Monitoring Therapy in Advanced Disease

Following the commencement of therapy for advanced disease, it is important to know as quickly as possible if the patient is responding to the treatment. If the patient is benefiting, clearly, treatment should be continued. If, on the other hand, treatment is not effective, an alternative therapy might be given. If an alternative therapy is unavailable, these patients could be willing to participate in clinical trials or they could decide to avoid further therapy.

A convenient and relatively inexpensive approach for helping to establish response is by measuring markers such as CA 15-3 or CEA. Generally, decreasing marker levels correlate with tumour response, while increasing markers levels correlate with tumour regression. According to the EGTM guidelines, markers should be measured prior to every chemotherapy course and at least at three-monthly intervals for patients receiving hormone therapy. The EGTM defines an increase in marker concentration of at least 25% to be significant. It is recommended that such an increase be confirmed with a second specimen obtained within a month. If the increase is confirmed, this provides evidence of progressive disease. Similarly, a confirmed decrease in serum levels of more than 50% was stated to be consistent with tumour regression.

In contrast to the EGTM recommendations, the ASCO guidelines state that neither CA 15-3 nor CEA should be routinely used for monitoring therapy in patients with advanced breast cancer.

Also, according to these guidelines:

Conclusion

It is clear from the above that tumour markers play a key role in the care of patients with breast cancer. Tissue markers such as hormone receptors and HER- 2 are now mandatory in determining prognosis and therapy planning. For post-operative surveillance, serum markers such as CA 15-3 and CEA can be used to detect recurrent or metastatic disease at an early stage. These serum makers can also aid the monitoring of therapy in patients undergoing treatment for advanced disease. Markers are particularly important in monitoring disease that cannot be evaluated by standard radiological criteria (e.g. those with irradiated lesions, pleural effusion, ascites, lytic bone disease and sclerotic bone disease).