Pig-a gene mutation assay study design: critical assessment of 3- versus 28-day repeat-dose treatment schedules.

The in vivo Pig-a assay is being used in safety studies to evaluate the potential of chemicals to induce somatic cell gene mutations. Ongoing work is aimed at developing an Organisation for Economic Cooperation and Development (OECD) test guideline to support routine use for regulatory purposes (OECD project number 4.93). Among the details that will need to be articulated in an eventual guideline are recommended treatment and harvest schedules. With this in mind, experiments reported herein were performed with Wistar Han rats exposed to aristolochic acid I (AA), 1,3-propane sultone, chlorambucil, thiotepa or melphalan using each of two commonly used treatment schedules: 3 or 28 consecutive days. In the case of the 3-day studies, blood was collected for Pig-a analysis on days 15 or 16 and 29 or 30. For the 28-day studies blood was collected on day 29 or 30. The effect of treatment on mutant reticulocytes and mutant erythrocytes was evaluated with parametric pair-wise tests. While each of the five mutagens increased mutant phenotype cell frequencies irrespective of study design, statistical significance was consistently achieved at lower dose levels when the 28-day format was used (e.g. 2.75 vs 20 mg/kg/bw for AA). To more thoroughly investigate the dose-response relationships, benchmark dose (BMD) analyses were performed with PROAST software. These results corroborate the pair-wise testing results in that lower BMD values were obtained with the 28-day design. Finally, mutagenic potency, as measured by BMD analyses, most consistently correlated with the mutagens' tumorigenic dose 50 values when the lengthier treatment schedule was used. Collectively, these results suggest that both 3- and 28-day treatment schedules have merit in hazard identification-type studies. That being said, for the purpose of regulatory safety assessments, there are clear advantages to study designs that utilise protracted exposures.

Toxicity of tandem high-dose chemotherapy and autologous stem cell transplantation using carboplatin-thiotepa-etoposide and cyclophosphamide-melphalan regimens for malignant brain tumors in children and young adults.

The number of studies examining the use of tandem high-dose chemotherapy and autologous stem cell transplantation (HDCT/auto-SCT) to treat high-risk or recurrent brain tumors is increasing. However, studies addressing the toxicity associated with tandem HDCT/auto-SCT, particularly during the second HDCT/auto-SCT, are very limited. For this reason, we retrospectively evaluated the toxicity of tandem HDCT/auto-SCT with carboplatin-thiotepa-etoposide (CTE) and cyclophosphamide-melphalan (CM) regimens when used to treat high-risk or recurrent brain tumors. A total of 109 patients who received a first HDCT/auto-SCT and 100 who proceeded to a second HDCT/auto-SCT between May 2005 and December 2013 were included. Hematologic recovery was rapid during both the first and second HDCT/auto-SCT. In the first HDCT/auto-SCT, mucositis-related gastrointestinal toxicity was frequent, and two (1.8 %) patients died from toxicity [one hepatic veno-occlusive disease (VOD) and one sepsis]. In the second HDCT/auto-SCT, mucositis-related toxicity was milder than in the first round. However, hepatic VOD frequency was high (20.0 %), and six (6.0 %) patients died from toxicity (four hepatic VODs, one asphyxia, and one sepsis). Multivariate analysis indicated that age younger than 8 years was the only significant predictor for hepatic VOD. All six patients who died from toxicity during the second HDCT/auto-SCT were younger than 9 years of age. This study demonstrates that tandem HDCT/auto-SCT using CTE/CM regimens was generally feasible. However, dose reduction during the second HDCT/auto-SCT in young children might be needed to decrease the death rate from toxicity.

Phase I trial of escalating pentoxifylline dose with constant dose thiotepa.

Pentoxifylline, a methylxanthine, is an effective modulator of alkylating agents in tissue culture and in human tumor explants in mice. In this Phase I trial, escalating dose controlled release pentoxifylline was administered p.o. 3 times daily for 5 days (15 doses) with a constant dose of thiotepa, 40 mg/m2 i.v. on day 2. Forty-four courses of escalating doses of pentoxifylline varying from 400 to 2400 mg were administered to 22 patients with refractory malignancies. Gastrointestinal toxicity, consisting mainly of nausea and vomiting, was dose limiting at 2400 mg pentoxifylline and subsided completely within 24 h of cessation of the drug. Nongastrointestinal toxicity of this thiotepa/pentoxifylline combination was infrequent and included bone marrow depression and supraventricular tachycardia. Increasing the dose of pentoxifylline did not increase the frequency of these rare toxic effects. Plasma concentrations of pentoxifylline and its major metabolites were determined by gas chromatography. Drug accumulation was noted within a cycle (i.e., by day 5) in only two patients and between cycles in no patient. The recommended Phase II dose of p.o. pentoxifylline is 1600 mg (four 400-mg tablets) when given 3 times daily for 5 days (15 doses) with 40 mg/m2 i.v. thiotepa. Based on an interspecies comparison, this dose exceeds that predicted from mouse models to enhance chemotherapy. This regimen can be safely administered on an outpatient basis, with adequate control of gastrointestinal symptoms achieved by standard antiemetics and intermittent dosing with meals. Phase II trials are required to determine the activity of alkylator/modulator combinations.

Phase I/pharmacokinetic reevaluation of thioTEPA.

Because the initial evaluation of N,N',N''-triethylenethiophosphoramide (thioTEPA) preceded the standardized approach to the Phase I trials, uncertainty surrounds the recommended dose. Since it has recently been demonstrated that an almost 100-fold increase in dose can be administered in bone marrow transplant regimens, we conducted a Phase I reevaluation of thioTEPA. ThioTEPA was administered i.v. in 50 ml 5% dextrose in water over 10 min. Twenty-seven patients were entered at doses ranging from 30 to 75 mg/m2. The major toxic effect was myelosuppression; thrombocytopenia greater than or equal to grade 3 occurred in four of seven patients, and leukopenia greater than or equal to grade 3 in two of seven patients at 75 mg/m2. Among eight patients at 65 mg/m2 only two had greater than or equal to grade 3 myelosuppression making this the recommended new phase II dose for the majority of patients. Moderate (grade 2) easily controlled nausea and vomiting was the only other major side effect. There was no alopecia or mucosal or neurological toxicity. Three partial remissions were observed among nine previously treated ovarian cancer patients. Plasma concentrations of thioTEPA and its major active metabolite triethylenephosphoramide (TEPA) were measured by gas chromatography. The half-life of thioTEPA ranged from 51.6 to 211.8 min, and its pharmacokinetics was dose dependent; total body thioTEPA clearance decreased with increasing dose. The half-life of TEPA was considerably longer than that of the parent compound (3.0 to 21.1 h); as a result, the area under the plasma concentration-time curve (AUC) of TEPA was severalfold greater than that of the parent compound. The ratio of TEPA AUC to thioTEPA AUC decreased with increasing dose, suggesting that formation of TEPA is a saturable step in elimination. The AUC and total body clearance of thioTEPA, but not of TEPA, were closely correlated with neutrophil but not platelet toxicity.

Cytotoxic, cell cycle, and chromosomal effects of methylxanthines in human tumor cells treated with alkylating agents.

Human tumor cells, like rodent cells, are sensitive to effects of methylxanthines (MEX) on lethality, cell cycle delays, and chromosome aberrations after DNA damage by anticancer drugs. Enhanced cytotoxicity of alkylating agents was observed when T24 human bladder tumor cells in culture were exposed to nontoxic concentrations of MEX such as caffeine or pentoxifylline. Tumor cell lethality was increased up to 10-fold by either caffeine or pentoxifylline (1 mM) present during the first cell cycle (16-24 h) after exposure to nitrogen mustard (HN2) or thiotepa. Cycloheximide, a protein synthesis inhibitor, abolished the enhanced lethality produced by MEX. In these synchronized human tumor cells further kinetic studies revealed that HN2 (0.5 microM X 1 h) delayed transit through S phase by about 1-2 h, and this delay was prevented by MEX. After completion of S phase, HN2-treated cells were delayed 3-6 h in G2, and MEX also prevented this delay, leading to mitoses at the rate of controls. Chromosome analysis of these mitotic cells revealed dramatic increases in aberrations induced by alkylator + MEX combinations. The greatest number of aberrations was seen in HN2-treated cells exposed briefly to MEX in late S-G2. In contrast, no increased chromosome damage was seen in cells exposed to MEX in mid-S phase. Taken together, our results are consistent with the model that MEX enhance lethality of alkylator-treated human tumor cells by preventing delays in cell cycle transit through G2, leading to chromosome aberrations which are lethal. G2 delays in human tumor cells may provide time for repair processes that are critical for survival after sublethal DNA damage by HN2 or other anticancer alkylating agents.

Retrovirus-mediated expression of the base excision repair proteins, formamidopyrimidine DNA glycosylase or human oxoguanine DNA glycosylase, protects hematopoietic cells from N,N',N"-triethylenethiophosphoramide (thioTEPA)-induced toxicity in vitro and in vivo.

Modulation of DNA damage repair activity could lead to new approaches to reduce cytotoxic side effects of chemotherapy. N,N',N"-Triethylenethiophosphoramide (thioTEPA) induces the formation of amino-ethyl adducts of guanine, resulting in imidazole ring opening [formamidopyrimidine (Fapy)] and is associated with significant myelosuppression in dose-intensive therapies. In Escherichia coli, Fapy lesions are repaired by the Fapy-DNA glycosylase (Fpg) protein. We hypothesized that the expression of the Fpg could increase resistance of hematopoietic cells to thioTEPA-induced cytotoxicity. Expression of Fpg in bone marrow (BM) cells via a retrovirus vector was associated with demonstrable 8-oxodeoxyguanosine DNA glycosylase activity. BM cells were infected with a recombinant retrovirus, SF91, containing the Fpg gene and expressing the enhanced green fluorescence protein (EGFP) via an internal ribosomal entry site element. Control mice received BM transduced with the backbone containing IRES-EGFP alone. Fpg-transduced and GFP+ BM hematopoietic cells were resistant in vitro to thioTEPA at multiple concentrations. Mice transplanted with transduced cells were treated with four doses of thioTEPA (10 mg/kg) given over 7 weeks. Despite low transduction efficiency, peripheral blood leukocytes, hemoglobin, and platelet counts of thioTEPA-treated Fpg mice were significantly higher than treated control mice (P < 0.05). In addition, after treatment, the BM, spleen, and thymic cellularity as well as the number of GFP+ progenitor cells in the BM of treated mice were significantly higher than those of control group. Selection of Fpg-transduced cells in vivo was demonstrated by an increase in the mean fluorescence intensity of peripheral mononuclear cells of Fpg mice compared with pretreatment value. In addition, a significant increase in the EGFP-bright cells was demonstrated, suggesting preferential survival of high-expressing hematopoietic cells. Similar results were demonstrated in vitro with primary BM expressing the human functional counterpart of Fpg, OGG1. These results show that expression of the Fpg or hOGG1 protein protects hematopoietic cells from thioTEPA-induced DNA damage and suggest that a high level of expression of these repair proteins is required to establish resistance to this drug. Expression of Fpg and/or OGG1 may provide an novel approach to preventing thioTEPA-induced toxicity of primary hematopoietic cells.

Evaluation of single-dose RBC Pig-a and PIGRET assays in detecting the mutagenicity of thiotepa in rats.

The Pig-a assay, which uses reticulocytes (PIGRET assay) as target cells, is anticipated to detect mutagenicity at earlier time points than the RBC Pig-a assay, which uses all red blood cells as target cells. As part of a collaborative study conducted by the Mammalian Mutagenicity Study (MMS) Group, we evaluated the PIGRET and RBC Pig-a assays to detect Pig-a gene mutations induced by the carcinogen thiotepa. A single dose of thiotepa at 7.5, 15, and 30mg/kg was administered to 8-week-old male Sprague-Dawley rats by oral gavage. PIGRET and RBC Pig-a assays were performed using peripheral blood collected from rats 7, 14, and 28days after thiotepa administration (Day 0 as the day of administration), and the resulting Pig-a mutant frequencies (MFs) were compared. Increased Pig-a MF was observed from Day 7 onwards using the PIGRET assay. Pig-a MF remained fairly constant thereafter until Day 28 in the 30mg/kg group, whereas it peaked on Day 14 in the 7.5 and 15mg/kg groups. Using the RBC Pig-a assay, on the other hand, no significant increase in MF was observed at any of the dosages on Days 7, 14, or 28. These findings show that Pig-a gene mutations following a single dose of thiotepa were detected using the PIGRET assay but not the RBC Pig-a assay, which suggests that PIGRET assay is more suitable than RBC Pig-a assay for evaluating the in vivo mutagenicity by a single dose.

A phase I-II study of bialkylator chemotherapy, high-dose thiotepa, and cyclophosphamide with autologous bone marrow reinfusion in patients with advanced cancer.

Twenty patients with disseminated cancer both untreated and previously treated received bialkylator chemotherapy, thiotepa, and cyclophosphamide and reinfusion of cryopreserved autologous bone marrow (ABMR). The cyclophosphamide dose was constant at 7.5 g/m2 over three days, while thiotepa was started at 1.8 mg/kg for three days in escalating dose by a modified Fibonacci schema to 7 mg/kg. The median time to recovery of more than 500 granulocytes and more than 50,000 platelets/microL was 18 and 27 days, respectively. Four patients died as a consequence of severe, overwhelming infections or progressive disease during their period of aplasia. Of the 18 evaluable patients, a complete response (CR) was achieved in three patients and a partial response (PR) in ten patients for an overall response rate of 72%. The median duration of response was 14 weeks. Other nonhematologic toxicities included nausea/vomiting, diarrhea, stomatitis, skin rash, and cardiomyopathy. The maximum tolerated dose (MTD) of thiotepa was 700 mg/m2 or 6 mg/kg for three doses. Although there are substantial toxicities associated with this regimen, high-dose thiotepa and cyclophosphamide produce high response rates in patients with disseminated cancer.

High-dose busulfan and thiotepa followed by autologous stem cell transplantation (ASCT) in previously irradiated medulloblastoma patients: high toxicity and lack of efficacy.

We previously demonstrated that Busulfan-Thiotepa (Bu-Thio) and ASCT effectively treated patients with locally relapsed medulloblastoma after surgery and conventional chemotherapy. We thus evaluated the administration of Bu-Thio in patients relapsing after conventional CNS irradiation. Patients were scheduled to receive Busulfan (600 mg/m(2)) and Thiotepa (900 mg/m(2)) and ASCT. Resection of residual tumour and additional irradiation were performed if necessary and feasible after Bu-Thio. Toxicity was compared to that observed in 35 patients treated without previous CNS irradiation. From 5/88 to 3/02, 15 patients were treated according to this strategy. Toxicity was significantly higher than that observed in unirradiated patients: thrombocytopenia <50,000/mm(3) lasting 56 days (13-732) (P=0.02) and 30 days (4-124), respectively, HVOD (10/15 and 12/35 patients, respectively) (P=0.06), neurological toxicity (8/15 vs 3/35 patients) (P=0.01). Tumour response was assessable in seven patients and consisted in two CR, three PR and two NR. Currently, two of 15 patients are alive with no evidence of disease. In conclusion, the toxicity of Bu-Thio was significantly more severe in previously irradiated patients. In spite of a high response rate, this strategy failed to improve the prognosis of previously irradiated patients with a relapse from a medulloblastoma.

Megakaryocyte DNA content and platelet formation in rats after a sublethal dose of thio-TEPA.

The megakaryocytopoiesis in rats was studied following a single dose of thio-TEPA to determine the mechanisms for the thrombocytopenia and subsequent recovery. The blood platelet number, platelet production (measured by 35S incorporation into platelets), mean platelet volume, and the number and DNA content of bone marrow megakaryocytes (MK) were observed. The blood platelet counts, platelet production, and total MK number decreased to low values following the administration of thio-TEPA, and stayed low until regeneration started around day 10. The mean platelet volume increased from the normal 6.6 fl to 7.8 fl during the early regeneration days 8-14. The MK were divided into four ploidy classes: 2N-4N, 8N, 16N, and 32N-64N. The number of MK within all ploidy classes decreased to nearly zero within four days after the injection of thio-TEPA. The regeneration started around day 10 with increasing numbers of 2N-4N and 8N MK, while the number of 16N and 32N-64N MK increased more than four days later. It is concluded that decreased or blocked influx of progenitor cells into the MK compartment is the main reason for thrombocytopenia after exposure to thio-TEPA.

Induction of Pig-a mutant erythrocytes in male and female rats exposed to 1,3-propane sultone, ethyl carbamate, or thiotepa.

Validation of the Pig-a gene mutation assay has been based mainly on studies in male rodents. To determine if the mutagen-induced responses of the X-linked Pig-a gene differ in females compared to males, groups of five male and female Sprague Dawley rats were exposed to the mutagens 1,3-propane sultone (80mg/kg/day), ethyl carbamate (600mg/kg/day), or thiotepa (7.5mg/kg/day) for three consecutive days (study days 1-3). Pig-a mutant phenotype reticulocyte (RET(CD59-)) and mutant phenotype erythrocyte (RBC(CD59-)) frequencies were determined on study days -4, 15, 30 and 46 using immunomagnetic separation in conjunction with flow cytometric analysis (In Vivo MutaFlow(®)). While the percentage of reticulocytes (%RET) was markedly higher for pre-treatment blood samples from males compared to females (6.6% vs. 3.5%), this sex effect was slight or nonexistent at later time points. Treatment-related effects to %RET were generally modest owing to the 12-day interval between last exposure and blood sampling. Mean RET(CD59-) and RBC(CD59-) frequencies were consistently low in vehicle control animals of both sexes, with 77% of samples exhibiting mutant cell frequencies ≤1×10(-6) over study days 15-46. Treatment with each mutagen caused significant increases to mean RET(CD59-) and RBC(CD59-) frequencies. Whereas genotoxicant-induced RET(CD59-) values were maximal on day 15, induced RBC(CD59-) frequencies were highest at the last sampling time. Sex did not affect 1,3-propane sultone- or thiotepa-induced mutant cell frequencies. While ethyl carbamate-exposed females exhibited higher mean mutant cell frequencies compared to like-treated males, statistical significance was achieved only for RBC(CD59-) at one time point (7.6±1.0×10(-6) compared to 4.7±0.6×10(-6) on day 30). Thus, while some quantitative differences were evident, there were no qualitative differences in how males and females responded to three diverse mutagens. These data support the use of both sexes for Pig-a gene mutation studies.

Reduced-intensity conditioning regimen with thiotepa and fludarabine followed by allogeneic blood stem cell transplantation in haematological malignancies.

The aim of this study was to investigate thiotepa (TT) and fludarabine (Fluda) as a preparative regimen for allogeneic peripheral stem cell transplant in patients not eligible for a standard myeloablative regimen due to comorbidities and/or poor performance status. TT was given at a dose of 10 mg/kg over 2 days and Fluda at 125 mg/m(2) over 5 days. In all, 21 patients (14 male, seven female; 10 acute leukaemia, eight myelodysplastic syndrome, two non-Hodgkin's lymphoma, one Hodgkin's disease) were treated. The median age was 51 years (range 30-55 years). All patients achieved full donor-type chimaerism. Adverse events included mild nausea and vomiting in two patients and a slight increase of serum amylase in three. A total of 13 patients received RBC transfusions (median 6 U, range 1-23), and all received platelets (median 4 U, range 1-27). Four patients died of nonrelapse causes and five of relapse. The 1-year probabilities of transplant-related mortality and relapse were 19 and 29%, respectively. In total, 12 patients remain in complete remission (median follow-up: 786 days). The 3-year overall survival probability was 58%. We conclude that this regimen is feasible and well tolerated.

Severe cardiac toxicity in hematological stem cell transplantation: predictive value of reduced left ventricular ejection fraction.

Eighty patients receiving hematological stem cell transplantation (HCT) with a preparative regimen consisting of total body irradiation (12.5 Gy), cyclophosphamide (4000 or 4500 mg/m2), and thiotepa (400 mg/m2) were evaluated for the development of cardiac toxicity. Patients in whom the pretransplant cumulative dose of anthracycline was more than or equal to 300 mg/m2 showed a lower left ventricular ejection fraction (EF) before HCT compared to patients with less than 300 mg/m2 (0.61 +/- 0.09 vs 0.67 +/- 0.06, P = 0.0010). Patients who had undergone more than or equal to six courses of chemotherapy showed a decreased EF before HCT compared to those after less than six courses (0.67 +/- 0.05 vs 0.63 +/- 0.09, P = 0.03). Three of seven patients (43%) whose pretransplant EF had been less than or equal to 0.55 developed severe cardiac toxicity, characterized by congestive heart failure (CHF) compared with none of 83 patients (0%) whose pretransplant EF had been more than 0.55 (P = 0.00026). Of the three patients who developed severe cardiac toxicity, two were given more than 300 mg/m2 of cumulative anthracycline and underwent 23 courses and six courses of chemotherapy, while the other patient received only two courses of chemotherapy with a total dose of 139 mg/m2 of anthracycline. These results indicate that an increased cumulative dose of anthracycline and number of chemotherapy treatments are correlated with a decrease of the EF and that the EF before HCT is useful for predicting the risk of cardiac complications for recipients who have received chemotherapy.

Safety and outcome after fludarabine-thiotepa-TBI conditioning for allogeneic transplantation: a prospective study of 30 patients with hematologic malignancies.

Fludarabine, thiotepa and total body irradiation (TBI) has been used as conditioning in haplo-identical transplantation. We studied this conditioning regimen in adults undergoing matched sibling transplantation and alternative donor transplantation. A total of 30 consecutive patients underwent matched related, haplo-identical related or matched unrelated donor transplantation with fludarabine, thiotepa and TBI conditioning. All but four had advanced hematologic malignancies. For haplo-identical transplant, ATG was added to the regimen. All patients received peripheral blood stem cells; these were T-cell depleted for 2-antigen or 3-antigen mismatched related transplantation. Additional graft-versus-host disease prophylaxis consisted of tacrolimus and mini-methotrexate. One recipient of haplo-identical transplant failed to engraft; all other evaluable patients had prompt engraftment. Four patients died of regimen-related toxicity. In all, 14 additional patients died of regimen-related causes including four from failure to thrive with persistent thrombocytopenia and four from delayed pulmonary toxicity. Six patients relapsed. Progression-free survival at 12 months was 47% (90% CI: 25-69%) for recipients of HLA-identical sibling transplants and 30% (90% CI: 14-46%) for all patients. Five of six long-term survivors have extensive chronic GVHD. As a result of the delayed complications and a relatively high recurrence rate, we abandoned this regimen.

High-dose carmustine, thiotepa and etoposide followed by autologous bone marrow rescue for the treatment of high risk central nervous system tumors.

Forty-two patients (29 newly diagnosed) with high grade gliomas (n = 37), medulloblastoma (n = 2) or non-biopsied tumors (n = 3) with supratentorial (n = 24), brain stem (n = 11), posterior fossa (n = 5) or spinal (n = 2) location were eligible for this study with adequate organ function and no bone marrow tumor infiltration. Median patient age was 12.2 years (range, 0.7-46.8). A total of 600 mg/m2 BCNU, 900 mg/m2 thiotepa and 1500 or 750 mg/m2 etoposide (VP-16) was administered followed by autologous bone marrow reinfusion (ABMR). Twenty-one newly diagnosed patients received local irradiation (RT) post ABMR. Nine early deaths were observed (21%), as well as one secondary graft failure. Half of the patients aged 18 years or older experienced toxic deaths, whereas only 15% of patients younger than 18 years experienced toxic death (P = 0.05). Of 25 evaluable newly diagnosed patients, 20% achieved complete remission (CR) and 4% partial remission (PR), while 28% remained in continuing complete remission (CCR) and 44% remained with stable disease prior to RT. Of eight evaluable patients with recurrent disease, one achieved CR and two PR, while one remained in CCR and four with stable disease for 1 to 110.2 months. Overall survival was 36%, 24% and 17% at 1, 2 and 3 years following ABMR, with three newly diagnosed patients and one patient treated for recurrent disease being alive, without disease progression 64.4, 67.0, 86.3 and 110.2 months after ABMR, respectively. The combination of high-dose BCNU/ thiotepa/VP-16 has substantial toxicity but definite activity for high risk CNS tumors. Similar protocols with lower toxicity merit further evaluation in both newly diagnosed and recurrent CNS tumors.

Thiotepa, busulfan, cyclophosphamide (TBC) and autologous hematopoietic transplantation: an intensive regimen for the treatment of multiple myeloma.

The study was designed to evaluate the efficacy and safety of an intensive, tri-alkylator conditioning regimen, consisting of thiotepa, busulfan and cyclophosphamide (TBC), prior to autologous hematopoietic cell transplantation in patients with multiple myeloma (MM) and to analyze factors associated with outcome. One hundred and twenty patients with MM received high-dose chemotherapy with TBC followed by autologous bone marrow (n = 24) or peripheral blood stem cell (PBSC) transplantation (n = 96). Fifty-four patients had chemosensitive disease and 66 had refractory disease at the time of transplantation. The overall response rate was 81% and the complete remission (CR) rate was 26%. Patients with chemosensitive disease had a CR rate of 52% vs 5% for patients with refractory disease. Multivariable analysis determined disease status at transplant as the factor most likely associated with long survival. Estimated median survival was 48, 35 and 9 months for patients with chemosensitive, primary refractory or disease in refractory relapse, respectively. Short interval from diagnosis to transplant among patients with primary refractory disease and younger age were also favorable prognostic factors for survival. Patients with refractory disease pre-transplant who achieved remission criteria rapidly after treatment had a worse outcome than the slow responders. Treatment-related mortality with the introduction of PBSC and better supportive care was 4.8%. In conclusion, TBC is an effective and relatively well-tolerated intensive conditioning regimen in patients with MM. A more favorable outcome was observed in patients with chemosensitive disease and with early treatment for primary refractory disease. TBC merits further study in these subgroups and comparison with alternative regimens in prospective studies is warranted.

Thiotepa improves allogeneic bone marrow engraftment without enhancing stem cell depletion in irradiated mice.

Thiotepa (TT) has long been considered for inclusion in clinical bone marrow transplant (BMT) conditioning regimens in an attempt to prevent allograft rejection and leukemia relapse. These studies have been encouraged by initial murine experiments showing a clear improvement in allogeneic bone marrow engraftment with addition of TT to total body irradiation (TBI) where it was assumed that TT enhances donor-type chimerism via ablation of competing stem cells in the recipient. The aim of the present study was to re-evaluate the hematological toxicity of TT among different stem cell subsets that included primitive cells capable of long-term repopulation and to assess how the combination of TT with TBI influences the development of donor engraftment in both syngeneic (B6-Gpi-1a --> B6-Gpi-1b) and H-2 compatible allogeneic (BALB.B10 --> B6) BMT models. At 24 h after TT (20 mg/kg) the femoral content of different stem cell subsets was determined from the frequency of transient repopulating, and the more primitive cobblestone area-forming, cells (CAFCs) growing in stroma-supported cultures. This assay showed a large TT-induced depletion (2% survival) of early clones developing at day 7 in culture but survival recovered towards normal for later appearing clones developing from more primitive CAFC subsets. The sparing of these primitive stem cells was reflected as undetectable levels of donor marrow repopulation in recipients given TT followed by syngeneic BMT. Addition of TT to TBI did not significantly improve long-term engraftment of syngeneic marrow while this combination had a dramatic effect in allogeneic BMT by preventing allograft rejection. In this respect TT shares similar properties with cyclophosphamide and suggests that the large improvement of allogeneic stem cell engraftment is attributable to the immune suppressive properties of TT rather than to its toxicity against host primitive stem cells.

Phase II trial of sequential high-dose chemotherapy with paclitaxel, melphalan and cyclophosphamide, thiotepa and carboplatin with peripheral blood progenitor support in women with responding metastatic breast cancer.

A single high-dose cycle of chemotherapy can produce response rates in excess of 50%. However, disease-free survival (DFS) is 15-20% at 5 years. The single most important predictor of prolonged DFS is achieving a complete response (CR). Increasing the proportion of patients who achieve a complete response may improve disease-free survival. Women with metastatic breast cancer and at least a partial response (PR) to induction chemotherapy received three separate high-dose cycles of chemotherapy with peripheral blood progenitor support and G-CSF. The first intensification was paclitaxel (825 mg/m(2)), the second melphalan (180 mg/m(2)) and the third consisted of cyclophosphamide 6000 mg/m(2) (1500 mg/m(2)/day x 4), thiotepa 500 mg/m(2) (125 mg/m(2)/day x 4) and carboplatin 800 mg/m(2) (200 mg/m(2)/day x 4) (CTCb). Sixty-one women were enrolled and 60 completed all three cycles. Following the paclitaxel infusion most patients developed a reversible, predominantly sensory polyneuropathy. Of the 30 patients with measurable disease, 12 converted to CR, nine converted to a PR*, and five had a further PR, giving an overall response rate of 87%. The toxic death rate was 5%. No patient progressed on study. Thirty percent are progression-free with a median follow-up of 31 months (range 1-43 months) and overall survival is 61%. Three sequential high-dose cycles of chemotherapy are feasible and resulted in a high response rate. The challenge continues to be maintenance of response and provides the opportunity to evaluate strategies for eliminating minimal residual disease.

A phase II study of two cycles of high-dose chemotherapy with autologous stem cell support in patients with metastatic breast cancer who meet eligibility criteria for a single cycle.

Multi-cycle high-dose chemotherapy with autologous stem cell support (HDC-ASCS) may improve the results obtained with single-cycle HDC-ASCS in metastatic breast cancer (MBC). However, the tolerability and efficacy of additional cycles of HDC-ASCS in patients selected using standard eligibility criteria for single cycle HDC-ASCS is uncertain. Twenty-nine patients with MBC and a CR or PR to induction chemotherapy were selected by standard institutional eligibility criteria for single-cycle HDC-ASCS. Cycle 1 HDC-ASCS (cyclophosphamide 6 g/m2; mitoxantrone 70 mg/m2; carboplatin 800 mg/m2) was followed by a planned second cycle (etoposide 1.6 g/m2; thiotepa 800 mg/m2; carboplatin 800 mg/m2 modulated by tamoxifen 120 mg/m2/day x 5 days) with a median interval of 3.2 months. CR rate was 20% after induction chemotherapy and 33% and 54% after HDC cycles I and II, respectively. Sixteen patients (55%) failed to complete HDC cycle II within 200 days because of disease progression, toxicity, inadequate stem cell collection, insurance denials or patient choice. Median progression-free survival (PFS) for all 29 patients entered is 301 days from date of HDC cycle I and actuarial PFS at 2 years is 35%. For the 13 patients who received the two cycles of HDC-ASCS, actuarial PFS at 2 years was 54% (P = NS compared to those receiving only one cycle). These data show that a second cycle of full-dose intensity HDC-ASCS may increase the proportion of patients with MBC that achieve CR and may increase PFS. However, a large proportion of patients that complete HDC-ASCS cycle I may fail to proceed to cycle II in a timely fashion. Bone Marrow Transplantation (2000) 25, 519-524.

Prophylaxis of bladder tumor implantation. Intravesical and systemic chemotherapy.

Several antitumor agents have been evaluated for their effectiveness in reducing the implantation and progressive growth of transitional cell carcinoma in an animal model. This system allows the evaluation of both the topical cytotoxic action as well as the systemic toxicity of the drugs given intravesically. Systemic cyclophosphamide and intravesical epipodophyllotoxin significantly reduced the incidence of tumor cell implantation.