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Erlotinib: Preclinical Investigations

November 2nd 2003

Erlotinib (Tarceva) is an orally available selective small-moleculeinhibitor of HER1/EGFR tyrosine kinase with a 50% inhibitory concentrationof 2 nM for purified tyrosine kinase. This agent has beenshown to produce stasis or regression of tumor growth in human cancerxenograft models, including non-small-cell lung cancer models.Ongoing preclinical investigations indicate that inhibition of the MAPKand Atk signaling pathways downstream of HER1/EGFR may be requiredfor optimal antitumor effects. Erlotinib exhibits inhibition ofMAPK and Atk kinases at concentrations higher than those requiredfor HER1/EGFR tyrosine kinase inhibition; such findings suggest thatmaximal inhibition of HER1/EGFR, requiring high erlotinib doses, isnecessary for optimum antitumor activity. These considerations aresupported by tumor models, including non-small-cell lung cancermodels, showing dose-related antitumor effects up to high doses oferlotinib. Erlotinib exhibits additive antitumor effects when combinedwith chemotherapeutic agents (cisplatin, doxorubicin, paclitaxel,gemcitabine [Gemzar], and capecitabine [Xeloda]), radiation therapy,and other targeted agents (eg, bevacizumab [Avastin]). Recent studiesindicate that erlotinib inhibits the EGFRvIII mutant at concentrationshigher than those required for inhibition of wild-type receptor. Ongoinginvestigation will help to determine optimal dosing and dose frequencyof erlotinib in various cancers in the clinical setting.


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Risk Models for Neutropenia in Patients With Breast Cancer

November 1st 2003

Breast cancer is the most common noncutaneous malignancy inwomen in industrialized countries. Chemotherapy prolongs survival inpatients with early-stage breast cancer, and maintaining the chemotherapydose intensity is crucial for increasing overall survival. Manypatients are, however, treated with less than the standard dose intensitybecause of neutropenia and its complications. Prophylactic colonystimulatingfactor (CSF) reduces the incidence and duration of neutropenia,facilitating the delivery of the planned chemotherapy doses.Targeting CSF to only at-risk patients is cost-effective, and predictivemodels are being investigated and developed to make it possible forclinicians to identify patients who are at highest risk for neutropeniccomplications. Both conditional risk factors (eg, the depth of the firstcycleabsolute neutrophil count nadir) and unconditional risk factors(eg, patient age, treatment regimen, and pretreatment blood cell counts)are predictors of neutropenic complications in early-stage breast cancer.Colony-stimulating factor targeted toward high-risk patients startingin the first cycle of chemotherapy may make it possible for fulldoses of chemotherapy to be administered, thereby maximizing patientbenefit. Recent studies of dose-dense chemotherapy regimens with CSFsupport in early-stage breast cancer have shown improvements in disease-free and overall survival, with less hematologic toxicity than withconventional therapy. These findings could lead to changes in how earlystagebreast cancer is managed.


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Current Role of Irinotecan in the Treatment of Non-Small-Cell Lung Cancer

September 1st 2002

Lung cancer remains the primary cause of cancer-related death in both men and women in the United States. Chemotherapy has been shown to provide a survival benefit in patients with advanced non-small-cell lung cancer (NSCLC), and current regimens have produced median survivals of approximately 8 months and 1-year survival rates of 30% to 35% in patients with stage IIIB and IV disease. Nevertheless, there remains room for improvement. Irinotecan (CPT-11, Camptosar) has demonstrated efficacy in the treatment of small-cell lung cancer (SCLC). It also appears to have promising activity in advanced NSCLC, producing overall response rates of up to 32%. Combinations of irinotecan and cisplatin or carboplatin (Paraplatin) have resulted in overall response rates of 25% to 56% in phase II and III studies in patients with advanced disease, with median survivals ranging from 9 to 13 months and 1-year survival rates of 33% to 58%. Current irinotecan-based doublet and triplet regimens appear to produce promising response rates with manageable toxicities. In addition, irinotecan has demonstrated potential as a radiosensitizing agent and is currently being evaluated in several trials of combined-modality therapy in patients with locally advanced NSCLC. Early trials of irinotecan in combination with cisplatin or carboplatin along with radiation therapy have reported overall response rates of 60% to 67%. The approach appears to have potential and warrants further study. [ONCOLOGY 16:1153-1168, 2002]

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