Youcef M. Rustum

A prospective randomized trial of 5-fluorouracil versus 5-fluorouracil and high-dose leucovorin versus 5-fluorouracil and methotrexate in previously untreated patients with advanced colorectal carcinoma.

Seventy-four previously untreated patients with metastatic colorectal adenocarcinoma were prospectively randomized into one of three treatment regimens: (1) 5-fluorouracil (5-FU) 450 mg/m2 as an intravenous (IV) bolus daily for five days or toxicity, then 200 mg/m2 IV bolus every other day for six doses; (2) methotrexate (MTX) 50 mg/m2 in normal saline by IV infusion over four hours followed by an IV bolus of 5-FU 600 mg/m2. This was administered weekly for 4 weeks and then every 2 weeks. (3) Leucovorin 500 mg/m2 in a two-hour IV infusion of normal saline with 5-FU 600 mg/m2 as an IV bolus one hour after the Leucovorin began every week for 6 weeks. The combined complete and partial response rates in the three regimens were 11%, 5%, and 48%, respectively (P = .0009). The median duration of response in the 5-FU and Leucovorin regimen was 10 months. There was no statistically significant difference between the treatment regimens with respect to survival time (P = .6). Toxicity in the 5-FU and Leucovorin regimen was predominantly diarrhea (13 of 30 patients, 40%). In this regimen, eight of 13 patients (52%) who developed diarrhea not only required a dose reduction of 5-FU, but also hospitalization for IV hydration. The predominant toxicity in the 5-FU alone regimen and the 5-FU and MTX regimen was leukopenia. One drug-related death occurred in each regimen.

Irinotecan in the Treatment of Colorectal Cancer: Clinical Overview

PURPOSE AND METHODS For more than three decades, the therapeutic options for patients with advanced colorectal cancer have almost exclusively been based on fluoropyrimidines. With the recognition that topoisomerase-I (TOP-I) is an important therapeutic target in cancer therapy, irinotecan, a semisynthetic TOP-I-interactive camptothecin derivative, has been clinically established in the treatment of colorectal cancer. RESULTS Irinotecan was investigated as second-line chemotherapy after prior treatment with fluorouracil (FU)-based regimens in two large randomized phase III trials comparing irinotecan with either best supportive care or an infusional FU/leucovorin (LV) regimen. The outcomes of these trials established irinotecan as the standard therapy in the second-line treatment of colorectal cancer. The therapeutic value of irinotecan in the first-line treatment of metastatic colorectal cancer was investigated in two large randomized phase III trials comparing the combination of irinotecan and FU/LV with FU/LV alone. Both trials demonstrated significant superior efficacy for the combination of irinotecan and FU/LV in terms of response rate, median time to disease progression, and median survival time. Consequently, the combination of irinotecan and FU/LV has been approved as first-line chemotherapy for patients with metastatic colorectal cancer and constitutes the reference therapy against which other treatment options must be tested in the future. CONCLUSION In this review, the clinical rationale and update of the present clinical status of irinotecan in the treatment of colorectal cancer and future prospects of irinotecan-based combinations are discussed.

P-glycoprotein in human sarcoma: evidence for multidrug resistance.

Overexpression of an immunologically conserved, cell-surface glycoprotein (P-glycoprotein) is consistently associated with multidrug resistance in cell lines in vitro. A preliminary survey of specimens from 12 solid tumor types in our laboratories indicates significant overexpression of P-glycoprotein in some sarcomas. When tested by immunoblotting with monoclonal antibodies directed against P-glycoprotein; tumors from six of 25 sarcoma patients displayed elevated levels of P-glycoprotein. Three of the sarcoma patients exhibiting P-glycoprotein had not previously been exposed to chemotherapy, implying that overexpression of this marker and possible concomitant multidrug resistance may not depend only on selection during prior drug treatments. The P-glycoprotein overexpression in the sarcoma specimens is evidence for the presence of multidrug resistant cells in these tumors; thus, our data suggest that this mode of resistance may have clinical significance in sarcoma patients.

Characterization, toxicity and therapeutic efficacy of adriamycin encapsulated in liposomes.

The inherent toxicities of drug-free liposomes were compared. Positively charged liposomes were more toxic in vitro (chick heart cells) and in vivo (5-fold reduction in LD50 in mice) than neutral or negatively charged liposomes. Based on these findings, adriamycin was encapsulated in negatively charged liposomes (PG: PC: Chol--1:4:5), sequentially extruded through polycarbonate membranes (to 0.2 micrometer pore size) and purified by exhaustive dialysis. This preparation had a mean vesicle diameter of 0.24 micrometer and was stable in serum (24 hr drug retention of 85%). As compared with free drug, liposome-encapsulated adriamycin was less toxic in vitro to chick heart cells. In mice, adriamycin displayed short- (4-14 day) and long- (45-70 day) term toxicity. Encapsulating adriamycin increased both short- (20-50 mg/kg) and long- (10-15 mg/kg to 25-30 mg/kg) term LD50 levels. As compared with free drug, administering encapsulated adriamycin in vivo reduced the incidence of cardiac histopathologic lesions at 20 and 40 mg/kg. Compared in vivo, plasma levels of liposome-encapsulated adriamycin were 2/3-fold higher than free drug up to 24 hr post drug administration. Cardiac uptake of adriamycin was reduced 2-fold (conc x time value for 48 h) following encapsulated drug administration. Encapsulating adriamycin in liposomes did not alter its therapeutic effect against L1210 leukemic cells in vivo.

Selective Modulation of the Therapeutic Efficacy of Anticancer Drugs by Selenium Containing Compounds against Human Tumor Xenografts

Purpose: Studies were carried out in athymic nude mice bearing human squamous cell carcinoma of the head and neck (FaDu and A253) and colon carcinoma (HCT-8 and HT-29) xenografts to evaluate the potential role of selenium-containing compounds as selective modulators of the toxicity and antitumor activity of selected anticancer drugs with particular emphasis on irinotecan, a topoisomerase I poison. Experimental Design: Antitumor activity and toxicity were evaluated using nontoxic doses (0.2 mg/mouse/day) and schedule (14–28 days) of the selenium-containing compounds, 5-methylselenocysteine and seleno-l-methionine, administered orally to nude mice daily for 7 days before i.v. administration of anticancer drugs, with continued selenium treatment for 7–21 days, depending on anticancer drugs under evaluation. Several doses of anticancer drugs were used, including the maximum tolerated dose (MTD) and toxic doses. Although many chemotherapeutic agents were evaluated for toxicity protection by selenium, data on antitumor activity were primarily obtained using the MTD, 2 × MTD, and 3 × MTD of weekly ×4 schedule of irinotecan. Results: Selenium was highly protective against toxicity induced by a variety of chemotherapeutic agents. Furthermore, selenium increased significantly the cure rate of xenografts bearing human tumors that are sensitive (HCT-8 and FaDu) and resistant (HT-29 and A253) to irinotecan. The high cure rate (100%) was achieved in nude mice bearing HCT-8 and FaDu xenografts treated with the MTD of irinotecan (100 mg/kg/week × 4) when combined with selenium. Administration of higher doses of irinotecan (200 and 300 mg/kg/week × 4) was required to achieve high cure rate for HT-29 and A253 xenografts. Administration of these higher doses was possible due to selective protection of normal tissues by selenium. Thus, the use of selenium as selective modulator of the therapeutic efficacy of anticancer drugs is new and novel. Conclusions: We demonstrated that selenium is a highly effective modulator of the therapeutic efficacy and selectivity of anticancer drugs in nude mice bearing human tumor xenografts of colon carcinoma and squamous cell carcinoma of the head and neck. The observed in vivo synergic interaction is highly dependent on the schedule of selenium.

Thymidylate synthase inhibitors in cancer therapy: direct and indirect inhibitors.

PURPOSE AND METHODS Although fluoropyrimidines, in particular, fluorouracil (5-FU) and fluorodeoxyuridine (FdUrd), are active alone and in combination with other agents in a variety of human malignancies, therapeutic selectivity, resistance, and efficacy have been a major limitation in cancer therapy. Preclinical and clinical results in advanced and adjuvant colorectal cancers confirmed that the therapeutic efficacy of fluoropyrimidines, with thymidylate synthase (TS) as a primary target, can be improved significantly with leucovorin (LV) modulation. With the recognition that TS is an important therapeutic target, direct and specific inhibitors have been developed and are under intensive preclinical and clinical evaluation, primarily in patients with colorectal cancer, with demonstrable activity. The direct TS inhibitors have been shown to be potent, with a high level of specificity under therapeutic conditions for TS. This includes ZD1694, AG337, and LY231514. To date, although the therapeutic activity of both direct and indirect inhibitors of TS is similar, differences in the magnitude and profile of toxicity have been observed. A phase III comparative evaluation of a direct inhibitor of TS (ZD1694) with an indirect inhibitor (5-FU/LV) has been completed and showed similar activity but reduced toxicity in favor of ZD1694. RESULTS Recognition that greater than 95% of the injected dose of 5-FU is rapidly inactivated by dihydropyrimidine dehydrogenase (DPD) to therapeutically inactive products, but with toxicity to normal tissues, led to the development of inhibitors of this enzyme with the aim to modify the therapeutic index of 5-FU. Several inhibitors in combination with 5-FU are under preclinical and clinical evaluation, including uracil and 5-chloro-2,4-dihydroxy pyridine, as modulators of 5-FU derived from its prodrug tegafur and 5-ethynyluracil as a modulator of 5-FU. CONCLUSION In this review, an update of the present status of direct and indirect inhibitors of TS is discussed, as well as the future prospect for new drugs alone and in combination.

Potential Regional Differences for the Tolerability Profiles of Fluoropyrimidines

PURPOSE We conducted a retrospective analysis of safety data from randomized, single-agent fluoropyrimidine clinical trials (bolus fluorouracil/leucovorin [FU/LV] and capecitabine) to test the hypothesis that there are regional differences in fluoropyrimidine tolerability. METHODS Treatment-related safety data from three phase III clinical studies were analyzed by multivariate analysis: two comparing capecitabine with bolus FU/LV in metastatic colorectal cancer (MCRC) and one comparing capecitabine plus oxaliplatin (XELOX) with bolus FU/LV as adjuvant treatment for colon cancer. The United States (US) was compared with non-US countries (all three studies) and with the rest of the world and East Asia (adjuvant study). RESULTS In the MCRC studies (n = 1,189), more grade 3/4 adverse events (AEs; relative risk [RR], 1.77), dose reductions (RR, 1.72), and discontinuations (RR, 1.83) were reported in US versus non-US patients. Likewise, in the adjuvant colon cancer study (n = 1,864), more grade 3/4 AEs (RR, 1.47) and discontinuations (RR, 2.09) were reported in US versus non-US patients. After further dividing non-US patients into those in East Asia and the rest of the world, differential RRs for related grade 3/4 AEs, grade 4 AEs, and serious AEs were again observed, with East Asian patients having the lowest and US patients the highest RR. CONCLUSION Regional differences exist in the tolerability profiles of fluoropyrimidines. More treatment-related toxicity was reported in the US compared with the rest of the world for bolus FU/LV and capecitabine in first-line MCRC and adjuvant colon cancer. In the adjuvant setting, a range of fluoropyrimidine tolerability was observed, with East Asian patients having the lowest, and US patients the highest, RR.

Phase I Study of a Weekly Schedule of Irinotecan, High-Dose Leucovorin, and Infusional Fluorouracil as First-Line Chemotherapy in Patients With Advanced Colorectal Cancer

PURPOSE To determine the maximum-tolerated dose (MTD) of a weekly schedule of irinotecan (CPT-11), leucovorin (LV), and a 24-hour infusion of fluorouracil (5-FU24h) as first-line chemotherapy in advanced colorectal cancer and to assess preliminary data on the antitumor activity. PATIENTS AND METHODS Twenty-six patients with measurable metastatic colorectal cancer were entered onto this phase I study. In the first six dose levels, fixed doses of CPT-11 (80 mg/m2) and LV (500 mg/m2) in combination with escalated doses of 5-FU24h ranging from 1.8 to 2.6 g/m2 were administered on a weekly-times-four (dose levels 1 to 4) or weekly-times-six (dose levels 5 to 6) schedule. The dose of CPT-11 was then increased to 100 mg/m2 (dose level 7). RESULTS Seventy-nine cycles of 5-FU24h/LV with CPT-11 were administered in an outpatient setting. No dose-limiting toxicities were observed during the first cycle at dose levels 1 to 6, but diarrhea of grade 4 (National Cancer Institute common toxicity criteria) was observed in three patients after multiple treatment cycles. Other nonhematologic and hematologic side effects, specifically alopecia and neutropenia, did not exceed grade 2. With the escalation of CPT-11 to 100 mg/m2 (dose level 7), diarrhea of grade 3 or higher was observed in four of six patients during the first cycle; thus, the MTD was achieved. Sixteen of 25 response-assessable patients (64%; 95% confidence interval, 45% to 83%) achieved an objective response. CONCLUSION The recommended doses for further studies are CPT-11 80 mg/m2, LV 500 mg/m2, and 5-FU24h 2.6 g/m2 given on a weekly-times-six schedule followed by a 1-week rest period. The addition of CPT-11 to 5-FU24h/LV seems to improve the therapeutic efficacy in terms of tumor response with manageable toxicity.

Chromosomes and causation of human cancer and leukemia. XLIV. A method for chromosome analysis of solid tumors

Mechanical and enzymatic disaggregation procedures have been utilized for the preparation of materials suitable for chromosome examination of tissues from various kinds of solid tumors. A great number of the cells disaggregated with the latter procedure were observed to attach to the bottom of culture flasks after 2 days in vitro; cells obtained with the former method were not attached. In general, the enzymatic procedure yielded a significantly larger number of viable cells that would undergo mitosis after short term culture and considerably improved the quality of banding as compared to the mechanical method. However, there were no significant differences among the basic karyotypes observed in the cells obtained by the mechanical approach versus those seen following the enzymatic method. This evidence, together with the high success rate of karyotyping in the enzyme-treated preparations, suggest that this should be the procedure of preference for cytogenetic examination of various tumors, particularly where in the past karyotypic examination has been very difficult, e.g., the early stages of tumor development.

Enhancement of the antitumor effects of 5-fluorouracil by folinic acid.

Although 5-fluorouracil (FUra) is one of the most effective cytotoxic agents in the treatment of various solid tumors (carcinomas of the gastro-intestinal tract, breast, head and neck), remissions occur in only 20-30% of cases and usually are of short duration. Recently, preclinical studies have shown that the antitumor activity of FUra can be potentiated by modulating the metabolism of this drug by using other substances, in particular 5-formyltetrahydrofolate (folinate, LV). Reduced folates (LV and 5-methyltetrahydrofolate) at concentrations greater than or equal to 1 microM can, by raising the intracellular levels of 5,10-methylenetetrahydrofolate, increase and prolong the inhibition of the target enzyme, thymidylate synthase, with formation of a stable ternary complex formed by the enzyme, the folate coenzyme and the fluoropyrimidine inhibitor (5-fluorodeoxyuridylate). After phase II clinical trials reported encouraging results with the combination LV-FUra in the treatment of patients with various solid tumors, randomized controlled studies in patients with colorectal carcinoma have documented an increase in the response rate of the combination compared to treatment with FUra alone. The integration of the LV-FUra combination into multidrug regimens is now under investigation for the treatment of carcinomas of the breast, stomach, and head and neck.