BRCA or Broad Panel? Choosing the Right Genetic Test in Breast Cancer
Reviewed by Ann Dietrich, MD, FAAP, FACEP
The germline testing conversation in breast cancer has changed quickly. A decade ago, many clinicians framed hereditary evaluation mainly around the breast cancer (BRCA) gene and a strong family pedigree. Today, the question is broader and more immediate: Which germline test will answer the clinical question in front of you, fast enough and accurately enough to affect treatment, local therapy planning, surveillance, and family counseling? That shift is one reason the 2024 American Society of Clinical Oncology (ASCO)-Society of Surgical Oncology (SSO) guideline now recommends BRCA1/2 testing for all patients with newly diagnosed stage I to III or de novo stage IV/metastatic breast cancer who are 65 years of age or younger, with selective testing for older patients based on treatment relevance and hereditary risk features.
That does not mean every patient with breast cancer needs the largest multigene panel a laboratory can sell. It also does not mean BRCA-only testing is enough in every case. Current panel-selection guidance emphasizes that the genes ordered should match the patient’s personal and family history, and that smaller panels can reduce uncertain findings while broader panels can be more efficient when more than one syndrome is plausible. In practice, the most useful choice rarely is “small equals good” or “bigger equals better.” The most useful choice is the one that captures the actionable genes most relevant to the patient’s phenotype without creating more noise than the result can justify.
That is the real decision behind choosing the right genetic test in breast cancer. When a patient or colleague asks whether the right test is BRCA or a broad panel, the answer is not a slogan. It is a clinical judgment about actionability. Will the result affect poly (ADP-ribose) polymerase (PARP) inhibitor eligibility? Will it alter the discussion about contralateral breast cancer risk? Will it identify a high-penetrance syndrome outside BRCA that changes surveillance or preventive surgery for the patient and their relatives? Or will it mostly increase the chance of a variant of uncertain significance (VUS) that adds confusion in the middle of active breast cancer care?
Why this decision has changed in breast cancer
The strongest reason this question looks different now is that BRCA no longer is the entire hereditary story in breast cancer. The National Cancer Institute Physician Data Query (NCI PDQ) summary classifies PALB2, TP53, PTEN, CDH1, and STK11 as relatively high-penetrance breast cancer susceptibility genes, while CHEK2 and ATM are moderate-penetrance genes associated with increased breast cancer risk. The ASCO-SSO guideline goes further and states that testing for high-penetrance genes beyond BRCA1/2 should be offered to appropriate patients because those results can inform medical therapy, influence surgical decision-making, refine risk estimates for second primary cancer, and guide family risk assessment.
The second reason is yield. Multigene testing does not just find more information in theory. It finds more clinically relevant pathogenic variants in practice. In the NCI PDQ review of an unselected breast cancer population, BRCA1/2 pathogenic variants were found in 6.1% of patients, while pathogenic variants in other breast and ovarian cancer predisposition genes were found in 4.6%. In a study of 35,409 women with breast cancer tested on a 25-gene panel, 9.3% had a pathogenic variant, and fewer than half of those positive results were in BRCA1 or BRCA2. That matters because a testing strategy that stops at BRCA can miss a substantial fraction of inherited findings that still carry management implications.
The third reason is that many patients with breast cancer were tested years ago, often with limited assays or BRCA1/2-only approaches that no longer reflect modern practice. The NCI notes that in two studies of women who previously had tested negative for BRCA1/2, reflex multigene panel testing identified pathogenic variants in additional genes in 8% to 11% of cases. The question is not only what to test now, but whether a patient’s earlier negative BRCA result still is enough to close the hereditary workup. In many cases, it is not.
When BRCA-only testing still makes sense
There still are situations in which a focused BRCA1/2 strategy is the clearest and most clinically efficient test. The most obvious is a therapy-driven question. In breast cancer, the Food and Drug Administration (FDA)-approved PARP inhibitor indications remain BRCA-specific. Olaparib is approved for germline BRCA-mutated human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer and for certain patients with germline BRCA-mutated HER2-negative high-risk early breast cancer after chemotherapy. Talazoparib is approved for germline BRCA-mutated HER2-negative locally advanced or metastatic breast cancer. If the immediate question is whether the patient has a BRCA-associated breast cancer that would qualify for a current labeled PARP inhibitor strategy, BRCA1/2 testing is the minimum answer that cannot be skipped.
Focused BRCA testing also has an interpretive advantage. The ASCO-SSO guideline on germline panel selection notes that smaller panels avoid including genes with uncertain clinical validity and limit the number of variants of uncertain significance, which can lead to misinterpretation and overtreatment. That is especially relevant in newly diagnosed breast cancer, where clinicians may need to counsel patients quickly about surgery, systemic therapy, or family implications. A narrow test does not make uncertainty disappear, but it can reduce the volume of uncertainty at the moment when the patient’s treatment decisions are most time sensitive.
Speed also matters more than many clinicians might assume. In the ABOARD study, which evaluated BRCA testing timing relative to surgery in a national commercially insured population, only 54.4% of respondents received genetic test results before surgery, while 23.2% tested before surgery but received results afterward, and 22.3% tested after surgery. That does not mean broad testing alone is the problem, but it does mean that ordering a test without a plan for turnaround time can undermine the reason the test was ordered in the first place. If a genetic result is expected to affect the operative plan, the testing strategy should be built around timeliness, not just comprehensiveness.
For that reason, BRCA-only testing often is defensible when the clinical question is immediate and narrow. A patient with metastatic HER2-negative breast cancer who is being evaluated for PARP inhibitor eligibility needs BRCA1/2 status at a minimum. A patient older than 65 years of age with triple-negative breast cancer or a likely PARP-relevant scenario also clearly meets current BRCA testing guidance. In those settings, a broader panel still may be appropriate, but it should not be allowed to delay the result that directly affects current management.
When a broad panel is the better test
A broad panel becomes the better choice when the clinician’s question extends beyond PARP eligibility and into syndrome definition, second primary risk, family implications, or organ-specific surveillance outside the breast. This is where testing beyond the BRCA gene becomes high-value rather than merely expansive. ASCO specifically names PALB2, TP53, PTEN, STK11, and CDH1 as high-penetrance genes beyond BRCA1/2, whose detection can inform therapy, surgery, estimates of second primary risk, and family risk assessment. In other words, a broad panel is not just a wider net. In the right patient, it is the test that actually answers the hereditary question.
This is especially important because not all non-BRCA results mean the same thing. The CARRIERS study showed that contralateral breast cancer risk differs by gene. BRCA1, BRCA2, and CHEK2 pathogenic variant carriers with breast cancer had significantly elevated contralateral breast cancer risk, whereas PALB2 carriers showed increased risk mainly in the estrogen receptor-negative subgroup, and ATM carriers did not have a significantly increased contralateral risk. That is exactly why broad testing can be useful in breast cancer when bilateral surgery, enhanced surveillance, or long-term risk counseling is being discussed. It gives clinicians a more accurate gene-specific framework instead of forcing all positive results into the same BRCA-shaped box.
Broader testing also can uncover findings that matter even if they do not change the treatment of the index breast cancer. The ASCO-SSO guideline states that testing for moderate-penetrance breast cancer genes currently offers no benefit for treatment of the index cancer, but it may inform risks of second primary cancer or family risk assessment, and may therefore be offered to appropriate patients undergoing BRCA1/2 testing. The accompanying ASCO clinical insights article adds that moderate-penetrance variants may support intensified secondary breast screening, including magnetic resonance imaging (MRI), even though current approved systemic therapies outside BRCA remain limited. That makes these results clinically relevant, but in a different way than BRCA.
A broad panel also is the better test when more than one hereditary syndrome is plausible. The ASCO panel-selection guideline states that simultaneous testing of multiple genes is more efficient, especially in patients whose personal or family history suggests a pathogenic variant in more than one gene. That is a common breast oncology scenario. A young patient with triple-negative breast cancer initially may look like a BRCA case, but if the family history also includes early-onset colorectal or endometrial cancer, the relevant question may be broader than breast genes alone. In that situation, a phenotype-directed multigene approach often is more rational than sequencing one hypothesis at a time.
Why bigger is not always better
The strongest argument against reflexively ordering the broadest possible panel in every patient with breast cancer is that broader testing comes with broader ambiguity. Larger panels increase the likelihood of finding genes with uncertain clinical validity and raise the rate of VUS results. The NCI’s cancer genetics counseling summary notes that VUS rates rise as the number of genes tested increases. It also notes that multigene testing can reveal pathogenic variants that fit poorly with the patient’s personal or family history, creating a discordant result that is harder to interpret responsibly.
This is where pretest counseling becomes critical. The NCI emphasizes that pretest genetic counseling is an important part of the risk assessment process and helps patients understand their testing options and potential outcomes. Informed consent prepares patients for the possibility of pathogenic findings, negative results, and uncertain results, and it reduces misunderstanding about what a positive or ambiguous result does and does not mean. The broader the panel, the more important that conversation becomes.
The second problem with indiscriminate panel expansion is incidental syndromic discovery. The ASCO clinical insights article notes that some laboratories include genes associated with other hereditary cancer syndromes (such as Lynch syndrome) on very large panels, and that testing those genes in a patient with breast cancer but no suggestive personal or family history essentially is population screening. That same article gives a vivid example: An unexpected CDH1 finding may create a discussion about prophylactic gastrectomy in a patient whose original question seemed limited to breast cancer. That may be appropriate in some families, but it should happen because the phenotype justifies it, not because the default panel was oversized.
The third problem is overtreatment after a finding of a moderate penetrance gene. The 2020 ASCO guideline on hereditary breast cancer management states that for women with newly diagnosed breast cancer who carry a mutation in a moderate-penetrance gene, mutation status alone should not determine local therapy decisions for the index tumor or contralateral risk-reducing mastectomy. That point deserves emphasis because broad panels make CHEK2 and ATM results much more common in routine practice. Those results matter, but they do not justify treating every positive panel the way clinicians treat BRCA1/2 or TP53.
How family history should shape the panel
Family medical history still matters. It remains one of the most important tools for deciding whether BRCA-only testing is enough or whether a broader syndrome-oriented panel is needed. The NCI highlights several red flags that increase suspicion for inherited breast cancer susceptibility: a large number of affected relatives, diagnosis of breast cancer at young ages, bilateral breast cancers, multiple ipsilateral primaries, male relatives with breast cancer, multiple cancers within a family, and two or more primary cancers in a single individual. Those features do not just increase the chance of a positive result, they help determine which genes belong on the panel.
The ASCO panel selection guidance makes this point concrete. Its clinical insights example describes a 35-year-old with triple-negative breast cancer who is eligible for testing of breast cancer genes but adds that if the family history includes early-onset colorectal cancer, genes associated with Lynch syndrome should be added. That is a practical model for real-world testing. Start with the breast cancer phenotype, then broaden deliberately when the pedigree points to a second hereditary pattern. The point is not to test every possible syndrome in every patient. The point is to avoid missing the syndromes the history is actively suggesting.
Family medical history also is essential after the result returns. The same ASCO clinical insights source notes that a patient with negative genetic testing still may merit high-risk surveillance or prevention strategies on the basis of family history. Likewise, the NCI notes that models such as Breast and Ovarian Analysis of Disease Incidence and Carrier Estimation Algorithm (BOADICEA)/CanRisk incorporate both BRCA and non-BRCA genes, including CHEK2, ATM, and PALB2, alongside pedigree information. A negative test does not end risk assessment. It shifts the work from mutation identification to absolute risk estimation and family-based management.
Practical testing choices in common breast cancer scenarios
Newly diagnosed patient age 65 years or younger
For a newly diagnosed patient with stage I to III or de novo stage IV/metastatic breast cancer who is 65 years of age or younger, BRCA1/2 testing should be offered under the current ASCO-SSO guideline. The harder question is whether to stop there. In many such patients, especially younger patients with significant family history, multiple primaries, triple-negative disease, or concern about second primary risk, a breast-focused multigene panel that includes high-penetrance non-BRCA genes is more informative than BRCA-only testing.
Patient older than 65 years of age
In patients older than 65 years of age, the ASCO-SSO guideline narrows the BRCA testing indication to settings with clear treatment or hereditary relevance: candidacy for PARP inhibitor therapy, triple-negative disease, suggestive personal or family history, male sex at birth, or founder-population ancestry (such as Ashkenazi Jewish ancestry). This is a good place to resist automatically ordering broad-panel testing. If the only current question is the relevance of BRCA-related treatment, BRCA1/2 testing may be sufficient. If the pedigree or phenotype suggests something more, broaden the panel in a targeted way.
Prior BRCA-negative testing from the pre-panel era
A prior negative BRCA result always should be interpreted in historical context. Was the earlier test limited to founder mutations? Was it performed before PALB2 and other high-penetrance genes were commonly included? Did the family history evolve after the original test? The NCI’s PDQ summary notes that reflex multigene testing after an earlier BRCA-negative result found additional pathogenic variants in 8% to 11% of cases. That makes updated testing reasonable in many survivors and in newly presenting patients whose old records show only narrow testing.
Urgent surgical decision-making
If the genetic result is expected to shape the surgical plan, do not order testing passively. Build a testing strategy around the date by which the answer is needed. The ABOARD study showed that a substantial share of patients either received results after surgery or tested only after surgery, even when providers had ordered BRCA testing within a year of diagnosis. In practice, this means using a pathway that can return the needed result before the operation. If a broad panel can do that, fine. If not, a staged approach that secures the urgent BRCA answer first and expands later can be more clinically sound than waiting for an oversized panel.
Recurrent disease or second primary breast cancer
ASCO also gives specific guidance outside the newly diagnosed setting. All patients with recurrent breast cancer who are candidates for PARP inhibitor therapy should be offered BRCA1/2 testing regardless of family history, and BRCA1/2 testing also should be offered to patients with a second primary cancer in the ipsilateral or contralateral breast. These are settings where BRCA status can remain immediately relevant, even years after the first breast cancer diagnosis. Broadening beyond BRCA in these patients depends on whether the result also will inform personal risk management or family risk assessment.
Mixed-syndrome clues in the phenotype or pedigree
When the phenotype or pedigree points outside a pure hereditary breast cancer pattern, the argument for a broader panel becomes much stronger. Examples include breast cancer plus early-onset colorectal or endometrial cancer in the family, multiple primary cancers in one person, or family histories suggestive of diffuse gastric cancer or other syndromic patterns. The NCI specifically highlights multiple family cancers, early ages of onset, and multiple primary cancers as classic indicators of inherited cancer susceptibility, while ASCO’s panel guidance explicitly recommends broadening the panel when family history points to another syndrome (such as Lynch syndrome).
How to use the result without overusing it
A positive BRCA result remains one of the highest-actionability findings in breast cancer. It can affect systemic therapy, local therapy discussions, contralateral breast cancer counseling, ovarian risk management, and family cascade testing. But even here, the result needs to be used with precision. The fact that a test is actionable does not mean it dictates a single surgical choice for every patient. It means the risk discussion is materially different than it would be in noncarriers.
A positive high-penetrance non-BRCA result also should be treated as gene-specific information, not as a vague “other mutation.” PALB2, TP53, PTEN, CDH1, and STK11 do not carry the same cancer spectrum or the same downstream management. That is one of the best arguments for testing beyond the BRCA gene when the phenotype warrants it. A broad panel only adds value if the result is interpreted in the specific clinical context of that gene.
A positive moderate-penetrance result requires the most restraint. Moderate genes can matter greatly for long-term risk, surveillance, and family counseling, but mutation status alone should not determine the local treatment of the index breast cancer. The CARRIERS data reinforce that different moderate- or intermediate-risk genes do not confer uniform contralateral risk, and the ASCO hereditary management guideline explicitly warns against letting moderate-penetrance mutation status alone drive local therapy decisions. This is where broad testing can help or harm, depending on how disciplined the interpretation is.
A VUS should not be treated like a pathogenic variant. The NCI notes that VUS findings often reflect limited penetrance evidence, discordant phenotype, or uncertainty about the gene-disease relationship. That means a VUS should not trigger irreversible surgery or gene-specific screening recommendations as though it were a confirmed hereditary diagnosis. Broader testing makes these results more common, which is another reason informed consent and post-test counseling matter so much.
A negative result also needs disciplined interpretation. A negative multigene test does not reset a patient with a powerful pedigree to average risk. Family medical history still can justify high-risk surveillance and prevention strategies, and cascade implications remain important whenever a clearly pathogenic familial variant is found. The NCI’s counseling summary notes that cascade testing helps identify carriers before cancer presentation, yet follow-up cascade testing rates remain variable, ranging from 15% to 57% overall in the studies it summarizes. That gap is a reminder that the value of germline testing is realized only when the result is translated into family care.
BRCA or broad panel? The practical answer
In modern breast cancer care, BRCA1/2 often is the floor, not always the ceiling. BRCA-only testing still makes excellent sense when the main question is immediate therapeutic actionability, especially PARP inhibitor eligibility, or when a time-sensitive surgical decision requires a rapid, focused answer. But broad testing is the better test when the phenotype, pedigree, or long-term risk question extends beyond BRCA, especially when high-penetrance non-BRCA genes or additional hereditary syndromes are plausible.
The most practical answer to “BRCA or broad panel?” is this: Choose the panel that is broad enough to capture the actionable hereditary explanation for that patient’s breast cancer, but focused enough that the result can be interpreted, explained, and used well. That is the testing strategy most likely to improve treatment decisions now and risk management later.