Japan researchers discover new method to detect early breast cancer smaller than 0.5 mm

TOKYO -- A team of researchers at Osaka University announced that they have succeeded in showing high-precision images of miniscule tissues with early-stage breast cancer less than 0.5 millimeters in size, by using terahertz waves.

As the method does not require the staining of cells, it becomes possible during surgery to accurately identify areas where cancer has spread, which helps to reduce the burden on patients. The research findings were published on Oct. 22 in the Journal of Physics: Photonics, an open access British journal specializing in physics.

Terahertz radiation involves electromagnetic waves in the frequency range from 0.1 to 10 terahertz that are positioned between that of light and radio waves. The usage of terahertz waves has gathered expectations as a new means of diagnosis as terahertz radiation is equipped with both the quality of light that travels in straight lines, and the permeability of radio waves. However, controlling terahertz waves is difficult, and only cancer as large as several millimeters to several centimeters could be observed in the past.

The team focused on the phenomenon where terahertz waves were generated when light from lasers hit nonlinear optical crystals -- a special kind of crystal made of gallium arsenide, a semiconductor material. A breast cancer sample was placed on top of the crystal, and laser light was emitted from underneath the crystal to generate terahertz waves. When the team converted the radiation that passed through the sample into images, breast cancer tissues smaller than 0.5 millimeters were recorded. As the spread of terahertz radiation can be curbed compared to previous processes, the new method enables examinations with a high level of precision.

According to the research team, generally for cancer treatment, cells are chemically stained to check whether parts covered in surgical excision were appropriate. However, it is difficult to make such confirmations during surgery, as it requires time and labor. As a result, doctors have no choice but to cut off extra portions near the body parts where the cancer spread to ensure that it does not remain.

As staining is unnecessary for this newfound technique, doctors are able to identify cancer tissues onsite during surgeries. The burden on patients is reduced by minimizing the range of excision, and it is also hoped that the new method will help prevent the spread of cancer to other parts of the body at an early stage. The technique can also be applied to other types of cancer besides breast cancer.

Furthermore, breast cancer consists of non-evasive cancer, which means cancer cells have been contained within milk ducts and the breast lobules, and invasive cancer where they have spread outside milk ducts. Although it is difficult to distinguish between the two types, the team also succeeded in their discernment.

Masayoshi Tonouchi, an electrical engineering professor at Osaka University's Institute of Laser Engineering, said, "Although expanding the range covered in examinations and enhancing its detection sensitivity are necessary for practical use, we want to aim to develop a small device for detecting cancer that can be used during surgery in the future."

(Japanese original by Koki Matsumoto, Science & Environment News Department)