Theoretical framework = not mentionedSetting = 10 cancer centers in Estonia, Finland, Greece, Norway, Portugal, Spain, and SwedenPopulation = advanced or metastatic lung cancer (non–small cell lung cancer or small cell lung cancer) or HER2-positive breast cancerSample size = 153 patients and 70 HCPsAge = 62% of patients were 60 y and olderFemale = 45%Race and ethnicity = not mentionedTreatment type = anti–PD-L1 agents, other immunotherapy, combination therapies. Here, ERBB2 is linked to cancer.