For more than three years, she had suffered cramping and irregular bleeding, which her doctor thought was a side effect of her birth control implant, known as an intrauterine device, or IUD.
Her annual Pap smears were always normal, so no one suspected cancer.
Except it was cancer, and by the time the 34-year-old mother of two had the IUD removed and was finally diagnosed, her tumors had reached stage three and the disease was spreading through the lymph nodes in her abdomen and chest.
"I was told by a specialist that there wasn't any chemo that could kill it," Wallace told AFP. "And that I'd be gone in a year."
That was in February 2012. A few months later, Wallace's doctor told her about an immunotherapy trial at the National Institutes of Health Clinical Centre, a research hospital just outside the US capital.
Wallace enrolled. Doctors removed one of her tumours and collected some of the immune cells that were surrounding it. They selected specific T-cells that would attack human papillomavirus.
HPV is a common sexually transmitted disease, and most adults get it at some point in their lives. While HPV is often harmless, some strains can cause genital warts or lead to cancers of the cervix, anus, head, neck and throat.
Some 70 per cent of cervical cancers are caused by HPV types 16 and 18.
The idea behind HPV-targeted adoptive T-cell therapy is to boost the body's immune response to HPV in the tumours.
Wallace first endured a week-long regimen of strong chemotherapy to knock out her immune system. Then came the infusion, which aimed to rebuild her defences with more than 100 billion of her lab-grown T-cells that targeted the tumours.
After that, she was given two doses of aldesleukin, which helps the immune cells grow.