Hereditary Cancer Risk and What BRCA Testing Can Tell You

A BRCA test tells you whether a person carries a specific inherited variant. It does not tell you whether that person should have been tested in the first place, and it does not tell you what the result means for their life. Those are three separate questions, and treating them as one is the most common confusion about hereditary cancer risk. The 2019 US Preventive Services Task Force recommendation is easiest to understand when you read it as a short assembly line rather than a single yes-or-no verdict: a brief questionnaire decides who gets referred, a counselor decides who actually tests, and only then does a laboratory result carry meaning for the individual holding it.

To keep the vocabulary straight from the start: BRCA1 and BRCA2 are genes whose ordinary job is to repair damaged DNA. Certain inherited variants weaken that repair, which raises the lifetime risk of breast, ovarian, and several other cancers. Everything that follows depends on the gap between actually carrying such a variant and simply being flagged as worth checking for one. This article explains how the recommendation was built, not what any reader should do about a personal result, which is a conversation for a clinician and a genetic counselor.

Key points#

• Harmful BRCA1/2 variants are uncommon, roughly 1 in 400 in the general population, so testing everyone is inefficient.
• The USPSTF pathway runs in order: risk tool, then counseling, then testing only if counseling supports it.
• A positive result on a family-history questionnaire means "refer for counseling," not "a variant is present."
• A result can come back as a variant of uncertain significance, which is neither reassurance nor alarm.
• A negative test in a high-risk family is not an all-clear, and a positive test is a probability rather than a fate.

Why testing is not the first move#

Start with how rare the target is. The National Cancer Institute estimates that harmful BRCA1/2 variants occur in roughly 1 in 400 people in the general population, with a higher rate in certain founder populations. When a feature is that infrequent, screening the whole population produces a lopsided ratio: a small number of genuine findings buried under false alarms, ambiguous results, and incidental noise. That arithmetic is the engine behind the Task Force's decision to advise against routine testing for people whose history gives no signal.

So the recommendation does not open with a blood draw. It opens with a filter designed to answer a narrower question than the lab can: who is likely enough to carry a variant that a referral is worth making? Answering that well, before anyone touches a sample, is what makes the rest of the pathway efficient rather than wasteful.

Step one: a short questionnaire#

The first tool in the sequence is a familial risk assessment questionnaire. The USPSTF lists 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. Each is a brief set of questions about relatives, the cancers they had, and the ages at which those cancers were diagnosed.

None of these tools examines DNA. Their only task is to sort people into "reasonable to refer" and "not indicated." A positive result means the next step is a conversation, not that a variant has been found. This is the point patients most often misread, because a positive screening result feels like a diagnosis when it is really just a signal to keep going.

Step two: counseling, which the lab cannot replace#

Genetic counseling sits between the questionnaire and the test on purpose, and it does work that neither of the other two can. A trained counselor rebuilds the family history carefully, spells out what a given result would and would not change, and confirms that testing will genuinely inform a decision before any sample is drawn. Informed consent lives here. The limits of the test are laid out in advance, rather than discovered after the fact.

One of those limits catches people off guard. A test can return a variant of uncertain significance, which the NCI describes as a change for which there is not yet enough evidence to say whether it raises cancer risk. Many such variants are eventually reclassified, often as harmless. A result like that is neither a green light nor a red one, and without counseling it is easy to read it as whichever the person feared or hoped. The counseling step exists in part so that an ambiguous answer lands as the open question it actually is.

Step three: what a result can and cannot say#

A confirmed pathogenic variant is a substantial finding. NCI figures place the lifetime breast cancer risk for carriers above 60 percent and ovarian cancer risk well above the general-population baseline, which is why such a result opens discussion of closer surveillance and risk-reducing options. What the result cannot do is speak on its own. Its weight depends on which gene, which variant, and the surrounding family and clinical picture, the same context the counselor assembled on the way in.

Two mistakes follow from forgetting that. First, a negative test in someone with a strong family history is not a clean bill of health, because the family's risk may travel through genes this particular test did not read. Second, a positive test does not seal a person's future, because a variant shifts probability rather than deciding an outcome. The whole USPSTF sequence is built to hold both errors at bay: the questionnaire decides who is worth checking, counseling decides who should test and frames what a result will mean, and the result then informs a decision it was never designed to make by itself.

The grades, briefly#

The recommendation is really two statements in one document, published in JAMA in August 2019. For women with a personal or family history of breast, ovarian, tubal, or peritoneal cancer, or an ancestry linked to BRCA1/2 variants, the Task Force gives a B recommendation: assess with a brief tool, refer positives for counseling, and test if counseling supports it. For women without such a history or ancestry, it gives a D recommendation, advising against routine assessment, counseling, or testing. Under the USPSTF definitions, a B signals a service worth offering because the net benefit is at least moderate with reasonable certainty, while a D signals no net benefit or net harm. The same page endorses the pathway for one group and discourages it for another, which is exactly why "should I get the BRCA test" is the wrong first question to ask.