Carol Emanuele beat cancer. But for the past two years, the Philadelphia woman has been fighting her toughest battle yet. She has an open wound on the bottom of her foot that leaves her unable to walk and prone to deadly infection.

To treat her diabetic wound, doctors at a Philadelphia clinic have prescribed a number of treatments, like freeze-dried placenta, penis foreskin cells and high doses of pressurized oxygen.

"I do everything, but nothing seems to work," said Emanuele, 59, who survived stage 4 melanoma in her 30s. "I beat cancer, but this is worse."

The doctors who care for the 6.5 million patients with chronic wounds know the depths of their struggles. Their festering wounds don't heal for months and sometimes years, leaving bare bones and tendons.

Many patients end up immobilized, unable to work and dependent on Medicare and Medicaid. In their quest to heal, they turn to expensive and sometimes painful procedures, and products that often don't work.

According to some estimates, Medicare alone spends at least $25 billion a year treating these wounds. The wound-care product business, worth an estimated $5 billion a year, booms but many widely used treatments aren't supported by credible research. The vast majority of the studies are funded or conducted by companies that manufacture the products.

A 2016 review of treatment for diabetic foot ulcers found "few published studies were of high quality, and the majority were susceptible to bias." The review team included William Jeffcoate, a professor with the Department of Diabetes and Endocrinology at Nottingham University Hospitals Trust. Jeffcoate has overseen several reviews of such treatment since 2006 and concluded that "the evidence to support many of the therapies that are in routine use is poor."

While scientists struggle to come up with treatments that are more effective, patients with chronic wounds are dying.

The five-year mortality rate for patients with some types of diabetic wounds is more than 50 percent higher than that of breast and colon cancers, said an analysis led by David Armstrong, a professor of surgery and director of the Southern Arizona Limb Salvage Alliance.

Although doctors and researchers have been calling on the federal government to step in for at least a decade, the National Institutes of Health and the Veterans Affairs and Defense departments haven't responded with any significant research.

"The bottom line is that there is no pink ribbon to raise awareness for festering, foul-smelling wounds that don't heal," said Caroline Fife, a wound-care doctor in Texas. "No movie star wants to be the poster child for this."