microM after 2-hour, 4-hour, 24-hour, and continuous incubation, respectively). Sequential exposure of these cells to DCM followed by CDDP resulted in synergism at every dose studied. The synergy was maximal with short DCM pretreatment intervals and decreased with increasing lengths of exposure to the antifol. In contrast, simple additive effects were observed when DCM was given together with or following CDDP. Considering the significant hepatic inactivation of both these compounds, our in vitro data encourage the design of clinical protocols with the sequence DCM----CDDP for hepatic arterial infusion treatment of liver metastasis from colon cancer.

Chemosensitivity of human tumor clonogenic cells simultaneously assayed in agar diffusion chambers and in a two-layer agar culture system.

We have compared plating efficiencies (PE) of 20 fresh and cryopreserved samples of human solid tumors, disaggregated and cloned simultaneously in a two-layer agar culture system (2LACS) and in agar diffusion chambers (ADC). A significant correlation (0.001 less than P less than 0.01, paired t test) was found between PE, confirming that the two methods reflect the same property of tumor cells: their clonogenic potential. The median PE in ADC was 1.4 and 3.3 times higher than that in the 2LACS for cryopreserved and fresh specimens, respectively. One- and two-drug doses, approximately clinically achievable concentrations, were assayed simultaneously in the ADC and in the 2LACS, respectively, on 15 tumor specimens. In this way we evaluated the effects of eight drugs, two to five for each tumor, in a static (2LACS) versus a dynamic (ADC) system. The comparison of percent survival in ADC versus that in the 2LACS at both concentrations tested showed no statistically significant rank correlation. If the data regarding cyclophosphamide and mitomycin, which produced significant cell kill in the ADC and almost none in the 2LACS, were excluded, the rank correlation was still not significant. We conclude that the widely used 2LACS is unsuitable to study cyclophosphamide and mitomycin, for which the ADC technique may be a valid alternative.

Sequence-dependent synergism between dichloromethotrexate and 5-fluorouracil in a human colon carcinoma cell line.

Prior to their use in patients with hepatic metastasis of colon cancer, we studied the cell-killing effects of 5-fluorouracil, 5-fluoro-2'-deoxyuridine, 3',5'-dichloromethotrexate (DCM), and 5-fluoro-2'-deoxyuridine, 3',5'-dichloromethotrexate (DCM), and combinations of these fluoropyrimidines with DCM on a human colon carcinoma cell line (HCT-8). Sequential exposure of these cells to DCM followed by 5-fluorouracil resulted in significant synergistic cell killing at every dose and time studied, and the synergy was more evident with increasing doses of both drugs. In contrast, simple additive effects were observed when DCM was given together with or following 5-fluorouracil. When the antifolate was given before 5-fluoro-2'-deoxyuridine, simple additive effects, rather than synergy, were observed. Mild antagonism and even strong antagonism were found when 5-fluoro-2'-deoxyuridine preceded DCM administration or when the cells were exposed to the drugs simultaneously, respectively.