Is My Chemo Working? -- FLT PET Scans May Provide the Answer

I spend a lot of time thinking about the future of healthcare diagnostics and the role of pathology and lab medicine within it. One of the criticisms of the current histopatholologic examination of tumors by pathologists is that, first of all, it is an in-vitro process. The tissue sample is first fixed in formalin and then various dyes are applied to the cells, producing a set of artifacts that pathologists are trained to interpret to render a diagnosis. A second problem concerns tissue sampling. The pathology report is usually based on a small tissue sample, often from a much larger piece such as an entire organ or large tumor. Although pathologists have become very skillful over time as diagnosticians, many assumptions are made about the "biology" of a lesion and how it will behave in the future.

I have posted a number of notes about molecular imaging in the past. The expectation is that this type of in-vivo imaging will produce a more accurate picture about the behavior of a tumor, its prognosis, and how it will react to a particular type of chemotherapy. There is a school of thought that holds that the optimal form of in-vivo imaging in the future will be PET scans, which provide a means to analyze the in-vivo biology of neoplasms. A recent article discussed value of PET scans in determining the comparative effectiveness of chemotherapy (see: Is my chemo working? Scans may give faster answer). I recently delivered a lecture on this general topic (see: Using Diagnostics to Monitor the Effectiveness of Treatment). Below is an excerpt from the article with boldface emphasis mine:

Doctors typically must wait weeks or months to see if a treatment is shrinking tumors or at least halting their growth. But researchers are exploring a new use for medical imaging that could shorten the stay in purgatory, possibly revealing within a few days whether chemo is working....This experimental imaging relies on a familiar hospital workhorse: PET scans, typically used for things like detecting cancer or revealing the effects of a heart attack. Unlike CT scans or MRIs, PET scans can show a tumor's internal activity, not just its size.When used to assess the effects of cancer treatment, it can reveal inside information about what the therapy is doing to a tumor even when there's no outward sign....This scan is called FLT PET, after radioactive fluorothymidine. These scans show whether cancer cells are dividing. Uncontrolled division is a hallmark of active cancer, and stopping that division should be an early effect of successful chemotherapy....One report [on the value of this type of imaging] involved 28 patients in Korea who were treated for advanced lung cancer....The researchers reported that just one week after treatment began, they could tell with 93 percent certainty which patients would eventually respond to the drug and which would not.

There appears to be a substantial literature about the use of FLT (fluorothymidine) PET scans for both diagnostic and therapeutic assessments. Examples cited in these articles include the noninvasive assessment of proliferation in lesions like pulmonary nodules and monitoring tumor response to antiproliferative therapy. The take-home lesson is that in perhaps five years, we may look back at some of our current diagnostic tests with a sense of disbelief. At the very least, I think that we are on the verge of a new era for in-vivo diagnostics. This is one of the reasons why I have been a strong advocate for integrated diagnostics, by which I mean the merger of pathology, lab medicine, and radiology into the new field of Diagnostic Medicine. I believe that the specialists working in their various diagnostic silos will have much to learn from each other when they engage in closer collaboration.