Man's best friend can be a great source of company, but dogs might offer much more than that.

A study published in the March issue of the journal Integrative Cancer Therapies suggests that dogs' extraordinary sense of smell can detect people with both early and late-stage lung and breast cancers.

The dogs in the study detected breast and lung cancer 88 percent of the time, with few false-positives.

The research, led by Michael McCulloch of the Pine Street Foundation in San Anselmo, Calif., and Tadeusz Jezierski of the Polish Academy of Sciences, is the first to test whether dogs can detect cancers only by sniffing the exhaled breath of cancer patients.

The study included 86 cancer patients -- 55 with lung cancer and 31 with breast cancer -- and 83 healthy patients. Five household dogs -- three Labrador retrievers and two Portuguese water dogs -- received three weeks of training to detect cancer by scent. They were then presented with breath samples from the cancer patients and the controls, captured in a special tube.

The dogs were trained to identify cancer patients by sitting or lying down directly in front of the test station containing a cancer patient sample, while ignoring samples from healthy volunteers.

The researchers said the results of the study show promise in using dogs to help with cancer diagnoses, especially in the earliest stages. But they said more study is needed.

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