Detection of p53 gene mutations in sputum samples and their implications in the early diagnosis of lung cancer in suspicious patients

Objectives To evaluate the value of detecting p53 gene point mutations in s putum samples and its validity and reliability as a surveillance index in t he early diagnosis of lung cancer in suspicious patients. Methods Sputum samples were collected from 54 cases identified as lung canc er and 114 cases identified as pulmonary benign disease. The polymerase cha in reaction-single strand conformation polymorphism (PCR-SSCP) was performe d for the detection of point mutations at exons 5 - 8 of the p53 gene, and sputum smears were also used for each sample. Results The detected mutation rate of 55.56% (30/54) in the lung cancer gro up was significantly higher than that of 1.75% (2/114) in the control group (P < 0.001). In the lung cancer group, the sensitivity, specificity, and p ositive likelihood ratio (PLR) of p53 mutations as a diagnostic marker for lung cancer were 55.56%, 98.25% and 31.75%, respectively. Also, the detecti on rates were 35.19% (19/54) by smears and 55.56% (30/54) by PCR-SSCP-silve r stain, respectively. The differences both in rate and consistency were st atistically significant ( P < 0.01 and P < 0.05, respectively). Moreover, s tatistical analysis showed no significant relations between p53 mutations a nd clinical parameters such as gender, smoking habits, histotypes and stage s, but the detection rate of p53 mutations in older patients (greater than or equal to 60 years old) was significantly higher than that in younger pat ients ( P = 0.02). One case with p53 mutations at exon 5 in the control gro up was confirmed to be squamous cell carcinoma after 4 years of follow-up. Conclusion Detection of p53 gene alterations in sputum samples by PCR-SSCP- silver stain can be used as a follow-up surveillance index for the early di agnosis of lung cancer in suspicious patients.