Romiplostim is a medicine being tested to help children and teens with cancer who have low platelet counts due to chemotherapy. Platelets are tiny blood cells that help stop bleeding. Sometimes chemotherapy can cause thrombocytopenia, which means having very low platelets. This can make it hard for doctors to give the right amount of cancer medicine. This study will check if romiplostim can safely raise platelet counts so that chemotherapy can continue without delays or dose reductions.

Children and teens aged 1 to 18 with solid tumors and low platelet counts from chemotherapy can join. They must not have other cancers, liver cancer, or past blood clot problems. This study does not include those with other reasons for low platelets, like inherited conditions.

• Participants may need regular check-ups and blood tests during the study.
• Potential benefits include improved platelet levels and fewer transfusions.
• Risks might include side effects from romiplostim, which will be monitored closely.