WASHINGTON (Reuters) - The use of positron emission tomography, known as PET scans, can improve the diagnosis of people with lung cancer and better guide treatment decisions, Canadian researchers said on Tuesday.

Doctors often use imaging techniques like magnetic resonance imaging, MRI, or computed tomography imaging, called CT scans, along with other methods to see if a patient has lung cancer.

But researchers led by Dr. Yee Ung of the Odette Cancer Centre at Sunnybrook Health Sciences Centre in Toronto analyzed the results of several recent studies to see if PET scans might do the job better.

PET scans detect biochemical processes in the body that may indicate disease before the appearance of anatomical changes that other methods like MRIs and CT scans may detect.

PET scans can also accurately differentiate between malignant and benign tumors in the lung as small as four-tenths of an inch (1 cm), according to the study published in the Journal of the National Cancer Institute.

These scans can correctly distinguish between extensive and limited disease in people with small cell lung cancer, a fast-growing type that spreads more quickly than the more commonplace non-small cell lung cancer, the researchers said.

PET scans seem to be superior to CT scans for guiding treatment decisions in non-small cell lung cancer, they said.

The findings seem to support the idea of broader use of PET scans in lung cancer diagnosis and treatment, although more research is needed, Ung said in a telephone interview.

"Things that we cannot see with CT scans we are now able to pick up on the PET scans and, therefore, we're able to offer better and more appropriate treatment," Ung said.

"We still need to do very good clinical trials to see where PET scans fit into the overall treatment strategy," Ung added.

One key to treatment of lung cancer is how accurate doctors are in "staging" patients — finding out how much cancer there is in the body and where it is located, to figure how advanced it is — to give the most appropriate treatment, Ung said.

"So if you have somebody who truly has lung cancer confined to the chest, without being spread outside the chest, you would treat that very aggressively with a combination of surgery and/or chemotherapy and radiation, if indicated," Ung said.

"If the lung cancer is too far advanced where it's already spread outside of the chest area, then we cannot cure it, and then we don't want to put people through unnecessary treatment like putting them through surgery or putting them through high-dose radiation," Ung added.

PET scan equipment is less widely available than CT scan and MRI equipment, but generally is in use in larger medical institutions, according to Frederic Fahey, director of nuclear medicine physics and PET at Children's Hospital Boston.