Cancer growth is started by mutation(s) in a cell’s DNA. As the cancer tumor grows more mutations occur. Some tumors are chimeras – the cells don’t match because they have different mutations. Some breast cancers can accumulate dozens of mutations. A chemo drug that kills part of a tumor may spare a resistant part that continues to grow.
Most breast cancers are ER+. (They still possess the estrogen receptor which stimulates faster growth when exposed to estrogen.) The standard treatment includes drugs that suppress estrogen in the body. I took one of these for 5 years after my bilateral mastectomy for double breast cancer in 2015.
If the cancer has escaped the breast into the body (Stage 4) it is no longer curable. The focus is on control by chemotherapy. Unfortunately, cancer cells continue to mutate so the chemo that used to work stops working. Then a different chemo is tried.
Currently, the only way to tell if a chemo has stopped working is by periodic PET scans. PET scans are expensive and also the cancer can grow between scans.
Astra Zeneca has developed a new blood test that detects one specific mutation. Not coincidentally, AZ is also developing a drug that will control the cancer with this mutation.
The existing drug is a pill that costs $26,000 per month. (Elacestrant, made by Stemline Therapeutics.) This gives a significant increase in quality of life and disease-free progression.
The concept of a cancer mutation blood test can be applied to many other cancers. Naturally, it makes sense for a company that produces a drug that controls a specific mutation to develop a blood test that detects that specific mutation.
From a scientific and personal perspective, this is very exciting progress. From a Macroeconomic perspective, this will add to the overwhelming cost of medical care.
https://www.nytimes.com/2025/06/01/health/breast-cancer-blood-test-astrazeneca.html
Wendy