This study examines treatment for low platelet counts caused by chemotherapy in adults with non-small cell lung cancer, ovarian cancer, or breast cancer. Platelets are blood cells that help stop bleeding, and chemotherapy can lower their numbers, sometimes requiring doctors to delay or reduce cancer treatment doses. The study uses a medication called romiplostim, which is also known by the code name AMG 531, or placebo. Romiplostim is designed to help the body make more platelets. Participants will receive chemotherapy containing carboplatin combined with other cancer drugs such as gemcitabine, pemetrexed, liposomal doxorubicin, paclitaxel, nab-paclitaxel, or docetaxel. Some participants may also receive additional treatments like bevacizumab or other targeted therapies.
The purpose of this study is to find out if romiplostim can help maintain platelet counts high enough to allow patients to receive their full chemotherapy doses on time without delays or reductions. The study will compare romiplostim with placebo to measure its effectiveness. Participants entering the study must have a platelet count at or below a certain level and must have at least three more cycles of chemotherapy planned. The chemotherapy cycles are given every 21 or 28 days depending on the specific treatment plan.
During the study, participants will receive either romiplostim or placebo as an injection under the skin while continuing their regular chemotherapy treatment. The study medication will be given for a treatment period lasting up to 12 weeks. Doctors will monitor platelet counts, track whether chemotherapy doses need to be changed due to low platelets, and watch for any bleeding problems or other side effects. Participants will continue to be followed for safety monitoring for up to 36 months to check for any long-term effects.



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