Low Risk Oncotype, High Risk Mammaprint

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Loomisgal
Loomisgal Member Posts: 24
edited December 2021 in Stage I Breast Cancer

Hello all! with a low Oncotype 11 for Early stage ER+, very small tumor (.04) four years ago we chose to not do hormone therapy. I had severe sciatica, brain injury, etc. My oncologist and I thought it reasonable. Four years later, I conquered sciatica and brain issues much better so I wanted to go on hormone blockers. Recommended mammaprint to see if I was ultra low, would not proceed. Mammaprint came back HIGH RISK now. Has anyone heard of this? I started raloxifene but it seems I may need Femara. My oncologist didn't want to change course so I am looking for a new one familiar with Mammaprint. I can't believe this is happening.

Anyone had any experience with discordant tests? Please help!!

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  • Beesie
    Beesie Member Posts: 12,240
    edited December 2021

    It can happen.

    "Of the 50 ODX low RS cases, 33 were low risk by MP (66 % agreement)" https://ascopubs.org/doi/abs/10.1200/jco.2015.33.15_suppl.11017

    "Overall, 30% of cases showed a major discordance such as low risk for one assay and high risk for another." https://cancerres.aacrjournals.org/content/77/4_Supplement/P6-09-45

    What was the size of your tumor? 0.4cm (i.e. 4mm) or .04cm? Even at 4mm, it is questionable as to whether there was enough tissue to do a valid Oncotype test, never mind both an Oncotype test and a Mammaprint test. This is why Oncotype testing is not usually done for tumors smaller than 5mm. To me, that would be another question - are these results valid/accurate?


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  • Loomisgal
    Loomisgal Member Posts: 24
    edited December 2021

    Hi Beesie, thank you so much for the response! My tumor was 0.4cm. I had not realized that there might not be enough tissue for accurate testing. Great question to ask! Unfortunately, my oncologist of 4 years is not well-versed on Mammaprint and therefore referred me out to UCSF. First consult with the new onco and it was clear that he was biased toward Oncotype (had been a developer) and will order a BCI test in a couple of months as sort of a tie breaker. I am asking to be referred to the onco at UCSF who helped develop Mammaprint. I don't want to lose anymore valuable time and it sees that Letrozole is most appropriate and to get on it soon.

    Thank you again for your insight!

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