G-CSF induces elevation of circulating CA 15-3 in breast carcinoma patients treated in an adjuvant setting

BACKGROUND. Cancer antigen 15-3 (CA 15-3), a circulating marker that determ ines secreted products of the polymorphic MUC1 gene, has been established a s a conveniens tool for monitoring breast carcinoma patients. METHODS. The authors investigated alterations of soluble CA 15-3 in 57 post operative breast carcinoma patients while they were receiving intensified a djuvant chemotherapy with granulocyte colony stimulating factor (G-CSF) sup port; 26 patients had American Joint Committee on Cancer (AJCC) Stage II, a nd 31 patients had AJCC Stage III breast carcinoma. Serial CA 15-3 values r ecorded thoughout the treatment were compared with baseline values, analyze d for correlation with hematologic and biochemical parameters, and compared with clinicopathologic characteristics and patient outcome. At a median fo llow-up time of 32 months, 47 of these patients remained relapse-free. RESULTS. A twofold increase of CA 15-3 was detected at the end of the secon d week of treatment, remained significantly elevated in most patients at ab ove the cutoff level of 30 U/mL throughout the treatment period (P < 0.0001 ), and subsided to pretreatment values 1-2 months after treatment cessation . CA 15-3 values were found to be associated strongly with absolute neutrop hil count, serum lactate dehydrogenase, and alkaline phosphatase. The media n values and the kinetics of tumor markers did not differ over time in rega rd to hormonal receptor status and disease recurrence. CONCLUSIONS. These data provide strong evidence that G-CSF administration c an induce elevation of CA 15-3 and indicate that false-positive results sho uld be considered when evaluating CA 15-3 in patients who are receiving G-C SF. It is speculated that this phenomenon occurs through the induction of M UC1 antigen of unknown origin by G-CSF. Experimental investigation of this clinical observation is warranted. (C) 2001 American Cancer Society.