What happened, in summary

Halassy was a 50-year-old woman with recurrent triple-negative breast cancer. Her breast cancer was first diagnosed in 2016 and was treated with mastectomy followed by chemotherapy. A small local recurrence was later removed surgically, but a small fluid-filled area remained under observation. By 2020, that area had developed into a solid recurrent tumor that had grown into the pectoral muscle.

Halassy, a professional virologist, chose an unconventional self-experiment after discussing the plan with her oncologist. She injected experimental oncolytic virus preparations directly into the tumor, first using a measles vaccine strain and then vesicular stomatitis virus. Her oncologist monitored her during treatment and was prepared to intervene if the tumor progressed or serious problems developed. She did not experience serious treatment-related side effects.

After about 2 months of the experimental virus treatment, the tumor had shrunk substantially and was no longer invading the nearby muscle or skin. It was then surgically removed, and she later completed additional adjuvant treatment. After surgery for the recurrent tumor, Halassy remained in remission for 45 months.