The effect of short-term cyclophosphamide on estrogen therapy in metastatic breast cancer

Stimulation of tumor growth and induced hypercalcemia both may occur during the initiation of estrogen therapy in breast cancer. This study was conducted to determine whether cyclophosphamide (CTX) as an adjuvant to estrogen therapy might (1) prevent induced hypercalcemia or (2) achieve a higher tumoricidal effect during the phase of tumor stimulation. Fifty postmenopausal women with inoperable or recurrent disseminated breast carcinoma were divided into two random groups. Results could be evaluated in 44 patients; 21 received diethylstilbestrol (DES), and 23 received DES plus a 4-week course of cyclophosphamide (DES + CTX). The response rate was 5/21 (24%) in the DES group and 8/23 (35%) in the DES + CTX group (p greater than 0.05). The median duration of response for both groups was 9 months. The survival rate at 24 months was 52% in the DES group and 25% in the DES + CTX group (p = 0.05). Induced hypercalcemia occurred in 3 patients treated with DES + CTX. Short-term cyclophosphamide adjuvant to estrogen therapy did not prevent induced hypercalcemia nor prolong the duration of response or survival.