An early phase clinical trail evaluating gene therapy for treatment in non-small cell lung cancer failed to provide improved outcomes for patients over chemotherapy alone, according to a recent article published in the
Journal of Clinical Oncology. However, gene therapy is still in initial phases of development and warrants further investigation involving different strategies of implementation. The novel field of gene therapy encompasses many different methods of therapy, only one of which was evaluated in this particular trial.
Approximately 75% of individuals who have lung cancer have a type of cancer referred to as non-small cell lung cancer (NSCLC). Standard treatment options for NSCLC depend on the stage of cancer and may consist of surgery, chemotherapy, radiation and/or biologic therapy (treatment utilizing the immune system to fight cancer). Advanced NSCLC refers to cancer that has spread from its site of origin to distant areas in the body, often including vital organs. Currently, surgery is the only curative option for patients with advanced NSCLC. Unfortunately, some patients are unable to undergo the surgical removal of their cancer; these patients have a survival rate of less than 20% at 2 years following standard treatment. Thus, researchers continue to explore novel therapies for patients with this disease in order to improve upon the poor prognosis offered by standard therapies.
Previous clinical trials have demonstrated that treatment with gene therapy yields promising results in some cancers. Gene therapy involves transferring new genetic material into a cell for therapeutic benefit. This can be accomplished by replacing or inactivating a dysfunctional gene, replacing or adding a functional gene or inserting a gene into a cell to make it function normally. Approximately 50% of NSCLC patients have a mutation (alteration) in a gene called p53. The p53 gene is responsible for keeping normal cell replication under strict control. If there is a mutation in a cell’s DNA, the action of the p53 gene is to stop further replication of the damaged cell, inhibiting further progression of the mutation. In cells that have a mutation within their p53 gene, there is no restraint on replication, which leads to uncontrolled, rapid growth of the cell.
Recently, researchers conducted a clinical trial using gene therapy for patients with advanced NSCLC who could not undergo surgery and whose cancer had a mutated p53 gene. The goal of gene therapy was to insert a copy of a normal p53 gene into the cancer cell’s DNA, in the hopes that the normal p53 would override the effects of the mutated p53, and halt cancer growth. In order to facilitate the insertion of a normal p53 gene into a cancer cell’s DNA, researchers used a laboratory method in which a normal p53 gene was placed inside the DNA of an adenovirus (virus that causes the common cold). The adenovirus had been manipulated so that it could not replicate. This modified adenovirus was then injected directly into the cancer, where it could insert itself into the DNA of the cancer cell, thus enabling the normal p53 gene to also insert itself into the cancer cell’s DNA.
All patients in this study received a combination of chemotherapy agents plus injections of the modified virus. Since researchers wanted to be able to directly determine the effects of gene therapy on the regression of cancer in each individual patient, only some of the cancer in each patient’s body was injected with the modified adenovirus. This way, the researchers could measure the regression of the tumors that had been treated with gene therapy and compare the results with the tumors that had not been treated with gene therapy for each patient. Overall, there was no difference in the regression of tumors treated with gene therapy plus chemotherapy compared with chemotherapy alone. Overall survival for these patients was 10.5 months, with 44% surviving one year following therapy.
These results were disappointing, as researchers and patients hoped to discover an effective therapy for patients with advanced NSCLC. The researchers conducting this study speculate that perhaps an adenovirus without modifications to halt its own replication might produce more encouraging results, as this may allow the virus (and normal p53 gene) to reach more cancer cells. In addition, results from this clinical trial may be improved further through the utilization of different genetic therapy strategies.
Patients with advanced NSCLC may wish to speak with their physician about participating in a clinical trial evaluating novel gene therapy concepts or other promising new strategies. Two sources of ongoing clinical trials include comprehensive, easy-to-use listing services provided by the National Cancer Institute ( cancer.gov) and www.eCancerTrials.com. eCancerTrials.com also provides personalized clinical trial searches on behalf of patients. ( Journal of Clinical Oncology, Vol 19, No 6, pp1750-1758, 2001)
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