There has been controversy about the utility of Chromogranin A for many years now.  Specialists have been critical about its use but to be fair even those less critical still confirm that alone it would not be trusted to formally diagnose Neuroendocrine Cancer.  That said, it was still controversial when certain US guidelines were updated to recommend it is not regularly tested.  

It’s well known for being a sensitive but non-specific marker for most tumours of Neuroendocrine type, the non-specificity is mostly due to the other conditions, some of which are highly prevalent in many countries, including but not limited to the use of proton pump inhibitors, heart disease and kidney disease.  Another criticism has been the lack of faith in using it to assess reaction to treatment.

I have to say, I have always been a fan of Chromogranin A because my own personal experience was that it was elevated at diagnosis and then reduced to normal after cytoreductive treatment.  It has remained normal since save for a slight spike which prompted some lymph node removals.  I do not have any of the reasons above for false positives.  Despite being stable for some years with no evidence of progressive disease at any site, I still get tested annually.  That said, I still put more stock into my imaging reports as long as Chromogranin A remains in normal range. 

Given that (from what I have read) the harshest criticism has come from US specialists, I was very surprised to see that the US FDA has just approved a new test kit for Chromogranin A, thus this blog post to let you know.

So, what is different about this test kit? 

Using my own simplistic and layman overview, Chromogranin A is Chromogranin A and in the absence of any other approved marker, it technically remains the gold standard.  This test has gone through many years of clinical trials.  It is said to be the only automated immunoassay globally designed for evaluating tumour progression in gastroenteropancreatic neuroendocrine tumour (GEP-NET) patients (the explanation of that is quoted below in Reference 3).   Its use as a diagnostic tool is not mentioned although the manufacturers website does accept it may show elevated levels at diagnosis, but the marker is usually combined with other clinical findings for cancer diagnosis (this has always been the case).  The website goes on to say that “this is the reason why tumor markers are typically measured before and during cancer therapy to monitor how levels change”.

Approval coverage. You can see from the approval that is only appears to cover GEP-NETs which would exclude Thoracic NETs (lung, thymus) and based on WHO classification system terminology, would also exclude Neuroendocrine Carcinomas. However, the clinical trial dates back to 2014 and was based on Grades 1 and 2 and may therefore not be approved for the recently introduced Grade 3 GEPNET category. All of the above may be something to clarify when more info is known. 

Speedier results.  According to the manufacturer, this innovative test empowers laboratories and cancer centres to measure CgA concentration in human serum, offering valuable insights into tumour progression and treatment effectiveness evaluation. With FDA clearance, this assay becomes readily accessible for deployment in laboratories across the country, promising enhanced patient care and improved outcomes.  The company also said “This assay allows customers to replace manual laboratory-developed tests, streamline lab workflows, and provides clear result interpretation. The new assay is compatible with the Thermo Scientific B·R·A·H·M·S KRYPTOR compact PLUS random-access immunoassay analyser, utilising TRACE™ technology, rooted in Nobel Prize-winning chemistry, to deliver highly precise results in less than 30 minutes.”  That is of interest to me as it takes 4 weeks to get results in UK, some of that is based on the lack of laboratories with the test kits (my tests normally have to be sent to London or Manchester on ice).

If this does what it says on the box, there may be a resurgence in the use of Chromogranin A as this new test appears to dilute some of the criticisms I mentioned above.  I look forward to seeing how this plays out.