The identification of KRAS mutations at codon 12 in plasma DNA is not a prognostic factor in advanced non-small cell lung cancer patients
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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2015, Lung CancerCitation Excerpt :Currently, NSCLC is no longer one disease but a cohort diseases with different driver gene mutations including EGFR, KRAS, ALK, HER2, BRAF, ROS1, RET and so on [4,63–68]. Up to now, a lot of retrospective and perspective studies have indicated that detection of driver gene mutations in ctDNA of patients with NSCLC is feasible and reliable [38,43,46,50,51,55,69–77]. For instance, in 2007, Kimura et al. analyzed the EGFR mutation status in tumor and plasma of 42 patients treated with gefitinib [39].
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These authors contributed equally to this work.