Abstract
A 74-year-old man was referred to our hospital with an abnormal chest shadow. Computed tomography (CT) revealed a mass in the left upper lobe and interstitial pneumonia (IP). The patient underwent CT-guided needle biopsy and was diagnosed as lung adenocarcinoma with cT2aN1M1a Stage IVA (PUL). The patient was administered 6 cycles of CBDCA + nab-paclitaxel as first-line, 3 cycles of atezolizumab as second-line, and 8 cycles of S-1 as third-line treatment but finally showed tumor progression. Because comprehensive genome profiling test revealed KRAS G12C mutation, sotorasib was initiated as fourth-line treatment and showed tumor regression without exacerbation of pre-existing IP.