Research published today in Nature Medicine by scientists at the National Cancer Institute (NCI) has described a new immunotherapy approach, which led to a complete disappearance of tumors in a woman with advanced metastatic breast cancer who only had months to live.

The findings show how naturally-occurring tumor infiltrating lymphocytes (TILs) were extracted from the patient’s tumor, grown outside of her body to boost their numbers and injected back into the patient to tackle the cancer. The patient had previously received several treatments including hormone therapies and chemotherapy, but nothing had stopped the cancer progressing. After the treatment, all of the patient’s tumors disappeared and 22 months later, she is still in remission.

Researchers are particularly enthusiastic about the potential of TILs to treat a group of cancers termed ‘common epithelial cancers’, which include those of the colon, rectum, pancreas, breast and lung, together accounting for 90% of all deaths due to cancer in the U.S, around 540,000 people annually, most of these from metastatic disease.

“Once these cancers spread, most people die. We have no effective ways of eliminating metastatic cancers,” said Steven A. Rosenberg, M.D., Ph.D., chief of the Surgery Branch at NCI’s Center for Cancer Research (CCR).

The first step of this new treatment approach is to DNA sequence the tumor.  In the case of this patient, the researchers found 62 mutations in the breast tumor cells. The second is to isolate TILs, which are present naturally in 80% of epithelial cell tumors, but in tiny amounts, not substantial enough to attack the tumor. These are then analyzed for their ability to recognize and target the mutated proteins on the tumor.  In the case of the metastatic breast cancer patient, the researchers found TILs that recognized four of the mutant proteins.