A woman’s risk of getting ovarian cancer during her lifetime is about 1 in 75, it ranks fifth in deaths among American women, and it accounts for more deaths in the U.S. than any other cancer of the female reproductive system. The American Cancer Society estimates that in the United States in 2016, about 22,280 women will receive a new diagnosis of ovarian cancer and about 14,240 women will die from the disease. However, there is hope, and the rate at which women are diagnosed with ovarian cancer has been steadily slowing down over the past twenty years.
A new imaging technique that was tested in a small exploratory study led by Meiden University Medical Center in the Netherlands and published in the journal Clinical Cancer Research may help surgeons to find and remove nearly 30 percent more ovarian tumor tissue than normal. This tissue is critical in determining ovarian cancer patient survival, as leftover tissue from surgery is currently only removed by surgeons using just their eyes and hands.
Dr. Alexander L. Vahrmeijer, one of the study leaders, said that “Surgery is the most important treatment for ovarian cancer, and surgeons mainly have to rely on their naked eyes to identify tumor tissue, which is not optimal.”
The new technique that was used in the study uses a new type of fluorescent compound, and is called “near infrared (NIR) fluorescence imaging.” It uses a tumor-specific fluorescent agent and a dedicated imaging system in order to improve visualization of tumors during surgery. The way it works is that it detects the fluorescent signal in the tumor during surgery, thus making it easier to remove ovarian cancer tissue. The procedure is called cytoreduction.
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| Survival effect of maximal cytoreductive surgery. |
Dr. Vahrmeijer explained “This allowed resection of additional tumor lesions that were not visible to the surgeons’ naked eyes,” and that, “Although more research is needed, this is hopefully the first step toward improving the surgical outcome of cancer patients.”
The fluorescent agent used is called OTL38, which is a combination of NIR fluorescent dye and a folate analog; it works by binding to a protein called folate receptor-alpha (FRa), which is expressed in more than 90 percent of ovarian cancers but in much lower levels in healthy tissue. The NIR light penetrates centimeters deep into tissue, and with the dedicated imaging system, this allows the surgeon to visualize tumors under the surface of the tissue.
During the study, the fluorescent agent was tested on a group of 30 healthy volunteers in a randomized, double-blind, placebo-controlled clinical trial. These results helped researchers figure out the optimal dose range and time window for using the agent in patients with ovarian cancer.
12 patients with ovarian cancer were then tested with OTL38 guided surgery. The compound was found to accumulate in FRa-positive tumors and metastases, and the surgeons successfully removed an additional 29 percent of malignant lesions that were not previously identifiable by naked eyes or hands. Pathology tests then confirmed that the removed tissue was indeed malignant.
A larger study is now being designed by the researchers, in order to calculate how well the technique identifies malignant tissue and how well it correctly rules out non-malignant tissue. Other fluorescent agents for other tumor types that do not express FRa will also be tested.
It is noted that only long term follow-up studies in large patient groups will show whether the technique improves survival, as stated by Dr. Vahrmeijer, “A limitation of this study is that we cannot say yet what the impact of our findings is on cure or survival of the patients. It is reasonable plausible to assume that if more cancer is removed the survival will be better.”
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