Hereditary Cancer Risk and What BRCA Testing Can Tell You

A BRCA test result, a family-history questionnaire, and a session with a genetic counselor answer three different questions, and confusing them is the most common mistake people make about hereditary cancer risk. The 2019 US Preventive Services Task Force recommendation is best read as a sequence rather than a verdict: a brief tool decides who should be referred, counseling decides who should actually test, and only after that does a laboratory result mean anything for a given person. Testing is a step at the end of that path, not a general screen for everyone.

I write this as a physician-scientist who evaluates clinical evidence, explaining how a recommendation was built rather than telling anyone what to do about their own risk. This is general education, not medical advice, and decisions about testing belong with your own clinician and a genetic counselor. A definition to anchor the rest: BRCA1 and BRCA2 are genes whose normal job is repairing damaged DNA; certain inherited variants weaken that repair and raise the lifetime risk of breast, ovarian, and some other cancers. Everything below turns on the difference between carrying such a variant and being flagged as worth checking for one.

What the USPSTF actually recommended

The Task Force issued two statements in the same document, published in JAMA in August 2019. The first is a B recommendation: primary care clinicians should assess women who have a personal or family history of breast, ovarian, tubal, or peritoneal cancer, or an ancestry associated with BRCA1/2 variants, using an appropriate brief familial risk assessment tool. Women with a positive result on that tool should receive genetic counseling, and genetic testing if counseling indicates it. The second is a D recommendation: against routine risk assessment, counseling, or testing for women whose personal history, family history, or ancestry is not associated with harmful BRCA1/2 variants.

The grades carry precise meanings that are easy to lose. Under the USPSTF definitions, a B means high certainty that the net benefit is moderate, or moderate certainty that the net benefit is moderate to substantial; a service the Task Force advises clinicians to offer. A D means moderate or high certainty of no net benefit, or that harms outweigh benefits; a service it recommends against. So the same document both endorses a pathway for one group and discourages it for another. That contrast is the whole point, and it is why "should I get the BRCA test" is the wrong opening question.

Why a risk tool, not a blood draw, comes first

Harmful BRCA1/2 variants are uncommon in the general population. The National Cancer Institute puts the prevalence at roughly 1 in 400, higher in certain founder populations. When a condition is that infrequent, testing everyone produces a poor ratio of true findings to false alarms and incidental noise, which is the mechanism behind the D recommendation.

A familial risk assessment tool solves a narrower problem: it identifies who is likely enough to carry a variant that referral is worthwhile. The USPSTF names several validated ones, including the Ontario Family History Assessment Tool, the Manchester Scoring System, the Referral Screening Tool, the Pedigree Assessment Tool, the 7-Question Family History Screening Tool, and the Tyrer-Cuzick model. These are short questionnaires about relatives, cancers, and ages at diagnosis. None of them tests DNA. Their job is to sort people into "reasonable to refer" and "not indicated," and a positive result means proceed to counseling, not that a variant is present.

What genetic counseling does that a result cannot

Counseling sits deliberately between the tool and the test, and it does work neither of the others can. A trained counselor reconstructs the family history properly, explains what a given result would and would not change, and confirms that testing will actually inform a decision before any sample is drawn. This is where informed consent lives, and where the limits of the test are made explicit in advance rather than discovered afterward.

One limit deserves emphasis because it surprises people: a test can return a variant of uncertain significance. The NCI describes this as a change for which there is not yet enough evidence to say whether it raises cancer risk, and notes that most such variants are eventually reclassified, often as benign. A result like that is neither reassurance nor alarm, and without counseling it is easily misread as either. The counseling step exists partly so that an ambiguous result lands as the open question it is.

What a result can and cannot tell you

A confirmed pathogenic variant is meaningful. NCI figures put the lifetime breast cancer risk for carriers above 60 percent, and ovarian cancer risk far above the general-population baseline, which is why the finding opens conversations about enhanced surveillance and risk-reducing options. What the result does not do is speak in isolation. Its weight depends on which variant, which gene, and the family and clinical picture around it, the same context the counselor assembled going in.

Two errors follow from ignoring that. A negative test in someone with a strong family history is not a clean bill of health; it may reflect a risk that runs through genes this test did not examine. And a positive test does not fix a person's future, because a variant raises probability rather than settling an outcome. The USPSTF sequence is designed to keep both errors from taking hold: the tool decides who is worth checking, counseling decides who should test and frames what a result means, and the result informs a decision it was never meant to make alone.