[A check-list in order to optimise the deployment of computerized medicine cabinets in a hospital: An essential support]

In the medication management process, storage methods constitute a step at risk of errors that needs to be secured. As part of an institutional project, computerized medicine cabinets (CMC) have been deployed in our hospital's emergency and intensive care units. In order to meet the requirements of the certification, the deployment of CMC in all care units has been decided. Each deployment includes many steps and involves several trades that must be coordinated. We decided to formalize these steps in the form of a checklist. Two pharmacists listed all the tasks required to install a CMC. They were ordered chronologically, and a person responsible for each step is proposed. All those involved in the installation of CMC in the care units validated the checklist. The checklist is broken down into 13 major steps, from the assessment of the need to the installation of CMC in the care units. Before installation, several months are required, particularly in terms of the delivery time of the CMC. Support and training for the pharmacy technicians and caregivers are essential to ensure the teams enrolment. By better implying and empowering all intervenants, directed by the pharmacist, the checklist provides to dynamise and to frame the CMC deployment. Moreover, it contributes to save time and to improve the management of every ongoing deployments.

Ambulatory high-dose methotrexate administration as central nervous system prophylaxis in patients with aggressive lymphoma

High-dose methotrexate (HD-MTX) at 3 g/m² is one of the strategies for central nervous system (CNS) prophylaxis in the first-line treatment of aggressive lymphomas, especially in diffuse large B cell lymphoma patients with high-risk CNS-International Prognostic Index. The objective of our study was to retrospectively analyze the safety of 2 cycles of systemic HD-MTX administered as an ambulatory regimen. Between January 2013 and December 2016, 103 patients were carefully selected on 6 criteria, including age < 60, albumin > 34, performance status 0 or 1, normal renal and hepatic functions, good understanding of practical medical guidance, and no loss of weight. Strict procedures of HD-MTX infusion were observed including alkalinization, urine pH monitoring, and leucovorin rescue. Renal and hepatic functions were monitored at days 2 and 7. MTX clearance was not monitored. Toxicities and grades of toxicity were collected according to the NCI-CTCAE (version 4.0). Among the 103 selected patients, 92 (89%) patients successfully completed the planned 2 cycles of HD-MTX on an outpatient basis. Eleven patients completed only 1 cycle, 3 because of lymphoma progression and 8 because of toxicity including 3 grade II hepatotoxicity, 2 grade I/II renal toxicity, 1 grade III neutropenia, 1 active herpetic infection, and 1 grade III ileus reflex. Reported adverse events (AE) included 92 (84%) grade I/II and 18 (16%) grade III/IV. Grade III hepatotoxicity, mostly cytolysis, was the most frequent AE observed with 8 (8%) events. Grade III/IV hematologic toxicities concerned 9 patients with 8 grade III/IV neutropenia and 1 thrombocytopenia. Renal toxicity was rare, mild, and transient, observed with 4 (4%) grade I/II events. Ambulatory administration of HD-MTX at 3 g/m² without MTX clearance monitoring is safe with strict medical guidance. It requires careful selection of patients before administration, and a renal and hepatic monitoring after the administration.

Management of cancer-related thrombosis in the era of direct oral anticoagulants: A comprehensive review of the 2019 ITAC-CME clinical practice guidelines. On behalf of the Groupe Francophone Thrombose et Cancer (GFTC)

Venous thromboembolism (VTE) is a common disease complication in cancer patients and the second cause of death after cancer progression. VTE management and prophylaxis are critical in cancer patients, but effective therapy can be challenging because these patients are at higher risk of VTE recurrence and bleeding under anticoagulant treatment. Numerous published studies report inconsistent implementation of existing evidence-based clinical practice guidelines (CPG), including underutilization of thromboprophylaxis, and wide variability in clinical practice patterns across different countries and various practitioners. This review aims to summarize the 2019 ITAC-CME evidence-based CPGs for treatment and prophylaxis of cancer-related VTE, which include recommendations on the use of direct oral anticoagulants specifically in cancer patients. The guidelines underscore the gravity of developing VTE in cancer and recommend the best approaches for treating and preventing cancer-associated VTE, while minimizing unnecessary or over-treatment. Greater adherence to the 2019 ITAC guidelines could substantially decrease the burden of VTE and improve survival of cancer patients.

Mutagenicity assessment of environmental contaminations in a hospital centralized reconstitution unit

INTRODUCTION

Cytotoxic drug exposure of hospital staff preparing intravenous chemotherapy is a major issue and related mutagenic risks should be more explored. The aim of this study was to assess the mutagenicity of several cytotoxic mixtures prepared at fixed concentrations, and the mutagenicity of environmental samples collected in a hospital centralized reconstitution unit. In parallel cytotoxic exposure in environmental samples was quantified.

METHODS

Environmental samples were performed by wiping method using swabs in five critical production unit areas. Mutagenicity was assessed with a liquid microplate AMES test using two salmonella typhimurium strains (TA98 and TA100), in prepared cytotoxic mixtures containing 14 cytotoxic drugs (cyclophosphamide, cytarabine, dacarbazine, docetaxel, doxorubicin, epirubicin, etoposide, 5-fluorouracil, gemcitabine, ifosfamide, irinotecan, methotrexate, paclitaxel and pemetrexed) according a dichotomous strategy and in environmental samples. Cytotoxic drugs were quantified in samples using liquid chromatography coupled to mass tandem spectrometry.

RESULTS

Mutagenesis was observed for the mix of 14 cytotoxic drugs with TA98 strain ± S9 fraction but not TA100 strain. After dichotomous approach, only doxorubicin and epirubicin exposure were associated to mutagenesis. The mutagenesis observed was expressed at lower concentrations with the mix of the 14 drugs than with anthracyclins alone, assuming a synergistic effect. Despite measurable level of cytotoxic contamination in environmental samples, no mutagenesis was highlighted in Ames tests performed on these environmental samples.

CONCLUSIONS

The analyses carried out show the conservation of the mutagenicity of cytotoxic drugs found in very low quantities in the environment. The traces of cytotoxic drugs found in our unit regularly exceed the limits given by some authors. This approach may be considered as a new tool to monitor environmental contamination by cytotoxic drugs.

[Implementation and assessment of anticancer drugs batch preparation circuit in a teaching hospital]

INTRODUCTION

In 2011, the anticancer preparation unit in a teaching hospital implemented a circuit for batch preparation of anticancer drugs. In this circuit, a manual and a semi-automatic production process coexist. The aim of the study is to describe the circuit in 2016 and to assess the impact of batch preparation in a anticancer preparation unit.

MATERIAL AND METHODS

Eligible anticancer drugs for batch preparation satisfy two conditions: solution stability up to 28 days, prescription frequency up to one every two days. Batch worksheets are standardized. The pharmaceutical validation relies on the conformity of microbiological, analytical, gravimetric and visual controls of infusion bags. The duration of manual and semi-automatic batch preparation process and the time availability of an infusion bag were assessed.

RESULTS

In 2016, eleven anticancer drugs (33 dosages) were eligible for batch preparation: it represents 22% of total production. In total, 70% was semi-automatic. The mean batch sizes were 27±9 (semi-automatic) and 14±1 (manual). The mean duration of production process was respectively 78min and 113min for semi-automatic and manual batch preparation. The mean time availability of an infusion bag was 32min±17.

DISCUSSION AND CONCLUSION

Our process is secure. Batch preparation of anticancer drugs contributes to smooth production and spare nurses from preparing infusion bags outside opening hours of the anticancer preparation unit. Eligible anticancer drugs and batches size change constantly according to the evolution of prescription frequencies and anticancer drugs public tenders.

Major bleeding complications in patients treated with direct oral anticoagulants: One-year observational study in a Paris Hospital

Direct oral anticoagulants (DAOC) are indicated for the treatment of venous thromboembolism and the prevention of stroke or systemic embolism in patients with non-valvular atrial fibrillation. Given their advantages and friendly use for patient, the prescription of long term DOAC therapy has rapidly increased both as first line treatment while initiating anticoagulation and as a substitute to vitamins K antagonist (VKA) in poorly controlled patients. However, DOAC therapy can also be associated with significant bleeding complications, and in the absence of specific antidote at disposal, treatment of serious hemorrhagic complications under DOAC remains complex. We report and discuss herein five cases of major hemorrhagic complications under DOAC, which were reported to the pharmacological surveillance department over one year at Saint-Louis University Hospital (Paris, France). We further discuss the need for careful assessment of the risk/benefit ratio at time of starting DOAC therapy in daily clinical practice.

One-year metreleptin improves insulin secretion in patients with diabetes linked to genetic lipodystrophic syndromes

Recombinant methionyl human leptin (metreleptin) therapy was shown to improve hyperglycaemia, dyslipidaemia and insulin sensitivity in patients with lipodystrophic syndromes, but its effects on insulin secretion remain controversial. We used dynamic intravenous (i.v.) clamp procedures to measure insulin secretion, adjusted to insulin sensitivity, at baseline and after 1 year of metreleptin therapy, in 16 consecutive patients with lipodystrophy, diabetes and leptin deficiency. Patients, with a mean [± standard error of the mean (s.e.m.)] age of 39.2 (±4) years, presented with familial partial lipodystrophy (n = 11, 10 women) or congenital generalized lipodystrophy (n = 5, four women). Their mean (± s.e.m.) BMI (23.9 ± 0.7 kg/m(2) ), glycated haemoglobin levels (8.5 ± 0.4%) and serum triglycerides levels (4.6 ± 0.9 mmol/l) significantly decreased within 1 month of metreleptin therapy, then remained stable. Insulin sensitivity (from hyperglycaemic or euglycaemic-hyperinsulinaemic clamps, n = 4 and n = 12, respectively), insulin secretion during graded glucose infusion (n = 12), and acute insulin response to i.v. glucose adjusted to insulin sensitivity (disposition index, n = 12), significantly increased after 1 year of metreleptin therapy. The increase in disposition index was related to a decrease in percentage of total and trunk body fat. Metreleptin therapy improves not only insulin sensitivity, but also insulin secretion in patients with diabetes attributable to genetic lipodystrophies.

[Study impacto: Descriptive analyzis of pharmacist's clinical practice in onco-hematology]

Pharmaceutical analyses of chemotherapy prescriptions by hospital pharmacists are activities codified by regulation and rules (bon usage). The involvement of the pharmacists in clinical pharmacy activities in the oncology setting is not clearly identified, justifying the development of a mapping of these activities from a questionnaire addressed to the professionals. One hundred and seven centers have participated to this study at the national level (overall participation rate of 32.4%). More than 95% of them used a computerized ordering system and three quarter of them submit the introduction of new compounds to an analysis by the drug therapeutic committee. Prescription analysis allowed detecting around 2% of errors from the current prescription. Clinical pharmacist participates to tumor boards of onco-hematology (RCP) at a level of 46% for senior pharmacist and 42% for junior pharmacist. This involvement in the RCP allowed anticipating protocol's modification and temporary used authorization. Ninety-two percent of the senior pharmacists estimate that they highlight the risk of no reimbursement for prescription out of the guideline during RCP, resulting to a modification of the prescription for 40% of them. This level of intervention is lower with respectively 64% and 10% for the juniors. This study underlines the expert value of the clinical pharmacist dedicated to oncology setting in pre and post analysis prescriptions. It could be targeted by a prospective analysis of both clinical and pharmacoeconomics impact of these interventions.

Long-term efficacy and safety of alemtuzumab in advanced primary cutaneous T-cell lymphomas

BACKGROUND

Alemtuzumab has been proposed as salvage therapy for refractory cutaneous T-cell lymphomas (CTCLs). Long-term follow-up data are scarce.

OBJECTIVES

To assess the efficacy and safety of alemtuzumab in the treatment of advanced CTCL.

METHODS

A multicentre retrospective analysis was carried out of 39 patients with advanced CTCL treated with alemtuzumab between 2003 and 2013.

RESULTS

Thirty-nine patients (median age 62 years, range 20-83) with Sézary syndrome (SS, n = 23) or advanced mycosis fungoides (MF, n = 16) received alemtuzumab 30 mg two to three times per week for a median duration of 12 weeks (range 1-35). Fifteen patients received maintenance therapy for a median duration of 24 weeks (range 6-277). Eleven patients (28%) had transformed disease (MF, n = 10; SS, n = 1). After a median follow-up of 24 months (range 0.3-124), eight patients (21%) were still alive. The overall response rate was 51% in the whole study group (partial response, n = 13; complete response, n = 7); 70% in patients with SS and 25% in patients with MF (P = 0.009). The median time to progression was 3.4 months (range 0.4-42). Six patients (15%; SS, n = 5; MF, n = 1) remained progression free for > 2 years (median 56 months, range 28-117). Five patients experienced cutaneous large T-cell transformation during alemtuzumab treatment and one patient developed primary cutaneous large B-cell lymphoma. Twenty-four patients (62%) had a grade three or higher infectious adverse event and 10 (26%) a haematological toxicity, which led to treatment discontinuation in 17 cases (44%) and death in two (5%).

CONCLUSIONS

Alemtuzumab may induce long-term remission in SS but seems ineffective in MF and transformed CTCL.

The relationship between introduction of American society of clinical oncology guidelines and the use of colony-stimulating factors in clinical practice in a Paris university hospital

BACKGROUND

Clinical practice guidelines are issued periodically by professional medical societies or committees to assist practitioners in clinical decision making. However, it is unclear whether such guidelines have any lasting impact on clinical practice.

OBJECTIVE

The purpose of this study was to assess the impact of the American Society of Clinical Oncology (ASCO) guidelines regarding use of hematopoietic colony-stimulating factors (CSF) on cancer care in a university hospital in Paris.

METHODS

The study was performed at Hĵpital Tenon, an 830-bed university hospital in Paris, in 1996 and 1997, both before and after the ASCO guidelines were implemented. The guidelines were first disseminated as a continuing medical education program and then actively implemented using a CSF prescription order form summarizing the guidelines. This form had to be used during the patient consultation and was sent to the Hĵpital Tenon pharmacy for CSF dispensation. Even if CSF use did not comply with the ASCO guidelines, the pharmacy filled the prescription. Seven other university hospitals in Paris, where the ASCO guidelines were not actively implemented, comprised the control group. The main outcome measure was the proportion of prescriptions in compliance with the 1996 update of the ASCO guidelines. Secondary outcome measures were the proportions of prescriptions in compliance with ASCO guidelines regarding primary prophylactic, secondary prophylactic, and therapeutic CSF administration.

RESULTS

Before implementation of the ASCO guidelines, CSF use in compliance with the guidelines was 39% (41/105) at the study site and 31% (16/51) at the control sites (P > 0.05). Six months after dissemination and implementation of the guidelines, the proportion of CSF prescriptions complying with ASCO guidelines increased significantly versus baseline (P = 0.003) in the study group, to 61% (50/82). However, even after the guidelines were implemented, compliance with guidelines on primary prophylactic CSF administration did not change significantly versus before implementation in the study group (12% [5/41] before implementation vs 6% [2/33] after implementation; P > 0.05).

CONCLUSIONS

The results suggest an association between the active implementation strategy (continuing medical education and CSF prescription reminder form) and physician compliance with the ASCO guidelines. Implementation of the ASCO guidelines appears to have had some impact on medical practice.

Simultaneous determination of total plasma glutathione, homocysteine, cysteinylglycine, and methionine by high-performance liquid chromatography with electrochemical detection

We here describe an ion-exchange high-performance liquid chromatography technique with electrochemical detection for rapid quantification of glutathione, homocysteine, cysteinylglycine, and methionine. The analytical validation of the technique showed within-assay and between-assay coefficients of variation between 3.1 and 4.3%, and 3.7 and 8.6%, respectively. Percentages of recovery for overload and dilution tests were between 87 and 120%. Detection limits were 1 micromol/L for methionine and 0.5 micromol/L for other compounds. There was no interference with any physiological and pharmacological substances possessing a thiol function. Aminothiol concentrations determined in 100 control subjects (50 women and 50 men) showed no age- or sex-rated differences for except for homocysteine which was increased (+ 28%) in oldest subjects of both sexes. In 60 patients at risk (30 with chronic renal failure, 30 with diabetes), homocysteine concentration was significantly increased. No variation in other aminothiols was observed in diabetic subjects. Methionine was decreased and cysteinylglycine was increased in patients with chronic renal failure. The present technique-rapid, easy to use, and reliable-appears suitable for routine application in the exploration of aminothiol metabolic pathways including mechanisms of hyperhomocysteinemia.

Multicenter study of the impact of prescription guidelines on the use of colony stimulating factors

The aim of this work was to assess the impact of circulating guidelines for correct prescription practices of colony stimulating factors (CSF). Two hospital groups were compared, a 'guidelines' group (seven teaching hospitals) that circulated the guidelines and a control group (eight teaching hospitals) that did not. In addition, two periods were compared before and after distribution of the guidelines: from 17 February to 2 March 1996 and from 17 February to 2 March 1997. The assessment involved compliance with the guidelines for the following parameters: indications, dose regimen, time to start of CSF therapy and duration of CSF therapy between the control and guideline groups and also between the two periods. The population included 404 patients analyzed (209 in 1996 and 195 in 1997) for the indication of post-chemotherapy neutropenia. Total compliance in the first period (all four items) was 44.2% in the control group and 50.8% in the guideline group (nonsignificant), and during the second period was 31.9 and 59.6% in the two groups (p<0.001). During the first period, the differences in compliance with the guidelines for indication, dose regimen, time to start of treatment and duration between the groups were not significant. In the second period, this difference became significant and in favor of the guideline group for dose regimen (p = 0.009) and treatment duration (p = 0.02). The results of this study show the need to continuously define prescription reference systems according to available data, and to circulate them widely to improve the quality of health care and to control expenses.

Impact of ASCO guidelines for the use of hematopoietic colony stimulating factors (CSFs): survey results of fifteen Paris university hospitals

To assess whether physicians comply with American Society of Clinical Oncology (ASCO) guidelines for the use of CSFs, a prospective survey was performed in 15 Paris university hospitals involved in cancer treatment in 1997. If 45% of the prescriptions complied with the guidelines, primary prophylactic administration, which represented 52% of cases, did not comply with ASCO guidelines. These results suggested that primary prophylactic administration was one major clinical situation in which physicians could benefit from guidance to use a CSFs and that criteria defined by ASCO to allow primary prophylactic administration were not applied in clinical practice.

The ALBI trial: a randomized controlled trial comparing stavudine plus didanosine with zidovudine plus lamivudine and a regimen alternating both combinations in previously untreated patients infected with human immunodeficiency virus

A total of 151 previously untreated patients infected with human immunodeficiency virus type 1 (HIV-1) with CD4 cell counts >/=200/microL and plasma HIV-1 RNA levels of 10,000-100,000 copies/mL were randomly assigned to 24 weeks of open-labeled stavudine plus didanosine (group 1), zidovudine plus lamivudine (group 2), or stavudine plus didanosine followed by zidovudine plus lamivudine (group 3). The mean decrease in HIV-1 RNA level was greater in group 1 (2.26 log10 copies/mL) than in groups 2 (1.26 log10 copies/mL) or 3 (1.58 log10 copies/mL; P<.0001). The mean increase in CD4 cell counts was greater in groups 1 (124 cells/microL) and 3 (118 cells/microL) than in group 2 (62 cells/microL; P=.02). All regimens were generally well tolerated. The combination of stavudine plus didanosine reduced plasma HIV-1 RNA concentrations and increased CD4 cell counts more effectively than did the combination of zidovudine plus lamivudine or the regimen alternating both combinations.

Results of the ALBI trial: a randomized comparison of stavudine/didanosine, zidovudine/lamivudine and alternating treatment in antiretroviral-naive patients

In the ALBI trial, 151 antiretroviral-naive patients with plasma human immunodeficiency virus type 1 (HIV-1) RNA levels of 10,000 to 100,000 copies/ml and CD4 cell counts > or = 200 cells/mm3 received 24 weeks of treatment with stavudine/didanosine (n=51), zidovudine/lamivudine (n=51) or stavudine/didanosine for 12 weeks followed by zidovudine/lamivudine (n=49). Baseline plasma HIV-1 RNA and CD4 cell counts were comparable in the treatment groups. The mean decrease in plasma HIV-1 RNA at 24 weeks in the stavudine/didanosine group (2.26 log10) was significantly greater than that in either the zidovudine/lamivudine group (1.26 log10) or the alternating treatment group (1.58 log10) (P<0.0001 for both). Proportions of patients with plasma HIV-1 RNA level <500 copies/ml (91% vs 42% and 60%) and <50 copies/ml (47% versus 4% and 9%) were significantly greater in the stavudine/didanosine group (P<0.001 for pairwise comparisons). Stavudine/didanosine was associated with a mean increase in CD4 cell count (124 cells/mm3) significantly greater than that in the zidovudine/lamivudine group (62 cells/mm3, P<0.01) and comparable to that in the alternating group (118 cells/mm3). All study regimens were well tolerated. These findings, indicating superiority of stavudine/didanosine over zidovudine/lamivudine in virological and immunological response over 24 weeks, suggest that the combination should be considered as a basis for highly active antiretroviral therapy.

G-CSF (Granulocyte Colony-Stimulating Factor): follow-up and use in a French University hospital

Granulocyte Colony-Stimulating Factor or G-CSF (NEUPOGEN) was approved for use in France in November 1991 for prevention of chemotherapy-induced neutropenia. This retrospective study was conducted at Saint-Louis Hospital, Paris, France, from November 1991 to March 1993 with a more detailed analysis of patient profiles for courses ordered between November 1991 and December 1992. Data were collected on standardized G-CSF-treatment summary forms. The purpose of the study was to define, in clinical terms, the patients treated by G-CSF to determine the average cost per course of therapy and its impact on the hospital pharmacy budget. From November 1991 to December 1992 data from 307 patient profiles were collected and analyzed. The subcutaneous route was the preferred route and only 16.6% of courses were administered intravenously. 45.6% of patients received a single course, 24.3% received two courses, and 30.1% received more than two courses. Each patient completed an average of 2.3 courses at an average cost per course of $2,000.00 (Canadian dollars). During March 1993, 50% of vials dispensed were administered to outpatients. During the 14-month period, an average of 613.8 vials were dispensed per month corresponding to an average monthly expenditure of $104,000.00 (Canadian dollars). In the first 12 months following the commercial availability of G-CSF, G-CSF expenditures accounted for 8% of the pharmacy budget.

Phase I and pharmacokinetic study of the camptothecin derivative irinotecan, administered on a weekly schedule in cancer patients

Irinotecan (CPT-11) is a novel water-soluble, semisynthetic derivative of camptothecin, with inhibitory effects on mammalian DNA topoisomerase I, high cytotoxic activity in vitro and anticancer activity in animal models. Fifty-nine patients, with cancer refractory to conventional therapy, were entered in this phase I study, using a weekly schedule administration. A total of 304 weekly doses were administered at dose levels ranging from 50 to 145 mg/m2 (30-90 min i.v. infusion). Leukoneutropenia and diarrhea were the dose-limiting toxicities and appeared to be dose related, reversible and noncumulative. However, interpatient variability of toxic effects was substantial. Prolongation of the infusion time from 30 min to 90 min appeared to decrease the diarrhea. Other toxicities included moderate emesis, asthenia, alopecia, abdominal pain, and anemia. CPT-11 plasma disposition was bi- or triphasic with a terminal half-life of 9.3 h. CPT-11 area under the plasma concentration versus time curves increased linearly with dose (r = 0.47, P < 0.01). The active metabolite area under the plasma concentration versus time curve correlated significantly with that of CPT-11, but not with that of CPT-11 dose. Both CPT-11 and 7-ethyl-10-hydroxycamptothecin areas under the plasma concentration versus time curve correlated significantly with leukoneutropenia and diarrhea. One partial and 4 minor responses were observed at dose levels of 130 and 145 mg/m2. Using this weekly schedule, recommended doses for phase II studies are 100 mg/m2 in high risk patients and 115 mg/m2 in others.

Sequential modifications of topoisomerase I activity in a camptothecin-resistant cell line established by progressive adaptation

The DNA-topoisomerase I (Topo I) inhibitor, camptothecin (CPT), is a plant alkaloid with an important antitumor activity. In order to investigate the cellular mechanism leading to the development of the resistance to this agent, we have established by progressive adaptation a P388 subline resistant to CPT. After 5 months of continuous drug exposure, the resistance index reached a value of 20 and the resistant cell line, P388CPT0.3, was maintained in the presence of CPT. CPT-induced single strand breaks measured by alkaline elution were found drastically reduced in the resistant cell line. Topo I activity and CPT-induced DNA cleavage were measured on cells at different steps of resistance. We first observed that the Topo I activity was strongly decreased. In addition, the resistant cells recovered the ATP-independent relaxation activity after 3 months of exposure to CPT, but still kept a reduced CPT-induced DNA cleavage. Further evaluations at the final stage of the resistance induction have indicated that cells presented a CPT-resistant form of Topo I. Rearranged Topo I gene on one allele and a reduced Topo I transcription were also observed in resistant cells. The putative role of the rearrangement was discussed. These data show that the resistance mechanism has evolved from a decreased Topo I activity to an altered form of the enzyme, and suggest that multiple mechanisms of Topo I modifications could contribute to CPT resistance.