Getting a negative BRCA result feels like good news. And it is. But it’s not the whole story.

You asked for the test. You waited anxiously for the results. And then the call came- “Your BRCA1 and BRCA2 results are negative.” 

Relief. Exhale. Maybe even tears.(of happiness, obviously)  

But here is something your genetic counsellor may not have had time to fully explain in that appointment:  

“BRCA negative does not mean cancer risk-free!!” 

And for many patients, particularly those with a strong family history of breast, ovarian, or pancreatic cancer – it may not even mean low risk. 

Here is why. 

BRCA Is Just Two Genes Out of Thousands 

BRCA1 and BRCA2 are the most well-known cancer risk genes; and for good reason. Mutations in these two genes carry lifetime breast cancer risks of up to 72% for BRCA1 and 69% for BRCA2, compared to a general population risk of around 12-13%. 

But the human genome contains approximately 20,000 genes– and cancer risk is not carried by BRCA1 and BRCA2 alone. 

Imagine the human genome as an elephant, and you just looking at it’s tail and running to a conclusion. Actually it’s even smaller than a tail.  

There are dozens of other genes- PALB2, CHEK2, ATM, RAD51C, RAD51D, BRIP1, NBN– that also carry elevated cancer risk, sometimes nearly as significant as BRCA. Standard BRCA testing, by definition, does not look at any of them. 

When an oncologist orders a “BRCA test,” they are asking one very specific question about two very specific genes. The absence of a mutation in those two genes tells you nothing about the other risk genes in your genome. 

The HRD Connection: What BRCA Testing Was Really Pointing To:-

Here is where it gets scientifically interesting and clinically very important. 

BRCA1 and BRCA2 are not simply “cancer genes.” They are DNA repair genes; specifically, they are critical components of a repair pathway called Homologous Recombination (HR). When BRCA1 or BRCA2 are mutated, this repair pathway breaks down, and the cell loses its ability to fix certain types of DNA damage accurately. 

This state of impaired DNA repair is called Homologous Recombination Deficiency (HRD). 

The reason HRD matters so profoundly in cancer care is twofold: 

1. First – it is a strong indicator of cancer risk and aggressive tumour behaviour.
2. Second – tumours with HRD have a specific vulnerability.  

They are highly sensitive to a class of drugs called PARP inhibitors (olaparib, niraparib, rucaparib) and to platinum-based chemotherapy. These treatments exploit the already-broken DNA repair system in HRD tumours, making them significantly more effective than in HRD-negative tumours. 

Here is the critical point: HRD can exist even when BRCA1 and BRCA2 are completely normal. 

Mutations in any of the other HR pathway genes: PALB2, RAD51C, RAD51D, BRIP1, ATM, and more- can also cause HRD. And tumours can develop HRD through entirely non-genetic mechanisms- epigenetic silencing of BRCA genes, for instance, that would never appear on a standard BRCA test. 

What This Means in Practice

Consider two patients: 

• Patient A tests BRCA-positive. Her oncologist immediately considers PARP inhibitor therapy. Her family members are referred for genetic counselling. 

• Patient B tests BRCA-negative. She is told her genetic risk is low. No further testing is recommended. She receives standard chemotherapy, even though her tumour, when later profiled comprehensively, shows high HRD and would have been an excellent candidate for PARP inhibitor therapy. 

This scenario plays out more often than the field would like to acknowledge. 

In our own analysis of 642 pan-cancer patients using the OncoIndx® comprehensive genomic panel- presented at ASCO 2025; we found that high HRD scores occurred independently of BRCA1/2 mutations in a significant proportion of patients. BRCA-wild-type patients with high HRD scores represent a population that standard BRCA testing would entirely miss, yet they carry the same therapeutic vulnerability and may benefit equally from PARP inhibitor or platinum-based therapy. 

The Questions Worth Asking

If you have tested BRCA-negative but still carry any of the following, it is worth discussing comprehensive genomic profiling with your oncologist: 

• A strong personal or family history of breast, ovarian, pancreatic, or prostate cancer 

• A previous cancer diagnosis, particularly at a young age 

• A tumour that responded unusually well; or unusually poorly to platinum-based chemotherapy 

• An oncologist who has mentioned HRD, PARP inhibitors, or homologous recombination 

The questions to raise: 

1. “Has my tumour or germline been tested for HRD; not just BRCA?” 
2. “Are there other HR pathway genes that should be included in my testing?” 
3. “Could I be a candidate for PARP inhibitor therapy even with a negative BRCA result?” 

BRCA Is the Beginning of the Conversation, Not the End:- 

A negative BRCA result is genuinely good news. It removes one significant risk factor from the picture. But cancer genetics is not a binary: positive or negative, risky or safe. 

The complete picture requires looking at the complete genome, across all the HR pathway genes, across HRD scoring, across the full spectrum of variants that a two-gene test was never designed to capture. 

At 1Cell.ai, our OncoIndx® comprehensive genomic panel covers 50+ HRR genes, full HRD scoring (LOH + TAI + LST), and pharmacogenomic markers, giving oncologists and patients the molecular completeness that a BRCA-only test simply cannot provide. 

Because “BRCA negative” should be the beginning of the genetic conversation, not the last word in it. Learn more about OncoIndx® comprehensive genomic profiling at 1cell.ai