The experimental study shows that the new imaging system helped surgeons remove more tumor tissue in patients with ovarian cancer.
The new technique was tested in a small exploratory study led by Leiden University Medical Center (LUMC) in the Netherlands and published in the journal Clinical Cancer Research.
One of the study leaders, Dr. Alexander L. Vahrmeijer, who heads an image-guided surgery group at LUMC, says:
"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."
In their paper, he and his colleagues describe how they used a new technique called "near infrared (NIR) fluorescence imaging" to help improve visualization of tumors during surgery.
The new technique uses a tumor-specific fluorescent agent and a dedicated imaging system. The system detects the fluorescent signal in tumors in real time during surgery to remove ovarian cancer tissue - the procedure is called cytoreduction.
"This allowed resection of additional tumor lesions that were not visible to the surgeons' naked eyes," Dr. Vahrmeijer explains. "Although more research is needed, this is hopefully the first step toward improving the surgical outcome of cancer patients."
The new fluorescent agent is called OTL38 and is a combination of NIR fluorescent dye and a folate analog.
The agent binds to a protein called folate receptor-alpha (FRα), which is expressed in more than 90 percent of ovarian cancers but in much lower levels in healthy tissue.
Dr. Vahrmeijer says the main advantage of using NIR light is that it penetrates centimeters-deep into tissue. With the dedicated imaging system, this allows the surgeon to visualize tumors under the surface of the tissue.
Surgeons removed 29 percent more ovarian tumor tissue
In a randomized, double blind, placebo-controlled clinical trial, the team first tested how well the new fluorescent agent moved inside the body and how well it was tolerated in a group of 30 healthy volunteers.
- The rate at which women are diagnosed with ovarian cancer has been falling slowly over the past 20 years
- About half of the women diagnosed with the disease are aged 63 years or older
- A woman's risk of getting ovarian cancer during her lifetime is about 1 in 75.
The results of the trial helped the researchers decide the optimum dose range and time window for using the agent in patients with ovarian cancer.
The researchers then tested OTL38-guided surgery in 12 patients with ovarian cancer.
They found that the compound accumulated in FRα-positive tumors and metastases, and that the surgeons removed an additional 29 percent of malignant lesions that they could not identify with their naked eyes and/or by feeling with their hands.
The removed tissue was confirmed as malignant by pathology tests.
The researchers are now designing a larger study to calculate how well the technique identifies malignant tissue and how well it correctly rules out non-malignant tissue. They are also going to test other fluorescent agents for other tumor types that do not express FRα.
They note that only long-term follow-up studies in large patient groups will show whether the technique improves survival.
"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 reasonably plausible to assume that if more cancer is removed the survival will be better."
Dr. Alexander L. Vahrmeijer
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.
Ovarian cancer ranks fifth in cancer deaths among American women and accounts for more deaths in the U.S. than any other cancer of the female reproductive system.