Circulating tumor DNA are short DNA sequences of tumor cells shed into systemic circulation. Serial monitoring of ctDNA levels and immediate correlation with imaging findings has not been well-described in lung cancer.
We conducted a retrospective study including adult patients with lung cancer at William Beaumont - Royal Oak and Troy Hospitals, Michigan. We evaluated the correlation of ctDNA test results with corresponding imaging findings to detect changes in disease status.
Seventeen patients, 16 with non-small cell and 1 with small cell lung cancer were included. The median age at diagnosis was 64 years, and 58.8% were female. Majority (86.2%) had Stage III or IV disease. Out of the 34 total ctDNA samples, the 19 positive ctDNA results had presence of disease on corresponding imaging- 15 showed progression while 4 showed stable disease. All 15 negative ctDNA test results also had presence of disease on corresponding imaging, but majority showed regression (7) or stable disease (6) and only 2 showed progression. Sensitivity of a single positive ctDNA test to detect presence of disease on imaging was 55.8%. The positive ctDNA results detected disease progression with a median lead time of 52.4 days. Seven patients had multiple ctDNA test results with 11 pairs of positive ctDNA values, of which 8 were up-trending, and 3 were down-trending. Both sensitivity and specificity of up-trending ctDNA values to detect progression and down-trending ctDNA values to detect regression on imaging were 100%.
Given the high sensitivity and specificity of serial ctDNA monitoring in our study, we conclude that this may be a valid way to monitor disease progression or regression in lung cancer reliably. Further larger clinical studies are needed to prove its utility in detecting immediate changes in disease status and guiding changes in therapeutic intervention in lung cancer.