The immune system of one patient has been tweaked to completely eliminate breast cancer cells, offering a possible treatment for late-stage cancers for which all conventional therapies have failed, reports a paper published online this week in Nature Medicine. This is the first successful application of T cell immunotherapy for late-stage breast cancer.

The most successful clinical immunotherapeutic approaches to treat cancer are immune checkpoint blockade and adoptive T cell therapy. In the former, T cells are activated inside the patient’s body via injected antibodies. In the latter, T cells are taken from a patient’s blood or tumour, and only those that recognize the tumour are cultivated and subsequently returned into the patient. The success of these approaches varies greatly between cancer types. To date, clinical trials using immune checkpoint blockade to treat breast cancer have proved ineffective.

Steven Rosenberg and colleagues isolated and reactivated cancer-specific T cells from a single patient whose metastatic breast cancer was progressing despite several lines of therapy. These reactivated T cells eliminated all metastatic lesions in the patient, leaving her free of disease for two years now. The authors characterize the molecular features of these targeted cancer cells in detail, which enables them to estimate high odds for success of this approach in other patients with breast cancer - although this will need to be confirmed in larger, controlled clinical trials.