Do you still need the Scan if you can measure CTC in blood?

Dr. Weeks’ Comment:  

It would appear that the test for Nagalase levels (CTC) is more predictive of outcome than the Bone Scan or CAT scan.  That is good and eliminates more radiation consumption.  

Circulating Tumor Cells Superior to Imaging Tests

Researchers have also discovered that CTC evaluation may be more accurate than standard imaging tests at predicting the prognoses of metastatic breast cancer patients. Traditionally, imaging tests have been used to evaluate the effectiveness of treatment in those with metastatic breast cancer. The response to treatment is often determined by measuring changes in tumor size with CT and MRI scans. In a groundbreaking study performed in 2006, metastatic breast cancer patients had imaging tests done before and 10 weeks after they began therapy.10 The results of the imaging tests were reviewed by two independent radiologists. CTC were measured 4 weeks after the start of therapy. The researcher’s findings were astonishing—the group that responded to treatment based on imaging tests (i.e., the tumors got smaller) and had 5 or more CTC had a worse prognosis than the group with CTC counts less than 5 that showed worseningof their disease on imaging studies!

These findings suggest that the levels of CTC were far more important at predicting survival compared to the actual visual changes noted on imaging tests. Further analysis established that CTC testing had superior reproducibility compared to imaging studies. There was a 15% disagreement in the interpretation of the imaging tests between the two radiologists, compared to less than 1% variation in the results of CTC testing. The authors of this study declared that “this advantage in reproducibility implies that inaccurate disease status evaluations and inappropriate treatment decisions are less likely with the use of the CTC assay than with radiographic studies.” They went on to enthusiastically conclude that “the assessment of CTCs has several advantages over serial radiographic evaluation.

The CTC assay is more reproducible than radiographic evaluation, shows useful results at an earlier time point than do radiologic studies, and seems to be a more robust predictor of survival than is radiographic response.”


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