Hematologic Safety and Tolerability of Topotecan in Recurrent Ovarian Cancer and Small Cell Lung Cancer: An Integrated Analysis

Incidence and Risk Factors for Neutropenia After Intra-Arterial Chemotherapy for Retinoblastoma

Importance

Intra-arterial chemotherapy (IAC) has quickly gained popularity as a mainstay of treatment for retinoblastoma. Intra-arterial chemotherapy has been described as having several advantages over systemic chemotherapy, including reducing systemic toxicity and neutropenia; however, studies on the risk of neutropenia after IAC remain limited.

Objective

To estimate the incidence of neutropenia after IAC, as well as identify risk factors associated with the development of neutropenia.

Design, Setting, and Participants

This case series included pediatric patients with unilateral or bilateral retinoblastoma who were treated with IAC at a single quaternary care center from July 13, 2013, to January 6, 2023.

Exposure

All patients were treated with IAC and underwent multiple IAC cycles depending on treatment response. The primary chemotherapy agent used was melphalan, but topotecan or carboplatin could be used along with melphalan. Melphalan doses were kept to 0.4 mg/kg or less per cycle. After each IAC cycle, complete blood cell counts were obtained within 10 to 12 days and repeated until the absolute neutrophil count (ANC) was greater than or equal to 1000/μL.

Main Outcomes and Measures

The primary outcome was the minimum ANC after each IAC cycle. The secondary outcome was the development of severe (grade 3 or 4) neutropenia (ANC <1000/μL). Regression analyses were used to identify associations between variables and outcomes. Receiver operating characteristic curves were used to calculate threshold dose for each chemotherapy agent potentially associated with the development of severe neutropenia.

Results

A total of 64 eyes of 49 patients (mean [SD] age, 1.7 [1.2] years; 25 females [51.0%]) with retinoblastoma were treated with 171 cycles of IAC. The mean (SD) nadir ANC was 1325.3 (890.7)/μL and occurred a median (IQR) of 10 (10-14) days (range, 6-28 days) after IAC administration. The frequency distribution of post-IAC neutropenia grades 0, 1, 2, 3, 4, and missing was 31 (18.1% of cycles), 25 (14.6%), 40 (23.4%), 37 (21.6%), 26 (15.2%), and 12 (7.0%), respectively. Factors weakly correlated with a lower ANC were higher melphalan dose (β = -2356 [95% CI, -4120.6 to -611.2]; adjusted R2 = 0.251; P = .01) and higher topotecan dose (β = -4056 [95% CI, -7003.6 to -1344.5]; adjusted R2 = 0.251; P = .006).

Conclusions and Relevance

In this case series of patients with retinoblastoma, the incidence of severe neutropenia after IAC was nearly 40%, which is higher than previously reported. Extended laboratory monitoring may aid in capturing previously overlooked cases of neutropenia. Topotecan may be associated with the development of neutropenia; limiting topotecan doses, especially in the setting of a high melphalan dose, may be beneficial in reducing the risk of neutropenia.

Efficacy and Safety of Rovalpituzumab Tesirine Compared With Topotecan as Second-Line Therapy in DLL3-High SCLC: Results From the Phase 3 TAHOE Study

INTRODUCTION

DLL3, an atypical Notch ligand, is expressed in SCLC tumors but is not detectable in normal adult tissues. Rovalpituzumab tesirine (Rova-T) is an antibody-drug conjugate containing a DLL3-targeting antibody tethered to a cytotoxic agent pyrrolobenzodiazepine by means of a protease-cleavable linker. The efficacy and safety of Rova-T compared with topotecan as second-line therapy in patients with SCLC expressing high levels of DLL3 (DLL3-high) was evaluated.

METHODS

The TAHOE study was an open-label, two-to-one randomized, phase 3 study comparing Rova-T with topotecan as second-line therapy in DLL3-high advanced or metastatic SCLC. Rova-T (0.3 mg/kg) was administered intravenously on day 1 of a 42-day cycle for two cycles, with two additional cycles available to patients who met protocol-defined criteria for continued dosing. Topotecan (1.5 mg/m2) was administered intravenously on days 1 to 5 of a 21-day cycle. The primary end point was overall survival (OS).

RESULTS

Patients randomized to Rova-T (n = 296) and topotecan (n = 148) were included in the efficacy analyses. The median age was 64 years, and 77% had the extensive disease at initial diagnosis. The median OS (95% confidence interval) was 6.3 months (5.6-7.3) in the Rova-T arm and 8.6 months (7.7-10.1) in the topotecan arm (hazard ratio, 1.46 [95% confidence interval: 1.17-1.82]). An independent data monitoring committee recommended that enrollment be discontinued because of the shorter OS observed with Rova-T compared with topotecan. Safety profiles for both drugs were consistent with previous reports.

CONCLUSIONS

Compared with topotecan, which is the current standard second-line chemotherapy, Rova-T exhibited an inferior OS and higher rates of serosal effusions, photosensitivity reaction, and peripheral edema in patients with SCLC. A considerable unmet therapeutic need remains in this population.

Adverse Effects and Safety of Etirinotecan Pegol, a Novel Topoisomerase Inhibitor, in Cancer Treatment: A Systematic Review

Background:

Due to the increasing prevalence of cancer and the inadequacy of current therapies, the development of novel antitumor pharmaceutics with higher efficacies and lower adverse effects is considered a fundamental tenet of contemporary cancer management. Poly-Ethylene-Glycol (PEG) attachment is a novel pharmaceutical technology to improve the efficacy and safety of chemotherapies. Etirinotecan Pegol (EP), also known as NKTR-102, is the PEGylated form of Irinotecan (CPT-11), which causes cancer cell apoptosis by inhibiting the topoisomerase I enzyme.

Objectives:

The present study reviews and evaluates various reports of the EP’s anti-tumor activity in various cancers.

Data Sources:

Studies were identified using the Scopus database, with no exclusions. The search terms included Etirinotecan Pegol and NKTR-102, which yielded 125 articles (66 and 59 articles, respectively). In addition, the clinicaltrials.gov website was used to find ongoing studies, which resulted in the addition of two studies.

Study Eligibility Criteria:

Subsequently, we excluded studies that were published in languages other than English, duplicate articles, and studies with no data.

Results:

This systematic review clarifies that EP possesses numerous advantages over many other medications, such as safety, efficacy, increased half-life, increased health-related quality of life, increased overall survival, increased progression-free survival, and decreasing the adverse events in the treatment of various cancers.

Conclusion:

Therefore, Etirinotecan Pegol may represent a major contribution to the treatment of various cancers in the future.

Carvacrol effect on topotecan cytotoxicity in various human cancer cells in vitro

Purpose: To investigate the modulatory effect of the natural phytochemical, carvacrol, on Topotecan (TOPO) cytotoxicity and cellular uptake in different cancer cell lines.

Methods: The cytotoxicity of the carvacrol/TOPO combination therapy was determined in vitro using crystal violet assay. Coomassie blue and DAPI fluorescent stains were used for cellular morphology and molecular cell death assessments, respectively. Additionally, TOPO cellular uptake after carvacrol/TOPO combination therapy was determined.

Results: Treatment of HeLa and HCT116 with carvacrol/TOPO resulted in 7.70- and 5.71-fold reduction in TOPO half maximal inhibitory concentration (IC50), respectively, relative to TOPO single treatment. On the other hand, treatment of MCF-7, HepG2, SKOV3, and A549 cancer cells with carvacrol/TOPO resulted in increasing the IC50 of TOPO by 1.49-, 1.33-, 1.50- and 1.26-fold, respectively, relative to TOPO single treatment.

Conclusion: Carvacrol had enhanced TOPO cytotoxicity and cellular uptake in HeLa and HCT116 cancer cells but might cause TOPO resistance in MCF-7, HepG2, SKOV3 and A549 cells.

DNA topoisomerases as molecular targets for anticancer drugs

The significant role of topoisomerases in the control of DNA chain topology has been confirmed in numerous research conducted worldwide. The prevalence of these enzymes, as well as the key importance of topoisomerase in the proper functioning of cells, have made them the target of many scientific studies conducted all over the world. This article is a comprehensive review of knowledge about topoisomerases and their inhibitors collected over the years. Studies on the structure-activity relationship and molecular docking are one of the key elements driving drug development. In addition to information on molecular targets, this article contains details on the structure-activity relationship of described classes of compounds. Moreover, the work also includes details about the structure of the compounds that drive the mode of action of topoisomerase inhibitors. Finally, selected topoisomerases inhibitors at the stage of clinical trials and their potential application in the chemotherapy of various cancers are described.

A Brief Overview of the Antitumoral Actions of Leelamine

For the last couple of decades, natural products, either applied singly or in conjunction with other cancer therapies including chemotherapy and radiotherapy, have allowed us to combat different types of human cancers through the inhibition of their initiation and progression. The principal sources of these useful compounds are isolated from plants that were described in traditional medicines for their curative potential. Leelamine, derived from the bark of pine trees, was previously reported as having a weak agonistic effect on cannabinoid receptors and limited inhibitory effects on pyruvate dehydrogenase kinases (PDKs). It has been reported to possess a strong lysosomotropic property; this feature enables its assembly inside the acidic compartments within a cell, such as lysosomes, which may eventually hinder endocytosis. In this review, we briefly highlight the varied antineoplastic actions of leelamine that have found implications in pharmacological research, and the numerous intracellular targets affected by this agent that can effectively negate the oncogenic process.

Continuous and bolus intraventricular topotecan prolong survival in a mouse model of leptomeningeal medulloblastoma

Leptomeningeal metastasis remains a difficult clinical challenge. Some success has been achieved by direct administration of therapeutics into the cerebrospinal fluid (CSF) circumventing limitations imposed by the blood brain barrier. Here we investigated continuous infusion versus bolus injection of therapy into the CSF in a preclinical model of human Group 3 medulloblastoma, the molecular subgroup with the highest incidence of leptomeningeal disease. Initial tests of selected Group 3 human medulloblastoma cell lines in culture showed that D283 Med and D425 Med were resistant to cytosine arabinoside and methotrexate. D283 Med cells were also resistant to topotecan, whereas 1 μM topotecan killed over 99% of D425 Med cells. We therefore introduced D425 Med cells, modified to express firefly luciferase, into the CSF of immunodeficient mice. Mice were then treated with topotecan or saline in five groups: continuous intraventricular (IVT) topotecan via osmotic pump (5.28 μg/day), daily bolus IVT topotecan injections with a similar daily dose (6 μg/day), systemic intraperitoneal injections of a higher daily dose of topotecan (15 μg/day), daily IVT pumped saline and daily intraperitoneal injections of saline. Bioluminescence analyses revealed that both IVT topotecan treatments effectively slowed leptomeningeal tumor growth in the brains. Histological analysis showed that they were associated with localized brain necrosis, possibly due to backtracking of topotecan around the catheter. In the spines, bolus IVT topotecan showed a trend towards slower tumor growth compared to continuous (pump) IVT topotecan, as measured by bioluminescence. Both continuous and bolus topotecan IVT showed longer survival compared to other groups. Thus, both direct IVT topotecan CSF delivery methods produced better anti-medulloblastoma effect compared to systemic therapy at the dosages used here.

Analysis of two topotecan treatment schedules in patients with recurrent ovarian cancer

Two topotecan treatment schedules in patients with recurrent epithelial ovarian cancer were evaluated. Protocol A (21 days) was 1.5 mg/m(2)/day topotecan on days 1 through 5 of a 21-day cycle; Protocol B (weekly) 4 mg/m(2) on days 1, 8, and 15 of a 28-day cycle. Efficacy was determined by clinical exam, CT scan, and CA125 levels. Forty-three patients on Protocol A and 21 on Protocol B were evaluated. As second-line treatment, Protocol A response was 9/20 (45%). Response to Protocol B was 4/17 (23.5%; NS). As third line or more, the response on Protocols A and B together was only 3/27 (11%). High-grade haematological toxicity was reported in 12/43 (27.9%) on Protocol A and 1/21 (4.8%) on Protocol B (p = 0.04). There was no difference in progression-free-intervals between schedules in second-line treatment. The weekly protocol had lower severe haematological toxicity. Clinical response in third line or more was very low.

Synthetic lethal screen identifies NF-κB as a target for combination therapy with topotecan for patients with neuroblastoma

Background

Despite aggressive multimodal treatments the overall survival of patients with high-risk neuroblastoma remains poor. The aim of this study was to identify novel combination chemotherapy to improve survival rate in patients with high-risk neuroblastoma.

Methods

We took a synthetic lethal approach using a siRNA library targeting 418 apoptosis-related genes and identified genes and pathways whose inhibition synergized with topotecan. Microarray analyses of cells treated with topotecan were performed to identify if the same genes or pathways were altered by the drug. An inhibitor of this pathway was used in combination with topotecan to confirm synergism by in vitro and in vivo studies.

Results

We found that there were nine genes whose suppression synergized with topotecan to enhance cell death, and the NF-κB signaling pathway was significantly enriched. Microarray analysis of cells treated with topotecan revealed a significant enrichment of NF-κB target genes among the differentially altered genes, suggesting that NF-κB pathway was activated in the treated cells. Combination of topotecan and known NF-κB inhibitors (NSC 676914 or bortezomib) significantly reduced cell growth and induced caspase 3 activity in vitro. Furthermore, in a neuroblastoma xenograft mouse model, combined treatment of topotecan and bortezomib significantly delayed tumor formation compared to single-drug treatments.

Conclusions

Synthetic lethal screening provides a rational approach for selecting drugs for use in combination therapy and warrants clinical evaluation of the efficacy of the combination of topotecan and bortezomib or other NF-κB inhibitors in patients with high risk neuroblastoma.

Assessment of anti-cytogenotoxic effects of quercetin in animals treated with topotecan

The present investigation was directed to study the possible chemoprotective activity of orally administered quercetin against topotecan-induced cyto- and genotoxicity towards mouse somatic cells in vivo. DNA strand breaks, micronuclei formation, and mitotic activity were undertaken in the current study as markers of cyto- and genotoxicity. Oxidative stress markers such as intracellular reactive oxygen species generation, lipid peroxidation, and reduced and oxidized glutathione were assessed in bone marrow as a possible mechanism underlying this amelioration. Quercetin was neither cytotoxic nor genotoxic in mice at doses tested. Pretreatment of mice with quercetin significantly reduced topotecan-induced genotoxicity and cytotoxicity in bone marrow cells, and these effects were dose dependent. Moreover, prior administration of quercetin ahead of topotecan challenge ameliorated oxidative stress markers. In conclusion, quercetin has a protective role in the abatement of topotecan-induced cyto- and genotoxicity in the bone marrow cells of mice that resides, at least in part, on its antioxidant effects. Based on the data presented, strategies can be developed to decrease the topotecan-induced bone marrow suppression and secondary malignancy in cancer patients and medical personnel exposing to topotecan.

Molecular cytogenetic evaluation of the mechanism of micronuclei formation induced by camptothecin, topotecan, and irinotecan

We used the conventional bone marrow micronucleus test complemented with the fluorescent in situ hybridization with the minor satellite DNA probe to investigate the mechanisms of induction of micronuclei in mice treated with camptothecin and its clinical antineoplastic analogues topotecan and irinotecan. All experiments were performed with male Swiss albino mice. Single doses of 1 mg/kg camptothecin or 0.6 mg/kg topotecan were injected intraperitoneally and bone marrow was sampled at 30 hr (camptothecin) or 24 hr (topotecan) after treatment. A dose of 60 mg/kg irinotecan was injected intravenously, once every fourth day for 13 days and bone marrow was sampled 24 hr after the last treatment. In animals treated with camptothecin, a total of 1.07% micronuclei were found and 70% of them were centromere-negative, indicating their formation by DNA strand breaks and reflecting the predominant clastogenic activity of camptothecin. Exposure to topotecan and irinotecan yielded 1.71 and 0.83% micronuclei, respectively. About 52.7 and 48.8% of the induced micronuclei, respectively, were centromere-positive, indicating their formation by whole chromosomes and reflecting the aneugenic activity of both compounds. Correspondingly, about 47.3 and 51.2% of the induced micronuclei, respectively were centromere-negative, demonstrating that topotecan and irinotecan not only induce chromosome loss but also DNA strand breaks. Both the clastogenic and aneugenic potential of these drugs can lead to the development of secondary tumors and abnormal reproductive outcomes. Therefore, the clinical use of these agents must be weighed against the risks of secondary malignancies in cured patients and persistent genetic damage of their potential offspring.

Current role and future aspects of topotecan in relapsed ovarian cancer

BACKGROUND

Ovarian cancer is the fifth leading cause of cancer deaths in women. It is associated with a poor prognosis, as the majority of patients present with advanced disease and relapse after radical surgery, and following chemotherapy with carboplatin and paclitaxel.

OBJECTIVE

To review the role of topotecan in the treatment of advanced and relapsed ovarian cancer, and the efficacy and safety of novel dosing regimens and formulations of topotecan. It will also discuss further options of combination of topotecan with other cytotoxic agents and targeted therapies.

RESEARCH DESIGN AND METHODS

The authors searched for relevant references in the MEDLINE database and in congress abstracts of the American Society of Clinical Oncology.

RESULTS

Topotecan is an established second-line therapy for advanced and relapsed ovarian cancer; a regimen of 1.5 mg/m(2)/day 1-5 has been approved in the USA and many other western countries. Topotecan is well tolerated; associated haematological toxicity is generally manageable, reversible and non-cumulative. A number of alternative dosing regimens and formulations have been investigated in an attempt to improve the toxicity profile of topotecan without compromising anti-tumour activity. A novel oral formulation of topotecan has shown clinical promise in patients with advanced and relapsed disease. Administration of i.v. topotecan on a weekly basis produced encouraging results in several phase II trials, with less haematological toxicity and similar response rates to the day 1-5 regimen. Also, recent early studies demonstrate that topotecan is effective in combination with several other therapeutic agents in the relapsed setting.

CONCLUSION

The peer-reviewed literature reports that topotecan is an effective, well tolerated treatment option for relapsed ovarian cancer.

Nonplatinum Topotecan Combinations Versus Topotecan Alone for Recurrent Ovarian Cancer: Results of a Phase III Study of the North-Eastern German Society of Gynecological Oncology Ovarian Cancer Study Group

Purpose

The management of recurrent ovarian cancer remains controversial. Single-agent topotecan is an established treatment option, and preliminary evidence suggests improved tumor control by combining topotecan with etoposide or gemcitabine.

Patients and Methods

Women with relapsed ovarian cancer after primary surgery and platinum-based chemotherapy were randomly assigned to topotecan monotherapy 1.25 mg/m2/d, topotecan 1.0 mg/m2plus oral etoposide 50 mg/d, or topotecan 0.5 mg/m2/d plus gemcitabine 800 mg/m2on day 1 and 600 mg/m2on day 8 every 3 weeks. Patients were stratified for platinum-refractory and platinum-sensitive disease according to a recurrence-free interval of less or more than 12 months, respectively. The primary end point was overall survival. Secondary end points included progression-free survival, objective response rates, toxicity, and quality of life (as measured by the European Organisation for Research and Treatment of Cancer [EORTC] 30-item Quality-of-Life Questionnaire).

Results

The trial enrolled 502 patients with a mean age of 60.5 years (± 10.2 years), 208 of whom were platinum resistant. Median overall survival was 17.2 months (95% CI, 13.5 to 21.9 months) with topotecan, 17.8 months (95% CI, 13.7 to 20.0 months) with topotecan plus etoposide (log-rank P = .7647), and 15.2 months (95% CI, 11.3 to 20.9 months) with topotecan plus gemcitabine (log-rank P = .2344). Platinum-sensitive patients lived significantly longer than platinum-refractory patients (21.9 v 10.6 months). The median progression-free survival was 7.0, 7.8, and 6.3 months, respectively. Objective response rates were 27.8%, 36.1%, and 31.6%, respectively. Patients under combined treatment were at higher risk of severe thrombocytopenia.

Conclusion

Nonplatinum topotecan combinations do not provide a survival advantage over topotecan alone in women with relapsed ovarian cancer.

Resistance to chemotherapy in cancer: a complex and integrated cellular response

Inherent and acquired resistance pathways account for the high rate of failure in cancer chemotherapy. The mechanisms or pathways mediating resistance may be classified as pharmacokinetic (i.e. alter intratumour drug exposue) or pharmacodynamic (i.e. failure to elicit cytotoxicity). More often than not, the resistant phenotype is characterised by alterations in multiple pathways. Consequently, the pathways may act synergistically or generate a broad spectrum of resistance to anticancer drugs. There has been a great deal of systematic characterisation of drug resistance in vitro. However, translating this greater understanding into clinical efficacy has rarely been achieved. This review explores the phenomenon of drug resistance in cancer and highlights the gap between in vitro and in vivo observations. This gap presents a major obstacle in overcoming drug resistance and restoring sensitivity to chemotherapy.

[Small cell lung cancer--state of the art and future perspectives]

Lung cancer is the leading cause of cancer-related death in Portugal. Almost 3500 Portuguese are expected to be diagnosed with lung cancer in 2006; approximately 20% will have small cell lung cancer (SCLC). At presentation, 25% to 30% of patients will have local or regional disease, classified as limited stage disease. The concurrent chemovalidation therapy is the best choice. Once daily thoracic radiation therapy to doses in the range of 50 Gy to 60 Gy would reflect an accepted standard of care in daily practice. Because of the increase toxicity associated with hyper fractionated radiation, this approach is often limited to select patients. Etoposide plus cisplatin are synergistic, well tolerated and result in equal or superior survival compared with other regimens. This is the standard regimen for concomitant therapy in limited stage and for extensive disease SCLC. Despite good chemo sensitivity and radio sensitivity, the prognosis of SCLC is very poor because of the early development of resistance and the associated high tendency to recurrence, making second line treatment of SCLC a problem of real medical relevance. Topotecan now offers an effective and well tolerated monosubstance for second line therapy of recurrent SCLC. There has been a significant increase in median survival for patients with SCLC receiving topotecan plus symptomatic therapy versus symptomatic therapy. The efficacy of this drug is comparable to the efficacy of the three-drug combination CAV. The tolerability can be improved by means of toxicity-adapted dosing. In elderly and in patients with performance status 2, topotecan is also well tolerated and has good efficacy. Initial studies into weekly administration also demonstrate good efficacy. The combination of topotecan with cranial radiotherapy is well tolerated and effective in the treatment of cerebral metastases of SCLC. New classes of agents, such as antiangiogenic agents including bevacizumab, small molecule tyrosine kinase inhibitors and thalidomide are being evaluated with chemotherapy for patients with extensive stage SCLC.

Safety of topotecan in the treatment of recurrent small-cell lung cancer and ovarian cancer

The topoisomerase I inhibitor, topotecan, is approved for the treatment of recurrent small-cell lung cancer (SCLC) and ovarian cancer (OC). Patients with recurrent SCLC and OC typically experience multiple relapses and receive multiple rounds of chemotherapy. In these settings, disease stabilisation is considered a treatment benefit, and quality-of-life effects and cumulative toxicities of treatments should be considered. Many patients with recurrent cancer may be predisposed to treatment-related adverse events because of advanced age, renal impairment or extensive prior therapy. The standard regimen of topotecan, 1.5 mg/m(2) on days 1-5 of a 21-day cycle, has generally mild nonhaematological toxicity and a well-defined haematological toxicity profile characterised by reversible and noncumulative neutropenia. Alternative regimens may lower the incidence of haematological toxicities and maintain antitumour efficacy. Topotecan may provide physicians with a versatile therapeutic option for the treatment of patients with relapsed SCLC or OC.

Defective Mre11-dependent activation of Chk2 by ataxia telangiectasia mutated in colorectal carcinoma cells in response to replication-dependent DNA double strand breaks

The Mre11.Rad50.Nbs1 (MRN) complex binds DNA double strand breaks to repair DNA and activate checkpoints. We report MRN deficiency in three of seven colon carcinoma cell lines of the NCI Anticancer Drug Screen. To study the involvement of MRN in replication-mediated DNA double strand breaks, we examined checkpoint responses to camptothecin, which induces replication-mediated DNA double strand breaks after replication forks collide with topoisomerase I cleavage complexes. MRN-deficient cells were deficient for Chk2 activation, whereas Chk1 activation was independent of MRN. Chk2 activation was ataxia telangiectasia mutated (ATM)-dependent and associated with phosphorylation of Mre11 and Nbs1. Mre11 complementation in MRN-deficient HCT116 cells restored Chk2 activation as well as Rad50 and Nbs1 levels. Conversely, Mre11 down-regulation by small interference RNA (siRNA) in HT29 cells inhibited Chk2 activation and down-regulated Nbs1 and Rad50. Proteasome inhibition also restored Rad50 and Nbs1 levels in HCT116 cells suggesting that Mre11 stabilizes Rad50 and Nbs1. Chk2 activation was also defective in three of four MRN-proficient colorectal cell lines because of low Chk2 levels. Thus, six of seven colon carcinoma cell lines from the NCI Anticancer Drug Screen are functionally Chk2-deficient in response to replication-mediated DNA double strand breaks. We propose that Mre11 stabilizes Nbs1 and Rad50 and that MRN activates Chk2 downstream from ATM in response to replication-mediated DNA double strand breaks. Chk2 deficiency in HCT116 is associated with defective S-phase checkpoint, prolonged G2 arrest, and hypersensitivity to camptothecin. The high frequency of MRN and Chk2 deficiencies may contribute to genomic instability and therapeutic response to camptothecins in colorectal cancers.

Second-line treatment of small-cell lung cancer

Approximately 45,000 new cases of small-cell lung cancer were diagnosed in 2005 in the United States. Although response to first-time therapy is up to 90%, the majority of patients will ultimately relapse. Therefore, active second-line therapy is needed for this patient population. The only second-line treatment for small-cell lung cancer approved by the US Food and Drug Administration is topotecan. Other agents have been investigated and have shown modest efficacy. These include vinorelbine, irinotecan, etoposide, paclitaxel, and gemcitabine. Novel "targeted therapies" have shown disappointing results in this disease. Much of the recent work has focused on investigating alternative dosing and scheduling of topotecan. Combination therapies have also been investigated, and some have been shown to increase activity over single agents, but toxicity and quality of life variables are imperative in the treatment of this patient population.

Topotecan in the treatment of elderly patients with relapsed small-cell lung cancer

BACKGROUND

Almost 70% of all patients with lung cancer in the United States are>65 years of age, and the incidence of small-cell lung cancer (SCLC) increases with age until the eighth decade of life. However, elderly patients are underrepresented in clinical trials and are often suboptimally treated. The validity of age as a prognostic factor for toxicity or survival remains controversial.

PATIENTS AND METHODS

To investigate the safety and efficacy of topotecan (an approved treatment for relapsed SCLC) in older patients, we performed a retrospective analysis in patients >or= 65 years of age versus patients < 65 years of age from 5 large topotecan trials. In all 5 trials, patients received topotecan 1.5 mg/m2 per day via a 30-minute intravenous infusion on days 1 through 5 of a 21-day cycle. Efficacy and tolerability outcomes were assessed for both age groups.

RESULTS

Topotecan was similarly tolerated in both age groups, with generally manageable hematologic toxicity. The incidence, duration, and onset of severe hematologic toxicities did not vary significantly with age. In the<65 age group, grade 4 neutropenia and leukopenia were reported in 72% and 32% of patients, respectively; in the >or= 65 age group, grade 4 neutropenia and leukopenia were reported in 77% and 31% of patients, respectively. Grade 4 thrombocytopenia was less common in the<65 age group. Nonhematologic toxicities, median time to progression, and overall survival were comparable between groups.

CONCLUSION

This is the first demonstration of the safety and efficacy of topotecan in older patients with recurrent SCLC. Future studies are needed to fully characterize the role of topotecan in the treatment of older patients.

Topotecan: weighing in when there are many options

The manuscript by Armstrong et al. in this issue of The Oncologist, reviewing the toxicity and efficacy of full-dose topotecan delivered as second-line therapy in individuals with small cell lung cancer or ovarian cancer, will likely serve as both the most comprehensive and the final review of this active agent delivered at the U.S. Food and Drug Administration-approved dosage and schedule. The review represents large, relative lyhomogeneous patient populations with prior platinum exposure and convincingly describes topotecan as an agent with activity that is comparable with those of all other approved drugs in this setting and a well-defined and relatively circumscribed set of toxicities. While the activity of topotecan in small cell carcinoma provides individuals with the hope for further palliation at the time of tumor recurrence, as discussed by Dr. Markman in this issue, the best use of this agent in the management of recurrent ovarian cancer is far from clear because, in part, of a growing list of approved active agents, most notably liposomal doxorubicin, gemcitabine, and weekly paclitaxel; a return to platinum; or a host of other agents such as vinorelbine, altretamine, irinotecan, docetaxel, etoposide, and others. The most pressing need is to accept that palliative therapies are designed to palliate and improve symptoms, and to move away from end points of radiologic and marker response to a focus on "clinical benefit" and clinically more meaningful end points.

Topotecan as second-line therapy for ovarian cancer: dosage versus toxicity

In this issue of The Oncologist, Armstrong et al. present an analysis of the use of topotecan (Hycamtin; GlaxoSmithKline, Philadelphia, http://www.gsk.com) in the second-line treatment of both ovarian cancer and small cell carcinoma of the lung. This cytotoxic agent has clearly been demonstrated to be a useful drug in a population of patients with both of these conditions. However, the description of the nature of the toxicity, as stated in the manuscript, must be questioned along with comments made regarding the relative toxicity of alternative cytotoxic agents frequently used in similar settings. The purpose of this discussion absolutely is not to negate the unquestioned, demonstrated usefulness of topotecan as second-line therapy in ovarian cancer but rather to point out that the U.S. Food and Drug Administration-approved dose level of 1.5 mg/m(2) per day x 5 days can cause substantial and highly clinically relevant bone marrow toxicity. Whether this toxicity, which can result in a level of fatigue that may cause responding patients to discontinue treatment, should simply be labeled "excessive" rather than "cumulative" appears to be a matter of semantics rather than an important distinction. Whether delivery of a lower dose of topotecan (1 mg/m(2)-1.25 mg/m(2) per day x 5 days) will essentially eliminate concern for the development of severe clinically relevant marrow toxicity is uncertain, but the risk will certainly be substantially reduced.