A Phase-3, Open-Label, Randomized Study of Dato-DXd Versus Investigator's Choice of Chemotherapy (ICC) in Participants With Inoperable or Metastatic HR-Positive, HER2-Negative Breast Cancer Who Have Been Treated With One or Two Prior Lines of Systemic Chemotherapy (TROPION-Breast01)

To join this study, you would need to be at least 18 years old and have a specific type of breast cancer that doctors can't remove with surgery or that has spread. Your cancer must be 'HR-positive' and 'HER2-negative', and you would have already received one or two rounds of chemotherapy for this advanced cancer, but it has started to grow again (progressed).

Additionally, your doctor needs to confirm that you are healthy enough in general to receive one of the standard chemotherapy options included in this trial. You'll also need to have good blood test results, showing your organs like your heart, liver, and kidneys are working well. The study also requires that your general health and day-to-day activities are not severely affected by your cancer or its previous treatments. For example, you shouldn't have specific types of brain metastases unless they are stable and not causing symptoms.

There are also specific measurements of your tumour that need to be met, and certain conditions that would prevent you from joining, such as having significant heart problems or other serious medical conditions that might make the treatment unsafe for you. The research team will carefully check all these details to ensure the study is safe and appropriate for everyone involved.

If you decide to take part in this study, you would be randomly assigned to receive either the new drug, Dato-DXd, or one of the standard chemotherapy treatments already available. This is like flipping a coin, so neither you nor your doctor can choose which treatment you get. Throughout the study, you'll have regular hospital visits for treatments, blood tests, physical exams, and scans (like CT scans) to check how the treatment is working and monitor for any side effects. You might also be asked to fill out questionnaires about how you're feeling and your quality of life. The doctors and nurses will be on hand to support you and answer any questions you have. Once your treatment period ends, you'll continue to have follow-up appointments to track your health and the progress of your cancer for a longer period.