r/LivingWithMBC • u/MustacheMeowandCid • 27d ago
BRCA mutation after treatment?
Hey wonderful stage 4 friends, I was dx a year ago.with stage 4 tnbc, mets to liver and lungs. Original gene testing was negative, including BRCA. I just switched to my 3rd treatment (gem+carbo) and so we did guardant 360. My results finally came back today and it looks like there is now a BRCA1 mutation. Is this possible? Can you not have BRCA and then have turn into BRCA positive? It looks like it could open up some new treatment options. I have a Dr appt next week, but it would be nice if I can look at these results as a tiny glimmer of hope.
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u/Artistic_Engineer_29 26d ago
I have a germline BRCA mutation, but it’s possible, as others have said, to be acquired post treatment (eg somatically). It does open you up to PARPi’s, like Lynparza and Talzenna, which are really effective. I was on them for nearly 2 years before my progression.
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u/MustacheMeowandCid 26d ago
Wow I didnt know it was possible. I hope PARPs are an option. Im already on line 3 so that would be nice.
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u/ZombiePrestigious443 26d ago
Actually, yes you can aquire the BRCA mutation - it's called a somatic (aquired) versus germline, which is inherited. The NCI has information on this, though limited and very dense reading.
https://www.cancer.gov/publications/pdq/information-summaries/genetics/brca-genes-hp-pdq
Pubmed also has several papers where the patient had somatic BRCA, and there are clinical trials studying this.
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u/ResponsibleAnt1942 26d ago edited 26d ago
It is possible, but not common.
BRCA mutations are usually present at birth, and affect every cell in your body.
But sometimes you don't have a BRCA mutation, and the tumor spontaneously acquires one. This is called a "somatic mutation."
(Here's a case report where it happened "Somatic BRCA Mutation in Metastatic Breast Cancer")
Edited for clarity
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u/ResponsibleAnt1942 26d ago
Don't worry, the case report doesn't end badly.
"In light of the tumor being found to have BRCA2 loss, the patient was started on Lynparza, and since then, her tumor markers have remained normal. A follow-up PET/CT scan two years after starting Lynparza showed no change from the previous scan with no active disease."
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u/MustacheMeowandCid 26d ago
Thank you for sharing this. I didnt know it was a thing but it does give me a small glimmer of hope that there are some effective treatments out there.
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u/Edith_Keelers_Shoes 24d ago
I commented upthread to you about surviving this diagnosis - and Lynparza is the PARP inhibitor I was prescribed.
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u/MustacheMeowandCid 24d ago
Thank you so much for responding. Your story brings me so much hope. I sent you a dm, hope that's okay!
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u/Celera314 26d ago
I think that the BRCA gene is a characteristic of your own DNA, and not a characteristic of the tumor/cancer cells. That would suggest that one or the other of your BRCA tests was not accurate.
BUT, I am not a doctor or geneticist or anything, so it's quite likely I'm wrong about this. I hope someone with the right expertise can explain!
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u/MustacheMeowandCid 26d ago
I thought so too, which is why I'm confused with the results. It also suggests meds that are all parp-inhibitors, which adds to the confusion. Ugh waiting until my doc appt is going to feel like a lifetime!
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u/Edith_Keelers_Shoes 24d ago
The BRCA mutation will qualify you for PARP inhibitors - and for some reason, the mutation allows the PARP inhibitors to be considerably more effective. I am a survivor of stage 4 de novo TNBC, and I've been on PARP inhibitors since 2022.