Plasma DNA, microsatellite alterations, and p53 tumor mutations are associated with disease-free survival in radically resected non-small cell lung cancer patients - A study of the Perugia multidisciplinary team for thoracic oncology

Introduction: This prospective study examined association between circulating plasma DNA, microsatellite alterations (MA), p53 mutations with time to relapse and survival in surgically treated non-small cell lung cancer (NSCLC) patients (pts). Methods: Plasma samples, adjacent lung tissue, and lung tumor tissue specimens were collected from consecutive patients with stage I-III NSCLC. Blood samples of 66 matched healthy donors with positive smoking history were collected as controls. The plasma DNA amount was determined by real-time PCR. The analysis of MA at loci D3S1300, D3S1289, D3S1266, and D3S2338 on chromosome 3p was performed by radiolabeled PCR. p53 Mutations (exons 5, 6, 7, and 8) were detected by PCR-single-strand conformational polymorphism assay. Results: There were 76 patients, 65 men; median age was 68 years (range, 42-86), 20 had stage I, 40 stage II, and 16 stage III, the majority of pts (48.7%) had squamous-cell histology. Sixty-nine (91%) were smokers and most had good Eastern Cooperative Oncology Group performance status (0/1:72/4). Mean circulating DNA of all pis was 60 ng/ml versus 5 ng/ml in smoker-matched controls (p < 0.000 1). In pis without recurrence, mean circulating DNA was 48.5 ng/ml at baseline, 32.8 ng/ml at 3(rd) month, and 20.6 ng/ml at 12(th) month after surgery. In pis with recurrence, mean circulating DNA at baseline was 97.1 ng/ml. At 3(rd) month after surgery, mean DNA concentration was significantly lower in disease-free pts than in patients with recurrent disease (32.8 versus 292.7 ng/ml; p = 0.0016). MA in at least one locus was found in 39.5% of NSCLC tumors. p53 Genomic mutations were observed in 54.0% of tumor samples. Statistically significant associations were observed between MA and squamous-cell histotype (p = 0.007) and between p53 mutations and lymph node involvement (p = 0.012). MA and p53 mutations were found to be significantly associated with recurrence of disease (p = 0.033 and 0.026, respectively). Conclusion: Our results suggest that MA and p53 mutations in tumor DNA have a potential prognostic role for disease recurrence in NSCLC patients, and elevated levels of plasma circulating DNA identify patients with possible systemic disease at diagnosis. This might be proposed as an early detection test of disease recurrence.