This study is for adults 18 and older with early-stage non-small cell lung cancer (NSCLC) who have a specific gene change called *HER2* mutation. This change affects how a protein works, leading to cancer growth. The study will see if a medicine called **zongertinib** helps stop cancer from coming back after surgery better than normal treatments. Zongertinib is taken by mouth daily for up to 3 years. In the study, people are randomly put in one of two groups: one gets zongertinib, while the other receives standard treatment, like medicine given through a vein every few weeks, or just regular check-ups.

• Participation lasts up to 11 years with regular doctor visits and scans.
• Frequent check-ups are needed, especially in the first few years.
• Participants may need to complete health questionnaires and receive calls from the study team.

Doctors use scans like CT or MRI every few months to check for cancer's return. People must meet certain health criteria to join, and some conditions or past treatments might prevent participation.