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Cancer in a new light

An experimental laser probe could provide an instant diagnosis, preventing unnecessary biopsies and delays in diagnosis and treatment.

October 13, 2003|Linda Marsa | Special to The Times

Stealing a page from "Star Trek" and other science fiction scenarios, scientists have invented a device that can detect cancers by merely beaming a light on the suspicious area.

The experimental laser probe eventually could be used to identify most malignancies before they gain a foothold in the body.

Preliminary studies show that the diagnostic tool is as accurate as current, more complicated tests in spotting precancerous cells in the linings of the body, where 85% to 90% of cancers originate. "Most cancers start on the surface of an organ, rather than inside," says Dr. Dale H. Rice, a head and neck cancer expert at USC's Keck School of Medicine. "This device could help us catch cancers at their earlier, more treatable, stages."

Cells on the verge of turning malignant, a condition called dysplasia, can't be detected by the naked eye even when viewed through an endoscope, a tiny instrument used to look inside the body. By the time patients have symptoms, the cancer may be advanced, Rice says.

Doctors usually diagnose cancer by performing a biopsy, a surgical procedure in which cells are collected from the suspicious region, shipped to a lab and analyzed under a microscope by a pathologist, a process that can take up to a week. "The current testing process is time-consuming, expensive and subject to human error," says Michael S. Feld, a physicist at the Massachusetts Institute of Technology in Cambridge who led the research team that devised the tool. The device could provide an instant diagnosis, preventing unnecessary biopsies and delays in diagnosis and treatment. It ultimately could prove more reliable than today's tests.

The portable probe is composed of a thin cable of optical fibers that beam pulsing laser and ordinary white light on tissue about 1 millimeter in diameter. The way the light changes color when it is reflected back by the cells gives a picture of the cells' structure, similar to the way ultrasound tests bounce sound waves off objects to determine their shape and density. The information is relayed to a computer, which uses this data to determine if the cells' nuclei are misshapen -- a telltale sign they are cancerous.

In initial experiments on more than 100 patients, five areas of the body were scanned, including the gastrointestinal tract, cervix, oral cavity and bladder. To look at the GI tract and the bladder, the probe was threaded through an endoscope, which was inserted through the mouth and the rectum. To determine whether the device was accurate, cells from these regions were removed and analyzed by pathologists. "The probe's findings corresponded very well with the consensus of multiple pathologists," says Dr. Maryann Fitzmaurice, a pathologist at Case Western Reserve University in Cleveland who helped develop the tool.

MIT scientists have taken this technology one step further with the development of an electronic camera that provides high-resolution images of tissues up to a few centimeters in diameter -- a much larger area than is highlighted by the probe. "You have to get a wide look before you can zero in on a small area to study," Feld says. The two devices when used together, he says, "give us a much more in-depth diagnosis."

In collaboration with researchers at five other institutions in Boston and Chicago, MIT scientists are starting human tests in the uterine cervix and the oral cavity, using the diagnostic probe in tandem with the experimental camera, which also creates a topography map of normal, precancerous and cancerous tissue the way a contour map highlights elevations. "This technology is really quite revolutionary because it's faster, less invasive and eliminates the possibility of human error," Fitzmaurice says.

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Detection sometimes comes far too late

Scientists hope that the development of more sensitive diagnostic tools will reduce cancer mortality rates.

Many of the cancers that kill Americans aren't apparent until the cancer is advanced. Lung and colorectal cancers, for example, often aren't diagnosed until their later stages, and together they'll claim the lives of more than 214,000 Americans this year.

Chest X-rays or colonoscopies can detect tumors, but they can also miss lesions. Such techniques have other problems as well: Colonoscopies occasionally cause bleeding and puncture the lining of the colon, while X-rays expose patients to radiation.

Screening for cervical, skin and oral cancers relies on visual detection of suspicious areas followed by biopsies. But both methods are subject to human error.

There are no reliable screening tests for many other cancers that start on the surface tissue, such as esophageal or bladder cancer.

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