DESTINY-PANTUMOUR04

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.

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