No CHIP Test Yet
All of which has led for some to call for CHIP testing.
However, there are currently no screening programs for CHIP and no plans to introduce any. “So most CHIP is actually being diagnosed incidentally, when patients get genetic testing for some other indication,” said Dr. Weeks.
“The patients that we see in our CHIP clinic at Dana-Farber have genetic testing because they have low blood counts,” she continued, “and somebody’s trying to figure out: Do you have MDS?”
Other patients have genetic testing due to a family history of other cancers, “and so they’re getting hereditary cancer panels to determine if they have Lynch syndrome, or other hereditary syndromes,” which are picking up gene mutations associated with CHIP.
In other cases, study protocols are identifying CHIP “in various research contexts, and then as a follow-up, some of those patients end up with our clinic,” added Dr. Weeks.
Due to the associated risks for CHIP, “obviously everyone wants to know whether they are at risk for hematologic malignancy, or not,” said Dr. Gondek. To those ends, Dr. Weeks and colleagues developed the clonal hematopoiesis risk score (CHRS).
Published by NEJM Evidence in 2023, the score takes a range of predictive variables, such as age, number of mutations and their degree of associated risk, the variant allele fraction, and a series of blood indices to define patients as low-, intermediate-, or high-risk.
“A little over half” of high-risk individuals “will develop a blood cancer” such as MDS or acute myeloid leukemia (AML)” over the next 10 years, Weeks explained, while “for your intermediate risk folks, in that same time period, 7%-8% of them will develop a blood cancer.”
In low-risk individuals, the 10-year risk for MDS or AML is just 1%.
Dr. Weeks noted the “caveat that there are environmental factors or patient-specific issues that might increase your risk that are not considered in the calculator,” such the presence of hereditary cancer syndromes, “or if you’re getting chemotherapy for other cancers.”
From a cardiology point of view, Dr. Ballantyne said that, above all, “cardiologists need to be aware that some of these people are at increased risk for cardiovascular events.” This prompted a team including Dr. Weeks and Dr. Ballantyne to study whether the CHRS can also predict cardiovascular risk.
They found that people designated low-risk on the score faced an 8% increased risk for all-cause mortality vs individuals without CHIP during a median follow-up of 7 years. This rose to a 12% increase in intermediate-risk individuals.
And those deemed high-risk had a 2.5-fold increased risk for early mortality and a threefold higher risk for cardiovascular death.
Dr. Weeks noted: “We have not done a dedicated study to define a cardiovascular disease-specific calculator for CHIP,” but in the meantime, the CHRS is a “very reasonable way to estimate what someone’s risk of progression or adverse events is for cardiovascular disease.”
For clinicians, however, the key question becomes: What can be done to mitigate the risks, particularly in high-risk individuals?
For malignant conditions, the approach is to monitor patients, although “we and other centers are in the process of developing various interventional clinical trials to test various agents on their ability to improve blood counts, as well as to mitigate the risk of progression to overt blood cancer,” said Dr. Weeks.