Mutational activation of the K-ras oncogene and the effect of chemotherapy in advanced adenocarcinoma of the lung: a prospective study

Abstract

Purpose: To determine whether the clinical course and the response to chemotherapy of patients with advanced adenocarcinoma of the lung depends on the presence or absence of a ras mutation in the tumor. Mutational activation of K-ras is a strong adverse prognostic factor in stage I or II lung cancer and laboratory studies have suggested that ras mutations lead to resistance against ionizing radiation and chemotherapy.

Patients and methods: Patients with advanced adenocarcinoma of the lung with measurable or assessable disease received chemotherapy with mesna, ifosfamide, carboplatin, and etoposide (MICE). Archival biopsies, fresh biopsies, or fine-needle aspirations were tested for the presence of ras gene mutations. Associations of ras mutations with clinical characteristics, response to chemotherapy, and survival were studied.

Results: The presence or absence of ras gene mutations could be established in 69 of 83 patients (83%). A total of 261 courses of MICE were administered to 62 informative patients, 16 of whom were shown to have a K-ras mutation-positive tumor. The frequency of mutations (26%) and the type of mutations closely matched the pattern we have previously reported in operable disease. Patients with a ras mutation in their tumor were more likely to have a close relative with lung cancer, but other clinical characteristics, such as pattern of metastases, response, and survival, were similar between the ras mutation-positive and ras mutation-negative groups.

Conclusion: Patients with advanced lung adenocarcinoma who harbor a ras mutation may have major responses to chemotherapy and have similar progression-free and overall survival as patients with ras mutation-negative tumors. K-ras mutations may represent one of several ways in which early tumors are enabled to metastasize to distant sites.