have you a CT scan yet? I've been on Enhertu for 20 cycles, which covers more than a year of 3-week infusions. Although around cycle 13 the CT scans showed NED, my ca 19-9 kept rising and I couldn't get a satisfactory answer so I asked Dr. Google. I read medical reports, not blogs. And this is what they call shedding of cancer from your tumor. My recent blood test showed that the ca 19-9 had declined to normal levels, finally!
So, keep at the treatment.