CK19 mRNA expression measured by reverse-transcription polymerase chain reaction (RT-PCR) in the peripheral blood of patients with non-small cell lung cancer treated by chemo-radiation: An independent prognostic factor☆
Introduction
Lung cancer was the leading cause of cancer death in both men and women in the USA [1]. It has also been one of the most common malignancies in China in the past decade, especially in big cities. The incidence of lung cancer was as high as that in North America with 53/100,000 for male and 21/100,000 for female in Shanghai in 2003 [2]. Unfortunately the prognosis of NSCLC has been dismal even after modern treatment modalities. The predominant cause of failure is believed to be distant metastases, even for early stages. For example, in over 20% of patients even with pathologic stage I, distant relapses finally occurred [3], which implied that the intrinsic biological characteristic of NSCLC is early development of distant metastases. However, current staging methods are not able to detect that these occult metastases existed when the patients were diagnosed. Therefore, there is need to develop more sensitive and accurate methods to detect occult distant metastases in advance.
In recent years, many research groups have attempted to detect occult tumor cells in lymph nodes [4], [5], [6], bone marrow [6], [7], and peripheral blood (PB) [8], [9], [10] of NSCLC patients with either immunohistochemistry, immunocytochemistry, or genetic methods with cytokeratin (CK), carcinoembryonic antigen (CEA) or mucin-1 as markers of tumor cells. Most studies were focused on early-stage patients treated with surgery. Unfortunately, in Shanghai only approximately one third of NSCLC patients are in the early stage, more than one third are locally advanced, and the remaining cases already have distant metastases when diagnosed. For locally advanced NSCLC, chemo-radiation was recommended as the standard care for those patients [11].
The current study was a prospective trial to measure CK19 mRNA by nested reverse-transcription polymerase chain reaction (RT-PCR) before and after treatments in PB samples from NSCLC patients with stage I–IIIb treated by definitive chemo-radiation to evaluate its significance as a prognostic predictor.
Section snippets
Patient eligibility
Patients meeting all the following requirements were eligible for enrollment: (1) diagnosis of NSCLC confirmed by cytology or histology; (2) stage I–II (UICC, 1997) medically inoperable, or IIIa–b unresectable (except for malignant pleural effusion); (3) Karnofsky performance status (KPS) of ≥70; (4) untreated and intent to treat with definitive chemo-radiation; (5) written informed consent obtained.
Criteria for patient withdrawal from the study were: disease progression, unacceptable toxicity,
Patient characteristics
Between February 2002 and March 2003, a total of 70 patients were enrolled in this study at Department of Radiation Oncology, Fudan University Cancer Hospital. Three patients were excluded from the study due to brain metastases in two cases and malignant pleural effusion in one case, which occurred within 2 weeks after initiating treatment. Therefore, 67 patients remained were analyzed and their clinical characteristics were summarized in Table 1. There were 60 males and 7 females with median
Discussion
NSCLC is extremely prone to spread distantly through the bloodstream, even at its early stage. Therefore, the detection of these occult tumor cells circulating in PB may both predict the potential of distant metastases and help make treatment decisions. Since Smith et al. [13] first developed a RT-PCR assay to detect circulating melanoma cells by the amplification of tyrosinase mRNA in 1991, this method has been widely applied in detection of occult metastasis from various tumors. CK19, a
Conclusion
This study illustrated that only the presence of circulating tumor cells detected by nested CK19 RT-PCR after the treatment was an independent unfavorable factor for inoperable NSCLC treated by definitive chemo-radiation. However, it should be interpreted with caution, given the small sample size and the limited follow-up time. Nevertheless, for patients with positive CK19 mRNA after initial chemo-radiation, it was suggestive that stronger systemic therapies be considered.
Acknowledgments
This study was supported by a grant # 2003269 from Ministry of Public Health, China PR.
Authors would like to thank Zhi-Ming Shao, M.D. and Yi Feng Hou, M.D. for their technical assistance, and Tai-Fu Liu, M.D., F.A.C.R. (Hon.) for his assistance in the editing of the English text.
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A part of this study was presented at the 46th American Society of Therapeutic Radiation Oncology (ASTRO), Atlanta, GA, USA, 3–7 October 2004 (Abstract 174).
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Present address: Department of Radiation Oncology, Jiangsu Province Cancer Hospital, 42 Bai Zi Ting, Nanjing, Jiangsu 210009, China.