Bacterial biosurgery promising for reducing size of inoperable tumors

Deep within most tumors lie areas that remain untouched by chemotherapy and radiation. These troublesome spots lack the blood and oxygen needed for traditional therapies to work, but provide the perfect target for a new cancer treatment using bacteria that thrive in oxygen-poor conditions. Recently, researchers demonstrated that injections of a weakened version of one such anaerobic bacteria, the microbe Clostridium novyi, shrunk tumors in rats, pet dogs, and a human patient.

The findings from BioMed Valley Discoveries in Kansas City, Missouri, and a nationwide team of collaborators demonstrate that C novyi-NT, a version without the ability to make certain toxins, can act as a new type of biosurgery that eats away tumors in hard-to-reach places. The bacteria excise tumor tissue in a precise, localized way that spares surrounding normal tissue.

The study, which represents a new take on an approach first attempted a century ago, indicates that further testing of this agent in selected patients is warranted. The study was published in Science Translational Medicine (2014; doi:10.1126/scitranslmed.3008982).

"We have encouraging signs that this bacteria could be used to treat certain inoperable tumors, and that could give hope to some patients who don't have any other options," said senior author Saurabh Saha, MD, PhD, a longtime cancer researcher at BioMed Valley Discoveries. "But we are still in the early stages, and need to further assess the safety and efficacy of the treatment, as well as explore how well it works in combination with other cancer therapies."

The idea of using bacteria to combat cancer dates back to the 1890s; cancer researcher William Coley noticed that some patients who developed postsurgical infections went into remission or were even cured of their disease. Despite the approach's initial promise, progress was slow for the next century.

The researchers tested C novyi-NT via directly injecting the bacteria into tumors in pet dogs with naturally occurring cancers and whose owners volunteered them for the trial. Each dog underwent 1 to 4 cycles of the new treatment, consisting of a single injection of 100 million spores directly into the target tumor. Of 16 dogs evaluated after treatment, three had significant shrinkage of their tumors and three had tumors that were completely destroyed.

The next step was to attempt the treatment in humans. The first patient to enroll in this Phase I investigational study was a 53-year-old woman with retroperitoneal leiomyosarcoma whose disease, despite eight rounds of chemotherapy and radiation, had spread to her liver, lungs, abdomen, upper arm, and shoulder.

The researchers injected 10,000 spores into the patient's metastatic right shoulder tumor. Within days, CT scans and biopsies demonstrated that the bacteria had infiltrated the tumor and had begun destroying tumor cells. Weeks later, a follow-up MRI showed that a significant amount of tumor had been destroyed. As a result of the treatment, the patient's shoulder pain subsided and she was able to move her arm again.

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