Gene Therapy for Prostate Cancer - A New Therapeutic Hope?

Prostate cancer remains a major killer in the westernised world. In the United States alone, around 230,000 men each year are diagnosed with the disease, accounting for over 30,000 deaths annually. Low risk (early stage) cancer can be managed with surgery and radiotherapy, resulting in good 10 year progression free survival rates. For more advanced cases, the prognosis is significantly poorer with a high chance of recurrence. In this scenario, the development of new generations of therapies including gene therapies could improve patient survival.

Previously, the same group had developed a type of virus (adenovirus) that replicates selectively within cancer cells whilst simultaneously expressing genes that make the cancer more sensitive to drugs and radiotherapy. In the present study, Dr. Kenneth Barton and colleagues describe observations made in a small cohort of patients with clinically localised high risk prostate cancer who received adenoviral gene therapy. The recruited patients (6 in total) received 12 injections directly into the prostate. The doses administered were 5 times higher than previously tested. The higher dose did not result in any serious adverse events, but did increase the severity and incidence of milder side effects. When assessed 2 days later, 100% (6/6) of the patients successfully expressed the adenoviral genes across a wide area of the prostate (18-83%). Importantly, gene expression was not observed in other organs.

Although encouraging, the authors conclude that the data reported may not be sufficient to fully sensitise the tumour to subsequent radiotherapy treatment. Continued improvements in vector development coupled with larger clinical trials will be necessary to fully delineate the utility of this treatment clinically.