Once a tumor grows back, or metastasizes to another site, the therapy is considered failed.
It has nothing to do with the stock.
It's medical terminology.
U.S. National Library of Medicine. Treatment Failure
A measure of the quality of health care by assessment of unsuccessful results of management and procedures used in combating disease, in individual cases or series.
If the first therapy does not cure disease xthe treatment is considered failed and the patient goes on to the the next one.
You must be aware that Insurance companies will often not cover the the newest or most expensive drug first. The patient has to fail older, less expensive drugs or procedures first.