Adjuvant chemoradiation using 5-fluorouracil/folinic acid/cisplatin with or without paclitaxel and radiation in patients with completely resected high-risk gastric cancer: two cooperative phase II studies of the AIO/ARO/ACO

BACKGROUND

The current two studies evaluate the feasibility, toxicity and efficacy of an adjuvant combined modality treatment strategy containing a three to four-drug chemotherapy regimen plus 5-fluorouracil (FU)-based radiochemotherapy.

PATIENTS AND METHODS

Between December 2000 and October 2003, a total of 86 patients were included in both studies. Patients with completely resected gastric adenocarcinoma including a D1 or D2 lymph node dissection (LND) were eligible. Treatment consisted of two cycles of folinic acid 500 mg/m2, 5-FU 2000 mg/m2 continuous infusion over 24 h once weekly for 6 consecutive weeks, paclitaxel 175 mg/m2 in weeks 1 and 4 and cisplatin 50 mg/m2 in weeks 2 and 5 (FLPP; n=41) or two cycles of the same 5-FU/folinic acid schedule but with cisplatin 50 mg/m2 only in weeks 1, 3 and 5 (FLP; n=45). Radiation with 45 Gy plus concomitantly applied 5-FU 225 mg/m2/24 h was scheduled in between the two cycles.

RESULTS

Patients characteristics were: D1/D2 LND FLP group 53%/42%; FLPP group 27%/68%; stage distribution: UICC stages III/IV(M0) FLP group 63% and FLPP group 66%. Median follow-up was 10 months (3-25) for FLP and 18 months (2-51) for FLPP patients. CTC grade 3/4 toxicities during the first cycle/chemoradiation/second cycle of FLP: granulocytopenia 3%/0/27%, anorexia 6%/10%/8%; diarrhea 8%/0/4%, nausea 3%/0/4%; FLPP: granulocytopenia 0/0/37%, anorexia 5%/11%/6%; diarrhea 5%/0/3, nausea 3%/8%/0%; early death in one patient due to Pneumocystis carinii pneumonia. Projected 2-year progression-free survival was 64% (95% CI 56% to 68%) for the FLP and 61% (95% CI 42% to 78%) for the FLPP group.

CONCLUSIONS

Both chemoradiation regimens appear feasible with an acceptable toxicity profile indicating that cisplatin can be added to 5-FU/FA and that even a four-drug regimen can be investigated further in prospective clinical trials in completely resected gastric cancer patients. Treatment should be given in experienced centres in order to avoid unnecessary toxicity.

Secondary leukemia after first-line high-dose chemotherapy for patients with advanced germ cell cancer

PURPOSE

We investigated the incidence of secondary leukemia in patients treated with first-line high-dose chemotherapy (HDCT) plus autologous stem cell transplantation (PBSCT) for advanced testicular cancer.

METHODS

Three hundred and twenty-three patients who were entered into two consecutive prospective Phase-II studies of the German Testicular Cancer Study Group were analyzed. A total of 221 patients had received HD-VIP containing cisplatin, ifosfamide, and etoposide and 102 patients were treated with Tax-HD-VIP containing cisplatin, ifosfamide, etoposide, and paclitaxel, each cycle supported by autologous PBSCT.

RESULTS

Patients had received a median cumulative etoposide dose of 4.9 g/m(2) (range, 2.2-9.4 g/m(2)). The median follow-up duration for all patients was 36 months (range, 0-128) with a median follow up time of 50 months (range, 0-128) for patients surviving at least 1 year after therapy. One patient developed a secondary acute myeloid leukemia (s-AML) involving a chromosomal translocation t(11;19)(q23;p13.3) 24 months after the start of chemotherapy resulting in a cumulative incidence of 0.48% [95% confidence interval (CI) 0-1.42]. Additionally, two patients with primary mediastinal germ cell cancer developed a myelodysplastic syndrome. No solid tumors had occurred.

CONCLUSIONS

HDCT including high-dose etoposide with autologous PBSCT as first-line therapy for advanced testicular cancer was associated with an acceptably low risk of developing secondary leukemia.

A phase I clinical and pharmacokinetic study of the camptothecin glycoconjugate, BAY 38-3441, as a daily infusion in patients with advanced solid tumors

BACKGROUND

The aim of this study was to define the maximum tolerated dose (MTD), dose-limiting toxicity (DLT) and pharmacokinetics of the camptothecin glycoconjugate BAY 38-3441, administered as an infusion for 30 min on two separate schedules every 3 weeks.

PATIENTS AND METHODS

A total of 81 patients with advanced solid tumors were treated with BAY 38-3441 either at doses of 20, 40, 67, 100, 140, 210, 315, 470 and 600 mg/m2/day for 1 day every 3 weeks (single-dose schedule), or at doses of 126, 189, 246, 320 and 416 mg/m2/day once daily for three consecutive days every 3 weeks (3-day schedule). Plasma sampling was performed to characterize the pharmacokinetics of BAY 38-3441 and camptothecin with these schedules.

RESULTS

DLTs included renal toxicity, granulocytopenia and thrombocytopenia on the single-day schedule at doses > or = 470 mg/m2/day, and diarrhea and thrombocytopenia on the 3-day schedule at doses > or = 320 mg/m2/day. Other non-DLTs were gastrointestinal, dermatological and hematological. Pharmacokinetics of BAY 38-3441 and camptothecin appear to be dose-dependent, but not linear.

CONCLUSIONS

Renal toxicity was dose-limiting for BAY 38-3441 using 30-min infusions on the single-dose schedule. Dose escalation to 470 mg/m2/day is feasible using a 2-h infusion. However, because of the superior safety profile, we recommend the 3-day schedule for BAY 38-3441 at a dose of 320 mg/m2/day as 30-min infusions for further phase II studies.

Long-term results of first-line sequential high-dose etoposide, ifosfamide, and cisplatin chemotherapy plus autologous stem cell support for patients with advanced metastatic germ cell cancer: an extended phase I/II study of the German Testicular Cancer Study Group

PURPOSE

Patients with disseminated germ cell cancer and poor prognosis (International Germ Cell Cancer Collaborative Group [IGCCCG] classification) achieve only a 45% to 50% long-term survival by standard chemotherapy. First-line high-dose chemotherapy might be able to improve the result. This analysis reports toxicity and long-term results of a large phase I/II study of sequential high-dose etoposide, ifosfamide, and cisplatin (VIP) in patients with advanced germ cell tumors.

PATIENTS AND METHODS

Between July 1993 and November 1999, 221 patients with either Indiana "advanced disease" (n = 39) or IGCCCG "poor prognosis" criteria (n = 182) received one cycle of VIP followed by three to four sequential cycles of high-dose VIP chemotherapy plus stem cell support, every 3 weeks, at six consecutive dose levels.

RESULTS

Dose limiting toxicity occurred at level 8 (100 mg/m2 cisplatinum, 1750 mg/m2 etoposide, 12 g/m2 ifosfamide) with grade 4 mucositis (three of eight patients), grade 3 CNS toxicity (one of eight patients), grade 4 renal toxicity (one of eight patients), and prolonged granulocytopenia (one of eight patients). After 4-year median follow-up, progression-free survival and disease-specific survival rates in the poor prognosis subgroup were 69% and 79% at 2 years and 68% and 73% at 5 years, with 76% for gonadal/retroperitoneal versus 67% for mediastinal primaries. Severe toxicity included treatment related death (4%), treatment-related acute myeloid leukemia (1%), long-term impared renal function (3%), chronic renal failure (1%), and persistent grade 2-3 neuropathy (5%).

CONCLUSION

Repetitive cycles of high-dose VIP with peripheral stem cell support can be successfully applied in a multicenter setting. Dose level 6 with cisplatin 100 mg/m2, etoposide 1500 mg/m2, and ifosfamide 10 g/m2 is recommended for further investigation in randomized trials. An ongoing randomized trial within the European Organization for Research and Treatment of Cancer evaluates this protocol against four cycles of standard cisplatin, etoposide, and bleomycin.

Capecitabine and irinotecan as first-line chemotherapy in patients with metastatic colorectal cancer: results of an extended phase I study

BACKGROUND

To define the maximum-tolerated dose (MTD) and to evaluate the dose-limiting toxicities (DLTs) of the combination of capecitabine and irinotecan in patients with metastatic colorectal cancer.

PATIENTS AND METHODS

Thirty-seven patients with measurable metastatic colorectal cancer with no prior chemotherapy for metastatic disease were treated at three dose levels (DLs). For the first two dose levels, irinotecan (70 mg/m(2)) was administered once a week for 6 weeks in combination with 2 weeks of capecitabine at 1000 mg/m(2) (DL1) or 1250 mg/m(2) (DL2) twice daily, starting on days 1 and 22. In the last dose escalation step, the dose of irinotecan was increased to 80 mg/m(2) (DL3). One cycle lasted 7 weeks.

RESULTS

In the subsequent phase I trial, 96 cycles of capecitabine and irinotecan were administered. At DL3, three out of six patients experienced DLTs (diarrhea, neutropenia, asthenia). In order to confirm the safety of the recommended dose, DL2 was extended to 15 patients. Five patients (33%) showed DLTs at this dose level, which was considered too high to embark on further clinical studies. Subsequently, the starting dose (DL1) was extended to a total of 16 patients, with diarrhea being the main toxicity. The overall response rate was 38% [95% confidence interval (CI) 21% to 58%], with a median response duration of 8.7 months (95% CI 6.4-11.5 months).

CONCLUSIONS

The recommended doses for further studies are irinotecan 70 mg/m(2) and capecitabine 1000 mg/m(2). The combination of capecitabine and irinotecan appears to have significant therapeutic efficacy with manageable toxicity.

First-line sequential high-dose VIP chemotherapy with autologous transplantation for patients with primary mediastinal nonseminomatous germ cell tumours: a prospective trial

To determine the efficacy of first-line sequential high-dose VIP chemotherapy (HD-VIP) in patients with primary mediastinal nonseminomatous germ cell tumours (GCT), 28 patients were enrolled on a German multicentre trial. High-Dose VIP chemotherapy consisted of 3-4 cycles of dose-intensive etoposide and ifosfamide plus cisplatin, q22days, each cycle followed by autologous peripheral blood stem cell transplantation plus granulocyte-colony stimulating factor (G-CSF) support. One cycle of standard-dose VIP was applied to harvest peripheral blood stem cells. Ten patients had mediastinal involvement as the only manifestation (36 %), 18 of 28 patients had additional metastatic sites, such as lung (n=17; 61%), liver (n=7; 25%), bone (n=5; 18%), lymph nodes (n=3; 11%) and CNS (n=3; 11%). Median follow-up was 43 months (range, 7-113) for all patients and 52 months (range, 22-113) for surviving patients. Nineteen of 28 patients obtained a disease-free status; 11 with HD-VIP alone and eight with adjunctive surgery. In addition, one of the four patients with marker negative partial remission after HD-VIP without resection of residual masses is currently alive. Two patients developed recurrence of GCT or teratoma. Two patients have died due to an associated haematologic disorder. The 2-year progression-free survival and overall survival rates are 64 and 68%, respectively. This report represents a subgroup analysis of 28 patients with mediastinal nonsemina within the German first-line study for 'poor prognosis' GCT. Compared to data of an international database analysis including 253 patients with mediastinal nonseminoma treated with conventional chemotherapy, the results may indicate that HD-VIP results in an approximately 15% survival improvement.

Analysis of salvage treatments for germ cell cancer patients who have relapsed after primary high-dose chemotherapy plus autologous stem cell support

The aim of this study was to identify treatment strategies and therapeutic or clinical factors that predict for response to salvage therapy and survival in patients with metastatic 'Indiana advanced' or International Germ-Cell Cancer Collaborative Group (IGCCCG) poor prognosis' germ cell cancer (GCT) failing first-line sequential high-dose chemotherapy plus autologous stem cell support (HD-CT). A total of 58 'poor prognosis' patients who had relapsed after HD-CT were identified within two large prospective German first-line HD-CT trials (n=286) performed between March 1993 and March 2001. Salvage treatment consisted of the following: cisplatin-based conventional dose CTx+/-resection (19/58; 33%), non-cisplatin based CTx (16/58; 28%) or salvage HD-CT (14/58; 24%)+/-resection; resection (n=3) and/or radiation (n=5) only: 7 patients (12%); no specific therapy: 2 patients. 21 (38%) patients responded favourably (Complete Response (CR)/Partial Response (PR) marker-negative) to salvage therapy. The use of salvage HD-CT (2-year survival 48%; P=0.03, the complete resection of residual masses (2-year survival 42%; P=0.015) as well as a favourable response to salvage therapy (2-year survival: 31%, P=0.014) were the only variables on univariate analysis associated with an improved survival. The estimated 2-year overall survival rate is 32% (95% Confidence Interval CI: 29-45%). Approximately 30% of patients relapsing after first-line HD-CT will survive>2 years, particularly those patients who can be treated with a second HD-CT +and/or surgical resection. If feasible, complete surgical resection of residual tumours appears to be the most efficient treatment.

Treatment-induced anaemia and its potential clinical impact in patients receiving sequential high dose chemotherapy for metastatic testicular cancer

First-line sequential high dose chemotherapy is under investigation in patients with "poor prognosis" metastatic germ cell tumours in order to improve survival. Despite the use of autologous peripheral blood stem cell transplantation and granulocyte colony stimulating factor chemotherapy dose intensification is associated with severe haematotoxicity including anaemia, which may significantly affect quality of life and tolerability of chemotherapy. This study investigates the frequency and degree of anaemia in patients receiving first-line sequential high dose chemotherapy for metastatic testicular cancer and the impact of anaemia on treatment outcome. A total of 101 newly diagnosed patients with "poor prognosis" metastatic nonseminomatous germ cell tumours were treated with one cycle of standard VIP followed by three cycles of HD-VIP-chemotherapy (etoposide, ifosfamide, cisplatin) within a large phase I/II study. Differential blood cell counts were taken prior, during and after every cycle of chemotherapy. Additionally, the numbers of red blood cell and platelet transfusions were recorded. Kaplan-Meier analyses were performed to correlate pre-treatment and post-treatment haemoglobin values to response and overall survival. Forty-eight per cent of the patients were classified anaemic (haemoglobin <12 g dl(-1)) prior to the start of chemotherapy. The application of sequential HD-VIP resulted in median haemoglobin nadirs between 7.8 g dl(-1) (range 5.5-11.1 g dl(-1)) in the first cycle and 7.6 g dl(-1) (range 6.0-11.4 g dl(-1)) in the third cycle despite the frequent use of red blood cell transfusions. Almost all patients (99%) had haemoglobin levels <10 g dl(-1) at some timepoint during first-line sequential high dose chemotherapy. Overall, 97 patients received red blood cell transfusions with a median of 10 units (range 2-25) per patient during the four consecutive cycles of therapy. The time to first transfusion was shortest in patients with the lowest initial haemoglobin values. While there was no prediction of response or outcome by baseline haemoglobin-levels, a significant survival difference in favour of patients with a haemoglobin value >10.5 g dl(-1) after completion of four cycles of therapy (at leukocyte recovery after the last cycle) compared to those with haemoglobin values <10.5 g dl(-1) was found with 3-year overall survival rates of 87% vs 68%, respectively (P<0.05). Severe anaemia is a very frequent side effect of sequential dose intensive therapy in patients with germ cell cancer, with almost all patients becoming transfusion dependent. Despite the frequent use of red blood cell transfusions, median haemoglobin nadirs remained about 7.5-8 g dl(-1) during therapy. A correlation of haemoglobin-values after completion of therapy to overall treatment outcome was found.

Activity of oxaliplatin in patients with relapsed or cisplatin-refractory germ cell cancer: a study of the German Testicular Cancer Study Group

PURPOSE

To investigate the efficacy and toxicity of oxaliplatin, a diaminocyclohaxane platinum derivative with incomplete cross-resistance to cisplatin in patients with relapsed or cisplatin-refractory germ cell cancer.

PATIENTS AND METHODS

Thirty-two patients with nonseminomatous cisplatin-refractory germ cell cancer or relapsed disease after high-dose chemotherapy (HDCT) plus autologous stem-cell support were treated with single-agent oxaliplatin 60 mg/m(2) on days 1, 8, and 15 repeated every 4 weeks (group 1; n = 16) or oxaliplatin 130 mg/m(2) given on days 1 and 15 of a 4-week cycle (group 2; n = 16). Patients were pretreated with a median of seven (range, three to 13) cisplatin-containing treatment cycles; 78% had received carboplatin/etoposide-based HDCT before oxaliplatin therapy. Twenty-seven patients (84%) were considered refractory (n = 20; 63%) or absolutely refractory (n = 7; 22%) to cisplatin therapy.

RESULTS

Overall, four patients achieved a partial remission (13%; 95% confidence interval, 1% to 24%). Two additional patients achieved disease stabilization. All responses were observed in cisplatin-refractory patients, including three who had not responded to previous HDCT. Patients received a median two cycles of oxaliplatin with a median cumulative dose of 350 mg/m(2). Hematologic toxicity was generally mild, with five patients developing grade 3/4 thrombocytopenia. Nonhematologic side effects consisted mainly of nausea/vomiting. One patient developed grade 3 neurotoxicity.

CONCLUSION

Considering the particularly unfavorable prognostic characteristics of this patient population compared with patients from previous trials for new drugs in germ cell cancer, eg, paclitaxel and gemcitabine, a 13% overall response rate and a 19% response rate in the group treated with oxaliplatin 130 mg/m(2) seems to be of interest. Oxaliplatin may be a palliative treatment option for this patient population, and evaluation in combination regimens is warranted.

Clinical impact of germ cell tumor cells in apheresis products of patients receiving high-dose chemotherapy

PURPOSE

High-dose chemotherapy (HD-Ctx) followed by autologous peripheral-blood stem-cell (PBSC) transplantation is currently investigated in patients with poor prognosis or relapsed metastatic germ cell tumor (GCTs). This study analyzed the presence and the clinical importance of contaminating tumor cells in PBSC preparations used to support HD-Ctx in GCT patients.

PATIENTS AND METHODS

Seven targets for reverse transcription polymerase chain reaction (RT-PCR)-based detection of GCT cells were able to detect seminomatous and different histologic variants of nonseminomatous tumor cells. PBSC preparations from 57 patients were investigated for the presence of contaminating tumor cells using this set of targets, including beta human chorionic gonadotropin (beta-hCG), fibronectin (EDB variant), epidermal growth factor receptor (EGFR), CD44 (v8 to 10 variant), germ cell and placental alkaline phosphatase (AP), human endogenous retrovirus type K (ENV and GAG), and XIST. Samples of PBSC preparations from four healthy donors for allogenic transplantations as well as blood specimens from 10 healthy volunteers served as negative controls.

RESULTS

Fifty patients (43 first-line and seven second-line Ctx) were assessable. Combining all RT-PCR results, 29 PBSC preparations (58%) were positive for tumor-specific amplification products (HERV-K 0, fibronectin 4, XIST 14, beta-hCG 19, AP 19, CD44 24, EGFR 26). Ten (35%) of 29 patients who underwent transplantation with positive PBSC preparations and seven (33%) of 21 patients with negative PBSC preparations have suffered relapse or progression (not significant [ns]). With a median follow-up of 22 months (2 to 66) post-HD-Ctx projected 3-year survival rates are 68% (RT-PCR+) and 58% (RT-PCR-) (ns). None of the 10 control peripheral-blood samples showed positivity for any of the targets studied.

CONCLUSION

GCT cells can be detected in more than 50% of PBSC preparations using a RT-PCR approach with multiple targets. Despite the presence of tumor cells, retransplantation of the PBSC products did not effect long-term outcome. Factors such as responsiveness to chemotherapy and tumor mass seem to overcome the importance of potentially re-infused tumor cells.

Phase II study of bendamustine in patients with relapsed or cisplatin-refractory germ cell cancer

Despite generally high cure rates in patients with metastatic germ cell cancer, patients with incomplete response to first-line cisplatin-based chemotherapy or with relapsed disease following high-dose salvage therapy exhibit a very poor prognosis. We investigated the efficacy and toxicity of bendamustine, a bifunctional alkylating benzimidol derivative with only partial cross-resistance to other alkylating agents such as ifosfamide or cyclophosphamide. Nineteen patients with cisplatin-refractory germ cell tumors (GCT) or relapse after high-dose chemotherapy plus autologous stem cell support were treated with bendamustine at a dose of 120 mg/m2 on 2 consecutive days at 3 week intervals. Patients had received a median of 9 (range 4-20) platinum-containing treatment cycles prior to bendamustine and 13 patients (68%) had previously received carboplatin/etoposide-based high-dose chemotherapy. One patient achieved a partial remission of only 6 weeks duration. No other responses were seen. Toxicity was low with one patient developing WHO grade 3 thrombocytopenia as the only WHO grade 3/4 toxicity observed. Hematologic toxicity was similar in patients pretreated with and without high-dose chemotherapy plus autologous stem cell support. We conclude that bendamustine has little or no clinically relevant activity in patients with cisplatin-refractory GCT or relapsed disease after high-dose chemotherapy.

First-line high-dose chemotherapy +/- radiation therapy in patients with metastatic germ-cell cancer and brain metastases

PURPOSE

To examine the feasibility and efficacy of first-line high-dose chemotherapy (HD-CTX) in patients with advanced metastatic germ-cell tumors (GCT) and brain metastases.

PATIENTS AND METHODS

Twenty-two patients with brain metastases at initial diagnosis were identified within a cohort of two hundred thirty-one consecutive patients with advanced metastatic disease, entered on a German multicenter trial between January 1993 and July 1998. All patients received first-line HD-CTX with cisplatin-etoposide-ifosfamide (HD-VIP) followed by autologous stem-cell transplantation. Brain irradiation (BRT) with 30-50 Gy +/- 10 Gy boost was applied in patients with symptomatic CNS disease or as consolidation in case of residual CNS lesions after HD-CTX.

RESULTS

A median number of 4 HD-CTX cycles (range 2-5) were applied to the 22 patients. Ten patients received HD-CTX alone and twelve patients were treated with HD-CTX plus BRT. Median duration of WHO grade 4 granulocytopenia and thrombocytopenia was seven and five days after each cycle, respectively. Non-hematologic toxicity consisted mainly of mucositis/enteritis (WHO grade 3-4 32%). Two early deaths occurred in twenty-two patients (one CNS-bleeding/one sepsis). Fourteen of twenty patients achieved a CR/PRm- status. Twenty patients (91%) responded in the brain (55% CR/36% PR). Two-year progression-free and overall survival rates were 72% and 81%, respectively. These survival rates are substantially higher compared to the available data in the literature.

CONCLUSIONS

High-dose chemotherapy with autologous stem-cell support +/- BRT appears to be feasible without increased therapy-related mortality in patients with advanced metastatic GCT and brain metastases. The results achieved emphasize the high chemosensitivity of CNS metastases from GCT and suggest a potential role for dose intensification. The dose of BRT in addition to HD-CTX may be tailored to the presence of clinical symptoms and the response of CNS metastases to chemotherapy.

Ifosfamide-based drug combinations: preclinical evaluation of drug interactions and translation into the clinic

Ifosfamide is an alkylating antineoplastic agent with documented activity against a variety of solid tumor types, most notably lung cancer, testicular cancer, and sarcoma. Ifosfamide has been included in various drug combination protocols, usually on an empirical basis. To gather more insight into the mechanisms that underlie these drug interactions and to develop guidelines for further improvement of clinical combination protocols, we performed a broad preclinical evaluation program of ifosfamide-based combination regimens using isobologram analysis of drug interactions. In established cisplatin-sensitive and cisplatin-refractory ovarian carcinoma cell lines, a schedule-dependent drug interaction between paclitaxel and activated hydroperoxy-ifosfamide (4-OOH-IF) could be demonstrated. When both drugs were given for 2 hours, simultaneous exposure or the sequence of paclitaxel followed by 4-OOH-IF were additive or synergistic. In contrast, application of 4-OOH-IF before paclitaxel resulted in pronounced antagonism. Based on the sequence-dependent synergistic interactions a phase I trial was initiated with paclitaxel given on day 1 and ifosfamide given on days 2 to 5 in patients with cisplatin-refractory ovarian cancer. Four dose levels were evaluated in 18 patients. The maximum tolerated dose was paclitaxel 175 mg/m2 on day 1 and ifosfamide 2,000 mg/m2 on days 2 to 5, with central nervous system toxicity and nephrotoxicity being dose-limiting. The recommended dose for further evaluation of this combination was paclitaxel 175 mg/m2 on day 1 and ifosfamide 1,500 mg/m2 on days 2 to 5. Although all patients were heavily pretreated with multiple agents, nine of 18 patients achieved an objective response. Ifosfamide also has been shown to reduce cellular glutathione content; thus, a series of experiments evaluated the ability of activated cyclophosphamide or ifosfamide to deplete cellular glutathione in vitro. It was demonstrated that glutathione depletion is dose- and time-dependent, with 4-OOH-IF leading to a more pronounced suppression of cellular glutathione compared with 4-OOH-Cy. The decrease in cellular glutathione content was maximal at 2 hours after drug treatment; however, cellular glutathione levels returned to normal within 24 hours. When 4-OOH-IF was combined in vitro with cisplatin, schedule-dependent interactions again became obvious. The highest antitumor activity was seen when both drugs were given concurrently; sequential application with 4-OOH-IF given before cisplatin resulted in antagonism. Since adequate glutathione levels are necessary for multidrug resistance protein (MRP) function, glutathione depletion might lead to reversal of MRP-mediated drug resistance. Preliminary data showed that 4-OOH-IF significantly decreases glutathione concentrations in MRP-expressing human HT1080/DR4 sarcoma cells, leading to maximum steady-state reduction after a 90-min exposure to 4-OOH-IF. Taken together the data reported here demonstrate that in vitro ifosfamide may potentiate the antitumor activity of a variety of cytotoxic agents and therefore merits further clinical evaluation in drug combinations (eg, taxanes, anthracyclines).

Reversal of MDR1-associated resistance to topotecan by PAK-200S, a new dihydropyridine analogue, in human cancer cell lines

Recent data suggest that expression of the membrane P170-glycoprotein (P-gp) may confer resistance to the topoisomerase-I-interactive agent topotecan. The present study describes the cellular effects of a new dihydropyridine analogue, PAK-200S, on P-gp-mediated resistance to topotecan in human breast and ovarian tumour cells. PAK-200S at a non-cytotoxic concentration of 2.0 microM completely reversed resistance to topotecan in P-gp-expressing MCF-7/adr (breast) and A2780/Dx5 (ovarian) tumour cells, respectively, with no effects on parental cells. Cellular pharmacokinetic studies by reversed-phase high-performance liquid chromatography analysis showed significantly lower cellular drug concentrations of the pharmacologically active closed-ring lactone of topotecan in multidrug-resistant cells than in parental cells. PAK-200S was effective in restoring the cellular lactone concentrations of topotecan in resistant MCF-7/adr cells to levels comparable to those obtained in parental cells. Furthermore, exposure of MCF-7/adr cells to topotecan in the presence of PAK-200S significantly increased the induction of protein-linked DNA breaks. PAK-200S did not alter nuclear topoisomerase I-mediated ex vivo pBR322 DNA plasmid unwinding activity and topoisomerase-I protein expression. These results suggest that reversal of P-gp-mediated resistance to topotecan by PAK-200S was related to the restoration of cellular drug concentrations of the active lactone form of topotecan rather than a direct effect on topoisomerase-I function.

Comparison between short or long exposure to 5-fluorouracil in human gastric and colon cancer cell lines: biochemical mechanism of resistance

Recent preclinical and clinical data indicate that the main mechanisms of 5-fluorouracil (5-FU) cytotoxicity depend on the mode of administration. To gather further insight into the major causes of acquired 5-FU resistance, drug-sensitive human gastric (M2), colon (HT29) and breast (MCF7) cancer cell lines were repeatedly exposed to a fixed concentration of 5-FU given either for 1 or 24 h. Although equieffective doses (IC50) of 5-FU were used, resistance to a 1 h exposure of 5-FU developed faster in all models than to a 24 h exposure. Cell lines with acquired resistance to a 1 h application of 5-FU were only partly cross-resistant to a 24 h exposure, whereas lines with resistance to protracted application of 5-FU displayed significant cross-resistance to the 1 h schedule. Resistance to methotrexate was only seen in cell lines with acquired resistance to 24 h of 5-FU. All 5-FU-resistant cell lines showed reduced incorporation of 5-FU into cellular RNA. Furthermore, elevations of thymidylate synthase were seen in all cell lines with resistance to 24 h of 5-FU but also in one cell line with resistance to a bolus schedule. No alterations in folylpolyglutamate synthase developed in the resistant cell lines. These data support the concept that the main mechanisms of 5-FU cytotoxicity depend on the mode of application. Incorporation of fluorouridine triphosphate into RNA appears to be the most important mechanism of action for 5-FU bolus schedules, whereas inhibition of thymidylate synthase becomes more important as the infusion time is prolonged. These data could have implications on the interaction of 5-FU given at different schedules with various other cytostatic agents.

Activity- and schedule-dependent interactions of paclitaxel, etoposide and hydroperoxy-ifosfamide in cisplatin-sensitive and -refractory human ovarian carcinoma cell lines

Paclitaxel has demonstrated broad clinical activity in a variety of malignancies both alone and in combination with other chemotherapeutic agents. The in vitro cytotoxicity of a 2 h exposure to paclitaxel, hydroperoxy-ifosfamide and etoposide alone, in combination and in sequence, was evaluated against established cisplatin-sensitive and cisplatin-refractory human ovarian carcinoma cell lines using isobologram analysis. The combinations of either paclitaxel-hydroperoxy-ifosfamide or paclitaxel-etoposide were found to be additive or synergistic when the drugs were given simultaneously or when paclitaxel was given 24 h before hydroperoxy-ifosfamide or etoposide respectively. However, when etoposide or hydroperoxy-ifosfamide were given before paclitaxel, antagonistic interactions were observed. With regard to etoposide this antagonism was evident for up to 24 h. In agreement with our data with the schedule-dependent interactions of paclitaxel and cisplatin in human gastric and ovarian carcinoma cell lines, these data demonstrate that the interactions of paclitaxel, etoposide and hydroperoxy-ifosfamide are also highly schedule dependent and applications of etoposide or ifosfamide before paclitaxel may result in pronounced antagonism. These findings could have implications for the design of further clinical protocols.

Activity of N-benzyl-adriamycin-14-valerate (AD198), a new anthracycline derivate, in multidrug resistant human ovarian and breast carcinoma cell lines

The new lipophilic anthracycline N-benzyl-adriamycin-14-valerate (AD198) was evaluated for its activity in comparison to doxorubicin in P-glycoprotein (Pgp)-positive and -negative cell lines. AD198 and doxorubicin showed comparable antitumor activity in the Pgp-negative breast cancer cell line MCF-7 and the Pgp-negative ovarian carcinoma cell line A2780. By contrast, AD198 was significantly more active than doxorubicin in the Pgp-positive breast cancer cell line MCF7AD (IC50 values 2.5 and 0.15 microM for 96 h continuous exposure) and the Pgp-positive ovarian carcinoma cell line A2780 DX5 (IC50 values 0.6 and 0.07 microM, respectively). Unlike doxorubicin, the activity of AD198 was not increased by concommittant application of cyclosporin A in cell line MCF7AD. Flow cytometry studies showed that, in contrast to doxorubicin, AD198 was not transported by Pgp and that verapamil did not change the intracellular pharmacokinetics of this new anthracycline. These data provide evidence that AD198 possesses high activity in human solid tumor cell lines expressing the classical multidrug resistant phenotype. Its further clinical development appears to be warranted.

Schedule-dependent antagonism of paclitaxel and cisplatin in human gastric and ovarian carcinoma cell lines in vitro

Paclitaxel has demonstrated broad clinical activity in a variety of malignancies both alone and in combination with other chemotherapeutic agents. The in vitro cytotoxicity of paclitaxel and cisplatin alone, in combination and in sequence, were evaluated against established human gastric and ovarian carcinoma cell lines using 2-h drug exposure. The combination of cisplatin and paclitaxel was found to be additive or even synergistic when paclitaxel was given 24 h prior to cisplatin as demonstrated by isobologram analysis. However, when both drugs were given simultaneously or when cisplatin was given prior to paclitaxel, a strong antagonistic interaction was observed. This antagonism was evident for up to 72 h after a 2-h exposure to cisplatin. Pretreatment with cisplatin caused no alteration in [3H]paclitaxel uptake in HM2 gastric carcinoma cells, but resulted in decreased intracellular retention of paclitaxel. Since cisplatin treatment led to a reduction in cellular glutathione content in these cells and reduced levels of glutathione have been associated with protection against cytotoxicity of paclitaxel, cells were pretreated with L-buthionine sulfoximine (L-BSO). However, depletion of glutathione had no influence on the activity of paclitaxel. A significant accumulation of cells in S-phase was observed 24 h after cisplatin, which resolved after 48 h and resulted in a pronounced increase of G2M phase. These data demonstrate that the interactions of paclitaxel and cisplatin are highly schedule-dependent and applications of cisplatin simultaneously with or prior to paclitaxel may result in pronounced antagonism. These findings could have implications for the design of further clinical protocols.