Q: This technique is minimally invasive, requiring a finger prick's worth of blood. Do you see screening for cancer evolving to methodologies such as these and away from radiology and more complex and costly techniques?

Dr. Liotta: We view this as supplementary and complementary to other tests. The most accurate means of diagnosis will be a combination of all of these methods. You can screen patients with this kind of method and then more efficiently choose who should get a thorough radiologic work-up or physical examination. This kind of methodology combined with other marker tests or genetic screening might end up being a good combination, much like a combination of different protein testing methods might be better than one marker.

Dr. Petricoin: We don't see this as being a stand-alone endpoint. Rather, we see it as something that hopefully will give physicians something to refer to in addition to all the other tests they have at their disposal. The physician is the ultimate intelligence tool to decide what's best for the patient.

Q: Is there evidence indicating a possible function of any of the key proteins in the pattern used to diagnose ovarian cancer?

Dr. Liotta: We don't know what the proteins are. We're investigating their identity. Nevertheless, even though we don't know what they are, the pattern is still discriminatory. When we find out what these proteins are, they may or may not provide a clear understanding of why they're altered. They could be several orders removed from the pathological source.

Dr. Petricoin: PSA is a very widely used biomarker and the fact that it is a cystein protease does not add additional value to its utility as a biomarker for prostate cancer or prostate volume. So knowing what a biomarker is and how it relates to the biologic underpinnings of the disease is a separate issue altogether from how well it behaves as a specific and sensitive marker for the presence of a disease.