Effective use of sotorasib in a patient with KRAS G12C-Positive invasive mucinous lung adenocarcinoma complicated by interstitial lung disease: A case report

Invasive mucinous adenocarcinoma (IMA) is a rare type of lung adenocarcinoma frequently associated with KRAS mutations and is generally considered to have an unfavorable prognosis. Given the risk of treatment-related pneumonitis, the co-occurrence of interstitial lung disease (ILD) can further complicate treatment selection. Although sotorasib, a KRAS G12C inhibitor, has demonstrated efficacy in treating non–small cell lung cancer (NSCLC) associated with KRAS G12C mutations, its safety and efficacy in patients with preexisting ILD, particularly those with IMA, remain insufficiently documented. Case Presentation: A man in his 50s with a history of heavy smoking who was diagnosed with KRAS G12C-positive IMA of the right lower lobe, complicated by non–usual interstitial pneumonia (non–UIP) pattern ILD, along with synchronous squamous cell carcinoma in the left upper lobe. Following progression after systemic therapy, sotorasib therapy was initiated and contributed to a significant tumor response without exacerbating ILD or causing drug-induced pneumonitis. This case highlights that with careful monitoring, sotorasib may be considered a therapeutic option for selected patients with KRAS G12C-positive NSCLC, even in the presence of ILD, including those with IMA histology.