The Oncologist, Vol. 10, No. 9, 686-694, October 2005; doi:10.1634/theoncologist.10-9-686 © 2005 AlphaMed Press
Hematologic Safety and Tolerability of Topotecan in Recurrent Ovarian Cancer and Small Cell Lung Cancer: An Integrated Analysisa Johns Hopkins Medical Institutions, Baltimore, Maryland, USA; b Memorial Sloan-Kettering Cancer Center, New York, New York, USA; c GlaxoSmithKline, Philadelphia, Pennsylvania, USA Key Words. Myelosuppression • Neutropenia • Noncumulative • Ovarian cancer • Small cell lung cancer • Topotecan Correspondence: Deborah K. Armstrong, M.D., The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Bunting Blaustein Cancer Research Building, Room 190, 1650 Orleans Street, Baltimore, Maryland 21231, USA. Telephone: 410-614-2743; Fax: 410-955-0125; e-mail: darmstro{at}jhmi.edu Received December 6, 2004; accepted for publication June 24, 2005.
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The purpose was to conduct an integrated analysis of the cumulative hematologic toxicity of topotecan in patients with relapsed ovarian cancer and small cell lung cancer (SCLC). Data were pooled from eight phase II and phase III clinical studies performed in patients with relapsed stage III/IV ovarian cancer or extensive SCLC treated with topotecan at a dose of 1.5 mg/m2 per day on days 15 of a 21-day course. Quantitative hematologic toxicities were assessed using the National Cancer Institute Common Toxicity Criteria. A total of 4,124 courses of therapy was administered to the 879 patients in the pooled population. Grade 4 neutropenia was experienced by 78% of patients. The lowest nadirs for neutrophils and platelets generally occurred after the first course of therapy, followed by improvement or stabilization in subsequent courses. Neutropenia was noncumulative. During the first course, significant risk factors were identified: renal impairment and advanced age (grade 3/4 thrombocytopenia and grade 4 neutropenia) and prior radiotherapy; performance status score 2; SCLC; and exposure to both cisplatin (Platinol®; Bristol-Myers Squibb, Princeton, NJ, http://www.bms.com) and carboplatin (Paraplatin®; Bristol-Myers Squibb) (grade 3/4 thrombocytopenia only). The most frequent interventions for hematologic toxicities were RBC transfusions, treatment delays, G-CSF support, and dose reductions. Analysis of neutrophil and platelet nadirs and dosing for each course of therapy showed no apparent evidence of cumulative neutropenia or thrombocytopenia. The risk of grade 3 or 4 anemia was higher during the first four courses of therapy and may need to be more aggressively managed with erythropoietin therapy.
Topotecan (Hycamtin® for Injection; GlaxoSmithKline, Philadelphia, http://www.gsk.com) is approved in more than 70 countries for the second-line treatment of metastatic ovarian cancer after failure of initial or subsequent chemotherapy and is approved in more than 30 countries including the U.S., Canada, Australia, and Switzerland for the treatment of patients with chemotherapy-sensitive small cell lung cancer (SCLC) after failure of first-line chemotherapy. The approved schedule is a 30-minute i.v. infusion at a starting dose of 1.5 mg/m2 per day on days 15 of a 21-day course. In patients with relapsed ovarian cancer, the overall response rates for topotecan range from 19%33% in platinum-sensitive patients [1, 2] and from 14%18% in platinum-resistant patients [3, 4]. In SCLC patients, topotecan has demonstrated overall response rates of 14%38% in patients with relapsed SCLC sensitive to previous chemotherapy [5, 6] and 2%11% in patients with chemotherapy-resistant SCLC [5, 7]. The dose-limiting toxicity for topotecan is myelosuppression, with the most common severe adverse event being noncumulative grade 4 neutropenia [8, 9]. Thus, toxicity is generally managed by treatment delays and dose reductions, and when appropriate, the administration of G-CSF and/or GM-CSF. Guidelines for managing topotecan-related hematologic toxicity have been published previously and include specific recommendations for dose reductions and the use of hematopoietic growth factors [10, 11]. An integrated analysis of the hematologic safety and tolerability of topotecan in patients with SCLC or ovarian cancer has not been previously reported. Based on the previous clinical trial reports, myelosuppression is the predominant toxicity observed in both these populations. The incidences of grade 4 neutropenia, leukopenia, and anemia appear to be slightly higher for patients with ovarian cancer than for patients with SCLC, whereas the incidence of grade 4 (<25 x 109/l) thrombocytopenia is slightly higher in patients with SCLC. Taking into account the different underlying diseases, background clinical conditions, and concomitant medications, the hematologic tolerability profiles for these two patient populations appear to be similar. Therefore, the safety data sets from these two patient populations can be combined to provide a greater overall clinical experience of the tolerability of topotecan. Herein, we report the results of such an integrated safety analysis.
Pooled Studies Safety data were pooled from the eight studies summarized in Table 1
Patient Population Ovarian Cancer Studies
SCLC Studies
Treatment
Safety and Tolerability Assessments
Data Handling For the safety data, summary statistics are presented to give a general description of the patients studied and an overview of the safety results. Categorical parameters, such as hematologic toxicities, adverse experiences, and febrile neutropenia, are summarized by the number and percentage of patients and courses for each toxicity or adverse experience. Time to onset and duration of toxicity are summarized with medians and ranges. Frequencies and percentages of patients with toxicities >7 days are also presented. Hematologic nadirs are summarized by the following three methods: mean value of each parameter, median value of each parameter, and median day. Computations were performed using SAS® (SAS Institute, Inc., Cary, NC, http://www.sas.com) computer software.
An additional analysis was performed to investigate whether any baseline patient characteristics correlated with a greater risk for either grade 3/4 thrombocytopenia or grade 4 neutropenia during the first course of treatment. Logistic regression was used to model the odds of a specific hematologic toxicity event (e.g., grade 4 neutropenia) as a function of one or more independent variables. For each independent variable in the logistic regression model, the odds ratio was estimated and a p value relative to the null hypothesis of no relationship with the response variable (i.e., an odds ratio of 1) was calculated. Independent variables included: sex (male/female), prior radiation therapy (yes/no), renal impairment (present/absent, defined as CTC grade
Study Population A total of 879 patients from eight clinical trials was included in the analysis. Among the 426 patients with SCLC, 283 were male and 143 were female, and the mean age across the four SCLC trials ranged from 57.561.3 years. The majority of patients with SCLC had extensive disease and had received one prior chemotherapy regimen. Among the 453 patients with ovarian cancer, the mean age across the four ovarian cancer trials ranged from 57.259.2.
Patient Disposition
Hematologic Toxicity The dose-limiting toxicity of topotecan in both ovarian cancer and SCLC patients was myelosuppression. A summary of severe hematologic toxicities by treatment course is provided in Table 3
The majority of the hematologic adverse events occurred during course 1 or 2 and, with the exception of anemia, most occurred during course 1. The incidence of grade 4 neutropenia or thrombocytopenia did not increase with increasing courses of therapy.
Across all treatment courses, the median time to onset of grade 4 neutropenia was 10 days, compared with 15 days for grade 4 thrombocytopenia and 13 days for grade 3/4 anemia. The median durations of severe toxicities (grade 3/4 anemia and grade 4 neutropenia or thrombocytopenia) for each course of therapy through course 10 are presented in Table 3
The median number of days to nadir for hemoglobin and platelets remained constant throughout treatment, but there was some fluctuation in the median number of days to neutrophil nadir. In course 1, the median onset of grade 4 neutropenia was 13 days, and the duration was longer than 1 week in 37% of affected patients. However, in subsequent courses, the median time to onset per course was generally 9 days, with a duration >1 week in 21%43% of affected patients. Overall, the median nadir values did not decrease with increasing courses of topotecan therapy. The median neutrophil nadirs plotted as a function of treatment course, dose, and G-CSF support are presented in Figure 1
The median hemoglobin and platelet nadirs plotted as a function of treatment course, topotecan dose, and RBC and/or erythropoietin and platelet support are presented in Figure 2 1.25 mg/m2 without any RBC/erythropoietin support decreased over the first three courses and then reached a plateau at course 4. Of the 862 patients with hemoglobin laboratory values reported during course 1, 192 (22%) received RBC transfusions or erythropoietin, and the median hemoglobin nadir was 9.8 g/dl. During subsequent courses, patients who received <1.25 mg/m2 of topotecan and did not require RBC/erythropoietin support had median hemoglobin nadirs similar to those of patients who received 1.25 mg/m2 of topotecan without RBC/erythropoietin support. After the first or second cycle, the majority of patients was able to receive 1.25 mg/m2 of topotecan without further dose reductions or RBC/erythropoietin support.
The median platelet nadir for all patients was 59 x 109 per l for course 1. For patients who received topotecan doses 1.25 mg/m2 and no platelet support, the median platelet nadir for course 1 was 67 x 109 per l. Median platelet nadirs were higher for these patients in subsequent courses, stabilizing at a median of approximately 90 x 109 per l for courses 210. Of the 862 patients with platelet laboratory values during course 1, 102 received platelet support because of a median platelet nadir of 14 x 109 per l. As expected, the median platelet nadirs for patients who required platelet transfusions and/or dose reductions were lower than those of patients who did not require intervention because of low platelet counts. However, there was no evidence that platelet nadirs worsened over treatment courses.
Management of Hematologic Toxicity
Suspected or documented sepsis or infections proximate to grade 4 neutropenia were reported in 204 (23%) patients and 278 (7%) courses. Sepsis induced by topotecan was considered related to death in 1% of patients. Treatment-related sepsis was the cause of death for eight (2%) SCLC patients and for two (<1%) ovarian cancer patients. Another important potential myeloid toxicity is treatment-related leukemia. There were no cases of secondary leukemia in patients treated in the clinical studies included in this analysis. One case of secondary leukemia possibly attributable to topotecan has been reported in a patient with SCLC who developed acute myeloid leukemia after receiving 27 courses of oral topotecan as first-line therapy. There have been six other reported cases of secondary leukemias in patients treated with topotecan. In each case, the patients had received many other chemotherapy agents known to cause late leukemia (GlaxoSmithKline, data on file).
Risk Factors for Course 1 Hematology Toxicity
In addition to these shared baseline risk factors for neutropenia and thrombocytopenia, other risk factors were identified for grade 3/4 thrombocytopenia: prior radiation therapy, higher ECOG PS score, disease type (SCLC), and prior exposure to multiple platinum agents. For the incidence of grade 3/4 thrombocytopenia, patients with prior radiation therapy had a 1.55-fold greater incidence than patients with no prior radiation therapy (p = .044), patients with PS scores
Topotecan, a novel topoisomerase-I inhibitor with established efficacy in recurrent ovarian cancer and relapsed chemotherapy-sensitive SCLC, has myelosuppression as its main toxicity. Data from the integrated analysis presented here indicate that myelosuppression associated with topotecan is reversible and can be generally managed with RBC transfusions, treatment delays, G-CSF support, and dose reductions. Neutropenia was noncumulative. After the first course, thrombocytopenia appeared to be noncumulative with <10% of patients experiencing grade 4 (<25 x 109/l) thrombocytopenia and 5% of patients receiving platelet transfusions. In contrast, anemia appeared to increase, with deeper nadirs through course 4, but stabilized thereafter. Fifty-two percent of patients required RBC transfusions. It is difficult to discern whether this was because of topotecan, prior treatment, or the disease in general. Intervention with erythropoietin was infrequent in this analysis, based on the usage patterns during the study period. Active intervention with erythropoietin may be a reasonable consideration, especially for patients with a predisposition for anemia. A multivariate analysis of risk factors for hematologic toxicity during the first course of therapy may provide insight for patient management. Consistent with the updated dosing guidelines based on the renal clearance of topotecan [16], renal impairment was identified as a significant risk factor for grade 3/4 thrombocytopenia and grade 4 neutropenia during the first course of topotecan therapy. Patients in the older age groups also had a higher risk for both toxicities than younger patients. Grade 3/4 thrombocytopenia also had additional significant risk factors, including prior radiation therapy, higher PS score, and prior exposure to both cisplatin and carboplatin. Patients with SCLC had a higher incidence of grade 3/4 thrombocytopenia during the first course than patients with ovarian cancer, perhaps reflecting differences in disease states or treatment histories. However, these correlations have not been examined prospectively in clinical trials. The overall incidences of grade 4 neutropenia and thrombocytopenia decreased in subsequent courses of therapy. An apparent lack of cumulative toxicity with topotecan has been reported previously. Goldwasser et al. [17], in a study of 21 heavily pretreated patients with ovarian cancer, concluded that treatment with topotecan at a dose of 1.25 mg/m2 per day as a 30-minute i.v. infusion for 5 days every 3 weeks is feasible without prophylactic G-CSF support. In that study, the severity of topotecan-induced grade 4 thrombocytopenia was maximal (43% of patients) in the first course but decreased without dose reduction to 15% and 19% of patients in the second and third courses, respectively. Möbus et al. [18] conducted a retrospective study of long-term therapy with topotecan in 33 patients with recurrent ovarian cancer who received a total of 343 courses of topotecan, an average of more than 10 courses per patient. The incidences of hematologic toxicities in that study were as expected but, as with the current analysis, showed no evidence of being cumulative. The percentages of patients with blood transfusions and growth factor support did not vary over all courses of therapy. Möbus et al. [18] concluded that long-term therapy with topotecan is feasible and may be conducted without an apparently higher risk for cumulative hematologic toxicities. Many of the agents used in the front-line and salvage treatment of patients with advanced ovarian cancer or SCLC are associated with cumulative and/or irreversible toxicities that pose challenges in long-term planning [19]. The irreversible effects associated with some of these therapies may render patients less tolerant of subsequent treatments and can lead to fewer treatment options with each remission and disease relapse. For example, in patients with recurrent ovarian cancer, cumulative renal tubule toxicity [20, 21] and neurotoxicity associated with cisplatin as first-line therapy may eliminate the option for retreatment with a platinum agent at relapse. Moreover, both cisplatin and carboplatin produce myelotoxicity that may be cumulative. Indeed, the current analysis identified that prior exposure to multiple platinum agents was associated with a significantly greater incidence of grade 3/4 thrombocytopenia during the first course of therapy. Furthermore, severe myelotoxicity and greater incidences of secondary myelodysplasia and leukemia are associated with prolonged and cumulative etoposide (Etopophos®, VePesid®; Bristol-Myers Squibb) treatment in patients with ovarian cancer [23]. Cumulative liposomal doxorubicin and paclitaxel exposure also lead to a greater risk for patient morbidity because of cardiotoxicity [24] and neuropathy [25], respectively. When selecting a chemotherapy regimen, the potential for patients to experience cumulative toxicities must be carefully considered. In conclusion, the dose-limiting toxicity with topotecan in this integrated safety analysis was myelosuppression. However, hematologic adverse events were predictable and could be managed in most patients. Furthermore, the magnitude of reductions in neutrophils, RBCs, and platelets from baseline appeared to be greatest after the initial course of therapy and then began to lessen or stabilize over ensuing courses. Neutropenia was noncumulative. After the first or second course, the rate of neutropenia per course was relatively low and in line with other standard chemotherapy regimens used for the treatment of recurrent ovarian cancer and SCLC. In this analysis, there was no evidence to suggest that thrombocytopenia was cumulative with topotecan therapy. The risk for grade 3 or 4 anemia was higher during the first four courses of therapy and may need to be more aggressively managed with erythropoietin therapy. Dose reductions, dose delays, and RBC transfusions were the most common interventions for hematologic toxicity. The majority of grade 3 or 4 hematologic episodes occurred during the first or second course, likely because modest (to 1.25 mg/m2 or more) dose adjustments were sufficient in ensuring that subsequent courses of therapy were well tolerated. The generally manageable hematologic toxicity profile of topotecan suggests that topotecan may be safely administered for multiple courses or, potentially, until disease progression. These results suggest that topotecan may be safely administered to patients whose disease warrants extended therapy. These data are of particular importance to patients with stable disease and to other patients for whom extended therapy might be indicated.
Markman, Maurie. Topotecan as Second-Line Therapy for Ovarian Cancer: Dosage Versus Toxicity. The Oncologist 2005;10:695-697.
Dr. Armstrong has received research grants from Sanofi-Aventis and EMD Pharmaceuticals and has acted as a consultant for Pfizer.
The authors thank the patients for their participation and the study coordinators and physicians for their assistance in the five clinical trials included in this meta-analysis. GlaxoSmithKline provided collaborative support and assistance to the authors for the analysis, writing, and preparation of this article.
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