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International Group Developing Point-of-Care Flow Cytometer for One-Day Diagnosis of Breast Cancer

NEW YORK ─ An international group of researchers has reported promising results for a portable flow-cytometry test that they are developing to enable breast cancer diagnosis and subtyping in one day.

The point-of-care test has the potential to address a critical unmet medical need, according to its developers ─ that of quickly ruling in or ruling out breast cancer in settings where hospital laboratories are not available.

On Wednesday, the group of diagnostic test developers ─ consisting of researchers from Boston-based Harvard Medical School, Singapore-based Nanyang Technological University, and elsewhere ─ reported findings from a prospective clinical study published in Science Translational Medicine, saying they saw 100 percent accuracy for the detection of breast cancer in a cohort involving 68 patients after they linked a fluorescent imaging-based flow cytometer with fine-needle biopsies.

"By combining flow cytometry with fine-needle biopsy, we are developing a test that could be inexpensive and also enable faster and less invasive cancer diagnosis than standard core biopsy and histopathology," said Hyungsoon Im, a study author and a researcher at Harvard Medical School and Massachusetts General Hospital. Core biopsy and histopathology procedures are frequently conducted to evaluate a patient for breast cancer after mammography reveals a suspect mass, he noted.

In studies, the platform provided test results within one hour, and if it can be commercialized, clinicians would be able to quickly consult with their patients about the findings ─ an important capability when patients don't live near a test center, Im said in an interview.

The device, a fluorescence-based imaging cytometer that the researchers have named CytoPAN, is small enough to fit on a desktop and uses inexpensive antibody kits that could, in the future, enable low-cost testing, Im said.

In use, the platform obtains cells by fine-needle aspiration that are stained on a glass substrate using lyophilized immunostaining kits containing relevant antibodies. Needle extraction typically provides up to 105 cells, and after the cells are mounted on a glass substrate, the system snaps images using a fluorescence-based laser controlled by a custom-designed computer chip.

A computer algorithm uses the image data to perform cell segmentation and analysis, and the system provides a report revealing size of the cancer cell population and molecular subtype distribution.

"The CytoPAN system holds enormous potential to expedite cancer diagnosis in resource-limited environments," Tony Jun Huang, a professor of mechanical engineering and materials science at Duke University, said in an interview. "It bypasses the need for extensive lab equipment and trained specialists through automated imaging and analysis and simple sample acquisition through [fine-needle aspiration], allowing for extremely fast test processing," said Huang, who is a developer of point-of-care diagnostic tests but not connected to the development of CytoPAN.

Overall, the system's low cost and ease of storing samples without refrigeration "makes the device an accessible and readily-available solution to address delayed cancer diagnosis in the developing world," he said.

For validation of the system, the researchers enrolled patients from Kyungpook National University Chilgok Hospital in Daegu, South Korea, who had been referred for primary surgery. The patients underwent fine-needle aspiration of breast lesions and then surgery and a standard pathological workup. Of the 68 patients enrolled, the investigators found sufficient numbers of harvested cells in 63 patients to evaluate CytoPAN.

To identify cancer cells, the investigators used a biomarker that includes the epithelial cell adhesion molecule, epidermal growth factor receptor, mucin-1, and HER2. Malignant cells were classified into subtypes based on estrogen receptor, progesterone receptor, and HER2 status.

In addition to observing 100 percent accuracy for breast cancer detection, the platform achieved 96 percent accuracy in detecting the human epidermal growth factor receptor 2 biomarker and 93 percent accuracy in detecting the hormonal receptor biomarker, both of which are important, established markers for breast cancer detection and treatment, Im noted.

As a result of its ability to do cancer subtyping, the platform may in the future be used to guide the choice of appropriate breast cancer treatment, Im said.

Potential adoption

The broadest adoption of the test, if it can be commercialized, is likely to be in low- and middle-income countries where more than two-thirds of cancer deaths occur, according to the developers. The group has taken steps to make the platform accessible where resources are scarce.

Though previous versions of the platform leveraged a smartphone for detection and analysis of test results, the researchers opted to develop an imaging device specifically for the platform, in part so that it could be more affordable than a smartphone, Im said.

When health systems apply current imaging and pathology equipment, it can take a few days and up to a week to obtain a diagnosis, he added. Without these standard technologies, breast cancers may be missed until a mass becomes visible to a patient or clinician. Because of challenges associated with available equipment, trained staff, and test demand in low- and middle-income countries, obtaining a result from breast cancer testing can take months, Im said.

The group is developing its test to require minimal training, making it usable and accessible not only in developing countries where hospitals to diagnose breast cancer are limited but also in remote settings in developed countries.

In developed countries, efficient screening and early cancer detection programs using mammography are common, and liquid biopsy tests that use genomic biomarkers for analyses are beginning to make inroads, the researchers noted. Still, the group believes that its technology could be used to speed up turnaround times between initiating intervention and obtaining results in established healthcare systems and it could be vital for people needing breast cancer diagnosis in remote settings in developed countries, Im said.

Test results from the STM study were preliminary and the group has at least a few years of work ahead of it in trying to commercialize the test, Im said.

Clinical trials

The current study had some limitations, the researchers noted. Its main goal was to develop, optimize, and validate the fine-needle biopsy-based system. However, the patient population in the study ─ "treatment-naive surgical candidates without other major comorbidities" ─ may not be representative of some patients in low-and middle-income countries," they noted in their paper.

As a result, the group has initiated broader validation studies to evaluate the test's clinical utility with the goal of enabling more rapid diagnosis of breast cancer in global and remote settings in the future, Im said.

In sub-Saharan Africa, where up to 40 percent of women diagnosed with breast cancer are HIV positive, the group has started recruiting patients for future prospective clinical trials. Supported by a National Cancer Institute grant, the group is enrolling patients to validate the test with a group of breast cancer patients in Botswana.

The goal overall is to enroll 200 patients. The group has already collected more than 100 samples and has an estimated timeline of about two years to complete the study, Im said. If the data look promising, the researchers may engage in additional studies or form a company to seek regulatory clearances, including US Food and Drug Administration clearance.

The developers estimate that the cost per test could be as low as $5, and the cost of an instrument to run the test would be around $2,000. Clinicians would use an ultrasound imaging system to help them locate unseen masses that are potentially cancerous, but Im said this shouldn't be an obstacle to test adoption because the systems are already in use worldwide by clinicians attending to pregnant women.