Phd in ANGIO-CARDIO-THORACIC PATHOPHYSIOLOGY AND IMAGING

Thesis title: Impatto del DNA tumorale circolante e DNA libero circolante su diagnosi precoce di tumore al polmone in pazienti con riscontro radiologico di ground glass opacity (GGO)

Aim of the study Pulmonary Ground Glass Opacitys (GGOs) are frequently encountered in daily clinical practice due to the improvement of radiological tools. For the most they are benign and transitory inflammatory entities, but up to 37% of that are associated with early-stage lung cancer. A long-term radiological follow-up is to date the gold-standard for a differential diagnosis. Aim of this pilot study is a preliminary evaluation of the diagnostic role of circulating free DNA (cfDNA) and circulating tumor DNA (ctDNA) on peripheral blood of patients with radiological findings of GGOs. Materials and Methods For the pilot study, 10 consecutive patients (M:F=1:1, age 68.1±10.8 years) with first finding of GGO at CT scan were prospectively enrolled for the study. 20 mL of peripheral venous blood was taken at the time of the first visit and plasma stored at -80°C after centrifugation. The cfDNA extracted from plasma was quantified using Easy PGX. A targeted approach was used for the detection of ctDNA, using Myriapod ® NGS Cancer Panel DNA. Patients underwent radiological follow up or histological sample following the international guidelines. Radiological/histological diagnosis was compared to DNA data to evaluate a possible diagnostic role in malignant GGNs. Moreover, ctDNA results were compared to histological specimens to assess a possible correlation in gene mutations. At the end of the pilot study, the recruiting period was reopened for further evaluation. Results Six patients had a histological diagnosis of malignant GGO while 4 patients had a radiological/histological diagnosis of inflamatory nodule. Pure GGOs were more frequently benign than mixed GGOs (p-value=0.0228). The average amount of cfDNA was 1.23±1.68 ng/μL per patient. Patients with a malignant GGO showed a lower amount of cfDNA in the peripheral blood than patients with inflammatory GGOs (0.613 vs 2.156 ng/μL; p=0.031). Nine patients presented reliable results in ctDNA analysis. Among the 17 genes evaluated, the most frequently mutated were HRAS and KIT (40%), followed by NRAS (30%), IDH-2 (20%), RET (20%) and PIK3CA (20%). However, no concordant genes were found between ctDNA and tissue analysis. Considering these results, the second phase of the study was focused on the cfDNA assess. The final coohort consisted in 27 patients (M:F 0.59:1, age 67.9±11.3 years). Sixteen (59.3%) had diagnosis of adenocarcinoma while 11 (40.7%) had diagnosis of benign/inflammatory nodule. Patients with malignant disease revealed a lower mean cfDNA in peripheral blood (1.19 ± 0.68 vs 1.41 ± 1.57) but without statistical difference between groups (p-value 0.771). Conclusions From our preliminary analysis, lung cancer at its very early stage does not release relevant amounts of ctDNA into the peripheral blood. Therefore, ctDNA detection does not appear to have a role in the early diagnosis of lung cancer in patients with GGO, at present. However, in our sample, malignant GGOs showed a lower amount of cfDNA than patients with inflammatory disease. This aspect could open new lines of research in the future.