Polio as a Treatment for Cancer?
Glioblastoma tumors
are the most common form of malignant brain tumor and affect
approximately two to three adults per 100,000 each year. Due to the
aggressive nature of glioblastoma, existing treatments are relatively
ineffective and the prognosis for affected patients is quite poor.
According to the National Brain Tumor Society, the five-year survival
rate for those afflicted with glioblastoma is a mere 5.6%. In fact, the
majority of glioblastoma patients only survive 12 to 15 months
post-diagnosis. With the recent passing of U.S. Senator John McCain, as
well as former Vice President Joe Biden’s
son, Beau, who both succumbed to this
dreaded brain cancer, the search for an effective treatment has been
brought back into the limelight.
Recently,
researchers at the Duke Cancer Institute have seen promising
experimental results using a genetically modified poliovirus (called
PVS-RIPO) in patients diagnosed with a glioblastoma brain tumor. The
poliovirus is administered directly into the cancerous mass by inserting
a catheter through the skull and into the tumor.
The
virus subsequently infects only the cancerous cells, which ultimately
induces the patient’s immune response, engendering the use of the body’s
natural defenses against its own mutated cells. The genetically
modified virus affects only tumor cells while leaving normal cells
unharmed. With this novel treatment, 21% of the 61 patients enrolled in
the initial trial were still alive three years post-treatment. This
represents a 7% increase in the survival rate after 18 months and a 17%
increase in the survival rate after three years when compared to
patients who did not receive the poliovirus therapy but were treated
with standard chemotherapy instead (the control).
Based on these results,
the poliovirus therapy has now been designated as a “breakthrough
therapy” by the FDA. This means that the development of the treatment
and its review process will be expedited by the FDA and a response will
be provided within 60 days of receipt of the new drug submission.
Unfortunately, this treatment does not come without potential
complications; at higher doses of PVS-RIPO, the treatment has been shown
to cause brain inflammation, leading to seizures. Additionally, some
patients have been observed to exhibit no response to the poliovirus
therapy, though the reasons why are unknown. At this time, there is no
way to identify whether or not a patient will respond to the treatment.
While the results of this
Phase I Clinical Trial are promising, many other cancer trials have also
shown similar long-term survival statistics. Therefore, it is difficult
to determine whether these long-term survivors are truly benefiting
from the therapy. Phase II of this study is currently underway, which
will compare the effectivity of a poliovirus/chemotherapy combination
therapy with poliovirus therapy alone.
Scientists are
currently working with other viruses in addition to polio; such as
herpes, vaccinia, and respiratory viruses to battle cancer. With continued efforts towards an efficacious cure, glioblastoma patients may have hope of an improved treatment in the future.
Meet the author
TECHNICAL SERVICES SPECIALIST II at HARDY DIAGNOSTICS
Sara Decker, B.S. Microbiology
Sara graduated with a B.S. in Microbiology from CSU Chico in late 2016 and joined the Hardy Diagnostics team shortly after in May 2017. Her Hardy tenure began in the Technical Services Department, which was her home for two and a half years before moving to a sales position while living in the Kansas City Metro area. After relocating back to the western United States, she rejoined the Technical Services Team in May 2023. Sara and her husband, Ben, enjoy spoiling their four cats and spend the majority of their free time outdoors (especially camping)!
