Aug 12, 2019 08:25AM - edited Aug 12, 2019 08:28AM by gingerstx
I am in my 8th year on Femara/Letrozole. Although I'd continued taking it after my 5th year, last year I decided I wanted to stop taking any meds I didn't really need. To see if this med fit in that group, my MO suggested I take the Prosigna assay. It is performed on preserved tissue that was removed during the original biopsy or surgery and looks at the activity of 58 genes (called the PAM50 gene signature) to estimate the risk of distant recurrence of hormone-receptor-positive breast cancer from 5 to 10 years after diagnosis after 5 years of hormonal therapy treatment in postmenopausal women. Based on these activity levels, Prosigna assay results are reported as a risk of recurrence (ROR) score from 0 to 100 in two ways:
- node-negative cancers are classified as low (0-40), intermediate (41-60), or high (61-100) risk
- node-positive cancers are classified as low (0-40) or high (41-100) risk
My test showed a score of 67 out of 100 which placed me in the high risk category with an estimated 16% (range 11-22%) 10 year risk of distant recurrence outside of the breast and/or armpit area (eg lung, liver, bone etc). This estimate is different from that of the Oncotype DX score (7%) because the test's characteristics (it tests 50 genes) and the validation population are quite different. The Prosigna essay evaluates outcomes of endocrine therapy whereas the Oncotype DX tests the utility of chemotherapy (which I'd not had to have). Since I seemed to be tolerating letrozole well, and given these results, my doctor suggested that I remain on letrozole for 10 years. He also recommended continuing calcium and vitamin D supplements and that we monitor my bone density closely.