Phase I study of gemcitabine using a once every 2 weeks schedule

Nucleo(s)tide metabolism as basis for drug development; the Anne Simmonds award lecture

Aberrant metabolism of purines and pyrimidines led to development of drugs for treatment of various diseases, such as inflammatory, neurological, cardiovascular, viral infections and cancer. Purine and Pyrimidine Symposia are characterized by close interactions, leading to extensive cross-fertilization on methodology and translating not only from bench-to-bedside, but also between various disciplines such as medicinal chemistry, pharmacology, oncology, virology, rheumatology, biochemistry, pediatrics, cardiology, surgery and immunology. This background was fundamental in our studies on how to optimize application of existing drugs (5-fluorouracil [5FU], thiopurines, antifolates such as methotrexate) but also to support development of novel drugs such as gemcitabine, novel antifolates, S-1, TAS-102 and fluorocyclopentenylcytosine. Knowledge of their metabolism helped to design rational combinations such as of gemcitabine with cisplatin, one of the most widely used drug combinations for various cancers. The combination of 5FU with uridine, led to the development of triacetyluridine registered for emergency treatment of patients with lethal 5FU toxicity. Mechanisms of action were studied by careful analysis of their metabolism, using classical enzyme assays with radioactive precursors and HPLC analysis. Drug metabolism moved from manually operated HPLC systems with UV-detection for peak identification and paper rolls for quantification, to computer-operated HPLC with automatic multi-wavelength and fluorometric peak detection and more recently to ultrasensitive, highly specific mass-spectrometry-based systems. Some aspects, however, never changed; careful analysis of the results and being prepared for the unexpected. The latter actually led to the most interesting results. Investigation of (nucleoside/nucleotide) metabolism remains an exciting field of research.

Clinical sonochemotherapy of inoperable pancreatic cancer using diagnostic ultrasound and microbubbles: a multicentre, open-label, randomised, controlled trial

OBJECTIVES

Sonochemotherapy, which uses microbubble (MB)-assisted ultrasound (US) to deliver chemotherapeutic agents, has the potential to enhance tumour chemotherapy. The combination of US and MB has been demonstrated to prolong the survival of patients with pancreatic cancer. This phase 2 clinical trial aimed to determine the clinical efficacy and safety of sonochemotherapy for inoperable pancreatic ductal adenocarcinoma by using US and MB.

METHODS

Eighty-two patients with stage III or IV pancreatic cancer were recruited from July 2018 to March 2021 and followed up until September 2022. US treatment was performed with a modified diagnostic US scanner for 30 min after chemotherapeutic infusion. The primary endpoint was overall survival (OS), and the secondary endpoints were Eastern Cooperative Oncology Group (ECOG) status < 2, progression-free survival (PFS), disease control rate (DCR), and adverse events.

RESULTS

Seventy-eight patients were randomly allocated (40 to chemotherapy and 38 to sonochemotherapy). The median OS was longer with sonochemotherapy than with chemotherapy (9.10 vs. 6.10 months; p = 0.037). The median PFS with sonochemotherapy was 5.50 months, compared with 3.50 months (p = 0.080) for chemotherapy. The time of ECOG status < 2 was longer with sonochemotherapy (7.20 months) than with chemotherapy (5.00 months; p = 0.029). The DCR was 73.68% for sonochemotherapy compared with 42.50% for the control (p = 0.005). The incidence of overall adverse events was balanced between the two groups.

CONCLUSIONS

The use of sonochemotherapy can extend the survival and well-being time of stage III or IV pancreatic cancer patients without any increase in serious adverse events.

TRIAL REGISTRATION

ChineseClinicalTrials.gov ChiCTR2100044721 CLINICAL RELEVANCE STATEMENT: This multicentre, randomised, controlled trial has proven that sonochemotherapy, namely, the combination of diagnostic ultrasound, microbubbles, and chemotherapy, could extend the overall survival of patients with end-stage pancreatic ductal adenocarcinoma from 6.10 to 9.10 months without increasing any serious adverse events.

KEY POINTS

• This is the first multicentre, randomised, controlled trial of sonochemotherapy for clinical pancreatic cancer treatment using ultrasound and a commercial ultrasound contrast agent. • Sonochemotherapy extended the median overall survival from 6.10 (chemotherapy alone) to 9.10 months. • The disease control rate increased from 42.50% with chemotherapy to 73.68% with sonochemotherapy.

Gemcitabine-induced pseudocellulitis: a case report and review of the literature

Gemcitabine is a chemotherapeutic agent used in a wide variety of solid tumours. Known side effects include a dose-limiting myelosuppressive toxicity, mild rash, and radiation-dependent dermatitis. Rarely, localized inflammation in the form of pseudocellulitis has also been observed. We present the case of a 77-year-old woman with a history of a Whipple procedure for pancreatic adenocarcinoma who presented to the emergency department after the start of gemcitabine therapy with increased erythema, swelling, and tenderness in her lower legs. Relevant past medical history included peripheral vascular disease, dyslipidemia, and hypertension. A diagnosis of gemcitabine-induced pseudocellulitis aggravated by venous stasis was confirmed after an extensive workup. This case report and the literature review describe this rare reaction, highlighting the need for increased recognition to avoid unnecessary therapeutic intervention.

A rash diagnosis: Gemcitabine-associated pseudocellulitis

Gemcitabine is an antitumor agent with broad clinical application. The most common cutaneous toxicities are mild rash and pruritus; however, a severe ‘pseudocellulitis’ rash, which resembles infectious cellulitis in clinical presentation, has increasingly been recognized as a rare complication of this agent. Though the specific pathophysiology related to this condition is not clear, it has been observed to occur primarily in regions of significant lymphadenopathy or prior radiation exposure typically after 24–48 h following administration of gemcitabine. It is a self-limiting reaction, with most cases resolving within two to seven days of onset without any specific treatment for the rash. Treatment with gemcitabine may be safely continued in patients with this complication, though recurrence of the rash is common following repeated doses. We report a case of biopsy confirmed gemcitabine associated pseudocellulitis in a patient treated for metastatic pancreatic adenocarcinoma. Knowledge of this complication is important to avoid unwarranted hospitalizations and antibiotic use in patients treated with gemcitabine.

A Phase I Study of a New Nucleoside Analogue, OSI-7836, Using Two Administration Schedules in Patients with Advanced Solid Malignancies

PURPOSE

To investigate the safety, tolerability, and pharmacokinetic profile of the novel nucleoside analogue OSI-7836 in patients with advanced solid malignancies.

EXPERIMENTAL DESIGN

OSI-7836 was initially given as a 60-minute i.v. infusion on day 1 every 21 days. In view of its dose-limiting toxicities, the administration time was amended to a 5-minute bolus, and subsequently, the schedule was amended to weekly for 4 weeks followed by a 2-week rest. Blood and urine samples were collected for pharmacokinetic studies. Analyses of cytokines and lymphocyte subsets were added later in the study to elucidate a mechanism for the severe fatigue and lymphocyte depletion observed in earlier patients.

RESULTS

Thirty patients received a total of 61 treatment cycles. Fatigue was the main dose-limiting toxicity. Maximum-tolerated dose was defined as 300 mg/m2 in the 60-minute infusion, (three times per week) schedule; 400 mg/m2 in the 5-minute bolus infusion, (three times per week) schedule; and 100 mg/m2 in the weekly schedule. Other common toxicities were nausea, vomiting, rash, fever, and a flu-like syndrome. There were no clinically significant hematologic toxicities. Following the initial dose, OSI-7836 was eliminated from plasma with a median (range) elimination half-life of 48.3 minutes (22.6-64.8 minutes). Lymphocyte subset analysis showed a significant drop in B cell counts, which persisted to day 14 and beyond. Cytokine analysis showed significant elevations of interleukin-6 and interleukin-10 in all patients who received > or = 200 mg/m2 OSI-7836. Best response was disease stabilization in seven patients.

CONCLUSION

OSI-7836 was associated with excessive fatigue, and despite changes in its schedule and duration of administration, we did not observe an improvement in its tolerability. Its potentially selective effect on B lymphocytes could be exploited in further studies in specific hematologic malignancies.

Gemcitabine in combination with paclitaxel for the treatment of metastatic breast cancer

Gemcitabine and paclitaxel are active drugs in the treatment of patients with metastatic breast cancer which seem to have synergistic anticancer activity. Seven Phase II trials of gemcitabine/paclitaxel and one Phase III trial have been published. Two dosing or admistration schedules have been preferred in the clinical development of the combinations: gemcitabine on days 1 and 8 plus paclitaxel on day 1 or 8, every 3 weeks or gemcitabine plus paclitaxel on day 1, every 2 weeks. In first-line Phase II trials, up to 71% of patients responded to gemcitabine/paclitaxel therapy. Response rates were lower among patients who had received previous chemotherapy for metastatic disease (46%). Responses were observed in patients refractory to docetaxel monotherapy. Toxicity of gemcitabine/paclitaxel regimens has been low, with infrequent neutropenia or nonhematologic toxicity. In the randomized Phase III registration trial, the gemcitabine/paclitaxel combination demonstrated a clear advantage over paclitaxel alone in terms of the primary end point of survival and other efficacy end points, with manageable toxicity. Gemcitabine/paclitaxel showed a survival advantage of approximately 22% over paclitaxel alone (hazard ratio of 0.775). Gemcitabine plus paclitaxel represents an active and well-tolerated treatment alternative for first-line treatment of anthracycline-treated metastatic breast cancer. Triplet combinations, in which an anthracycline or trastuzumab are added to gemcitabine/paclitaxel, are being explored in the metastatic and neoadjuvant settings with excellent results. In addition, gemcitabine/paclitaxel is being evaluated in two large adjuvant multicenter studies.

A phase I human trial of mitoguazone and gemcitabine sequential bi-weekly treatment of cancer patients

Our previous studies have demonstrated the existence of synergism in a combination therapy using mitoguazone and gemcitabine when the mitoguazone is administered 24 hours before gemcitabine. Based on the cell culture and animal experimental results, a phase I clinical trial was performed in order to determine the toxicity of the combined treatment. Mitoguazone and gemcitabine were administered sequentially: mitoguazone on day 1 and gemcitabine on day 2. This cycle was repeated every 2 weeks. The dosages of these two drugs were varied between patients. Ten patients were enrolled in the study. Six patients began treatment at dose level 1 (mitoguazone 500 mg/m2, gemcitabine 1500 mg/m2), three at dose level 2 (mitoguazone 500 mg/m2, gemcitabine 2000 mg/m2), and one at dose level 3 (mitoguazone 600 mg/m2, gemcitabine 2000 mg/m2). Dose-limiting toxicity (DLT) was only observed in two patients treated at dose level 1 and one patient treated at dose level 3, while all the other patients only experienced nonhematologic toxicity, such as asthenia and mucositis. Two melanoma patients showed responses (one partial and one minor) to the treatment. One lymphoma patient also showed a brief partial response. This phase I trial indicated that the combination of mitoguazone and gemcitabine had limited but noticeable activity for treatment of cancer patients. Further study on the toxicity and on the effect of the scheduled mitoguazone-gemcitabine combination is needed.

Chemosensitivity testing and test-directed chemotherapy in human pancreatic cancer

Human pancreatic cancer is a devastating disease with poor prognosis. In many cases it is diagnosed at stages in which a complete resection is not possible. However, even after complete resection most tumors recur. Therefore, several chemotherapeutic strategies have been developed, so far, with little impact on the clinical outcome. Because one of the hallmarks of human pancreatic cancer is its general resistance to chemotherapeutic agents, it seems important to develop strategies to individualize chemotherapy and to render cells more sensitive to chemotherapeutic agents. In this summary we describe our methods of in vitro chemosensitivity testing using the human tumor colony-forming assay for pancreatic cancer in comparison with other solid tumors and describe how the in vitro results influence chemotherapy. Furthermore, we point out new developments of mRNA quantitation of chemoresistance target enzymes based on real-time PCR, which may help in the future to individualize chemotherapy of pancreatic cancer. Finally, we present results of studies of cyclin D1 inhibition. Suppression of cyclin D1 by cyclin D1 antisense mRNA expression was associated with growth inhibition and an increase in chemosensitivity to fluoropyrimidines and platinum compounds. Because human pancreatic cancers are relatively chemoresistant and material for chemosensitivity testing with the human tumor colony-forming assay (HTCA) is in most cases difficult to obtain, future investigations should aim at the development of methods requiring only very small samples to analyzemarkers of chemosensitivity. Our results further suggest that chemotherapy in combination with strategies to increase chemosensitivity may be a reasonable regimen for the treatment of human pancreatic cancer in the future.

Phase I trial of gemcitabine and paclitaxel in advanced solid tumors

PURPOSE

Gemcitabine and paclitaxel are chemotherapeutic agents with clinical antitumor activity in a broad range of malignant solid tumors. Because of preclinical synergy, unique mechanisms of action and resistance, and nonoverlapping toxicities, gemcitabine and paclitaxel combinations are attractive for testing in clinical trials. Prior weekly gemcitabine and paclitaxel regimens administered on a 28-day cycle have been limited by cumulative hematological toxicity on day 15, thus reducing the planned gemcitabine dose intensity. We therefore conducted a phase I trial of a 21-day schedule of weekly gemcitabine and paclitaxel to determine the tolerability, maximum tolerated dose (MTD), and preliminary estimates of efficacy of this regimen.

PATIENTS AND METHODS

Forty-one patients with advanced malignant solid tumors were accrued. Gemcitabine was given at a fixed dose of 1000 mg/m2 while paclitaxel was administered at an initial dose of 60 mg/m2, then escalated by 15 mg/m2 increments over seven dose levels to a prospectively planned maximum dose of 150 mg/m2. Both agents were infused intravenously on days one and eight every 21 days. At least three patients were enrolled per dose level. No intrapatient dose escalation was allowed.

RESULTS

All patients were assessable for toxicity and 31 were assessable for response. The regimen was generally well-tolerated. Dose-limiting thrombocytopenia was observed in one patient at a paclitaxel dose of 135 mg/m2/week (dose level 6). After expansion of this dose level by 14 additional patients, no further dose-limiting toxicities were observed although one patient at dose level seven died of neutropenic sepsis after completing three cycles. There were eight partial responders for an overall response proportion of 26% (95% CI: 11, 41). Twelve patients (39%) had stable disease.

CONCLUSION

This 21-day schedule of gemcitabine and paclitaxel is safe, well-tolerated, and active. The recommended phase II dose is gemcitabine 1000 mg/m2 and paclitaxel 150 mg/m2 on days one and eight every 21 days. The antitumor activity observed with this regimen warrants further investigation.

Synergistic effect of sequential administration of mitoguazone (MGBG) and gemcitabine in treating tissue cultured human breast cancer cells and mammary rat tumors

Modulation of cancer chemotherapeutic drugs has been attempted to increase efficacy and overcome resistance to the chemotherapeutic agent. Studies have shown schedule-dependent interactions in combined use of chemotherapeutic drugs. Mitoguazone (MGBG), an old drug with possible modulating activity, was used in combination with gemcitabine, a relatively new cancer drug, in treating tissue cultured human breast cancer cells and mammary rat tumors. Tissue cultured BOT-2 cancer cells were first treated with varying concentrations of gemcitabine and MGBG, independently. Combinations of the two drugs were then used with different scheduled administrations. Marked synergistic activity was found between gemcitabine and MGBG when the MGBG was given first, followed by gemcitabine 24 hours later. A non-toxic dose of MGBG enhanced the toxicity of gemcitabine by eight orders of magnitude using MTT assays in the tissue cultured human breast cancer cell study. The sequential administration of MGBG and gemcitabine also increased the survival rate of rats bearing mammary tumors in our pilot animal study.

Concurrent infusional gemcitabine and radiation in the treatment of advanced unresectable GI malignancy: a phase I study

PURPOSE

Preclinical studies have demonstrated significant synergistic tumor cell death when gemcitabine is combined with radiation therapy. The optimal mode for concomitant delivery of drug and radiation therapy remains to be determined. A phase I/II study was undertaken to establish the maximum tolerated dose of infusional gemcitabine when combined with radiation therapy in advanced gastrointestinal malignancies and to assess the response to treatment.

MATERIALS AND METHODS

Twenty-five patients with advanced or recurrent gastrointestinal malignancy were entered in this dose-escalation study. The initial dose of gemcitabine was 50 mg/m2 as a 24-hour continuous intravenous infusion given weekly x 3 with concurrent radiation therapy. The patients were given a week off chemotherapy after the third injection. The radiation therapy was continued during that week. Gemcitabine was thereafter resumed weekly for another 3 weeks or until the patient completed the radiation therapy (whichever was earlier). Five patients were treated at each dose level. The dose of the drug was escalated in increments of 50 mg/m2 if the toxicity was acceptable at the previous level until the maximum tolerated dose was established. Thirteen patients with advanced unresectable colorectal cancer and 12 patients with advanced unresectable pancreaticobiliary cancers were enrolled on the study. Radiation was delivered at 180 cGy/fraction to a total dose of 4000 cGy +/- boost. Because toxicity was severe at the 150 mg/m2 dose level, three additional patients were entered at this dose level. The dose was then dropped to 125 mg/m2, and five more patients were entered at this dose level. Two additional patients were then added in order to assess toxicity. Patient follow-up ranged from 4 to 22 months, and the median was 8 months.

RESULTS

All patients were evaluable for toxicity. The doses of 50 and 100 mg/m2 were well tolerated, but at 150 mg/m2, six of eight patients experienced grade 3 or greater toxicity. The dose was de-escalated to 125 mg/m2, and three of seven patients showed grade 3 diarrhea and weight loss. Clinical tumor response was evaluable in 20 patients. Ten patients had a complete clinical response (50%), five patients had a partial response (25%), three patients had no response, and two patients had progression of disease. No patients experienced late toxicities related to either gemcitabine administration or radiation therapy. Twelve patients are currently alive.

CONCLUSION

Based on these results, it appears that the maximum tolerated dose for weekly 24-hour infusion of gemcitabine combined with radiation therapy is 100 mg/m2. Gemcitabine appears to be a potent radiation sensitizer, and when combined with radiation therapy, it has shown encouraging tumor responses. In this study, we found an overall response rate of 75% in patients with locally advanced stage of disease. Further evaluation of gemcitabine at 100 mg/m2 is being undertaken in preparation for a confirmatory multi-institutional phase II study.

Noncardiogenic pulmonary edema: an unusual and serious complication of anticancer therapy

Noncardiogenic pulmonary edema (NCPE) is a rare and less well-recognizable pulmonotoxic syndrome of anticancer therapy than pneumonitis/fibrosis. NCPE is a clinical syndrome characterized by simultaneous presence of severe hypoxemia, bilateral alveolar infiltrates on chest radiograph, and no evidence of left atrial hypertension/congestive heart failure. The diagnosis of drug-related NCPE relies upon documented exclusion of any infectious, metabolic, or cancer-related causes. The time proximity to therapy with drugs that are known to precipitate NCPE, any preceding episodes of flu-like symptoms during previous chemotherapy courses and possible response to corticosteroids may further support such a diagnosis. Cancer therapeutic agents clearly associated with NCPE are cytarabine, gemcitabine, and interleukin-2, as well as all-trans retinoic acid in acute promyelocytic leukemia patients, while a few other compounds have rarely or occasionally been implicated. The pathophysiology of lung injury in drug-induced NCPE remains unclear. There are indications suggesting that both a direct cytotoxic insult to the lung epithelial cells and induction of a cytokine-triggered inflammatory response may be involved in its pathogenesis. By distinction to drug-induced pulmonary pneumonitis that may lead to permanent pulmonary fibrosis, NCPE if not fatal, can be reversed upon prompt recognition, following immediate discontinuation of the offensive drug and start of intensive supportive treatment and intravenous corticosteroids.

Unexpected severe myelotoxicity of gemcitabine in pretreated breast cancer patients

Gemcitabine is a chemotherapeutic agent with proven antitumor effects in pancreatic and non-small cell lung cancer; however, studies establishing the definite significance in other solid tumors are still in progress. We herein present three female patients with advanced breast cancer who received gemcitabine as salvage chemotherapy. Gemcitabine at a dose of 1250 mg/m2 was scheduled for days 1, 8 and 15 with a subsequent rest for 1 week. However, within 1 week after the very first administration of gemcitabine myelotoxicity WHO grade IV occurred in all patients, leading to discontinuation of therapy. In two patients this gemcitabine-induced hematotoxicity could be overcome by means of vigorous supportive care, but one patient died after cerebral bleeding due to severe thrombocytopenia. We conclude that gemcitabine in heavily pretreated breast cancer patients should only be used with extreme caution with special focus on platelet counts until solid data from clinical studies for doses and schedules are available.

Pre-clinical evaluation of the activity of gemcitabine as a basis for regional chemotherapy of pancreatic and colorectal cancer

AIMS

To estimate the potential activity of gemcitabine for hepatic arterial infusion (HAI) chemotherapy in pancreatic and colorectal cancer.

METHODS

The anti-proliferative effects of gemcitabine were determined in MIA PaCa-2 and PMH2/89 pancreatic and HT29 and NMG64/84 colon cancer cell lines and in fresh tumours from patients with liver metastases of colon, rectal and pancreatic cancer in vitro using the human tumour colony forming assay.

RESULTS

Gemcitabine showed concentration and time-dependent cytotoxic effects in all tested cell lines. The IC(50)of gemcitabine in MIA PaCa-2, PMH2/89, HT29 and NMG64/84 cells at 2 h exposure time were >100, 18, 100 and 2.5 microg/ml, respectively, at 4 h 15, 1.2, 45 and 0.5 microg/ml, respectively, and at 24 h 0.2, 0.1, 1.8 and 0.1 microg/ml, respectively. All tumours displayed concentration dependent inhibition of colony formation after exposure to gemcitabine for 2 h. The IC(50)values of gemcitabine in six of the 10 metastases were </=100 microg/ml.

CONCLUSIONS

Based on our results and theoretical considerations regarding hepatic arterial infusion therapy gemcitabine seems to be suitable for HAI therapy phase II studies. Moreover, patients with colorectal or pancreatic tumours that demonstrated in vivo sensitivity may benefit from regional chemotherapy with gemcitabine.

Gemcitabine-cisplatin: a schedule finding study

PURPOSE

To evaluate the tolerability of four alternating cisplatin-gemcitabine schedules. A secondary aim was to evaluate the clinical efficacy of this combination.

PATIENTS AND METHODS

Forty-one patients with advanced solid tumors received alternating sequences with a 4- and 24-hour interval of cisplatin and gemcitabine. Gemcitabine 800 mg/m2 was administered as a 30-min infusion on day 1, 8 and 15, and cisplatin 50 mg/m2 over 1 hour on day 1 and 8; in case of the 24-hour time interval the second drug was administered one day later. Four cisplatin-gemcitabine schedules were studied: gemcitabine four hour before cisplatin (10 patients), or vice versa (14 patients) and gemcitabine twenty-four hours before cisplatin (9 patients) or vice versa (8 patients). The sequence of drug administration was reversed in the second cycle of therapy in each individual patient, enabling the evaluation of sequence-dependent side effects. Twenty-six patients had received prior chemotherapy, of which twenty-one platinum-based.

RESULTS

The main toxicity was myelosuppression. Overall, grade 3 and 4 thrombocytopenia was observed in 27 out of 41 patients (66%) and was not schedule dependent. No serious bleeding occurred. Leukopenia was significantly different between the 4 alternating schedules (P = 0.01); gemcitabine 24 hours before cisplatin was significantly less toxic compared to both cisplatin 4 hours and 24 hours before gemcitabine (P = 0.01 and P = 0.003, respectively). Furthermore, paired analysis of the 4-hour and 24-hour data sets showed that leukopenia was significantly more serious when cisplatin preceded gemcitabine (P = 0.005). Although most patients received prior treatment, both prior chemotherapy and radiotherapy were not related to toxicity. Overall, grade 3 and 4 leukopenia occurred in 19 out of 41 patients (46%). Anemia (Hb < or = 6.0 mmol/l) was not sequence dependent and was observed in 63% of patients. Myelotoxicity was cumulative between cycles and caused frequent omission of gemcitabine on day 15. Overall, in 51% of administered cycles there was no omission of gemcitabine. A mean of 3.5 therapy cycles was administered. Non-hematological toxicity was moderate, consisting mainly of grade 1 and 2 nausea/vomiting and fatigue, and was not schedule dependent. Recently, we described that the schedule in which cisplatin was administered 24 hours before gemcitabine produced the best pharmacological profile. Based on this and because toxicity was manageable, the schedule cisplatin 24 hours prior to gemcitabine was chosen for phase II evaluation. Nine out of thirty-six evaluable patients had an objective response. These responses were observed in head and neck squamous-cell carcinoma (HNSCC), non-small-cell lung cancer (NSCLC), melanoma, adenocarcinoma of unknown origin, ovarian and esophageal carcinoma.

CONCLUSIONS

Myelosuppression was the most important toxicity. Leukopenia was schedule dependent: gemcitabine before cisplatin was less toxic than the reversed sequence, in this respect. Some encouraging responses were seen in patients with esophageal cancer. Currently, a phase II study with cisplatin 24 hours before gemcitabine is ongoing in patients with advanced upper gastro-intestinal tumors.