Circulating Tumor Cells

Who's going to do well in chemotherapy?

It seems like that's the million dollar question in cancer research these days, as diseases are becoming better understood and treatments are getting more effective.  Certain genetic variations and disease staging can be indicative of how well someone will respond to chemotherapy, but peripheral tumor cells in the blood indicate an all around poor prognosis.

A study presented at the San Antonio Breast Cancer Symposium in Texas last week is the largest of it's type to look at prognoses based on circulating tumor cells (CTCs), according to a National Institute of Health update this week.  The presence of CTCs, which have broken off from the main tumor, suggest that the patient may not do well in the long run.  The French study involved 267 people whose cancer had metastasised and were receiving chemotherapy for the first time.  After following them for 16 months, researchers determined that the more CTCs someone had, the worse they did.  Even a single CTC indicates a poor prognosis.

A German study observed 3,754 patients with high-risk but early stage breast cancer who had surgery followed by chemotherapy, then additional "acid therapy" treatments.  Those who tested positive for CTCs after surgery had an 88.1% three-year survival rate, compared to 93.7% for those who tested negative.  Of the 2,026 patients with completed CTC analyses and monitored for a median of 35 months, 114 have suffered recurrent disease and 66 have died.

Dr Andrew J Armstrong at Duke University and the Duke Cancer Institute in Durham, N.C. commented that while CTCs might not indicate which treatment is best, they might indicate the need for more aggressive treatment.  He also notes their importance due to being the actual cancer cell rather than some spin-off mutation, thus they could be useful for monitoring an individual's response to treatment and tailoring further therapy.

The presence of CTCs may allow earlier detecion of metastasis-capable cancer.  These reports give the basic findings of a large study, but don't provide much information about the mechanisms by which CTCs are detrimental to the patient.  It seems that a high CTC count would suggest that the cancer has reached a later stage and thus be more resilient to chemotherapy, but the German study sites CTC cells present in early-stage patients.

If just a single CTC yields a poor response to treatment, and small increases in CTC count go with rapid declines in prognosis, does this open a new area of research into when and how CTCs are released from the main tumor?  Are CTCs a necessary prerequisite for metastastic cancer or are they just an indicator?  Does metastasised cancer exist without any CTC, and are treatment effects different?

Definitely something about which to read more...

http://www.nlm.nih.gov/medlineplus/news/fullstory_106528.html
http://www.medpagetoday.com/MeetingCoverage/SABCS/23918