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I am hoping to help explain. Your first question is in regard to those who are resistant to Herceptin from the very beginning. Some reasons for this include that some of us may have the P95 truncated version of the external cellular domain (the receptor on the outside of the cancer cell is misshapen or missing altogether so that Herceptin cannot bind there). Another reason may also be that you may not be FISH positive and may not really be Her2+ at all and another mechanism is driving the cancer. Also, you may be Her1+, ER+, PR+ IGR+ or tons of other positive receptors we know nothing about yet and you are only blocking Her2 (and perhaps the hormonals if hormone positive).
For the second part - acquiring resistance over a long period of time. This may actually have to do with the cancer further mutating (life will find a way) and the cancer may become ER/PR positive (if you started out as negative) or it becomes positive for something else (Her1 or something that is still undiscovered).
Tykerb, since it works on the inside of the cancer cell versus the outside would help with those who have abnormal or missing Her2 receptors on the outside. But like Herceptin resistance over time, I suspect the same would be true with any biological drug (like Tykerb or others) that another mechanism would take over UNLESS the drug actually killed all the cancer cells and this has happened of course. But if it only shrinks the tumor and then creates stable disease, I think resistance will occur at some point. Remember though, resistance does not mean that Herceptin (or Tykerb) does not bind to the intended site but rather, a different mechanism is fueling the cancer to grow.
I hope this helps
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Kind regards
Becky
Found lump via BSE
Diagnosed 8/04 at age 45
1.9cm tumor, ER+PR-, Her2 3+(rt side)
2 micromets to sentinel node
Stage 2A
left 3mm DCIS - low grade ER+PR+Her2 neg
lumpectomies 9/7/04
4DD AC followed by 4 DD taxol
Used Leukine instead of Neulasta
35 rads on right side only
4/05 started Tamoxifen
Started Herceptin 4 months after last Taxol due to
trial results and 2005 ASCO meeting & recommendations
Oophorectomy 8/05
Started Arimidex 9/05
Finished Herceptin (16 months) 9/06
Arimidex Only
Prolia every 6 months for osteopenia
NED 18 years!
Said Christopher Robin to Pooh: "You must remember this: You're braver than you believe and stronger than you seem and smarter than you think"
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Please explain....
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