Will the NOS recognize both dissolving and removable stitches? Perhaps if the OP's are dissolving, that's what the doctor is referring to?

Also, what's the difference between a surgical and regular bra? Does the surgical one have some sort of prosthetic? If that's the case, perhaps consider wearing a thin shirt between your skin and that bra? That way you can even take it off and put it through the x-ray machine; just make sure your outer shirt is loose enough if you're self conscious about your appearance (though that doesn't sound like the case).

Lastly, if you are hassled at all, make sure you remind the TSO that if they spend too many days operating the cancer machines, this may be them in a few years.