Secondary Breast Cancer CA15-3

I was diagnosed with secondary breast cancer eleven days ago and my CA15-3 tumor marker reading was 157.  I have read that the tumor marker is used by oncologists to get an idea of the amount of cancer in a patients system and to measure the effectiveness of treatment.  Can anyone please tell me whether they had similar tumor marker readings at diagnosis and what treatments were effective?


From what I know about tumour markers (and it’s not a lot!) I’d say obviously the lower they are the better. However what might be one person’s starting point may not be the same as someone else’s. I’ve read that even different laboratories will give different results for the same patient. What the oncologists use them for is a non intrusive sign that a treatment is working as generally the trend will be a reduction in the number. Having said that mine have before now risen when a treatment was still working. My hospital didn’t used to use them but they do now so it doesn’t matter for how long you might have had SBC it will still be the trend they are looking at. Any real anomalies or sharp rises would be invested further generally with scans. As tumour markers are tracked using blood tests they don’t need any further intrusion.

Hope that helps and someone else may come along with a more comprehensive explanation.

Hi Icemaiden,

I couldn’t give you a more comprehensive explanation than Nicky already has as her wealth of knowledge and clear way of explaining things is top notch in my opinion.

I was diagnosed nearly one year ago and although I’ve had regular blood tests I wasn’t aware of my tumour markers until 3 weeks’ ago when I had my first face to face appointment with my oncologist since March. He told me that pre-treatment, prior to December 2019, my markers were 112 and are now at 32. 

I am ER+ (Oestrogen Receptive) and my treatment is Palbociclib and Letrozole. I am peri menopausal so also have Zoladex injections to shut down my ovaries. 

Best wishes to you xxxx.

Hi icemaiden

The AC-15.3 are proteins produced by cancer cells. By the amount of them in our blood oncologists can see that cancer is present in our body, or it maybe active. However, the amount of AC-15.3 in the blood doesn’t indicate how many metastases someone has, or how big they are. AC-15.3 mostly indicates that cancer is active, but it’s only guidance! In some case, like it was previously mentioned, the amount can change, but tumors would stay stable. That’s why oncologists monitor us closely and order scans to get a better picture.

I hope it will help a bit. xx