DESTINY-PANTUMOUR04

Inclusion Criteria: 1. Adults aged ≥18 years 2. Patients with locally advanced, unresectable, or metastatic HER2-positive (IHC 3+) solid tumors who have received prior systemic treatment for metastatic or advanced disease and have no satisfactory alternative treatment options as determined by the Investigator (see Exclusion Criterion 1 for excluded solid tumors); 3. A clinician decision has been made for treatment with T-DXd in accordance with the FDA label; 4. HER2-positive (IHC 3+) by local testing prior to study enrolment at the time of signed and dated informed consent; 5. Patients who are willing and able to provide a signed and dated informed consent. Exclusion Criteria: 1. Primary diagnosis of adenocarcinoma of the breast, adenocarcinoma of the colon or rectum, NSCLC, adenocarcinoma of the gastric body or gastroesophageal junction or hematological malignancies; 2. Prior T-DXd therapy; 3. Patients without a baseline assessment of tumor burden undertaken prior to initiating T-DXd. 4. Patient is participating in a clinical trial at time of enrolment