Detection of chromosome 3p alterations in serum DNA of non-small-cell lung cancer patients

Background: The generally dismal outcome of non-small-cell lung cancer (NSCLC) is believed to be associated with the systemic nature of this disease. In current practice, the decision to begin adjuvant chemotherapy in completely resected early stages is based on empirical criteria and has not yet been influenced by the presence of individual risk factors. Nonetheless, recent studies indicate that soluble tumor DNA is found in the serum and plasma of cancer patients, and microsatellite alterations have been identified in small-cell lung cancer and in head and neck neoplasms.Patients and methods: We have investigated serum DNA from 22 completely resected stage I–IIIA NSCLC patients using a polymerase chain reaction microsatellite analysis with four microsatellite markers at chromosome 3p (D3S1038, D3S1611, D3S1067 and D3S1284).Results: Our analyses showed serum tumor DNA in 6 of 22 (28%) cases, with microsatellite alterations, either as a shift (changes in the size of the microsatellite sequence in the autoradiograph) or as a loss of heterozygosity (LOH). LOH in both tumor and serum DNA at one or more microsatellite markers was found in four patients. Although it is still premature to look for prognostic implications, one patient with stage I serum DNA was identified prior to the development of distant metastases.Conclusions: The findings suggest that detection of free circulating DNA in sera of NSCLC patients is incidentally linked to the systemic nature of lung cancer even at the earliest stage. These observations provide the first hint that serum tumor DNA is present in NSCLC patients. The detection of DNA from cancer cells in the sera of NSCLC patients could be useful for monitoring relapse in a relatively non-invasive way, and the potental sensitivity of this test may help in selecting candidates for adjuvant chemotherapy.