Guardant360 cdx genetic test

[DDIL1]

My onc ordered a second genetic test. guardant360cdx.com/getting-... I had invitae first. I’m going on 3 months in of Ibrance, Letrozole and Xcheva. Wondering if anyone had more than one genetic test and was it different results. Just curious I know everyone is different.

[Hidden]

Hi DDIL1! You don’t say which Invitae test you had but typically the Invitae and Guardant tests are different tests looking for different things. The Invitae test is a blood test that detects germline mutations. Theses are mutations that you are born with and which may be passed on to those genetically related to you. BRCA 1 and 2 are examples of germline mutations that increase your risk of breast and ovarian cancer. They are also important once you have cancer as there are specific treatments that are targeted to patients with these mutations. My Invitae test showed a BARD-1 and RET germline mutation. Neither of these inform targeted treatment but the BARD-1 is associated with a higher risk of developing breast cancer. I will share these result with my biological relatives.

The Guardant 360 test detects mutations in circulating tumor DNA (ctDNA). Most tumor(s) shed their DNA into the blood stream. This test can isolate the ctDNA and detect mutations in the tumor which may be useful to identify targeted therapies which may work. An example of a mutation that could be picked up in ctDNA is PIK3CA which identifies patients likely to respond to the drug Pikray.

Molecular profiling of your tumor tissue or your ctDNA should be done at the time when a treatment change is being considered. As profiling your tumor(s) needs a new biopsy, it is now becoming more common for oncologists to use the ctDNA tests as they are a simple blood test.

This is a complex subject but I hope that my simple explanation helps. If you have any additional questions feel free to DM me.

Liz

[DDIL1 in reply to Hidden]

Liz,Thank you, this is more than I got from my onc! It makes complete sense. I’m a bit nervous they could find more issues. I already have the CHEK2 mutation. But knowledge is power especially dealing with this cancer. I’m lobular ER/PR+ HER-. I have. FES/Pet scheduled for end of April , scanaxiety already setting in.

[Aquamoron]

Hi DDIL1. I am at about the same stage in my treatment as you and have had the guardant run twice. Both were a month apart and I will continue to get done monthly moving forward to track the shedding as UKCAGirl explained below. There was a very nominal difference between the two readings (.01 or less) and my oncologist stated that its more of a tracking tool to make sure treatment does not need to be tweaked. He likes it because it gives a better overall picture than simply the CA 27,29 for efficacy, but reminded the real litmus is the scan. To me, I'm glad that they can have these extra screenings in to catch any things that may otherwise fall through the cracks.

I am BRCA2 so the thought is to be more proactive than reactive to my treatments. I received a great second opinion over at UPenn who explained to me that my dna can only be tricked so long on a particular line of treatment, and then it will figure out how to become resistant and then I will need to switch for another line of treatment to try and fool it into submission. There are currently 10 lines of treatment and more in development, and this primary cocktail (Faslodex/Ibrance/ Xgeva ) is the gold standard for my ER+, ER/Her- issue. Long may it last! I am tolerating the s/e better with each cycle (starting my 4th Ibrance, 5th Faslodex and 2nd Xgeva) and the fatigue is waning.

I will be thinking of you and sending good mojo for your upcoming scans. I pushed mine out a few weeks and will be going in early May since I just started the Xgeva/Xchevia (sp?) at the end of March.

[DDIL1 in reply to Aquamoron]

So basically it can see if the tumor is changing as it sheds. But it will not say if it’s progressing or stable that is where the scans come into play and I guess the CA27.29.

Thank you

[hurricaneheather]

with initial dx in 2011, did KRAS-variant assay; negative for the genetic variant, comprehensive BRAC analysis; no mutation detected, and BRAC analysis Rearrangement Test; no large rearrangement detected. did Oncotype to choose treatment plan.with mets dx in 2015, did Foundation One; three genetic alterations detected, 0 therapies, and 0 clinical trails. the onc expressed she was 'not concerned' about the alterations. did a Personalized TumorGraft, by Champions Oncology, to choose treatment plan.