Is it true that chemotherapy makes it worse if you have sarcoma cancer?

No: Chemotherapy does not make sarcoma worse. However, some kinds of sarcomas are quite resistant to many chemotherapies. Other types like ewing's sarcoma, osteosarcoma, rhabdomyosarcoma, and even synovial sarcoma can respond to chemotherapy very well and chemo is an essential part of the the cure of these diseases. There are also new drugs available that can slow the growth of more resistant types.

Chemotherapy does: Not make the cancer worse, but sarcomas are very hard to cure even with chemo and the cancer progresses despite chemo and people die.