Updated clinical information on multitargeted antifolates in lung cancer

Metabolic impairment of non-small cell lung cancers by mitochondrial HSPD1 targeting

Background

The identification of novel targets is of paramount importance to develop more effective drugs and improve the treatment of non-small cell lung cancer (NSCLC), the leading cause of cancer-related deaths worldwide. Since cells alter their metabolic rewiring during tumorigenesis and along cancer progression, targeting key metabolic players and metabolism-associated proteins represents a valuable approach with a high therapeutic potential. Metabolic fitness relies on the functionality of heat shock proteins (HSPs), molecular chaperones that facilitate the correct folding of metabolism enzymes and their assembly in macromolecular structures.

Methods

Gene fitness was determined by bioinformatics analysis from available datasets from genetic screenings. HSPD1 expression was evaluated by immunohistochemistry from formalin-fixed paraffin-embedded tissues from NSCLC patients. Real-time proliferation assays with and without cytotoxicity reagents, colony formation assays and cell cycle analyses were used to monitor growth and drug sensitivity of different NSCLC cells in vitro. In vivo growth was monitored with subcutaneous injections in immune-deficient mice. Cell metabolic activity was analyzed through extracellular metabolic flux analysis. Specific knockouts were introduced by CRISPR/Cas9.

Results

We show heat shock protein family D member 1 (HSPD1 or HSP60) as a survival gene ubiquitously expressed in NSCLC and associated with poor patients’ prognosis. HSPD1 knockdown or its chemical disruption by the small molecule KHS101 induces a drastic breakdown of oxidative phosphorylation, and suppresses cell proliferation both in vitro and in vivo. By combining drug profiling with transcriptomics and through a whole-genome CRISPR/Cas9 screen, we demonstrate that HSPD1-targeted anti-cancer effects are dependent on oxidative phosphorylation and validated molecular determinants of KHS101 sensitivity, in particular, the creatine-transporter SLC6A8 and the subunit of the cytochrome c oxidase complex COX5B.

Conclusions

These results highlight mitochondrial metabolism as an attractive target and HSPD1 as a potential theranostic marker for developing therapies to combat NSCLC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02049-8.

miR-124-3p Regulates FGF2-EGFR Pathway to Overcome Pemetrexed Resistance in Lung Adenocarcinoma Cells by Targeting MGAT5

Objective

To investigate whether miR-124-3p regulates the fibroblast growth factor 2 (FGF2)–epidermal growth factor receptor (EGFR) pathway by targeting MGAT5 to affect the pemetrexed resistance in lung adenocarcinoma cells.

Methods

PC9-MTA and H1993-MTA anti-pemetrexed lung adenocarcinoma cell lines were constructed. The cell viability of anti-pemetrexed and parent lung adenocarcinoma cells was analyzed using MTS assay and reverse transcription PCR to determine the expression of miR-124-3p. CCK8 assay, colony formation assay, and flow cytometry were used to determine cells’ proliferation and apoptosis. FGF2–EGFR signaling pathway-related proteins and MGAT5 protein expression were quantified by Western blotting. The target relationship between miR-124-3p and MGAT5 was verified by double luciferase assay. A nude mouse model with a transplanted tumor was established using the anti-pemetrexed lung adenocarcinoma cells. Tumor volume and weight were determined, and the apoptosis of tumor cells was observed.

Results

The half-maximal inhibitory concentration of pemetrexed in anti-pemetrexed lung adenocarcinoma cells was higher than that in parent lung adenocarcinoma cells, and the expression of miR-124-3p in the anti-pemetrexed cells was lower than that of the parent cells. In the miR-124-3p overexpression group, MGAT5 silencing group, and miR-124-3p+MGAT5 overexpression group, compared with the control group, the proliferation ability of cells and tumors was markedly reduced; their apoptosis rates were increased significantly; expression levels of FGF2 and p-EGFR/EGFR were decreased; and the growth rate and tumor volume and mass were reduced; however, the opposite results were obtained in the miR-124-3p silencing group (p<0.05).

Conclusion

miR-124-3p may inhibit the FGF2–EGFR pathway by targeting MGAT5 to decrease pemetrexed resistance in lung adenocarcinoma cells.

Thymidylate synthase drives the phenotypes of epithelial-to-mesenchymal transition in non-small cell lung cancer

Background

Epithelial-to-mesenchymal transition (EMT) enhances motility, stemness, chemoresistance and metastasis. Little is known about how various pathways coordinate to elicit EMT’s different functional aspects in non-small cell lung cancer (NSCLC). Thymidylate synthase (TS) has been previously correlated with EMT transcription factor ZEB1 in NSCLC and imparts resistance against anti-folate chemotherapy. In this study, we establish a functional correlation between TS, EMT, chemotherapy and metastasis and propose a network for TS mediated EMT.

Methods

Published datasets were analysed to evaluate the significance of TS in NSCLC fitness and prognosis. Promoter reporter assay was used to sort NSCLC cell lines in TS^HIGH and TS^LOW. Metastasis was assayed in a syngeneic mouse model.

Results

TS levels were prognostic and predicted chemotherapy response. Cell lines with higher TS promoter activity were more mesenchymal-like. RNA-seq identified EMT as one of the most differentially regulated pathways in connection to TS expression. EMT transcription factors HOXC6 and HMGA2 were identified as upstream regulator of TS, and AXL, SPARC and FOSL1 as downstream effectors. TS knock-down reduced the metastatic colonisation in vivo.

Conclusion

These results establish TS as a theranostic NSCLC marker integrating survival, chemo-resistance and EMT, and identifies a regulatory network that could be targeted in EMT-driven NSCLC.

A non-proliferative role of pyrimidine metabolism in cancer

Background

Nucleotide metabolism is a critical pathway that generates purine and pyrimidine molecules for DNA replication, RNA synthesis, and cellular bioenergetics. Increased nucleotide metabolism supports uncontrolled growth of tumors and is a hallmark of cancer. Agents inhibiting synthesis and incorporation of nucleotides in DNA are widely used as chemotherapeutics to reduce tumor growth, cause DNA damage, and induce cell death. Thus, the research on nucleotide metabolism in cancer is primarily focused on its role in cell proliferation. However, in addition to proliferation, the role of purine molecules is established as ligands for purinergic signals. However, so far, the role of the pyrimidines has not been discussed beyond cell growth.

Scope of the review

In this review we present the key evidence from recent pivotal studies supporting the notion of a non-proliferative role for pyrimidine metabolism (PyM) in cancer, with a special focus on its effect on differentiation in cancers from different origins.

Major conclusion

In leukemic cells, the pyrimidine catabolism induces terminal differentiation toward monocytic lineage to check the aberrant cell proliferation, whereas in some solid tumors (e.g., triple negative breast cancer and hepatocellular carcinoma), catalytic degradation of pyrimidines maintains the mesenchymal-like state driven by epithelial-to-mesenchymal transition (EMT). This review further broadens this concept to understand the effect of PyM on metastasis and, ultimately, delivers a rationale to investigate the involvement of the pyrimidine molecules as oncometabolites. Overall, understanding the non-proliferative role of PyM in cancer will lead to improvement of the existing antimetabolites and to development of new therapeutic options.

Efficacy and safety of first-line pemetrexed plus carboplatin followed by single-agent pemetrexed maintenance in elderly Chinese patients with non-squamous non-small-cell lung cancer

Chemotherapy with pemetrexed plus carboplatin followed by pemetrexed maintenance therapy is a first-line regimen for patients with advanced non-squamous non-small-cell lung cancer. This phase II clinical study investigated the efficacy and safety of this regimen in older patients (aged ≥65 years) with advanced non-squamous non-small-cell lung cancer. All patients received 4 courses of induction therapy with pemetrexed (500 mg/m²) combined with carboplatin once every 3 weeks. If patients had stable disease or achieved a complete or partial tumor response after 4 courses of pemetrexed + carboplatin therapy, maintenance treatment with pemetrexed monotherapy was administered until either disease progression or intolerable toxicity occurred. The primary endpoint was progression-free survival, while secondary endpoints were the objective response rate, overall survival, and tolerability. A total of 105 elderly patients (median age, 71 years) with advanced lung adenocarcinoma were enrolled in the trial. The ORR with induction therapy was 36.2% and the disease control rate was 70.5%. Sixty-two patients (59.0%) subsequently received pemetrexed maintenance therapy. The median progression-free survival for all patients was 8.23 months (95% CI 5.85-10.62 months) and the median overall survival was 22.6 months (95% CI 20.09-25.11 months). Grade 3 or greater toxicities included neutropenia (15.3%), thrombocytopenia (9.5%), anemia (8.6%), leukopenia (4.8%), nausea (1.0%), vomiting (1.0%), and fatigue (1.0%). No treatment-related deaths occurred. These results indicate that pemetrexed combined with carboplatin therapy maintained by single-agent pemetrexed treatment of elderly patients with advanced non-squamous non-small-cell lung cancer was effective and tolerable.

ClinicalTrials.gov identifier: NCT01860508.

Pemetrexed-related interstitial lung disease reported from post marketing surveillance (malignant pleural mesothelioma/non-small cell lung cancer)

Background

Interstitial lung disease (ILD) is important drug related toxicity because it commonly forced to discontinue the treatment.

Methods

To characterize the prevalence and patterns of pemetrexed induced ILD, an independent ILD advisory board composed of external experts performed reassessment of ILD in two post marketing surveillance (PMS) studies for malignant pleural mesothelioma (MPM) and non-small cell lung cancer (NSCLC).

Results

ILD incidences were originally 1.6% and 2.6% in 903 MPM and 683 NSCLC patients in safety analyses, respectively. Based on the reassessment by the board, the incidence was 1.1% MPM and 1.8% NSCLC. Common possible risk factors of ILD in MPM and NSCLC patients were male gender, 60 years or older age, and pre-existing ILD. Asbestosis in MPM, and smoking history in NSCLC are also considered as risk, respectively. In terms of computed tomography (CT) pattern, 7 of 10 cases in MPM patients had acute interstitial pneumonia pattern, which four were fatal. Eight of the 12 NSCLC patients had diffuse grand glass opacity, which all had recovered. Onset of ILD in MPM varied between the first and the fifth courses of pemetrexed treatment, and the latest onset was 48 days after the last administration. For NSCLC, it was between the second and the ninth course, 7 and 56 days after the last administration.

Conclusions

The risk of pemetrexed-related ILD is similar level as other anti-cancer drugs under clinical settings. Careful observations continuously during and at least for 2 months after the last administration of pemetrexed are advised.

Associations between TS, TTF-1, FR-α, FPGS, and overall survival in patients with advanced non-small-cell lung cancer receiving pemetrexed plus carboplatin or gemcitabine plus carboplatin as first-line chemotherapy

INTRODUCTION

Pemetrexed is effective in the treatment of non-small-cell lung cancer, mainly in nonsquamous cell carcinomas. Inhibition of thymidylate synthase (TS) is considered the key mechanism of action. Folate receptor-α facilitates uptake of pemetrexed. Polyglutamation by folylpolyglutamate synthetase enhances activity and prolongs cellular retention of pemetrexed. Thyroid transcription factor-1 (TTF-1) is mainly positive in nonsquamous cell carcinoma and has been proposed as a marker for sensitivity to pemetrexed. The aim was to investigate associations between these biomarkers and survival in patients who participated in a phase III trial comparing pemetrexed plus carboplatin with gemcitabine plus carboplatin as first-line chemotherapy in advanced non-small-cell lung cancer (n = 436). In this study, there was no difference in overall survival between the two regimens.

METHODS

Formalin-fixed, paraffin-embedded biopsies were collected. Percentages of tumor cells positive and highly positive for the biomarkers were assessed using immunohistochemistry (IHC) and an IHC score was calculated (range, 0-200).

RESULTS

Two hundred thirty-six biopsies were analyzed (pemetrexed plus carboplatin: n = 114, gemcitabine plus carboplatin: n = 122). There was a significant difference in overall survival between those with TTF-1-positive and -negative tumors (10.4 versus 6.0 months; p < 0.001) and those with a low and a high TS IHC score (9.7 versus 6.2 months; p < 0.001). Folate receptor-α and folylpolyglutamate synthetase were not significant prognostic factors. In multivariate analyses adjusting for established prognostic characteristics, TS (p = 0.002) and TTF-1 (p = 0.003) remained significant. There were no differences in survival between the treatment arms depending on biomarker scores.

CONCLUSIONS

TTF-1 positivity and low TS level were associated with prolonged survival. The associations between the biomarkers and overall survival were similar for both chemotherapy regimens.

KRAS mutation status is associated with enhanced dependency on folate metabolism pathways in non-small cell lung cancer cells

KRAS gene mutation is linked to poor prognosis and resistance to therapeutics in non-small cell lung cancer (NSCLC). In this study, we have explored the possibility of exploiting inherent differences in KRAS-mutant cell metabolism for treatment. This study identified a greater dependency on folate metabolism pathways in KRAS mutant compared with KRAS wild-type NSCLC cell lines. Microarray gene expression and biologic pathway analysis identified higher expression of folate metabolism- and purine synthesis-related pathways in KRAS-mutant NSCLC cells compared with wild-type counterparts. Moreover, pathway analysis and knockdown studies suggest a role for MYC transcriptional activity in the expression of these pathways in KRAS-mutant NSCLC cells. Furthermore, KRAS knockdown and overexpression studies demonstrated the ability of KRAS to regulate expression of genes that comprise folate metabolism pathways. Proliferation studies demonstrated higher responsiveness to methotrexate, pemetrexed, and other antifolates in KRAS-mutant NSCLC cells. Surprisingly, KRAS gene expression is downregulated in KRAS wild-type and KRAS-mutant cells by antifolates, which may also contribute to higher efficacy of antifolates in KRAS-mutant NSCLC cells. In vivo analysis of multiple tumorgraft models in nude mice identified a KRAS-mutant tumor among the pemetrexed-responsive tumors and also demonstrated an association between expression of the folate pathway gene, methylenetetrahydrofolate dehydrogenase 2 (MTHFD2), and antifolate activity. Collectively, we identify altered regulation of folate metabolism in KRAS-mutant NSCLC cells that may account for higher antifolate activity in this subtype of NSCLC.

Expression of thymidylate synthase predicts clinical outcomes of pemetrexed-containing chemotherapy for non-small-cell lung cancer: a systemic review and meta-analysis

PURPOSE

Observational and preclinical studies suggested an association between the expression of thymidylate synthase (TS) and clinical effects of pemetrexed-based chemotherapy in non-small-cell lung cancer (NSCLC) patients. However, the predictive value of TS for pemetrexed-containing chemotherapy regimen remained controversial. The aim of the study was to further appraise the association between the expression of TS and clinical efficacy pemetrexed-based chemotherapy in NSCLC patients.

METHODS

We searched in MEDLINE (PubMed), EMBASE, and Cochrane Library from January 1945 to May 2013. Two authors independently extracted information from the characteristics of study participants. Primary outcomes included therapeutic response (TR; i.e., complete response + partial response vs. stable disease + progressive disease), progression-free survival (PFS), and overall survival (OS). Relative risk (RR) and hazard ratio (HR) were used for evaluating the risk or hazard.

RESULTS

Eight studies were included in the meta-analysis. Better response usually appeared in NSCLC patients with a lower expression of TS [RR = 2.06 95 % confidence intervals (CI) 1.44, 2.96]. There was a significant association between TS expression and outcomes of pemetrexed-based chemotherapy for NSCLC (PFS: HR = 0.63 95 % CI 0.52, 0.76; OS: HR = 0.74, 95 % CI: 0.63, 0.88). In addition, no evidence of publication bias was observed.

CONCLUSIONS

This meta-analysis evaluated the predictive value of TS and provided evidence that NSCLC patients with lower TS expression could significantly benefit from pemetrexed-based chemotherapy. This increased level of TS was probably an independent risk factor of potential resistance against pemetrexed.

Association of thymidylate synthase gene 3'-untranslated region polymorphism with sensitivity of non-small cell lung cancer to pemetrexed treatment: TS gene polymorphism and pemetrexed sensitivity in NSCLC

Background

Thymidylate synthase (TS) is a key enzyme responsible for DNA synthesis and repair. Altered expression of TS protein or TS gene polymorphisms has been associated with cancer progression and treatment response. This study investigated the expressions of TS and its gene SNPs in non-small cell lung cancer (NSCLC), and then its association with sensitivity to pemetrexed treatment. Immunohistochemistry and qRT-PCR were performed on 160 resected NSCLC specimens and corresponding normal tissues to assess the expressions of TS protein and TS mRNA, and for associations with clinicopathological data. Blood samples of 106 lung adenocarcinoma patients were examined for polymorphisms of the TS gene 3’-UTR 1494del 6 bp, which was then investigated for associations with responses of the patients to pemetrexed treatment and survival.

Results

Expression of both TS protein and its mRNA was elevated in NSCLC tissues compared with matched normal tissues, and significantly higher in lung squamous cell carcinoma than in lung adenocarcinoma. TS expression was associated with poor tumor differentiation. Furthermore, the genotyping data showed that 56% of lung adenocarcinoma patients had the TS gene 3’-UTR 1494 bp (−6 bp/-6 bp) genotype and the rest had TS gene 3’-UTR 1494 bp (−6 bp/+6 bp). There was no TS 3’-UTR 1494 bp (+6 bp/+6 bp) genotype in any patients. Statistical analysis revealed that gender, tumor stage, and TS 3’-UTR 1494del 6 bp polymorphism were significant prognostic factors after short-term pemetrexed treatment. Log-rank analysis revealed that patients with the (−6 bp/-6 bp) genotype had significantly better progression-free and overall survival than patients with (−6 bp/+6 bp).

Conclusions

This study showed that TS protein is highly expressed in NSCLC and that polymorphisms of TS 3’-UTR 1494del 6 bp are associated with sensitivity of lung adenocarcinoma patients to pemetrexed treatment. This suggests that TS gene polymorphisms should be further evaluated as prognostic markers for personalized therapy in lung adenocarcinoma.

High expression of folate receptor alpha in lung cancer correlates with adenocarcinoma histology and EGFR [corrected] mutation

INTRODUCTION

Folate receptor alpha (FRα) and reduced folate carrier-1 (RFC1) regulate uptake of folate molecules inside the cell. FRα is a potential biomarker of tumors response to antifolate chemotherapy, and a target for therapies using humanized monocloncal antibody. Information on the protein expression of these receptors in non-small-cell lung carcinoma (NSCLC) is limited.

MATERIAL AND METHODS

Expressions of FRα and RFC1 were examined by immunohistochemistry (IHC) in 320 surgically resected NSCLC (202 adenocarcinomas and 118 squamous cell carcinomas) tissue specimens and correlated with patients' clinico-pathologic characteristics. Folate receptor α gene (FOLR1) mRNA expression was examined using publicly available microarray datasets. FRα expression was correlated with thymidylate synthase and p53 expression in NSCLCs, and with epidermal growth factor receptor (EGFR) and V-Ki-ras2 Kirsten rat sarcoma viral (KRAS) gene mutations in adenocarcinomas.

RESULTS

NSCLC overexpressed FRα and RFC1. In a multivariate analysis, lung adenocarcinomas were more likely to express FRα in the cytoplasm (OR = 4.39; p < 0.0001) and membrane (OR = 5.34; p < 0.0001) of malignant cells than squamous cell carcinomas. Tumors from never-smokers were more likely to express cytoplasmic (OR = 3.35; p<0.03) and membrane (OR = 3.60; p=0.0005) FRα than those from smokers. In adenocarcinoma, EGFR mutations correlated with higher expression of membrane FRα and FOLR1 gene expressions. High levels of FRα expression was detected in 42 NSCLC advanced metastatic tumor tissues.

CONCLUSIONS

FRα and RFC1 proteins are overexpressed in NSCLC tumor tissues. The high levels of FRα in lung adenocarcinomas may be associated to these tumors' better responses to antifolate chemotherapy and represents a potential novel target for this tumor type.

A phase 1 study of TRC102, an inhibitor of base excision repair, and pemetrexed in patients with advanced solid tumors

INTRODUCTION

TRC102 potentiates the activity of cancer therapies that induce base excision repair (BER) including antimetabolite and alkylating agents. TRC102 rapidly and covalently binds to apurinic/apyrimidinic (AP) sites generated during BER, and TRC102-bound DNA causes topoisomerase II-dependent irreversible strand breaks and apoptosis. This study assessed the safety, maximum-tolerated dose (MTD), pharmacokinetics and pharmacodynamics of TRC102 alone and in combination with pemetrexed.

PURPOSE

Patients with advanced solid tumors received oral TRC102 daily for 4 days. Two weeks later, patients began standard-dose pemetrexed on day 1 in combination with oral TRC102 on days 1 to 4. The pemetrexed-TRC102 combination was repeated every 3 weeks until disease progression.

METHODS

Twenty-eight patients were treated with TRC102 at 15, 30, 60 or 100 mg/m(2)/d. The MTD was exceeded at 100 mg/m(2)/d due to grade 3 anemia in 50 % of patients. TRC102 exposure increased in proportion to dose with a mean t1/2 of 28 h. A pharmacodynamic assay confirmed that TRC102 binds to pemetrexed-induced AP sites at all doses studied. Stable disease or better was achieved in 15 of 25 patients evaluable for response (60 %), including one patient with recurrent metastatic oropharyngeal carcinoma that expressed high levels of thymidylate synthase, who achieved a partial response and was progression free for 14 months.

CONCLUSIONS

When administered with pemetrexed, the maximum tolerated dose of oral TRC102 is 60 mg/m(2)/d for 4 days. Randomized controlled studies are planned to evaluate the clinical benefit of adding TRC102 to pemetrexed and other agents that induce BER.

Personalized choice of maintenance therapies in non-small-cell lung cancer

Lung cancer has become a leading cause of cancer-related death in the world. Patient survival has improved with the introduction of new chemotherapy regimens and targeted drugs, but still, because of tumour progression or deterioration in performance status, a high percentage of patients do not receive more than one line of treatment. Given this situation, studies of maintenance therapies have begun, with results that have led to the clinical use of various drugs in a maintenance scenario. Additionally, results obtained in various clinical trials have raised the question of personalized approaches based on the clinical, pathologic, and molecular features of the cancer-not only in the initial approach, but also in the context of maintenance. Overall, the survival benefit seen with maintenance treatment has introduced a new therapy option that should be considered and discussed with patients, and (given the controversies that currently remain) chosen based on the preferences of patients and physicians.

NF-kappaB in lung cancer, a carcinogenesis mediator and a prevention and therapy target

Lung cancer ranks as the first malignant tumor killer worldwide. Despite the knowledge that carcinogens from tobacco smoke and the environment constitute the main causes of lung cancer, the mechanisms for lung carcinogenesis are still elusive. Cancer development and progression depend on the balance between cell survival and death signals. Common cell survival signaling pathways are activated by carcinogens as well as by inflammatory cytokines, which contribute substantially to cancer development. As a major cell survival signal, nuclear factor-kappaB (NF-kappaB) is involved in multiple steps in carcinogenesis and in cancer cell's resistance to chemo- and radio-therapy. Recent studies with animal models and cell culture systems have established the links between NF-kappaB and lung carcinogenesis, highlighting the significance of targeting NF-kappa signaling pathway for lung cancer treatment and chemoprevention. In this review, we summarize progresses in understanding the NF-kappaB pathway in lung cancer development as well as in modulating NF-kappaB for lung cancer prevention and therapy.

Phase 2 trial of pemetrexed disodium and carboplatin in previously untreated extensive-stage small cell lung cancer, N0423

BACKGROUND

In extensive-stage small cell lung cancer (SCLC), the combination of pemetrexed plus carboplatin has shown activity and appeared to be well-tolerated. We conducted a trial to confirm the efficacy and to assess the tolerability of this chemotherapy combination.

METHODS

Patients with untreated extensive-stage SCLC were enrolled in this phase 2 open-labeled study. They receive pemetrexed 500 mg/m(2) and carboplatin (area under the curve of 5) every 21 days for a maximum 6 cycles. The primary endpoint for this trial was the confirmed response rate and the accrual goal was 70 patients.

RESULTS

Forty-six eligible patients (29 aged <70 years, 17 aged >or=70 years) were accrued to this study. The efficacy outcomes were similar between the 2 age groups. Overall, the confirmed response rate was 35% (16 of 46; 95% confidence interval [CI], 21%-50%), where all 16 were partial responses. On the basis of these results, we had strong evidence that the study would not meet the preset efficacy criteria and was, therefore, closed before full accrual. The median duration of response was 4.4 months (95% CI, 2.9-5.2). Median overall survival for patients aged <70 years and aged >or=70 years was 9.2 months (95% CI, 5.4-11.6) and 10.8 months (95% CI, 2.2-14.3), respectively. Grade 3 or higher toxicity rates were similar between the younger and older patients. Grade 3/4 and grade 4 hematological toxicities were observed in 46% and 26% of patients, respectively.

CONCLUSIONS

Although well-tolerated, the combination of pemetrexed and carboplatin is not as effective as standard therapy in patients with untreated extensive-stage SCLC.