A state-of-the art imaging process that uses light to generate sound waves in tissue could help to guide surgeons ensure that no fragments are left behind while removing breast tumors.
Surgeons removing breast tumors must excise enough tissue to ensure all the cancer is gone, while retaining as much healthy tissue around the edges, or margins, of the tumor as possible. A new method, developed by an A*STAR-led team, is able to better distinguish cancerous- from non-cancerous breast tissue in real-time. This enables the method to be used during an operation.
“You really want to conserve the breast, especially for a lot of our younger patients,” says Malini Olivo, principal investigator with the A*STAR Singapore Bioimaging Consortium. “You want to remove as much of the tumor as possible but you need to be very precise in the amount of healthy tissue you have to remove.”
The current approach is to remove the tumor, then send it to a pathologist for analysis using conventional ultrasound and light microscopy — a process which can take a week or two. If it is found that the surgery didn’t remove the entire tumor, the patient must undergo the procedure again to remove any remaining malignant tissue. The probability of this outcome in breast cancer is as high as 40 per cent, Olivo says.
“It’s very traumatic to have to go through the first procedure, and then to have to go back and do the second,” she observes. The trauma is exacerbated by the knowledge that there’s a chance the tumor could progress during the required healing period between the first and second surgery.
Multispectral optoacoustic tomography, or MSOT, uses different light wavelengths to excite the molecules in the tissue sample, such as, fats, water molecules or other compounds. When excited with light, these compounds give off distinctive soundwaves that can penetrate deeper into the tissue and be picked up by an ultrasound detector. This enables researchers to build a 3D picture of the tissue around the edge of the excised tumor. The approach is far more sophisticated than conventional ultrasound, Olivo says.
“Ultrasound cannot tell you the difference between lipids in the tissue and water in the tissue, it cannot tell you the difference between oxygenated and deoxygenated blood, it cannot tell you where the blood vessels are,” she says. “Ultrasound is not a functional-based imaging technique, whereas MSOT, like MRI, is.”
The technique has applications in any scenario where tumors need to be surgically removed. It has already been tested in patients with non-melanoma skin cancer, but in a new study, the research group used the imaging method to examine the margins of a breast tumor that had been surgically removed.
While conventional ultrasound showed the tumor within the surgically-removed specimen, the MSOT went beyond that, showing the biochemical makeup of the specimen, including the fats and hemoglobin. This revealed that there was a good margin of normal breast tissue around the removed tumor, a conclusion that was also supported by examination under a microscope by a pathologist.
A larger study in 90 patients has recently been completed. If MSOT can be shown in enough patients to be better than x-ray, ultrasound and examination by a pathologist, the new imaging approach could soon be incorporated into breast cancer surgery.
“The goal would be — if we image as many patients as possible, and we use artificial intelligence to assess those images — that eventually we will have the confidence that we don’t need histopathology during the operation,” Olivo says.
The A*STAR-affiliated researchers contributing to this research are from the Singapore BioImaging Consortium.