Elsevier

Lung Cancer

Volume 72, Issue 3, June 2011, Pages 365-369
Lung Cancer

The identification of KRAS mutations at codon 12 in plasma DNA is not a prognostic factor in advanced non-small cell lung cancer patients

https://doi.org/10.1016/j.lungcan.2010.09.005Get rights and content

Abstract

Background

Qualitative analysis of circulating DNA in the blood is a promising non-invasive diagnostic and prognostic tool. Our aim was to study the association between the presence of KRAS mutations at codon 12 and several clinical variables in advanced non-small cell lung cancer (NSCLC) patients.

Methods

We examined 308 stage IIIB and IV NSCLC patients who were treated with cisplatin and docetaxel. Blood samples were collected before chemotherapy, and circulating DNA was extracted from the plasma using commercial adsorption columns. The KRAS mutational status was determined by an RT-PCR method that is based on allelic discrimination.

Results

The median age of the patients was 60 years [31–80], 84% were male, 98% had a performance status of 0–1 and 84% of the patients were in stage IV. The histological subtypes were as follows: 30% squamous cell carcinoma (SCC), 51% adenocarcinoma (ADC) and 19% others. Of the 277 response-evaluated patients, 1% achieved a complete response (CR), 26% achieved a partial response (PR), 34% had stable disease (SD) and 39% had progressive disease (PD). Additionally, 27 (8.8%) patients had KRAS mutations; 26 had a KRAS codon 12 TGT mutation, and 1 had a codon 12 GTT mutation. Plasmatic KRAS mutations were found in patients presenting SCC or ADC. Patients with KRAS mutations in plasma DNA had a median progression free survival (PFS) of 5.77 months [3.39–8.14], whereas for patients with wild-type (wt) KRAS, the PFS was 5.43 months [4.65–6.22] (p = 0.277). The median overall survival (OS) in KRAS-mutated patients was 9.07 months [4.43–13.70] vs 10.03 months [8.80–11.26] in wt patients (p = 0.514).

Conclusions

In advanced NSCLC patients, there were no significant differences between patients with or without KRAS mutations in plasma-free DNA with respect to the baseline characteristics, response rates, PFS or OS.

Introduction

Due to a low cure rate (6–15%) and the lack of adequate screening measures, lung cancer is the leading cause of cancer death [1]. These facts have motivated the search for new ways to detect, predict, and monitor lung cancer [2], [3], [4], [5], [6]. Cancer is a multi-step process involving key cancer-related genes [7], [8]; mutations in the KRAS gene have recently gained attention because KRAS is part of several signaling pathways, and genetic alterations in KRAS might thus lead to tumor development [9]. In fact, KRAS mutations are found in up to 30% of non-small cell lung cancer (NSCLC) tumors, are primarily (90%) in codon 12 [6], [10], [11], [12], occur early in the development of malignancy and in some cancers have been detected in free DNA in the blood before clinical diagnosis [13]. NSCLC KRAS mutations have been associated with larger tumors, lymph node metastases, and poorer progression and survival [14], [15].

Bremnes et al., reviewed the utility of analyzing circulating tumor derived DNA in blood for the development of sensitive molecular biology approaches to analyze gene mutations (such as in KRAS) in these kinds of samples [16]. This technique is of interest because there are reports of correlation between the presence of KRAS mutations in the serum/plasma DNA and the mutational status of KRAS in tumors [17], [18], [19], [20], [21], [22], [23]. Recently, several NSCLC trials demonstrated that KRAS mutations in circulating DNA correlated with survival and response to treatment [19], [22], [24]; on the other hand, a study conducted by our group failed to demonstrate this prognostic role [23], and another NSCLC study did not reveal any circulating mutant KRAS [25].

Therefore, because there are substantial discrepancies in several studies on KRAS mutational status in both tumor and blood, the goal of this study was to investigate the prognostic significance of the codon 12 KRAS mutations in the plasma DNA from 308 well-characterized advanced NSCLC patients.

Section snippets

Patients

This study was performed retrospectively with blood samples from 308 patients diagnosed with advanced NSCLC who were enrolled in a multicentric clinical trial of the Spanish Lung Cancer Group. All patients had clinical stage IIIB or IV cancer and had not undergone previous chemotherapy treatment. Patients were excluded if they had two primary tumors at the time of diagnosis. The histological diagnosis of the tumor was based on the World Health Organization criteria. The TNM classification and

Results

The most relevant demographic and baseline clinico-pathological characteristics of the 308 studied patients are summarized in Table 1. The median age was 60 years (range [31–80]), and 84% of the patients were men. Sixteen percent of the patients’ cancers were defined as stage IIIB, and the remaining 84% were defined as stage IV.

There were 75 patients (24.4%) with clinical responses (CR or PR), and 202 patients (65.6%) with SD or PD (see Table 2). Some of these patients (158/308, 51%) received

Discussion

High levels of DNA derived from the primary tumor are present in the serum or plasma of cancer patients. In fact, patients with larger tumors have more DNA in the plasma. We have focused on KRAS mutations in the plasma DNA because point mutations appear early in cancer development and the detection of these mutations in plasma DNA has been demonstrated to be feasible [23], [28], [29]. Also, KRAS mutational status analysis, together with other molecular markers may have value in determining

Conclusion

We have developed a molecular biology technology that is affordable for large-scale studies and is not time consuming. In our cohort of NSCLC patients, the presence of mutant KRAS in the plasma DNA did not correlate with the disease stage, performance status, objective response rates, or survival. Based on this work, the prognostic relevance of KRAS mutations in the plasma/serum DNA of NSCLC patients remains controversial.

Conflict of interest statement

The authors declare no conflicts of interest or any financial disclosure.

Funding

This work was sponsored in part by a grant from the Spanish Society of Medical Oncology (SEOM) and by a grant (RD06/0020/1024) from Red Temática de Investigación Cooperativa en Cáncer (RTICC), Instituto de Salud Carlos III (ISCIII), Spanish Ministry of Science and Innovation & European Regional Development Fund (ERDF) “Una manera de hacer Europa”. None of the funding agencies were involved in the design, data management, data analysis, manuscript preparation and review, or decision to submit.

Acknowledgements

The authors gratefully acknowledge the collaboration of the following investigators from the Spanish Lung Cancer Group (GECP): R. de las Peñas, G. Alonso, G. López Vivanco, M. Provencio, R. Rosell, J.L. González Larriba, A. Artal, R. García Gómez, N. Viñolas, J. Terrasa, F. Barón, B. Massuti, E. Pujol Obis, A. Carrato, R. Colomer, J.M. Puerto-Pica, P. Martínez, P. Diz, P. Bueso, P. Lianes, B. Medina, I. Barreto, D. Gutierrez Abad, C. Mesía, I. Moreno, C. Madroñal, T. de Portugal, M. Saldaña, M.

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