Peripheral neuropathy associated with weekly oral 5-fluorouracil, leucovorin and eniluracil.

5-Fluorouracil (5-FU)-associated neurotoxicity is uncommon; symptoms may occur abruptly or more gradually during the course of chemotherapy. Peripheral neuropathy with 5-FU therapy has only rarely been reported. Two patients treated in a phase I trial of oral 5-FU, leucovorin and eniluracil, an inhibitor of dihydropyrimidine dehydrogenase (DPD), developed delayed onset symptoms of unsteady gait and reduced sensation in the legs. Magnetic resonance imaging scans of the brain and neurologic examination did not support a CNS basis for the condition. Electromyograms and nerve conduction studies revealed sensorimotor polyneuropathy. Other common etiologies of peripheral neuropathy were excluded. The neurological condition of these patients stabilized after 5-FU dose reduction and partial resolution gradually occurred when protocol therapy was stopped. Although CNS symptoms may rarely complicate 5-FU therapy, peripheral neuropathy is unexpected. Patients with DPD deficiency treated with conventional doses of 5-FU typically develop acute CNS toxicity shortly after therapy, accompanied by extremely high systemic exposure to 5-FU. Patients with normal 5-FU clearance may also experience CNS toxicity, particularly with high-dose schedules, and both parent drug and its catabolites may be contributory. Since DPD was profoundly inhibited during eniluracil therapy in these two patients, it is likely that 5-FU or its active metabolites were contributing factors to the peripheral neuropathy.

N-(phosphonacetyl)-L-aspartate and calcium leucovorin modulation of fluorouracil administered by constant rate and circadian pattern of infusion over 72 hours in metastatic gastrointestinal adenocarcinoma.

BACKGROUND: We have reported that N-(phosphonacetyl)-L-aspartic acid (PALA) 1266 mg/m2 can safely be given 24 hours prior to the start of a 72-hour infusion of fluorouracil (FUra) and leucovorin (LV) at doses of 2000 and 500 mg/m2/day. Since inhibition of aspartate carbamoyltransferase (ACTase) activity was evident 4 hours post PALA, we wished to evaluate PALA given 1 hour prior to FUra. Further, we studied the toxicity and pharmacokinetics with FUra given by either fixed- or variable-rate infusion. PATIENTS AND METHODS: Twenty-seven patients with gastrointestinal tract adenocarcinomas were treated with PALA 1266 mg/m2/15 min followed by a 72-hour infusion of FUra and LV (1750 & 500 mg/m2/day) given by fixed- or variable-rate (peak at 4:00 A.M.). RESULTS: Clinical toxicity was similar in two consecutive cycles in 17 patients receiving fixed- and variable-rate infusion at the same FUra dose. Overall, grade 3 stomatitis and hand-foot syndrome occurred in 12% and 4% patients receiving fixed- and in 16% and 10.5% of patients receiving variable-rate infusions. Six of 24 evaluable patients (25%) had a partial response. The profile of FUra plasma levels (Cp) over a 24-hour period during fixed- and variable-rate infusions were strikingly different, but the average Cp and area under the concentration-time curves were comparable. ACTase activity was significantly decreased at 4 and 24 hours after PALA (12% and 18% of baseline; P < 0.001), but enzyme activity had recovered to 40% by 72 hours. CONCLUSIONS: This regimen was active and well tolerated with similar toxicities with FUra given by either fixed- or variable rate infusion. PALA 1266 mg/m2 significantly inhibited ACTase activity for at least 24 hours.

Phase I and pharmacokinetic trial of weekly oral fluorouracil given with eniluracil and low-dose leucovorin to patients with solid tumors.

PURPOSE: Fluorouracil (5-FU) given as a weekly, high-dose 24-hour infusion is active and tolerable. We evaluated an oral regimen of eniluracil (which inactivates dihydropyrimidine dehydrogenase [DPD]), 5-FU, and leucovorin to simulate this schedule. PATIENTS AND METHODS: Patients received a single 24-hour infusion of 5-FU (2,300 mg/m(2) on day 2) with leucovorin (15 mg orally [PO] bid on days 1 through 3) to provide reference pharmacokinetic data. Two weeks later, patients began treatment with eniluracil (20 mg) and leucovorin (15 mg) (PO bid on days 1 through 3) and 5-FU (10 to 15 mg/m(2) PO bid on day 2). RESULTS: Dose-limiting toxicity (diarrhea, neutropenia, and fatigue) was seen with 5-FU 15 mg/m(2) PO bid on day 2 given weekly for either 6 of 8 weeks or 3 of 4 weeks, whereas five of seven patients tolerated 5-FU 10 mg/m(2) PO bid given weekly for 3 of 4 weeks. Eniluracil led to a 35-fold reduction in 5-FU clearance. Fluoro-beta-alanine, a 5-FU catabolite, was not detected in plasma during oral 5-FU-eniluracil therapy. DPD activity was markedly suppressed in all patients during eniluracil therapy; the inactivation persisted after the last eniluracil dose; percentages of baseline values were 1.8% on day 5, 4.5% on day 12, and 23.6% on day 19. CONCLUSION: The recommended oral dosage of 5-FU (10 mg/m(2) PO bid) given with eniluracil and leucovorin is approximately 115-fold lower than the reference dosage for 24-hour infusional 5-FU. This difference is greater than expected given the reduction in 5-FU clearance. DPD inactivation persisted for several weeks after completion of eniluracil therapy.

High inter- and intrapatient variation in 5-fluorouracil plasma concentrations during a prolonged drug infusion.

The purpose of the study was to examine inter- and intrapatient variation in 5-fluorouracil (5-FU) plasma concentrations in adult cancer patients receiving a 3-day drug infusion. Fourteen patients received 1266 mg/m2 N-(phosphonacetyl)-L-aspartate (PALA) infused i.v. over 15 min on day 1, followed immediately by a loading dose of 500 mg/m2 calcium leucovorin over 30 min. Then a prolonged infusion of leucovorin at 500 mg/m2/day and 5-FU at 1750 mg/m2/day was administered as either a constant rate or as a circadian infusion over 72 h. During constant rate infusions, 5-FU concentrations within individuals varied by 1.7-fold, but no uniform time of peak or trough concentration was observed. Transformation of these data by setting the time of peak to 0 h and by expressing concentrations as the percentage of the 24-h mean value revealed a nonrandom distribution of the time from peak to trough with a median time of 12 h (P = 0.027). These transformed data were also successfully fit to a circadian cosinor function (P < 0.001). During multiple constant rate 5-FU infusions, the intrapatient variability was high; the times of peak 5-FU concentration occurred at the same approximate sampling time 43% of the time, and troughs coincided 17% of the time. No difference in clinical toxicity was observed when matched constant rate and circadian infusions of 5-FU were compared. High inter- and intrapatient variability exists in 5-FU plasma concentrations in adult cancer patients during constant rate infusions with no evidence of a consistent circadian rhythm in untransformed data.

Adjuvant 5-fluorouracil and leucovorin with or without interferon alfa-2a in colon carcinoma: National Surgical Adjuvant Breast and Bowel Project protocol C-05.

BACKGROUND: National Surgical Adjuvant Breast and Bowel Project (NSABP) protocol C-03 showed a benefit from leucovorin (LV)-modulated 5-fluorouracil (5-FU) adjuvant therapy (5-FU + LV) in patients with Dukes' stage B or C carcinoma of the colon. Preclinical and clinical phase I/II data suggested that interferon alfa-2a (IFN) enhanced the efficacy of 5-FU therapy. Accordingly, in NSABP protocol C-05, the addition of recombinant IFN to 5-FU + LV adjuvant therapy was evaluated. METHODS: Data are presented for 2176 patients with Dukes' stage B or C cancer entered onto protocol C-05 during the period from October 1991 through February 1994. Individuals with an Eastern Cooperative Oncology Group performance status of 0-2 (ranges from fully active to ambulatory and capable of self-care but unable to work), a life expectancy of at least 10 years, and curative resection were stratified by sex, disease stage, and number of involved lymph nodes and were randomly assigned to receive either 5-FU + LV or 5-FU + LV + IFN; the mean time on the study as of June 30, 1997, was 54 months. All statistical tests were two-sided. RESULTS: There was no statistically significant difference in either disease-free survival (5-FU + LV, 69%; 5-FU + LV + IFN, 70%) or overall survival (5-FU + LV, 80%; 5-FU + LV + IFN, 81%) at 4 years of follow-up. Toxic effects of grade 3 or higher were observed in 61.8% of subjects in the group treated with 5-FU + LV and in 72.1% of subjects in the group treated with 5-FU + LV + IFN; fewer patients in the latter group completed protocol-mandated 5-FU + LV therapy than in the former group (77.1% versus 88.5%). CONCLUSION: The addition of IFN to 5-FU + LV adjuvant therapy confers no statistically significant benefit, but it does increase toxicity.

Systemic treatment options in advanced colorectal cancer: perspectives on combination 5-fluorouracil plus leucovorin.

A variety of 5-fluorouracil (5-FU)- based chemotherapy regimens have been investigated in colorectal cancer patients in randomized trials over the past decade. The standard regimen for treatment of colorectal cancer is combination 5-FU plus leucovorin (LV). The results from 12 randomized trials indicate that 5-FU/LV is more active than single-agent 5-FU (25% v 14% of evaluable patients); however, median survival was unchanged (12.2 months v 11.4 months, respectively). Furthermore, the weekly and monthly schedules of 5-FU/LV are therapeutically equivalent, although the spectrum of toxicity differs. On the monthly schedule, a LV dose of 200 mg/m2 appears to have no advantage over 20 mg/m2; however, on the weekly schedule, high-dose LV appeared to be slightly more effective than low-dose LV (2-hour infusion) (25% v 18%) at the cost of a higher incidence of severe diarrhea (26% v 14%). Furthermore, similar response rates are observed with the racemic commercial formulation of LV and the pure (I-LV) active stereoisomer. Other modulatory strategies that appear to produce higher response rates than single-agent intravenous push 5-FU include sequential methotrexate/5-FU (19% v 10%) and continuous infusion schedules (22% v 14%). Although 5-FU-modulated strategies improve response rates over those observed with single-agent 5-FU, median survival in multi-institutional trials unfortunately has not generally exceeded 12 months. The mechanism of action, clinical activity, and toxicity of single-agent 5-FU and 5-FU-modulated regimens are reviewed.

New concepts for the development and use of antifolates.

Approximately one-third of all cases of colorectal carcinoma present in an advanced and, therefore, incurable stage. For these patients, the development of new chemotherapeutic strategies is of central importance. Biochemical modulation of 5-fluorouracil (5-FU) has resulted in approximately a two-fold increase in activity of 5-FU. Recent preclinical investigations suggest that interferon can also modulate the activity of 5-FU and may result in enhanced response rates in patients. One of the critical mechanisms of resistance to 5-FU appears to be the acute induction in thymidylate synthase (TS) levels following therapy with inhibitors of this enzyme. This mechanism is based on a novel autoregulatory feedback pathway wherein the TS protein regulates its own translational efficiency. Regulatory function of the enzyme is dependent on its state of occupancy by either the physiologic ligands or inhibitors, including fluoropyrimidines and antifolates. Ongoing efforts are directed towards utilizing knowledge of this protein/messenger RNA interaction for therapeutic benefit. Given the importance of TS, our laboratory has developed antibodies capable of quantitating the levels of this enzyme in fresh or paraffin-embedded tissues. Preliminary investigations suggest that the level of TS has prognostic importance in patients with rectal carcinoma and may be used to predict responsiveness to fluoropyrimidine agents. Novel strategies utilizing dual modulation of 5-FU with leucovorin and interferon are under investigation in both the advanced and adjuvant disease settings. Emerging mechanistic concepts regarding TS, along with the development of new, more potent inhibitors will hopefully result in future therapeutic gains.

Thymidylate synthase protein expression: Association with response to neoadjuvant chemotherapy and resection for locally advanced gastric and gastroesophageal adenocarcinoma.

PURPOSE: A phase II study of neoadjuvant fluorouracil, leucovorin, and interferon alpha-2a was conducted to determine the feasibility of this regimen's use and the response rates in patients undergoing resection for locally advanced gastric or gastroesophageal adenocarcinoma. Also, tumor protein expression of free, total, or bound thymidylate synthase before and after initial exposure to fluorouracil was quantitated to determine if thymidylate synthase expression is associated with response in this treatment setting. PATIENTS AND METHODS: Twenty-two patients with T3-4N0-2M0 gastric or gastroesophageal adenocarcinoma were treated with three cycles of neoadjuvant fluorouracil (370 mg/m2 intravenously on days 2 through 6), leucovorin (500 mg/m2 intravenously on days 2 through 6), and interferon alpha-2a (5x106 U/m2 subcutaneously days 1 through 7), followed by resection and three cycles of consolidation therapy. Endoscopic tumor biopsies were done in 13 patients before therapy and during cycle 2 of the 5-fluorouracil/leucovorin/interferon regimen, and total thymidylate synthase, free thymidylate synthase, bound thymidylate synthase, and percent complexed thymidylate synthase were quantitated by Western blot. Tumor protein expression was evaluated for its association with response to neoadjuvant therapy and patient survival. RESULTS: Eight of 21 (38%) evaluable patients had a partial response, and another 5 of 21 (24%) had a minor response (25% to 49% tumor reduction) after three cycles of neoadjuvant fluorouracil/leucovorin/interferon. The pretreatment total thymidylate synthase level was significantly higher in five nonresponders than in eight responders. After exposure to fluorouracil, levels of free thymidylate synthase were significantly lower and the percent bound thymidylate synthase was higher in responders than in nonresponders. The median potential follow-up period is 24 months, and 11 of 21 patients have died from disease. CONCLUSIONS: These preliminary results indicate that a response to neoadjuvant fluorouracil-based therapy may be associated with decreased levels of total thymidylate synthase before therapy and free thymidylate synthase after exposure to fluorouracil in patients with locally advanced gastric cancer. Quantification of thymidylate synthase protein expression before and after exposure to fluorouracil may provide a method to select patients for fluorouracil therapy in the neoadjuvant, adjuvant, or advanced-disease setting based upon the fundamental sensitivity of the tumor.

A phase I study of continuous infusion 5-fluorouracil plus calcium leucovorin in combination with N-(phosphonacetyl)-L-aspartate in metastatic gastrointestinal adenocarcinoma.

Preclinical studies suggest that the biochemical effects of N-(phosphonacetyl)-L-aspartate (PALA), an inhibitor of aspartate carbamoyltransferase (ACTase), may increase the metabolic activation of 5-fluorouracil (5-FU) and enhance its cytotoxicity through both RNA- and DNA-directed mechanisms. In this Phase I trial, 22 evaluable patients with adenocarcinoma of the gastrointestinal tract were entered at escalating doses of 5-FU starting at 1150 mg/m2/day given as a concurrent 72-h i.v. infusion with a fixed dose of leucovorin (LCV), 500 mg/m2/day. The dose of 5-FU was escalated within patients according to individual tolerance, and then PALA at 250 mg/m2 was added 24 h prior to the initiation of the 5-FU/LCV infusion of the subsequent cycle. Dose-limiting mucositis and myelosuppression occurred during the initial cycle in 3 of 5 patients treated with 2300 mg/m2/day 5-FU; therefore, the recommended dose of 5-FU with concurrent LCV is 2000 mg/m2/day. Twenty-seven additional patients were then treated with escalating doses of PALA ranging from 375 to 2848 mg/m2, i.v., followed 24 h later by 2000 mg/m2/day 5-FU with high-dose LCV. Dose-limiting mucositis and myelosuppression occurred during the initial cycle in 2 of 3 patients entered at 2848 mg/m2 PALA. Dose-limiting mucositis and skin rash ultimately required both PALA and 5-FU dose reductions in 4 of 6 patients treated with 1899 mg/m2 PALA. Toxicity was similar, however, in patients receiving PALA at doses ranging from 375 to 1266 mg/m2. The mean steady-state plasma concentration of 5-FU at 2000 mg/m2/day was 6.5 +/- 0.9 microM; patients with 5-FU levels > 9 microM had a significantly higher incidence of serious gastrointestinal and hematological toxicity. Compared to each patient's own baseline, a significant trend for decreasing ACTase activity with increasing PALA dose was evident using cytosol isolated from peripheral blood mononuclear cells 24 h after PALA treatment (P2 = 0.01). PALA < or = 844 mg/m2 failed to appreciably inhibit ACTase activity at 24 h in most patients; furthermore, a decrease in ACTase activity by > 50% from baseline was seen in only 29% of cycles. More consistent inhibition of ACTase activity was seen with PALA > or = 1266 mg/m2. Even with the highest PALA doses, however, ACTase activity returned to baseline by 96 h in most patients.(ABSTRACT TRUNCATED AT 400 WORDS)

A phase II study of continuous infusion 5-fluorouracil and leucovorin with weekly cisplatin in metastatic colorectal carcinoma.

BACKGROUND: Prolonged infusional 5-fluorouracil (5-FU) and bolus 5-FU modulated by leucovorin are associated with higher response rates than bolus 5-FU alone. Cisplatin enhances 5-FU cytotoxicity in some preclinical models. METHODS: The authors tested the feasibility of combining concurrent infusional leucovorin (500 mg/m2/d) with protracted infusional 5-FU (200 mg/m2/d) and weekly bolus cisplatin (20 mg/m2) in 22 patients with metastatic colorectal cancer. RESULTS: Four partial responses (PR) were noticed among 21 evaluable patients (19%). The median time to treatment failure and median survival were 6 months and 11 months, respectively. All but two patients required 5-FU dose reduction after a median of 2 weeks because of mucositis. However, severe mucositis and diarrhea occurred in only 18% and 5% of the patients, respectively. Palmar-plantar erythrodysesthesia of mild to moderate severity occurred in 55% of patients. Megaloblastic changes were evident in the peripheral blood during therapy, and may reflect prolonged DNA-directed toxicity of 5-FU. The median tolerated dose level of 5-FU was 113 mg/m2/d (range, 64-150 mg/m2/d). Mean steady-state plasma concentrations (Cpss) of 5-FU appeared to increase linearly from 0.19 microM to 0.39 microM over the dose range 64 to 200 mg/m2/d. Patients with grade 2 gastrointestinal toxicity had significantly higher 5-FU Cpss than patients with grade 0 or 1 toxicity. CONCLUSIONS: The early onset of toxicity with this regimen of protracted infusional 5-FU/high-dose leucovorin and weekly cisplatin required marked attenuation of the 5-FU dose intensity, and the results were no better than that expected with infusional 5-FU alone.

Dose-dependent inhibition of aspartate carbamoyltransferase in peripheral blood mononuclear cells in patients receiving N-(phosphonacetyl)-L-aspartate.

Forty-eight patients with adenocarcinoma of the gastrointestinal tract were treated on this trial. The MTD of 5-FU given as a 72 hour infusion with high-dose leucovorin was initially determined to be 2000 mg/m2/d. Patients were treated at PALA dose levels ranging from 250 to 2848 mg/m2. Biochemical assessment of target enzyme activity was performed at each PALA dose level. We conclude that compared to each patient's own baseline, PALA at 250 mg/m2 failed to appreciably inhibit ACTase activity at 24 hours in most patients. More consistent inhibition of ACTase activity was seen with PALA at or above 1266 mg/m2, but toxicity was prohibitive with 2848 mg/m2 PALA. Even with the highest PALA doses, ACTase activity was back to baseline by 96 hours in most patients. PALA at 1266 mg/m2 given 24 hours prior to the start of 72 hour infusional 5-FU plus high-dose leucovorin was associated with acceptable toxicity and did not appear to compromise 5-FU dose-intensity. Finally, because of interpatient variability in the degree of ACTase inhibition following PALA, biochemical monitoring of target enzyme activity may permit more rational adjustment of the PALA dose in individual patients.

Decreased catabolism of fluorouracil in peripheral blood mononuclear cells during combination therapy with fluorouracil, leucovorin, and interferon alpha-2a.

BACKGROUND: We previously reported that recombinant interferon alpha-2a (IFN alpha-2a) therapy was associated with a dose-dependent decrease in fluorouracil (5-FU) clearance. PURPOSE: In this study, we used peripheral blood mononuclear cells (PBMCs), which are responsive to IFNs, as surrogate tissue to determine whether the change in clearance might be explained by decrease in 5-FU catabolism during IFN alpha-2a therapy. METHODS: The study population consisted of 45 patients with adenocarcinoma arising in the gastrointestinal tract. Thirty-seven patients received therapy containing IFN alpha-2a at a median dose of 5 million U/m2 per day (range, 1.7-7.5 million U/m2 per day) starting on day 1 and continuing through either day 7 or day 14 in conjunction with intravenous high-dose leucovorin (LV) followed by bolus 5-FU on days 2-6. Eight patients received the same schedule of 5-FU and LV daily for 5 days without IFN alpha-2a but with granulocyte-macrophage colony-stimulating factor starting on day 6 and ending at least 3 days prior to the start of the next cycle. Peripheral blood was collected during 70 cycles on days 1, 2, and 4 prior to the daily treatment with IFN alpha-2a + 5-FU+LV and during 19 cycles on days 1 and 4 prior to the daily treatment with 5-FU+LV without IFN alpha-2a. In a given patient cycle, matched samples were drawn at approximately the same time of day. PBMCs were isolated, and the intact cells were exposed to 4 microM [3H]5-FU, and the formation of [3H]dihydrofluorouracil was determined by reverse-phase high-performance liquid chromatography. RESULTS: In 47 matched patient cycles from IFN alpha-2a + 5-FU+LV-treated patients in which samples were available on days 1, 2, and 4, 5-FU catabolism decreased by 20% (P2 = .03) and 41% (P2 = .0001) from the baseline catabolic rate (2.5 +/- 0.2 pmol/min per 10(6) cells [mean +/- SE]) on days 2 and 4, respectively. Using information from all paired samples, the mean change from baseline on day 2 was -0.4 +/- 0.2 pmol/min per 10(6) cells (n = 54; P2 = .05), and the change from baseline on day 4 was -1.3 +/- 0.3 pmol/min per 10(6) cells (n = 63; P2 = .0001). In contrast, changes in 5-FU catabolism were not evident in the PBMCs of the reference population receiving 5-FU+LV without IFN alpha-2a. CONCLUSIONS: The magnitude of the change in 5-FU catabolism is similar to the magnitude of the decrease in 5-FU clearance in our previous study. These observations suggest that changes in 5-FU catabolism during therapy with IFN alpha-2a, 5-FU, and LV may account for the decreased 5-FU clearance.

A pilot study of interferon alfa-2a in combination with fluorouracil plus high-dose leucovorin in metastatic gastrointestinal carcinoma.

Thirty-one assessable patients with metastatic adenocarcinoma of the gastrointestinal tract were entered onto a pilot study designed to assess the impact of recombinant interferon alpha-2a (rIFN alpha-2a) on the toxicity and pharmacokinetics of fluorouracil (5-FU) and leucovorin (LV). Patients received an initial cycle of 5-FU (370 or 425 mg/m2/d) with LV (500 mg/m2/d) for 5 days. If tolerated, the patient received the same dose of 5-FU/LV for the second cycle on days 2 to 6, with rIFN alpha-2a at 5 x 10(6) or 10 x 10(6) U/m2/d on days 1 to 7, or with 3 x 10(6) U/m2/d on days 1 to 14. In 26 matched cycles, rIFN alpha-2a administration was associated with an increased incidence of dose-limiting mucositis and diarrhea and a significantly lower median platelet nadir; rIFN alpha-2a did not significantly affect the median WBC or granulocyte nadir. Dose-limiting toxicity occurred in all six patients entered at 425 mg/m2/d of 5-FU/LV within two cycles. The majority of patients treated with 370 mg/m2/d of 5-FU/LV and 10 x 10(6) U/m2/d rIFN alpha-2a experienced grade 3 to 4 mucositis and diarrhea, whereas patients receiving 3 x 10(6) and 5 x 10(6) U/m2/d rIFN alpha-2a had acceptable toxicity. Administration of rIFN alpha-2a was associated with a dose-dependent decrease in 5-FU clearance. The increase in the area under the 5-FU concentration-time curve (AUC) was 1.3-fold and 1.5-fold in patients receiving 5 x 10(6) and 10 x 10(6) U/m2/d rIFN alpha-2a, respectively. Thus, the increase in 5-FU toxicity with rIFN alpha-2a may be explained by alterations in 5-FU pharmacokinetics. In 22 patients without prior 5-FU therapy, three complete (13.6%) and seven partial (31.8%) responses were seen, for an overall response rate of 45.4% (95% confidence interval, 24.4% to 67.8%). Since the 5 x 10(6) U/m2/d dose of rIFN alpha-2a increased the 5-FU drug exposure and was associated with acceptable toxicity, we recommend its further evaluation as given on days 1 to 7 in combination with 5-FU 370 mg/m2/d, with high-dose LV given on days 2 to 6.

Adjuvant treatment of node-positive colon carcinoma with levamisole and 5-fluorouracil.

Levamisole, an anthelminthic drug, has been studied clinically as a nonspecific immunomodulator in the adjuvant treatment of a variety of malignancies. Over a decade ago, a small, non-randomized trial of levamisole versus no further therapy after primary surgical resection of colorectal carcinoma showed a survival benefit for the cohort receiving levamisole, particularly among patients with transmural penetration or positive regional nodes. Since this seminal trial, numerous adjuvant trials of levamisole alone or in combination with 5-fluorouracil have been conducted. Two randomized, placebo-controlled trials failed to show a benefit of levamisole in patients with node-positive colon carcinoma. Three adjuvant trials have shown a therapeutic benefit of levamisole plus 5-fluorouracil compared to observation. Adjuvant therapy with levamisole and 5-fluorouracil reduced the risk of cancer recurrence by 41% and the death rate by 33% in patients with node-positive disease. The results of this trial have defined a new standard of care in the treatment of patients with Stage C colon carcinoma.

Current treatment approaches in colorectal cancer.

Fluorouracil (5-FU) is still the mainstay of adjuvant treatment for colorectal cancer. Two trials have shown a disease-free and overall survival benefit for 5-FU combined with levamisole in patients with node-positive colon cancer. This regimen is fairly well tolerated and devoid of long-term sequelae, and is now considered standard treatment for node-positive colon cancer. One trial showed a modest improvement in disease-free survival for the semustine/vincristine/5-FU combination; the leukemogenicity and renal toxicity caused by semustine have prevented this regimen from being adopted. Although administering 5-FU directly into the portal vein may improve disease-free survival, most trials have failed to demonstrate a reduction in the incidence of hepatic metastases. This technique, therefore, remains investigational. Several trials in rectal cancer show an advantage for 5-FU combined with semustine and radiation therapy in terms of disease-free survival, overall survival, or both; the contribution of semustine has been questioned and is currently being investigated. In patients with metastatic disease, hepatic arterial infusion of floxuridine produces a higher objective response rate than intravenous administration, but has not resulted in a survival benefit; hepatobiliary toxicity limits the duration of therapy. Biochemical modulation of 5-FU with leucovorin increases the response rate produced by 5-FU alone; a survival benefit has also been observed. N-(phosphonacetyl)-L-aspartate has shown initial promise in combination with high-dose 5-FU infusions. Among the many new drugs tested, only tauromustine seems worthy of further study.

Toxicity of levamisole and 5-fluorouracil in human colon carcinoma cells.

The combination of 5-fluorouracil (5-FU) with the immunomodulator levamisole (Lev) has been clinically tested in patients with metastatic colorectal carcinoma and as adjuvant therapy following primary tumor surgery. In some studies in advanced disease, the addition of Lev to 5-FU improved the median duration of response; in the adjuvant setting, the combination was associated with improvement in the disease-free survival. We studied whether Lev was directly toxic to three human colorectal carcinoma cell lines (HCT 116, SNU-C4, and NCI-H630). We also evaluated the toxicity of Lev in combination with 5-FU in these three cell lines. Lev inhibited the growth of all three colorectal cell lines, but only at concentrations two logs above that achieved with a standard 150-mg oral dose of Lev. In cell growth studies, 500 and 1,000 microM Lev increased the toxicity of 5-FU in HCT 116 cells in an additive fashion. In clonogenic assays, continuous exposure to 10 or 100 microM Lev was minimally toxic and did not enhance the lethality associated with a 24-hour exposure to 5-FU in any of the cell lines. Lev alone at 1,000 microM decreased colony formation by 45% in HCT 116 cells. A combination of 1,000 microM Lev with 10 microM 5-FU resulted in a decrease in HCT 116 colony formation from 54% to 6% of control levels. Continuous exposure of NCI-H630 cells to 500 microM Lev decreased colony formation to 76.5% of control levels; when Lev was combined with 50 microM 5-FU, colony formation was decreased from 59.5% to 27.5% of control levels. We conclude that at concentrations achievable with conventional doses of Lev, there was no evidence of direct toxicity in these colorectal cell lines. Furthermore, an additive interaction with 5-FU was evident only at suprapharmacologic doses of Lev.

Enhancement of 5-fluorouracil's anticancer activity by dipyridamole.

Although the interaction between FUra and DP in HCT 116 cells is fairly complex, data from other investigators indicate that in cell lines in which inhibition of TS is growth limiting at relatively low concentrations of fluoropyrimidines, DP appears to augment the cytotoxicity of FUra and FdUrd by blocking the salvage of dThd (Miller et al., 1987; Schwartz et al., 1987). The previous in vitro data regarding the ability of DP to modulate the toxicity of fluoropyrimidines was obtained in exponentially growing cells. An additional observation that warrants consideration is a report that the inhibition of nucleoside incorporation by DP changed as a function of time in culture (Zhen et al., 1986). Hepatoma 3924A cells in lag and log phase were highly sensitive to DP with IC50 values for dThd incorporation of 0.2 and 0.32 microM, respectively. In contrast, stationary phase cells were insensitive to DP (IC50 = 38.9 microM). Amphotericin B, an antifungal agent which perturbs cell membranes, restored the sensitivity to DP in stationary cells. Several investigators have presented information on the effect of DP on fluoropyrimidines in normal tissues. Lee and Park (1987) examined the effect of DP on FUra and MTX toxicity in a soft-agar cloning assay against two human cancer cell lines and on pooled normal human bone marrow (CFU-C). DP (1 microM) potentiated the action of both MTX (0.1 microM) and FUra (5 microM) on Hep-2 (epidermoid carcinoma), MCF-7 (breast carcinoma) and CFU-C in medium supplemented with either non-dialyzed or dialyzed serum. Woodcock et al. (1987) incubated gallbladder mucosa, obtained from patients undergoing elective surgery for cholelithiasis, with control medium or varying concentrations of DP for 1 hr, and then exposed the mucosal cells to 2.5 microCi [3H]-FdUrd (2.5 microM). After 1 hr, the uptake of FdUrd into the tissue was inhibited to 49% and 42% of control by 0.1 microM and 1 microM, respectively.