With CA19-9 not a specific marker solely to PDAC cancer but also occurs in benign conditions as well, oncologists won’t jump the gun and prescribe chemo unless other methods are done to confirm recurrence. The elevation you mention is well within a range that could be attributed to an inflammatory situation. Oncologists I have association with as a patient advocate with several national cancer organizations in the GI space generally start raising an eyebrow when a level of 250 is reached. I know of one post-Whipple patient whose CA19-9 at 5 years out is and has been 600 for a number of years and has remained steady with no disease detected. It is his new normal.

ctDNA is continually improving and is now very accurate for colon cancers. I just got off a Zoom call with a committee of GI oncologists and asked that question on accuracy improvements. I’ve been familiar with ctDNA for minimal residual disease having had a career in cancer and immunology research as well as a long-term survivor of stage IV pancreatic cancer. ctDNA has been used for long-term surveillance of my case since 2014. I have a BRCA mutation where the accuracy in ctDNA measurements is the highest. It is done quarterly and I have a low dose CT for chest and an MRI for abdomen every 6 months. The test results have always been in concordance.

Improving the accuracy of ctDNA in pancreas cancers is ongoing. The highest accuracy achieved in in those with BRCA mutations at 89.%. That means in 11% that have recurrence, it won’t be detected any earlier than by conventional imaging methods. In the 89% group, ctDNA is capable of detecting dna fragments of metastasis related to the primary tumor about 8 weeks earlier. Oncologists are still on the fence about beginning treatment before a confirmatory test. This was the case in treating colon cancers but as ctDNA improved in that area, oncologists became more comfortable with starting treatment earlier as they were more assured it was recurrence and not due to some inflammatory response.

Oncologists follow treatment protocols from the National Comprehensive Cancer Network based on recommendations from a working group oncology experts. These protocols are periodically reviewed and modified in conjunction with new findings from clinical studies. No oncologist I am aware of would use chemotherapy on the assumption of disease. There are side effects with chemo and adverse events of more serious nature that can cause permanent damage to tissues and organs-hence the cautious approach when a patient says start me back on chemo without confirmatory evidence of disease. When something is not visualized by CT or MRI, then it is worth inquiring about doing a PET scan which looks for increased metabolic activity in the body using a radioactive tracer attached to a sugar molecule that a cell with higher metabolic activity will utilize at a faster rate than surrounding normal cells.

Going back to ctDNA in cancers of the pancreas where the best accuracy achieve to date has been in BRCA mutations at 89%, in is lower in the other mutation types and drops to a low of 64%. There are many companies with ctDNA testing and all are actively working on improving the accuracy in pancreatic cancer as they did in colon and other solid tumor cancers. It is a matter of time and iterations in improving the methodology that higher accuracy will be achieved.

A short list on some benign conditions that can lead to an elevation of CA19-9:
Non-cancerous conditions that can cause high CA 19-9 levels include:
* Gallstones
* Biliary infection (cholangitis)
* Blockage of the bile duct (jaundice)
* Pancreatitis (swelling of the pancreas)
* Cystic fibrosis
* Liver disease