Sudden surge in CA 15-3

Hello,

i am quite concerned. After experiencing a lot of breast and back pain due to a large epithesis past 3 weeks, during the course of 2 last weeks, levels of CA 15-3 spiked quite high, test 1 = 30U/ml after 2 weeks, test 2 - over 90U/m. Currently on capecitabine after TNBC T2N1M0 after mastectomy and radiation. Primary tumour wasnt producing CA 15-3. CAE in norm. PET scan ordered.

Are such spikes even possible witout the possibility of not being malignant?

Thanks in advance