In an extraordinary case of medical self-experimentation, Croatian virologist Dr. Beata Halassy successfully treated her recurring breast cancer by injecting viruses directly into her tumor. The 50-year-old scientist, facing her third bout with the disease, took an unconventional path that resulted in complete tumor removal and has kept her cancer-free for nearly four years.
According to sources, Halassy’s journey began in 2016 with a diagnosis of triple-negative breast cancer, one of the most challenging subtypes to treat. After a mastectomy and chemotherapy, she experienced a recurrence in 2018, which was surgically removed. However, in 2020, what doctors had monitored as a small seroma at the surgical site had transformed into a 2-centimeter solid tumor that had invaded both the chest muscle below and the skin above.
Rather than immediately proceeding with conventional treatment, Halassy leveraged her expertise in virology to design her own therapy. Working in her laboratory at the University of Zagreb, she prepared two different viruses known for their safety profiles and ability to infect epithelial cells: the Edmonston-Zagreb measles vaccine strain and the vesicular stomatitis virus. These preparations were not clinical-grade products but research materials she produced herself.
The treatment protocol was intensive and strategic. Over two months, Halassy administered seven measles virus injections at three to four-day intervals, followed by three applications of vesicular stomatitis virus. The sequential approach was deliberate, designed to overcome a key challenge in oncolytic virotherapy where the body’s immune response to the first virus might reduce effectiveness. By switching to a different virus midway through treatment, she maintained continuous pressure on the tumor.
The results were remarkable. The tumor shrank from 2.47 cubic centimeters to 0.91 cubic centimeters. What began as a hard, inflamed nodule fixed to underlying tissue transformed into a smaller, softer, mobile mass without skin inflammation. Ultrasound imaging showed the tumor becoming less defined and significantly flattened. Most importantly, the tumor no longer invaded the chest muscle or skin, making surgical removal straightforward.
Throughout the treatment, Halassy’s oncologists monitored her progress, ready to intervene with conventional therapy if complications arose or the tumor progressed. The therapy was well tolerated, with only minor side effects. The most significant reaction was fever and chills twelve hours after the first vesicular stomatitis virus injection, which resolved within three days.
Analysis of the removed tumor revealed profound changes at the cellular level. Lymphocyte infiltration increased from 10 percent to 45 percent of the tumor mass, with some areas showing dense immune cells and fibrous tissue but no cancer cells. This pattern resembles what oncologists observe after successful chemotherapy. Specifically, CD20-positive B cells increased from 10 percent to 70 percent, and CD8-positive T cells rose from 30 percent to 60 percent, indicating strong activation of the adaptive immune system.
The tumor also changed its molecular profile during treatment. Initially testing negative for PD-L1, a protein that helps tumors evade immune detection, the post-treatment tumor showed PD-L1 expression. Additionally, the cancer had evolved from triple-negative to HER2-positive, allowing Halassy to receive targeted trastuzumab therapy for one year following surgery.
The case demonstrates several innovative elements. The intensive dosing schedule maintained high virus concentrations within the tumor, maximizing direct cancer cell destruction. The sequential use of two different viruses potentially overcame the limitation of developing antiviral immunity. The virus preparations, while not purified to pharmaceutical standards, contained complex biological components that may have contributed to the favorable outcome.
Oncolytic virotherapy works through two mechanisms: directly infecting and destroying cancer cells, and triggering an immune response against the tumor. The substantial increase in both T cells and B cells suggests the treatment activated multiple arms of the immune system. The presence of tumor-infiltrating B cells, which have only recently been recognized as important in cancer immunity, may have helped sustain the anti-tumor response.
Halassy has now been cancer-free for 45 months following the treatment, a significant milestone considering her previous recurrences occurred at 22-month and 21-month intervals. While this represents just one case and self-experimentation raises ethical questions, the outcome provides compelling evidence for exploring oncolytic virotherapy as a neoadjuvant treatment to shrink tumors before surgery.
The researchers emphasize that self-medicating with viruses should not become standard practice. However, they advocate for formal clinical trials evaluating oncolytic virotherapy in early-stage cancers, where patients have stronger immune systems compared to those with advanced disease who have undergone multiple rounds of chemotherapy and radiation. Several such trials are now underway for breast cancer, testing approved oncolytic viruses in combination with other treatments.
