Phase I study of topotecan for pediatric patients with malignant solid tumors

Leptomeningeal Dissemination of Low-Grade Neuroepithelial Tumor with FGFR1_TACC1 Fusion with Clinical and Radiographic Response to Pazopanib and Topotecan

INTRODUCTION

Low-grade neuroepithelial tumors are a heterogeneous group of central nervous system tumors that are generally indolent in nature but in rare instances can progress to include leptomeningeal dissemination.

CASE PRESENTATION

We present a case of a patient with a low-grade neuroepithelial tumor of indeterminate type with symptomatic leptomeningeal dissemination despite 3 chemotherapy regimens and radiotherapy. Somatic targetable mutation testing showed an FGFR1_TACC1 fusion. Therapy with pazopanib/topotecan was initiated, and disease stabilization was achieved. He received pazopanib/topotecan for a total of 2 years and is now >2 years from completion of treatment and continues to do well with no evidence of disease.

DISCUSSION

This case highlights the utility of targetable mutation testing in therapeutic decision-making and the novel use of systemic pazopanib/topotecan therapy for refractory low-grade neuroepithelial tumor within the context of this clinical situation and specific mutation profile.

Ewing Sarcoma-Diagnosis, Treatment, Clinical Challenges and Future Perspectives

Ewing sarcoma, a highly aggressive bone and soft-tissue cancer, is considered a prime example of the paradigms of a translocation-positive sarcoma: a genetically rather simple disease with a specific and neomorphic-potential therapeutic target, whose oncogenic role was irrefutably defined decades ago. This is a disease that by definition has micrometastatic disease at diagnosis and a dismal prognosis for patients with macrometastatic or recurrent disease. International collaborations have defined the current standard of care in prospective studies, delivering multiple cycles of systemic therapy combined with local treatment; both are associated with significant morbidity that may result in strong psychological and physical burden for survivors. Nevertheless, the combination of non-directed chemotherapeutics and ever-evolving local modalities nowadays achieve a realistic chance of cure for the majority of patients with Ewing sarcoma. In this review, we focus on the current standard of diagnosis and treatment while attempting to answer some of the most pressing questions in clinical practice. In addition, this review provides scientific answers to clinical phenomena and occasionally defines the resulting translational studies needed to overcome the hurdle of treatment-associated morbidities and, most importantly, non-survival.

Topotecan-Vincristine-Doxorubicin in Stage 4 High-Risk Neuroblastoma Patients Failing to Achieve a Complete Metastatic Response to Rapid COJEC: A SIOPEN Study

PURPOSE

Metastatic response to induction therapy for high-risk neuroblastoma is a prognostic factor. In the International Society of Paediatric Oncology Europe Neuroblastoma (SIOPEN) HR-NBL-1 protocol, only patients with metastatic complete response (CR) or partial response (PR) with ≤ three abnormal skeletal areas on iodine 123-metaiodobenzylguanidine ([123I]mIBG) scintigraphy and no bone marrow disease proceed to high dose therapy (HDT). In this study, topotecan-vincristine-doxorubicin (TVD) was evaluated in patients failing to achieve these criteria, with the aim of improving the metastatic response rate.

MATERIALS AND METHODS

Patients with metastatic high-risk neuroblastoma who had not achieved the SIOPEN criteria for HDT after induction received two courses of topotecan 1.5 mg/m2/day for 5 days, followed by a 48-hour infusion of vincristine, 2 mg/m2, and doxorubicin, 45 mg/m2.

RESULTS

Sixty-three patients were eligible and evaluable. Following two courses of TVD, four (6.4%) patients had an overall CR, while 28 (44.4%) had a PR with a combined response rate of 50.8% (95% confidence interval [CI], 37.9 to 63.6). Of these, 23 patients achieved a metastatic CR or a PR with ≤ 3 mIBG skeletal areas and no bone marrow disease (36.5%; 95% CI, 24.7 to 49.6) and were eligible to receive HDT. Toxicity was mostly haematological, affecting 106 of the 126 courses (84.1%; 95% CI, 76.5 to 90.0), and dose reduction was necessary in six patients. Stomatitis was the second most common nonhematological toxicity, occurring in 20 patients (31.7%).

CONCLUSION

TVD was effective in improving the response rate of high-risk neuroblastoma patients after induction with COJEC enabling them to proceed to HDT. However, the long-term benefits of TVD needs to be determined in randomized clinical trials.

Neuroblastoma chemotherapy can be augmented by immunotargeting O-acetyl-GD2 tumor-associated ganglioside

Despite recent advances in high-risk neuroblastoma therapy, the prognosis for patients remains poor. In addition, many patients suffer from complications related to available therapies that are highly detrimental to their quality of life. New treatment modalities are, thus, urgently needed to further improve the efficacy and reduce the toxicity of existing therapies. Since antibodies specific for O-acetyl GD2 ganglioside display pro-apoptotic activity against neuroblastoma cells, we hypothesized that combination of immunotherapy could enhance tumor efficacy of neuroblastoma chemotherapy. We demonstrate here that combination of anti-O-acetyl GD2 monoclonal antibody 8B6 with topotecan synergistically inhibited neuroblastoma cell proliferation, as shown by the combination index values. Mechanistically, we evidence that mAb 8B6 induced plasma cell membrane lesions, consistent with oncosis. Neuroblastoma tumour cells treated with mAb 8B6 indeed showed an increased uptake of topotecan by the tumor cells and a more profound tumor cell death evidenced by increased caspase-3 activation. We also found that the combination with topotecan plus monoclonal antibody 8B6 showed a more potent anti-tumor efficacy in vivo than either agent alone. Importantly, we used low-doses of topotecan with no noticeable side effect. Our data suggest that chemo-immunotherapy combinations may improve the clinical efficacy and safety profile of current chemotherapeutic modalities of neuroblastoma.

A comparison of safety and efficacy of cytotoxic versus molecularly targeted drugs in pediatric phase I solid tumor oncology trials

BACKGROUND

Prior reviews of phase I pediatric oncology trials involving primarily cytotoxic agents have reported objective response rates (ORRs) and toxic death rates of 7.9-9.6% and 0.5%, respectively. These data may not reflect safety and efficacy in phase I trials of molecularly targeted (targeted) drugs.

METHODS

A systematic review of pediatric phase I solid tumor trials published in 1990-2013 was performed. The published reports were evaluated for patient characteristics, toxicity information, and response numbers.

RESULTS

A total of 143 phase I pediatric clinical trials enrolling 3,896 children involving 53 targeted and 48 cytotoxic drugs were identified. A meta-analysis demonstrated that the ORR is 2.1-fold higher with cytotoxic drugs (0.066 vs. 0.031 per subject; P = 0.007). By contrast, the pooled estimate of the stable disease rate (SDR) is similar for cytotoxic and targeted drugs (0.2 vs. 0.23 per subject; P = 0.27).  The pooled estimate of the dose-limiting toxicity rate is 1.8-fold larger with cytotoxic drugs (0.24 vs. 0.13 per subject; P = 0.0003). The hematologic grade 3-4 (G3/4) toxicity rate is 3.6-fold larger with cytotoxic drugs (0.43 vs. 0.12 per treatment course; P = 0.0001); however, the nonhematologic G3/4 toxicities and toxic deaths occur at similar rates for cytotoxic and targeted drugs.

CONCLUSIONS

In phase I pediatric solid tumor trials, ORRs were significantly higher for cytotoxic versus targeted agents. SDRs were similar in targeted and cytotoxic drug trials. Patients treated with cytotoxic agents were more likely to experience hematologic G3/4 toxicities than those patients receiving targeted drugs.

Ocular Salvage and Vision Preservation Using a Topotecan-Based Regimen for Advanced Intraocular Retinoblastoma

Purpose To evaluate topotecan-based therapy for advanced intraocular retinoblastoma. Patients and Methods Twenty-seven patients with bilateral retinoblastoma (male patients, n = 14; median age, 8.4 months) received chemotherapy: two courses of topotecan plus vincristine followed by three alternating administrations of carboplatin and vincristine for two courses and topotecan plus vincristine for one course, with optional periocular carboplatin. Focal therapy was applied after cycle 2. Event-free survival was defined as avoidance of external-beam radiotherapy (EBRT) and enucleation. Results Of 54 eyes, 42 were Reese-Ellsworth group IV to V, and 37 were International Classification of Retinoblastoma group C to E. Eleven eyes were enucleated: one at diagnosis, nine with progressive disease including three eyes treated with EBRT, and one that developed neovascular glaucoma after completion of therapy. One patient was removed from protocol with prolonged infection in course 1; 26 patients (51 eyes) were analyzed. At 10 years, cumulative incidence of EBRT was 5.9% (SE ± 3), and event-free survival was 69.2% (SE ± 27.2). Ocular survival for Reese-Ellsworth group IV to V eyes was 77.5% (SE ± 21.2); it was 74.3% (SE ≥ 18.8) for International Classification group C to E eyes. Vision testing (median age, 7 years; range, 5 to 10 years) documented 20/70 vision or better in one eye of 23 patients; 19 (76%) of 25 patients demonstrated 20/40 vision or better in one eye. All patients experienced thrombocytopenia (41 episodes in 275 courses; 15%). There were 29 episodes of febrile neutropenia (10%). Grade 3 diarrhea was present in nine of 27 patients, and one patient had an allergic reaction to carboplatin. All patients are alive at median follow-up 7.4 years (range, 2.7 to 10 years). Conclusion Topotecan combined with vincristine, carboplatin, and aggressive focal therapies is an effective regimen for the treatment of advanced retinoblastoma and results in globe salvage with vision. Toxicities were anticipated and managed with appropriate supportive care.

Population Pharmacokinetics of Oral Topotecan in Infants and Very Young Children with Brain Tumors Demonstrates a Role of ABCG2 rs4148157 on the Absorption Rate Constant

For infants and very young children with brain tumors, chemotherapy after surgical resection is the main treatment due to neurologic and neuroendocrine adverse effects from whole brain irradiation. Topotecan, an anticancer drug with antitumor activity against pediatric brain tumors, can be given intravenous or orally. However, high interpatient variability in oral drug bioavailability is common in children less than 3 years old. Therefore, this study aimed to determine the population pharmacokinetics of oral topotecan in infants and very young children, specifically evaluating the effects of age and ABCG2 and ABCB1 on the absorption rate constant (Ka), as well as other covariate effects on all pharmacokinetic parameters. A nonlinear mixed effects model was implemented in Monolix 4.3.2 (Lixoft, Orsay, France). A one-compartment model with first-order input and first-order elimination was found to adequately characterize topotecan lactone concentrations with population estimates as [mean (S.E.)]; Ka = 0.61 (0.11) h(-1), apparent volume of distribution (V/F) = 40.2 (7.0) l, and apparent clearance (CL/F) = 40.0 (2.9) l/h. After including the body surface area in the V/F and CL/F as a power model centered on the population median, the ABCG2 rs4148157 allele was found to play a significant role in the value of Ka Patients homozygous or heterozygous for G>A demonstrated a Ka value 2-fold higher than their GG counterparts, complemented with a 2-fold higher maximal concentration as well. These results demonstrate a possible role for the ABCG2 rs4148157 allele in the pharmacokinetics of oral topotecan in infants and very young children, and warrants further investigation.

Review : Topoisomerase I inhibitors: 1. Topotecan

Purpose. The primary objective of this article is to discuss the pharmacology, pharmacokinetics, clin ical use, and adverse effects of the approved topoisomerase I inhibitors. This is the first in a series of two articles and will focus on topotecan.

Data Sources. We reviewed the literature through a MEDLINE search of English language articles from 1985 through 1997. Relevant articles cited in the titles obtained from the MEDLINE search were also used. The following terms were used for purpose of conducting the MEDLINE search: topoisomerase inhibitors, topotecan, topo isomerase I, Hycamtin, SKF 104864.

Data Extraction. We reviewed the current literature in order to discuss the pharmacology, pharmacokinetics, clinical use, toxicity, drug inter actions, indications, formulation, dosage and ad ministration, and pharmaceutical issues surround ing the use of topotecan.

Data Synthesis. The topoisomerase I inhibi tors are new antineoplastic agents with a unique mechanism of action. Promising areas of applica tion include ovarian cancer, lung cancer, radiation sensitization, and refractory leukemias. Clinical tri als detailing its activity in these areas are pre sented.

Intravitreal Topotecan Inhibits Laser-induced Choroidal Neovascularization in a Rat Model

Purpose:

A two-phase preclinical study was designed to determine the safe dose of intravitreal topotecan and its inhibitory effect on experimental choroidal neovascularization (CNV) in a rat model.

Methods:

In phase I, 42 rats were categorized into 6 groups, 5 of which received intravitreal topotecan injections of 0.125 μg, 0.25 μg, 0.5 μg, 0.75 μg, and 1.0 μg/5 μl, respectively; the control group received an injection of normal saline. Ophthalmic examination and electroretinography (ERG) were performed on days 7 and 28, and enucleated globes were processed for histopathology and immunostaining for glial fibrillary acidic protein. In phase II, CNV was induced via laser burns in 20 rats and the animals were divided into 2 groups. One group received topotecan and the other received normal saline intravitreally. Four weeks later, mean scores of fluorescein leakage on fluorescein angiography as well as mean CNV areas on histology sections were compared.

Results:

In phase I, clinical, ERG and histopathologic results were unremarkable in terms of retinal toxicity in all groups. Based on the results of phase I, a dose of 1 μg/5 μl topotecan was chosen for phase II. Leakage scores obtained from late-phase fluorescein angiography were significantly lower in topotecan-treated than control eyes (P < 0.01) four weeks after induction of CNV. Compared to control eyes, topotecan-treated eyes showed a significantly lower incidence of fibrovascular proliferation (8.7% vs. 96.2%) and significantly smaller areas of CNV (P < 0.01).

Conclusion:

Intravitreal injection of topotecan at a dose of 1 μg/5 μl is safe and may be a promising treatment for CNV.

Relapse after localized rhabdomyosarcoma: Evaluation of the efficacy of second-line chemotherapy

PURPOSE

About one-third of patients with rhabdomyosarcoma relapse despite appropriate treatment and experience a poor outcome. Little meaningful improvement in the outcome of this disease has been observed over the last 30 years. There is no clear international recommendation concerning the use of salvage chemotherapy at relapse. A retrospective multicenter analysis was therefore conducted to analyze the efficacy of various second-line chemotherapy regimens in this setting.

METHODS

Forty-nine patients under the age of 18, with initially localized rhabdomyosarcoma, who relapsed after first complete remission, treated in three SFCE centers (Société Française des Cancers de l'Enfant) between 1995 and 2013, were analyzed.

RESULTS

First relapse occurred after a median interval of 22 months and remained localized in 71.4% of cases. All patients received second-line chemotherapy with an overall response to this salvage therapy of 39.1%. Best specific response rates were 73.3 and 42.9% for carboplatin/epirubicin/vincristine-ifosfamide/vincristine/etoposide (CEV/IVE) (15 patients) and vincristine/irinotecan ± temozolomide (VI[T]) (seven patients), respectively. Overall, 40 patients (81.6%) were then eligible for delayed local treatment (surgery and/or radiotherapy) and 30 of them (61.2%) achieved second complete remission. After a median follow-up of 5.4 years since the diagnosis of first relapse, 5-year overall survival is 49.4% (95% CI: 34.2-64.6).

CONCLUSION

Salvage chemotherapy plays a central role in the management of patients with relapsed rhabdomyosarcoma. CEV/IVE and VI(T) regimens can be recommended as neoadjuvant chemotherapy before local treatment for patients with relapsed rhabdomyosarcoma.

Treatment of relapsed Wilms tumour (WT) patients: experience with topotecan. A report from the SIOP Renal Tumour Study Group (RTSG)

BACKGROUND

Topotecan has been variably incorporated in the treatment of patients with relapsed Wilms tumour (WT) who failed initial treatment with three or more effective drugs. Our objective was to describe outcome and to retrospectively investigate the potential role of topotecan in relapsed WT patients.

METHODS

Children who were treated with topotecan as part of their chemotherapeutic regimens for relapsed WT were identified and included in our retrospective study. Patient charts were reviewed for general patient characteristics, histology and stage at initial diagnosis, number and type of relapse, salvage treatment schedules, toxicity, response to treatment and outcome.

RESULTS

From 2000 to 2012, 30 children (median age at relapse 5.5 years, range 1.6-14.5 years) were identified to have received topotecan as part of their salvage regimens (primary progressive disease n = 3, first, second and third relapse n = 13, 9 and 2 respectively, partial response n = 3). Topotecan was administered as a single agent (12 patients) or in combination with other drugs (18 patients). Sixteen patients had high-risk histology according to the SIOP classification, 15 died within 12 months because of progressive disease. Fourteen patients had SIOP intermediate-risk histology of which four patients displayed objective responses to topotecan. Overall, 6 out of 14 intermediate-risk patients survived (median follow up of 6 years), however, three of whom (stage V) had bilateral nephrectomy after topotecan treatment.

CONCLUSIONS

Topotecan does not seem to show effectiveness in the treatment of relapsed WT patients with initial high-risk histology. In patients with intermediate-risk histology, the role of topotecan might deserve further attention, to prove its efficacy.

A novel trial of topotecan, ifosfamide, and carboplatin (TIC) in children with recurrent solid tumors

BACKGROUND

Ifosfamide, carboplatin, and etoposide (ICE) in children with refractory or recurrent solid tumors and lymphomas has resulted in good overall response rates (ORR). Etoposide, a topoisomerase-II inhibitor, however, has been associated with a significant increase in secondary leukemia. The rationale for substituting topotecan, a topoisomerase-I inhibitor, for etoposide in this regimen, a topoisomerase-II inhibitor, includes its limited toxicity profile and decreased leukemogenicity. Furthermore, topotecan in combination with both alkylators and platinating agents are additive and/or synergistic against a variety of solid tumors.

PROCEDURE

Patients with relapsed/refractory solid tumors received ifosfamide (9 g/m² ) and carboplatin (area under the curve: 3 mg/ml/min). Topotecan was also administered at 0.5 mg/m² /day × 3 days (N = 12) and in a small cohort (N = 3) at 0.75 mg/m² /day.

RESULTS

Fifteen patients were entered onto study. Two patients developed seizures/encephalitis secondary to ifosfamide. One patient had dose-limiting thrombocytopenia secondary to TIC that resolved with supportive care. Patients received a median of three cycles (1-3) of TIC. Of the 14 evaluable patients for response, 4/14 had a complete response (CR), 2/14 had a partial response (PR), and 1/14 patients had stable disease (SD). The ORR (CR + PR) was 43%.

CONCLUSION

TIC chemotherapy is feasible and tolerable in children and adolescents with refractory/recurrent solid tumors and lymphomas and results in a 43% excellent ORR in this poor-risk group of patients. A larger cohort of patients, especially in Wilms tumor and central nervous system (CNS) tumors, should be studied in the future to attempt to confirm these preliminary findings. Pediatr Blood Cancer 2015;62:274-278. © 2014 Wiley Periodicals, Inc.

Treatment with topotecan plus cyclophosphamide in children with first relapse of neuroblastoma

BACKGROUND

Reports of responses and toxicities of salvage therapies for relapsed neuroblastoma are rare and often confounded by effects of additional treatments. Our objective was to describe the outcomes and toxicities for a topotecan and cyclophosphamide (TOPO/CTX) regimen for first relapse or progression of high-risk neuroblastoma.

METHODS

We retrospectively reviewed charts of relapsed or refractory neuroblastoma patients treated between 1999 and 2009 with our standard-of-care outpatient TOPO/CTX (0.75 and 250 mg/m(2) /day × 5 days q3-4 weeks).

RESULTS

Twenty-seven patients received 343 cycles of TOPO/CTX (median 10 cycles per patient, range 1-32). Most patients (N = 25) had undergone autologous stem cell transplantation. Seventeen (63%) patients had an objective response (CR + PR + MR). The 3-year progression-free survival (PFS) after relapse was 11 ± 6% and 3-year overall survival (OS) after relapse was 33 ± 9%. The median PFS was 1.2 years and the median OS was 2.3 years. Five patients are alive with follow-up of 3.1-5.5 years. Shorter time from diagnosis to relapse (6-18 months) was associated with shorter OS. The majority of patients experienced chemotherapy delays, transfusions, and febrile neutropenia, including eight bacterial infections. The mean number of hospitalized days was less than one per cycle.

CONCLUSIONS

TOPO/CTX was well tolerated and resulted in response rates and PFS similar to those reported for patients treated on COG 9462. Our study provides additional toxicity, historical endpoints, and time-to-progression data against which new agents and combination therapies using TOPO/CTX as a backbone can be measured.

Phase II study of temozolomide in combination with topotecan (TOTEM) in relapsed or refractory neuroblastoma: a European Innovative Therapies for Children with Cancer-SIOP-European Neuroblastoma study

PURPOSE

To assess objective response rate (ORR) after two cycles of temozolomide in combination with topotecan (TOTEM) in children with refractory or relapsed neuroblastoma.

PATIENTS AND METHODS

This multicenter, non-randomised, phase II study included children with neuroblastoma according to a two-stage Simon design. Eligibility criteria included relapsed or refractory, measurable or metaiodobenzylguanidine (mIBG) evaluable disease, no more than two lines of prior treatment. Temozolomide was administered orally at 150mg/m(2) followed by topotecan at 0.75mg/m(2) intravenously for five consecutive days every 28days. Tumour response was assessed every two cycles according to International Neuroblastoma Response Criteria (INRC), and reviewed independently.

RESULTS

Thirty-eight patients were enroled and treated in 15 European centres with a median age of 5.4years. Partial tumour response after two cycles was observed in 7 out of 38 evaluable patients [ORR 18%, 95% confidence interval (CI) 8-34%]. The best ORR whatever the time of evaluation was 24% (95% CI, 11-40%) with a median response duration of 8.5months. Tumour control rate (complete response (CR)+partial response (PR)+mixed response (MR)+stable disease (SD)) was 68% (95% CI, 63-90%). The 12-months Progression-Free and Overall Survival were 42% and 58% respectively. Among 213 treatment cycles (median 4, range 1-12 per patient) the most common treatment-related toxicities were haematologic. Grade 3/4 neutropenia occurred in 62% of courses in 89% of patients, grade 3/4 thrombocytopenia in 47% of courses in 71% of patients; three patients (8%) had febrile neutropenia.

CONCLUSION

Temozolomide-Topotecan combination results in very encouraging ORR and tumour control in children with heavily pretreated recurrent and refractory neuroblastoma with favourable toxicity profile.

Carboplatin +/- topotecan ophthalmic artery chemosurgery for intraocular retinoblastoma

Purpose

Carboplatin administered systemically or periocularly can result in dramatic and prompt regression of retinoblastoma. However, both routes are rarely curative alone and have undesirable side effects. We aimed to assess the efficacy and toxicity of carboplatin +/− topotecan delivered by ophthalmic artery chemosurgery whereby chemotherapy is infused into the eye via the ophthalmic artery.

Methods

This retrospective, IRB-approved study investigated retinoblastoma patients whom received carboplatin +/− topotecan ophthalmic artery chemosurgery. Patient survival, ocular survival, hematologic toxicity, ocular toxicity, second cancer development and electroretinogram response were all evaluated.

Results

57 carboplatin +/− topotecan infusions (of 111 total) were performed in 31 eyes of 24 patients. The remaining infusions were melphalan-containing. All patients were alive and no patient developed a second malignancy at a median follow up of 25 months. The Kaplan-Meier estimate of ocular survival at two years was 89.9% (95% confidence interval [CI], 82.1–97.9%) for all eyes. Grade 3 or 4 neutropenia developed in two patients and one patient developed metastatic disease. By univariate analysis, neither increasing maximum carboplatin/topotecan dose nor cumulative carboplatin/topotecan dose was associated with statistically significant reduction in the electroretinogram responses.

Conclusion

Carboplatin +/− topotecan infusions are effective for ophthalmic artery chemosurgery in retinoblastoma: they demonstrate low hematologic and ocular toxicity and no statistically significant influence on electroretinogram responses, and used in conjunction with melphalan-containing OAC, demonstrate excellent patient survival and satisfactory ocular survival.

Escalating topotecan in combination with treosulfan has acceptable toxicity in advanced pediatric sarcomas

Patients with advanced pediatric sarcomas have a poor prognosis and novel combination therapies are needed to improve the response rates. Hematological and organ related toxicities have been observed when administering topotecan in combination with, e.g., high dose thiotepa. This study evaluates the toxicity of escalating doses of topotecan alone or in combination with thiotepa or treosulfan. We compared the toxicity including death of complication (DOC) of topotecan alone or in combination with thiotepa or treosulfan in advanced pediatric sarcomas (n = 12). Ten of 12 patients (0.83) suffered from advanced tumors of the Ewing family (i.e., bone or marrow metastases or relapse <24 month after diagnosis, including one neuroepithelial tumor of the kidney) and two from alveolar rhabdomyosarcoma stage IV (0.17). Median age was 15 years (range 5-28). Ratio of female to male was 1:1. Two patients received topotecan alone (1.25 mg/m(2) q 5d and 1.5 mg/m(2) q 5d), three patients received four courses of topotecan (2 mg/m(2) q d 1-5) in combination with thiotepa (100 mg/m(2) q d 1-5), and seven patients received topotecan (2 mg/m(2) q d 1-5) in combination with treosulfan (10g/m(2) q d 3-5). Overall toxicity was not different between all three groups; mean scores were 1.6, 1.8, and 1.7 according to WHO grading (Scale 0-4). Organ related toxicity ranged between 0 and 4 and was not different as well. DOC was 0/2, 1/3, and 0/7 patients respectively. Escalating therapy with topotecan in combination with treosulfan has acceptable toxicity and warrants further investigation in advanced pediatric sarcomas.

Pilot induction regimen incorporating pharmacokinetically guided topotecan for treatment of newly diagnosed high-risk neuroblastoma: a Children's Oncology Group study

PURPOSE

To assess the feasibility of adding dose-intensive topotecan and cyclophosphamide to induction therapy for newly diagnosed high-risk neuroblastoma (HRNB).

PATIENTS AND METHODS

Enrolled patients received two cycles of topotecan (approximately 1.2 mg/m(2)/d) and cyclophosphamide (400 mg/m(2)/d) for 5 days followed by four cycles of multiagent chemotherapy (Memorial Sloan-Kettering Cancer Center [MSKCC] regimen). Pharmacokinetically guided topotecan dosing (target systemic exposure with area under the curve of 50 to 70 ng/mL/hr) was performed. Peripheral-blood stem cell (PBSC) harvest and surgical resection of residual primary tumor occurred after cycles 2 and 5, respectively. Patients achieving at least a partial response received myeloablative chemotherapy with PBSC rescue and radiation to the presurgical primary tumor volume. Oral 13-cis-retinoic acid maintenance therapy was administered twice daily for 14 days in six 28-day cycles.

RESULTS

Thirty-one patients were enrolled onto the study. No deaths related to toxicity or dose-limiting toxicities occurred during induction. Mucositis rarely occurred after topotecan cycles (9.7%) in contrast to 30% after MSKCC cycles. Thirty patients underwent PBSC collection with median 31.1 × 10(6) CD34+ cells/kg (range, 1.8 to 541.8 × 10(6) CD34+ cells/kg), all negative for tumor contamination by immunocytochemical analysis. Targeted topotecan systemic exposure was achieved in 26 (84%) of 31 patients. At the end of induction, 26 patients (84%) had tumor response and one patient had progressive disease. In the overall cohort, 3-year event-free and overall survival were 37.8% ± 9.4% and 57.1% ± 9.4%, respectively.

CONCLUSION

This pilot induction regimen was well tolerated with expected and reversible toxicities. These data support investigation of efficacy in a phase III clinical trial for newly diagnosed HRNB.

Phase II randomized comparison of topotecan plus cyclophosphamide versus topotecan alone in children with recurrent or refractory neuroblastoma: a Children's Oncology Group study

PURPOSE

Single-agent topotecan (TOPO) and combination topotecan and cyclophosphamide (TOPO/CTX) were compared in a phase II randomized trial in relapsed/refractory neuroblastoma. Because responders often underwent further therapies, novel statistical methods were required to compare the long-term outcome of the two treatments.

PATIENTS AND METHODS

Children with refractory/recurrent neuroblastoma (only one prior aggressive chemotherapy regimen) were randomly assigned to daily 5-day topotecan (2 mg/m(2)) or combination topotecan (0.75 mg/m(2)) and cyclophosphamide (250 mg/m(2)). A randomized two-stage group sequential design enrolled 119 eligible patients. Toxicity and response were estimated. Long-term outcome of protocol therapy was assessed using novel methods-causal inference-which allowed adjustment for the confounding effect of off-study therapies.

RESULTS

Seven more responses were observed for TOPO/CTX (complete response [CR] plus partial response [PR], 18 [32%] of 57) than TOPO (CR+PR, 11 [19%] of 59;P = .081); toxicity was similar. At 3 years, progression-free survival (PFS) and overall survival (OS) were 4% +/- 2% and 15% +/- 4%, respectively. PFS was significantly better for TOPO/CTX (P = .029); there was no difference in OS. Older age at diagnosis and lack of MYCN amplification predicted increased OS (P < .05). Adjusting for randomized treatment effect and subsequent autologous stem-cell transplantation, there was no difference between TOPO and TOPO/CTX in terms of the proportion alive at 2 years.

CONCLUSION

TOPO/CTX was superior to TOPO in terms of PFS, but there was no OS difference. After adjustment for subsequent therapies, no difference was detected in the proportion alive at 2 years. Causal inference methods for assessing long-term outcomes of phase II therapies after subsequent treatment can elucidate effects of initial therapies.

Cancer therapies utilizing the camptothecins: a review of the in vivo literature

This review summarizes the in vivo assessment-preliminary, preclinical, and clinical-of chemotherapeutics derived from camptothecin or a derivative. Camptothecin is a naturally occurring, pentacyclic quinoline alkaloid that possesses high cytotoxic activity in a variety of cell lines. Major limitations of the drug, including poor solubility and hydrolysis under physiological conditions, prevent full clinical utilization. Camptothecin remains at equilibrium in an active lactone form and inactive hydrolyzed carboxylate form. The active lactone binds to DNA topoisomerase I cleavage complex, believed to be the single site of activity. Binding inhibits DNA religation, resulting in apoptosis. A series of small molecule camptothecin derivatives have been developed that increase solubility, lactone stability and bioavailability to varying levels of success. A number of macromolecular agents have also been described wherein camptothecin(s) are covalently appended or noncovalently associated with the goal of improving solubility and lactone stability, while taking advantage of the tumor physiology to deliver larger doses of drug to the tumor with lower systemic toxicity. With the increasing interest in drug delivery and polymer therapeutics, additional constructs are anticipated. The goal of this review is to summarize the relevant literature for others interested in the field of camptothecin-based therapeutics, specifically in the context of biodistribution, dosing regimens, and pharmacokinetics with the desire of providing a useful source of comparative data. To this end, only constructs where in vivo data is available are reported. The review includes published reports in English through mid-2009.

Initial testing of topotecan by the pediatric preclinical testing program

BACKGROUND

Topotecan is a small molecule DNA topoisomerase I poison, that has been successful in clinical trials against pediatric solid tumors and leukemias. Topotecan was evaluated against the Pediatric Preclinical Testing Program (PPTP) tumor panels as part of a validation process for these preclinical models.

PROCEDURES

In vivo three measures of antitumor activity were used: (1) an objective response measure modeled after the clinical setting; (2) a treated to control (T/C) tumor volume measure; and (3) a time to event (fourfold increase in tumor volume for solid tumor models, or > or =25% human CD45+ cells in the peripheral blood for acute lymphoblastic leukemia, ALL models) measure based on the median event-free survival (EFS) of treated and control animals for each xenograft.

RESULTS

Topotecan inhibited cell growth in vitro with IC(50) values between 0.71 and 489 nM. Topotecan significantly increased EFS in 32 of 37 (87%) solid tumor xenografts and in all 8 of the ALL xenografts. Seventy-five percent of solid tumors met EFS T/C activity criteria for intermediate (n = 17) or high activity (n = 7). Objective responses were noted in eight solid tumor xenografts (Wilms, rhabdomyosarcoma, Ewing sarcoma, neuroblastoma). Among the six neuroblastomas, three achieved a PR. For the ALL panel, two maintained CRs, three CRs, and two PRs were observed.

CONCLUSIONS

Topotecan demonstrated broad activity in vitro and in vivo against both the solid tumor and ALL panels, with significant tumor growth delay generated in all the panels. These results further demonstrate the validity of the PPTP panel for preclinical testing of new drugs.

A phase I study to characterize the safety, tolerability, and pharmacokinetics of topotecan at 4 mg/m2 administered weekly as a 30-minute intravenous infusion in patients with cancer

Topotecan pharmacokinetics at higher infusion rates (4 mg/m2 over 30 minutes) have not been studied. The authors report a pharmacokinetics and safety study of this dose in advanced cancer patients. Sixteen patients were given a 4-mg/m2 topotecan infusion intravenously (IV) over 30 minutes weekly for 3 weeks, repeated every 28 days. Pharmacokinetics were determined after the first dose. Plasma concentrations of total topotecan were measured to derive CL, V(ss), C(max), t(max), t(1/2), AUC(0-t), and AUC(0-infinity). Plasma total topotecan concentrations decreased biexponentially, with a mean CL value of 20.6 L/h, V(ss) value of 101 L, and t(1/2) value of 5.0 h. Nine significant adverse events (all hematologic) were topotecan related. Grade 3 or less adverse events included anemia, thrombocytopenia, leukopenia, and fatigue. Pharmacokinetics of the 4-mg/m2 infusion of topotecan over 30 minutes are comparable to findings from studies of lower and higher doses. Toxicities are similar to previous reports.

Application of a highly specific and sensitive fluorescent HPLC method for topotecan lactone in whole blood

Individualization of topotecan dosing reduces inter-patient variability in topotecan exposure, presumably reducing toxicity and increasing efficacy. However, logistical limitations (e.g. requirement for plasma, intensive bedside plasma processing) have prevented widespread application of this approach to dosing topotecan. Thus, the objectives of the present study were to develop and validate an HPLC with fluorescence detection method to measure topotecan lactone in whole blood samples and to evaluate its application to individualizing topotecan dosing. Plasma samples (200 microL) were prepared using methanolic precipitation, a filtration step and then injection of 100 microL of the methanolic extract onto a Novapak C(18), 4 microm, 3.9 x 150 mm column with an isocratic mobile phase. Analytes were detected with a Shimadzu Fluorescence RF-10AXL detector with an excitation and emission wavelength of 370 and 520 nm, respectively. This method had a lower limit of quantification of 1 ng/mL (S/N >or= 5; RSD 4.9%) and was validated over a linear range of 1-100 ng/mL. Results from a 5-day validation study demonstrated good within-day and between-day precision and accuracy. Data are presented to demonstrate that the present method can be used with whole blood samples to individualize topotecan dosing in children with cancer.

Using pharmacokinetic and pharmacodynamic modeling and simulation to evaluate importance of schedule in topotecan therapy for pediatric neuroblastoma

PURPOSE

The study aims to use mathematical modeling and simulation to assess the relative contribution of topotecan systemic exposure and scheduling in the activity and myelosuppression of topotecan in pediatric patients with neuroblastoma.

EXPERIMENTAL DESIGN

Pharmacokinetic and pharmacodynamic data were obtained from a phase II study for pediatric patients with high-risk neuroblastoma. The topotecan dosage was individualized to attain a topotecan lactone area under the plasma concentration-time curve between 80 and 120 ng/mL h and given over a protracted schedule (i.e., 10 days). Four mathematical models describing topotecan pharmacokinetics, tumor growth, and neutrophil and platelet dynamics were developed. The models were combined to simulate and compare different topotecan treatment strategies with respect to systemic exposure and schedule.

RESULTS

The median change in tumor volume was significantly different between schedules (5% increase for D x 5 versus 60% decrease for D x 5 x 2; P < 0.0001) when administering the same total systemic exposure. Whereas protracted schedules showed increased neutropenia (median of 7 versus 12 days below an absolute neutrophil count of 500/microL; P < 0.0001) and thrombocytopenia (median of 3 versus 10 days below a platelet count of 20,000/microL; P < 0.00001), simulations showed that delays in topotecan therapy would not be required. Simulations showed that an increase in topotecan exposure on the D x 5 schedule by 2.4-fold resulted in a modest decrease in tumor volume (i.e., median percentage change tumor volume of 24% versus 3%).

CONCLUSIONS

The present mathematical model gave an innovative approach to determining relevant topotecan schedules for possible evaluation in the clinic, which could lead to improved tumor response with minimized toxicities.

Population pharmacokinetic analysis of topotecan in pediatric cancer patients

PURPOSE

To characterize the population pharmacokinetics of topotecan lactone in children with cancer and identify covariates related to topotecan disposition.

PATIENTS AND METHODS

The study population consisted of 162 children in seven clinical trials receiving single agent topotecan as a 30-min infusion. A population approach via nonlinear mixed effects modeling was used to conduct the analysis.

RESULTS

A two-compartment model was fit to topotecan lactone plasma concentrations (n = 1874), and large pharmacokinetic variability was observed among studies, among individuals, and within individuals. We conducted a covariate analysis using demographics, biochemical data, trial effects, and concomitant drugs. The most significant covariate was body surface area, which explained 54% of the interindividual variability for topotecan systemic clearance. Interoccasion variability was considerable in both clearance and volume (20% and 22%, respectively), but was less than interindividual variability in both variables. Other covariates related to clearance were concomitant phenytoin, calculated glomerular filtration rate, and age (<0.5 years). Including them in the model reduced the interindividual variability for topotecan clearance by an additional 48% relative to the body surface area-normalized model. The full covariate model explained 76% and 50% of interindividual variability in topotecan clearance and volume, respectively.

CONCLUSIONS

We developed a descriptive and robust population pharmacokinetic model which identified patient covariates that account for topotecan disposition in pediatric patients. Additionally, dosing topotecan based on the covariate model led to a more accurate and precise estimation topotecan systemic exposure compared with a fixed dosing approach, and could be a tool to assist clinicians to individualize topotecan dosing.

Favorable response of intraommaya topotecan for leptomeningeal metastasis of neuroblastoma after intravenous route failure

A 3-year-old male, diagnosed with stage 4 neuroblastoma, developed recurrent leptomeningeal metastasis after multi-modality treatment including multi-agent chemotherapy, surgery, high dose chemotherapy plus stem cell rescue, cis-retinoic acid and intravenous (IV) topotecan. He then received intraommaya (IO) topotecan three times weekly (maximum dose; 0.4 mg). A complete response was achieved by a resolution of malignant cells in cerebrospinal fluid and resolution leptomeningeal enhancement by brain MRI. Treatment toxicities included low-grade fever and minimal headache. The duration of treatment response from IO topotecan was 18 weeks. The survival time from CNS recurrence in this patient was 13 months. We suggest IO topotecan be considered for neoplastic meningitis of tumors with known sensitivity to topotecan.

Topotecan is active against Wilms' tumor: results of a multi-institutional phase II study

PURPOSE

A phase II study was conducted to evaluate the activity and safety of topotecan in pediatric patients with recurrent Wilms' tumor.

PATIENTS AND METHODS

Patients with favorable histology Wilms' tumor (FHWT) and recurrence after at least one salvage chemotherapy regimen or with anaplastic histology Wilms' tumor (AHWT) in first or subsequent recurrence were eligible. Patients were stratified according to histology, with statistical considerations based on the FHWT stratum. Topotecan was administered intravenously over 30 minutes for 5 days on 2 consecutive weeks. Treatment dosages were adjusted to achieve a target area under the curve (AUC) of 80 +/- 10 ng/mL*h. Tumor responses were measured after two cycles of treatment.

RESULTS

Thirty-seven patients (26 patients with FHWT) were enrolled and received a total of 94 cycles of topotecan (range, one to six cycles). The median topotecan dosage required to achieve the target AUC was 1.8 mg/m2 (range, 0.7 to 3.2 mg/m2). Of 25 assessable patients with FHWT, 12 had partial response (PR), six had stable disease (SD), and seven had progressive disease (PD), for an overall response rate of 48% (95% CI, 27.8% to 68.7%). Of 11 assessable patients with AHWT, two had PR, one had SD, and eight had PD. The main toxicities were grade 3 and 4 neutropenia (median duration, 13 days) and thrombocytopenia (median duration, 7.5 days).

CONCLUSION

Topotecan administered on a protracted schedule is active against recurrent FHWT. Inclusion of topotecan in front-line clinical trials for patients with recurrent Wilms' tumor should be considered.

Topotecan, cyclophosphamide, and etoposide (TCE) in the treatment of high-risk neuroblastoma. Results of a phase-II trial

PURPOSE

Relapsed high-risk neuroblastoma patients still have a poor prognosis. This phase-II trial assessed a new topotecan containing chemotherapy approach in patients with active disease.

METHODS

Chemotherapy consisted of topotecan (1.0 mg/m(2)/day 168-h continuous infusion), cyclophosphamide (100 mg/m(2)/day 1-h-infusion days 1-7 starting 6 h prior to topotecan), and etoposide (100 mg/m(2)/day 1-h-infusion days 8-10). Patients with relapsed neuroblastoma were scheduled for six cycles, untreated patients for two cycles followed by standard high-risk treatment.

RESULTS

Main toxicity observed during 153 cycles were grade 3-4 leukopenia (97% of cycles), thrombocytopenia (92%), neutropenic fever (52%), and mucositis (10%). No treatment related fatal toxicity occurred. Complete or partial response was achieved in 19 of 31 (61%) evaluable relapsed patients and 8 of 11 (72%) untreated patients.

CONCLUSIONS

The combination of topotecan, cyclophosphamide, and etoposide is tolerable and effective in relapsed and untreated neuroblastoma. Myelotoxicity is the main side effect but seems justified in view of the encouraging response rates. A randomized phase-III trial in primary disease has been commenced.

Topotecan and etoposide in the treatment of relapsed high-risk neuroblastoma: results of a phase 2 trial

We initiated a phase 2 trial with a combination of topotecan and etoposide (TE) in patients with relapse after intensive first line chemotherapy for neuroblastoma. TE chemotherapy consisted of topotecan (schedule A: 1.0 mg/m2/d 30-minute-infusion days 1 to 5, B: 0.7 mg/m2/d continuous infusion days 1 to 7, and C: 1.0 mg/m2/d continuous infusion days 1 to 7) followed by etoposide (100 mg/m2/d 1-hour-infusion days 8 to 10). TE was repeated every 28 days. The treatment was continued until severe nonhematopoietic toxicity or progression occurred or the treating physician chose alternative consolidation treatment after response to TE. Forty patients received 153 TE cycles. Grades 3 to 4 leukopenia was frequently observed in all schedules (A 51% of cycles, B 48%, and C 74%, P=0.141). Thrombocytopenia (A 69%, B 63%, and C 93%, P=0.004) and neutropenic fever (A 12%, B 29%, and C 37%, P=0.048) occurred more frequently in schedule C. No treatment-related fatal toxicity was observed. Among 36 patients evaluable for response, 4 patients achieved complete and 13 patients achieved partial remission (47%). We conclude that the combination of TE is effective and tolerable in the treatment of relapsed high-risk neuroblastoma.

Interferon beta-mediated vessel stabilization improves delivery and efficacy of systemically administered topotecan in a murine neuroblastoma model

BACKGROUND

We have recently demonstrated that continuous delivery of interferon beta (IFN-beta) stabilizes solid tumor vasculature and improves tumor perfusion. In this study, we have further investigated the functional consequences of this effect by assessing delivery and efficacy of conventional chemotherapy against neuroblastoma xenografts when used in combination with IFN-beta.

METHODS

Mice with established retroperitoneal tumors received adeno-associated virus vector encoding IFN-beta (AAV IFN-beta) or control vector. One week later, at 1 hour before sacrifice, a 1 mg/kg i.v. bolus of topotecan (TPT) was given. Intratumoral levels of TPT were measured by high-performance liquid chromatography and then standardized to plasma levels to determine tumor TPT penetration. Subsequent experiments evaluated the antitumor efficacy of topotecan alone or in combination with AAV IFN-beta.

RESULTS

As observed in prior experiments, AAV IFN-beta resulted in a marked increase in tumor vessel association with stabilizing perivascular smooth muscle cells. These more "matured" vessels facilitated improved tumor TPT penetration (51.2% +/- 4.2%) compared with controls (30.8% +/- 4.7%, P = .004). In additional cohorts of mice, this resulted in an improved antitumor effect. Mice with established tumors (301.8 +/- 18.1 mm3) were treated with TPT (1 mg/kg daily for 5 days for 2 consecutive weeks) either alone or in combination with AAV IFN-beta (5 x 10(10) vector particles per mouse). Topotecan monotherapy resulted in a reduction in mean tumor volume of 12% (264.2 +/- 65.8 mm3, P = .66). However, when the same regimen was administered to mice receiving continuous IFN-beta therapy, a 61% (118.9 +/- 42.3 mm3, P = .004) reduction in mean tumor volume was achieved.

CONCLUSION

Interferon beta-mediated vessel stabilization resulted in improved intratumoral delivery of systemically administered TPT, enhancing its antitumor efficacy. This approach of altering the tumor vasculature provides a strategy to help overcome solid tumor resistance to traditional cytotoxic agents.

Topotecan, thiotepa, and carboplatin for neuroblastoma: failure to prevent relapse in the central nervous system

We report on a three-drug myeloablative regimen designed to consolidate remission and to prevent central nervous system (CNS) relapse of high-risk neuroblastoma (NB). Sixty-six NB patients received topotecan 2 mg/m2/day, x 4 days; thiotepa 300 mg/m2/day, x 3 days; and carboplatin approximately 500 mg/m2/day, x 3 days. Post-SCT treatments included radiotherapy, immunotherapy, 13-cis-retinoic acid, +/-oral etoposide. Significant nonhematologic toxicities were mucositis and skin-related in all patients, convulsions in three patients, and cardiac failure and venocclusive disease of liver in one patient each. Grade 2 hepatotoxicity led to truncating cytoreduction in two patients; both later relapsed in brain. Among 46 patients transplanted in first complete/very good partial remission (CR/VGPR), event-free survival is 54% (s.e.+/-8%) at 36 months post-SCT; notable events were three non-NB-related deaths (adenovirus on day +9, bowel necrosis at 5 months, multiorgan failure at seven months) and four relapses in brain. Of 12 patients transplanted with evidence of NB, two became long-term event-free survivors and two relapsed in the brain. Of eight patients transplanted in second or greater CR/VGPR, one became a long-term event-free survivor and seven relapsed though not in the CNS. This regimen has manageable toxicity but does not prevent CNS relapse.

Irinotecan for children with relapsed solid tumors

Irinotecan is expected to become a new drug for childhood solid tumors. Sixteen children with relapsed solid tumors received irinotecan 180 mg/m2/day for 3 consecutive days, repeated once after 25 days off. Their original tumors were neuroblastoma in 7, rhabdomyosarcoma in 3, nephroblastoma and undifferentiated sarcoma in 2 each, and primitive neuroectodermal tumor and leiomyosarcoma in 1 each. The average age at trials was 6 years. Partial response was achieved in 5 (31.3%) (neuro-blastoma, rhabdomyosarcoma, nephroblastoma, undifferentiated sarcoma, and leiomyosarcoma), and decrease in tumor marker in the other 2. Irinotecan appears promising, and could become included in the first-line treatment.

Using plasma topotecan pharmacokinetics to estimate topotecan exposure in cerebrospinal fluid of children with medulloblastoma

The purpose of this study was to estimate ventricular cerebrospinal fluid (vCSF) topotecan lactone (TPT) exposures in pediatric medulloblastoma patients from plasma concentration-time data by using a pharmacokinetic (PK) model. We studied children with high-risk medulloblastoma who received pharmacokinetically guided TPT (target plasma area under the concentration-time curve [AUC], 120-160 ng/ml-h) and obtained serial vCSF samples to assess TPT exposure. Population pharmacokinetic parameters were determined by using linear mixed-effects modeling via the two-stage approach. We simulated TPT vCSF exposure duration at plasma TPT AUC values of 120 to 200 ng/ml-h and determined percentages of studies meeting or exceeding the vCSF exposure duration threshold (EDT) of 1 ng/ml for 8 h. We then used bootstrap methods to estimate variability in vCSF EDT. Eighteen PK studies were conducted in six patients (median age, 4.8 years). In these patients, seven of nine studies attaining target plasma TPT AUC achieved the vCSF EDT. Given a plasma TPT AUC of 120 ng/ml-h, the median percentage of results meeting or exceeding EDT was 78% (95% CI, 61%-100%). One patient (four studies) with tumor blockage of CSF flow, which can alter CSF pharmacokinetics, was removed, and the bootstrap analysis was repeated. In this subset, a median 93% (95% CI, 79%-100%) of studies achieved vCSF EDT. Increasing plasma TPT AUC values resulted in increased ability to achieve vCSF EDT. We demonstrated that a plasma PK model could estimate vCSF TPT concentrations. Further, our results indicate that the TPT vCSF EDT can be achieved in more than 80% of studies targeted to a plasma TPT AUC of 120 ng/ml-h.

A phase II window trial of procarbazine and topotecan in children with high-grade glioma: a report from the children’s oncology group

The role of chemotherapy in the treatment of high-grade gliomas in children is unclear. Early reports were suggestive of improved outcome in children with high-grade glioma with the addition of chemotherapy after surgery and radiation therapy. Subsequent studies did not show similar favorable contribution of chemotherapy to the outcome of these children. Further efforts to identify active chemotherapy agents in children include use of agents that have shown efficacy in adult patients with high-grade glioma and agents that have shown promise in mice bearing human xenografts of brain tumors. A Pediatric Oncology Group (POG 9431) trial tested the activity of two such agents, procarbazine and topotecan in newly diagnosed patients with high-grade glioma who had measurable disease after diagnostic surgery. Neither agent showed efficacy within the confines of the statistical design of the study. This study showed that children with high-grade glioma have an innate resistance to alkylating agents based on mismatch repair deficiency and high levels of alkyguanine transferase (AGT). Future trials should consider strategies to overcome the resistance mechanisms in children with high-grade glioma.

[131I]MIBG and topotecan: a rationale for combination therapy for neuroblastoma

MIBG is selectively concentrated in neuroblastoma cells, and radioiodinated MIBG has been used with some success for targeted radiotherapy. However, long-term cure remains elusive, and the topoisomerase I inhibitor topotecan may improve upon existing [131I]MIBG therapy. While synergistic killing by combinations of ionising radiation and topoisomerase I inhibitors has been reported, there is no consensus on optimal scheduling. Furthermore, there has been no attempt to demonstrate radio-potentiation by topoisomerase I inhibitors and targeted radiotherapy. We are investigating various scheduled combinations of topotecan and [131I]MIBG on neuroblastoma cells, and preliminary data suggests that topotecan induces increased accumulation of [131I]MIBG in vitro.

Pediatric Phase I Trials in Oncology: An Analysis of Study Conduct Efficiency

Purpose

To determine the efficacy and safety of pediatric phase I oncology trials in the era of dose-intensive chemotherapy and to analyze how efficiently these trials are conducted.

Methods

Phase I pediatric oncology trials published from 1990 to 2004 and their corresponding adult phase I trials were reviewed. Dose escalation schemes using fixed 30% dose increments were studied to theoretically determine whether trials could be completed utilizing fewer patients and dose levels.

Results

Sixty-nine pediatric phase I oncology trials enrolling 1,973 patients were identified. The pediatric maximum-tolerated dose (MTD) was strongly correlated with the adult MTD (r = 0.97). For three-fourths of the trials, the pediatric and adult MTD differed by no more than 30%, and for more than 85% of the trials, the pediatric MTD was less than or equal to 1.6 times the adult MTD. The median number of dose levels studied was four (range, two to 13). The overall objective response rate was 9.6%, the likelihood of experiencing a dose-limiting toxicity was 24%, and toxic death rate was 0.5%.

Conclusion

Despite the strong correlation between the adult and pediatric MTDs, more than four dose levels were studied in 40% of trials. There appeared to be little value in exploring dose levels greater than 1.6 times the adult MTD. Limiting pediatric phase I trials to a maximum of four doses levels would significantly shorten the timeline for study conduct without compromising safety.

Phase I study of the combination of topotecan and irinotecan in children with refractory solid tumors

PURPOSE

We have shown in xenograft studies that the antitumor activities of topotecan and irinotecan are highly schedule- and dose-dependent, with a high frequency of response at low, protracted dose schedules. Preclinical and clinical data suggest that topotecan and irinotecan have different antitumor activities and mechanisms of resistance, and non-overlapping toxicities, providing a rationale for their combination. Combining both agents may increase the amount of camptothecin delivered to the tumor, without additive toxicity.

METHODS

We conducted a phase I study in children with refractory solid tumors to determine the maximum tolerated dose (MTD) of irinotecan when administered with a targeted systemic exposure (TSE) of topotecan and to define the dose-limiting toxicity (DLT) of this combination. Irinotecan was administered IV over 60 min followed by topotecan over 30 min daily for 5 days for two consecutive weeks. We initially fixed the topotecan-TSE to 80+/-10 ng*h/ml and investigated the ability to escalate irinotecan (starting dose 16 mg/m2/d). Topotecan and irinotecan pharmacokinetics were determined.

RESULTS

Eleven patients (median age 10 years) were enrolled. Owing to DLT, irinotecan was de-escalated to 12 (level -1; n = 3) and 9 (level -2; n = 3) mg/m2/day, and topotecan-TSE was reduced to 60+/-10 ng*h/ml (level -3; n = 2). DLTs were neutropenia (n = 8), typhlitis (n = 5), and skin rash (n = 1). MTD could not be reached. Median (range) irinotecan and topotecan lactone systemic clearances were 50.3 (16.6-76.2) l/h/m2 and 27.6 (14.7-55.9) l/h/m2, respectively. The pharmacokinetics profile of each agent was similar to that seen in previous single agent studies. One patient with neuroblastoma and one with rhabdomyosarcoma had a partial and a complete response, respectively.

CONCLUSION

Despite promising antitumor activity, the combination of topotecan and irinotecan given on a protracted schedule does not warrant further development in children due to unacceptable toxicity.

Ewing's sarcoma and primitive neuroectodermal family of tumors

Ewing's sarcoma (ES) initially was believed to be of perivascular endothelial origin. The Ewing's sarcoma family of tumors (EFT) includes ES of bone (ESB), extraosseous ES (EES), peripheral primitive neuroectodermal tumor of bone (pPNET), and malignant small-cell tumor of the thoracopulmonary region, or Askin's tumor, all of which are now known to be neoplasms of neuroectodermal origin. The degree of neuronal differentiation has been used for histopathologic subclassification of the EFT as classical ES (ESB or EES), which is characterized by minimal evidence of neural differentiation, and pPNET, which displays evidence of neural differentiation by standard microscopy, electron microscopy, or immunohistochemistry. Because the behavior, prognosis, and treatment appear to be similar for all subsets of EFT, this histopathologic subclassification may not be clinically significant, though some debate remains whether neural differentiation predicts for inferior outcome.

Topotecan, an active new antineoplastic agent: review and current status

Topotecan (Hycamtin) is a water soluble semisynthetic analogue of the alkaloid camptothecin which has antitumour activity in preclinical models in vitro and in vivo. A range of Phase I studies has been performed and a daily x 5 iv. schedule, which showed most promising evidence of activity, was selected for extensive clinical evaluation. To date, topotecan has been shown to be active in a number of malignancies, including metastatic ovarian cancer, recurrent small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), breast cancer, colorectal cancer and myelodysplastic syndrome. In ovarian cancer, response rates of around 15% were identified in patients who had failed standard chemotherapy, and in a randomised, comparative study with paclitaxel response rates of 20% (topotecan) and 13% (paclitaxel) were observed. In addition, overall time to progression was impressive at 23 weeks (topotecan) compared with 14 weeks (paclitaxel). In recurrent SCLC, topotecan has shown good activity in sensitive patients with a response rate of 39%, although the response rate in refractory patients was considerably lower (7%). Median survival of all patients was 5.4 months, acceptable for this difficult clinical scenario. Topotecan is well-tolerated in the majority of patients and subjective toxicities are uncommon. The principal side-effect is myelosuppression, mainly neutropenia. Serious clinical sequelae are relatively uncommon and non-cumulative. Nonhaematological toxicities are generally mild and not dose-limiting. In clinical use, topotecan has exhibited activity in multiple tumour types, with a side-effect profile that is predictable and manageable. The drug is under evaluation in other tumour types and in combination chemotherapy regimens.

A predictive model of human myelotoxicity using five camptothecin derivatives and the in vitro colony-forming unit granulocyte/macrophage assay

PURPOSE

Many promising anticancer drugs are limited by myelosuppression. It is difficult to evaluate human myelotoxicity before a Phase I study because of the susceptibility of humans and animals to hematotoxicity. The purpose of this study was to establish a reliable method to predict the human maximum tolerated dose (MTD) of five camptothecin derivatives: SN-38, DX-8951f, topotecan, 9-aminocamptothecin, and camptothecin.

EXPERIMENTAL DESIGN

The myelotoxicity of SN-38 and DX-8951f were evaluated on bone marrow from mice, dogs, and humans using a 14-day colony-forming unit, granulocyte-macrophage (CFU-GM) assay to determine the 50%, 75%, and 90% inhibitory concentration values (IC50, IC75, and IC90, respectively).

RESULTS

Species differences in myelotoxicity were observed for SN-38 and DX-8951f. Using human and murine IC90s for myelotoxicity of these compounds and other camptothecin compounds (topotecan, 9-aminocamptothecin, and camptothecin), in vivo toxicological data, and pharmacokinetic parameters (data referred to in the literature), human MTDs were predicted retrospectively. The mechanism-based prediction model that is proposed uses the in vitro camptothecin assay and in vivo parameters on the basis of free fraction of area under the concentration-curve at the MTD (r2 = 0.887) and suggests that the human MTDs were well predicted for the five camptothecin derivatives by this model rather than by other models.

CONCLUSION

The human MTDs of the camptothecin drugs were successfully predicted using the mechanism-based prediction model. The application of this model for in vitro hematotoxicology could play an important role for the development of new anticancer agents.

A Phase II trial of paclitaxel and topotecan with filgrastim in patients with recurrent or refractory glioblastoma multiforme or anaplastic astrocytoma

PURPOSE

Therapy for high-grade gliomas remains unsatisfactory. Paclitaxel and topotecan have separately demonstrated activity against gliomas. We conducted a Phase II trial of these agents in combination with filgrastim (G-CSF) in patients with recurrent or refractory glioblastoma multiforme or anaplastic astrocytoma.

PATIENTS AND METHODS

Adult patients with radiographic evidence of recurrent or progressive tumor following primary therapy were eligible for study. Patients received paclitaxel 175 mg/m2 IV over 3 h on day 1 and topotecan 1.0 mg/m2 IV over 30 min on days 1-5. Filgrastim 5 microg/kg was given days 6-14 for neutrophil support. Treatment cycles were repeated every 21 days.

RESULTS

Twenty patients were enrolled on study, and seventeen were considered evaluable for response. Two patients (12/%) exhibited partial remission and seven patients (41/%) exhibited stable disease in response to therapy. Hematologic toxicity was common with 25 /% of patients experiencing grade III or IV leukopenia despite G-CSF support. Two patients died of infectious complications on protocol, prompting suspension of further accrual.

CONCLUSION

Paclitaxel and topotecan with G-CSF support exhibits modest activity in adults with recurrent or refractory glioblastoma and anaplastic astrocytoma. The significant hematotoxicity encountered, however, cannot justify further investigation of this combination in patients with high grade brain tumors.

Response to paclitaxel, topotecan, and topotecan-cyclophosphamide in children with untreated disseminated neuroblastoma treated in an upfront phase II investigational window: a pediatric oncology group study

PURPOSE

Most children older than 1 year of age with metastatic neuroblastoma (NB) die despite intensive chemotherapy and bone marrow transplantation. The Pediatric Oncology Group conducted a study of paclitaxel, topotecan, and topotecan-cyclophosphamide (topo-cyclo) in newly diagnosed children with stage IV NB.

PATIENTS AND METHODS

There were 102 patients enrolled between September 1993 and October 1995; two of them were later shown to be ineligible. Of the remaining 100 patients, the first cohort of 33 patients received paclitaxel 350 mg/m(2) intravenously (IV) over 24 hours every 14 to 21 days; the next 33 patients received topotecan 2 mg/m(2)/d for 5 days IV every 21 days; a third cohort of 34 patients were treated with IV cyclophosphamide 250 mg/m(2) followed by topotecan 0.75 mg/m(2) each day for 5 days every 21 days. Patients were re-evaluated after two courses and then treated with intensive induction therapy and bone marrow transplantation.

RESULTS

Objective responses (complete response + partial response + mixed response) were documented in 67% of children who received topotecan, 76% after topo-cyclo, and 25% after paclitaxel. Four patients had grade 3 to 4 allergic reactions to paclitaxel; most patients developed grade 3 to 4 marrow suppression after topotecan or topo-cyclo. Neither disease-free survival nor overall survival differed significantly between children who received a phase II agent and those who did not. The 6-year disease-free survival and overall survival rates for all 100 children were 18% +/- 5% and 26% +/- 5%, respectively.

CONCLUSION

Topotecan and topo-cyclo are active in children with NB, are well tolerated, and should be evaluated further in combination regimens.

Results of a phase II upfront window of pharmacokinetically guided topotecan in high-risk medulloblastoma and supratentorial primitive neuroectodermal tumor

PURPOSE

To assess the antitumor efficacy of pharmacokinetically guided topotecan dosing in previously untreated patients with medulloblastoma and supratentorial primitive neuroectodermal tumors, and to evaluate plasma and CSF disposition of topotecan in these patients.

PATIENTS AND METHODS

After maximal surgical resection, 44 children with previously untreated high-risk medulloblastoma were enrolled, of which 36 were assessable for response. The topotecan window consisted of two cycles, administered initially as a 30-minute infusion daily for 5 days, lasting 6 weeks. Pharmacokinetic studies were conducted on day 1 to attain a topotecan lactone area under the plasma concentration-time curve (AUC) of 120 to 160 ng/mL.h. After 10 patients were enrolled, the infusion was modified to 4 hours, with dosage individualization.

RESULTS

Of 36 assessable patients, four patients (11.1%) had a complete response and six (16.6%) showed a partial response, and disease was stable in 17 patients (47.2%). Toxicity was mostly hematologic, with only one patient experiencing treatment delay. The target plasma AUC was achieved in 24 of 32 studies (75%) in the 30-minute infusion group, and in 58 of 93 studies (62%) in the 4-hour infusion group. The desired CSF topotecan exposure was achieved in seven of eight pharmacokinetic studies when the topotecan plasma AUC was within target range.

CONCLUSION

Topotecan is an effective agent against pediatric medulloblastoma in patients who have received no therapy other than surgery. Pharmacokinetically guided dosing achieved the target plasma AUC in the majority of patients. This drug warrants testing as part of standard postradiation chemotherapeutic regimens. Furthermore, these results emphasize the importance of translational research in drug development, which in this case identified an effective drug.

Topotecan disposition in an anephric child

Although limited data are available about topotecan disposition in patients with renal insufficiency, nothing has been reported in anephric patients. The objective of this report is to characterize topotecan disposition in an anephric child with Wilms tumor, both on and off hemodialysis. The patient received topotecan and cyclophosphamide for four cycles; topotecan was administered daily for 5 days, with hemodialysis on the second and fourth day. Therapy was well tolerated, with grade 3 thrombocytopenia and grade 2 neutropenia noted after cycle four. The median topotecan lactone clearance was 15.5 L/h/m off hemodialysis and 18.7 L/h/m on hemodialysis. Topotecan clearance was minimally affected by hemodialysis and was similar to that observed in children without renal failure.

Camptothecin analogs (irinotecan or topotecan) plus high-dose cyclophosphamide as preparative regimens for antibody-based immunotherapy in resistant neuroblastoma

PURPOSE

We used high-dose cyclophosphamide plus topotecan/vincristine (CTV) or irinotecan (C/I) in patients with resistant neuroblastoma. The aim was to use a regimen with little risk to major organs to (a) achieve or consolidate remission in heavily treated patients and to (b) induce an immunological state conducive to passive immunotherapy with the murine 3F8 antibody.

EXPERIMENTAL DESIGN

CTV and C/I included cyclophosphamide 140 mg/kg ( approximately 4200 mg/m(2)). With CTV, topotecan 2 mg/m(2) was infused i.v. (30 min) on days 1-4 (total, 8 mg/m(2)), and vincristine 0.067 mg/kg was injected on day 1. With C/I, irinotecan, 50 mg/m(2) was infused i.v. (1 h) on days 1-5 (total, 250 mg/m(2)). Mesna and granulocyte colony-stimulating factor were used.

RESULTS

Twenty-nine patients received 38 courses of CTV, and 26 patients received 38 courses of C/I. All patients had previously received topotecan, a hemopoietic stem-cell transplant, and/or high-dose cyclophosphamide. CTV and C/I caused myelosuppression of comparably prolonged duration as follows: absolute neutrophil counts <500/ micro l lasted 5-12 days in patients who had not previously received transplant and 7-21 days in patients who were post-transplant. Other significant toxicities included typhlitis (two CTV-treated patients, one C/I-treated patient) and hemorrhagic cystitis (one C/I-treated patient). Major responses were seen in 4 (15%) of 26 CTV and 4 (17%) of 24 C/I-treated patients with assessable disease. Bone marrow disease resolved in 5 (28%) of 18 CTV-treated patients and in 4 (27%) of 15 C/I-treated patients. 3F8 after CTV or C/I was not blocked by neutralizing antibodies, consistent with the desired immunosuppressive effect of high-dose cyclophosphamide.

CONCLUSIONS

CTV and C/I require transfusional and antibiotic support but otherwise entail tolerable morbidity. They have modest antineuroblastoma activity in heavily treated patients and are good preparative regimens for passive immunotherapy with monoclonal antibodies.

Phase I and pharmacokinetic study of topotecan administered orally once daily for 5 days for 2 consecutive weeks to pediatric patients with refractory solid tumors

PURPOSE

We conducted a phase I trial of the injectable formulation of topotecan given orally once daily for 5 days for 2 consecutive weeks (qd x 5 x 2) in pediatric patients with refractory solid tumors.

PATIENTS AND METHODS

Cohorts of two to six patients received oral topotecan at 0.8, 1.1, 1.4, 1.8, and 2.3 mg/m(2)/d every 28 days for a maximum of six courses. Twenty patients (median age, 10.6 years) received a total of 51 courses. Eight patients received topotecan capsules during course 2 only.

RESULTS

Dose-limiting toxicity occurred at 2.3 mg/m(2)/d and consisted of prolonged grade 4 neutropenia (n = 2), grade 3 stomatitis as a result of radiation recall (n = 1), grade 3 hemorrhage (epistaxis) in the presence of grade 4 thrombocytopenia (n = 1), and grade 3 diarrhea in the presence of Clostridium difficile infection (n = 1). Dose-limiting, prolonged grade 4 neutropenia and thrombocytopenia occurred in one patient at 1.4 mg/m(2)/d. Infrequent toxicities were mild nausea, vomiting, elevated liver ALT or AST, and rash. The maximum-tolerated dosage was 1.8 mg/m(2)/d; the mean (+/- standard deviation) area under the plasma concentration-time curve for topotecan lactone at this dosage was 20.9 +/- 8.4 ng/mL. h. The population mean (+/- standard error) oral bioavailability of the injectable formulation was 0.27 +/- 0.03; that of capsules was 0.36 +/- 0.06 (P =.16). Disease stabilized in nine of 19 assessable patients for 1.5 to 6 months.

CONCLUSION

Oral topotecan (1.8 mg/m(2)/d) on a qd x 5 x 2 schedule is well tolerated and warrants additional testing in pediatric patients.

Phase I study of oral cyclophosphamide and oral topotecan for children with recurrent or refractory solid tumors

BACKGROUND

To determine the maximum-tolerated duration and dose-limiting toxicity of a daily schedule of orally administered cyclophosphamide and topotecan in pediatric patients with recurrent or refractory malignant solid tumors.

METHODS

Patients received oral cyclophosphamide (50 mg/m2/dose) in the morning followed by topotecan (0.8 mg/m2/dose) 8-12 hr later for an escalating number of consecutive days (10, 14, and 17 days).

RESULTS

Seventeen pediatric patients were treated with oral cyclophosphamide and topotecan for durations of 10-17 days for a total of 58 treatment courses. Reversible hematologic toxicity (neutropenia and thrombocytopenia) was the dose-limiting toxicity. Nonhematologic toxicities of greater than grade 3 were not observed. A partial response (neuroblastoma following myeloablative chemotherapy and stem cell rescue) and prolonged stable disease (medulloblastoma) were each observed in one patient.

CONCLUSIONS

The recommended duration of therapy with a daily schedule of both oral cyclophosphamide (50 mg/m2/day) and topotecan (0.8 mg/m2/day) for previously treated pediatric patients with recurrent or refractory solid tumors is 14 consecutive days. The observed dose limiting toxicity (DLT) was reversible neutropenia. This regimen was well tolerated in heavily pretreated patients and demonstrated activity against recurrent pediatric solid tumors.