Olof H. Pearson

We hypothesize that the presence of progesterone receptors in human breast tumors may be a sensitive marker for predicting response to endocrine therapy. Progesterone receptors were found in 56 percent of tumors with estrogen receptors, but were absent in tumors without estrogen receptors. Preliminary clinical correlations show that only those breast tumors with progesterone receptors regressed after endocrine therapy.

Breast cancer is often hormone responsive, since growth or regression of tumors can often be modulated by appropriate endocrine manipulations. Estrogen and progesterone appear to be major hormones involved in regulation of breast tumor growth. It has been recently argued that a more accurate marker of hormonal responsiveness might result if an end product of an intact estrogen response system were measured instead of the initial hormone binding step. Progesterone receptor (PgR) has been investigated in this regard since it can be readily measured in human breast tumors and there is clear evidence in experimental breast tumor model systems that PgR is under acute estrogen control. PgR is rarely found in ER- metastatic breast tumors but is present in approximately 59% of ER+ metastatic tumors, especially in those tumors with high levels of ER. Preliminary clinical correlation of ER, PgR and response to endocrine therapy is encouraging. The response rate is significantly higher if the tumor contains both ER and PgR than if the tumor contains ER alone.

Assessment of the rates of disappearance of endogenous LH and HCG from serum following complete surgical hypophysectomy and removal of the placenta was made. The hormone levels were measured by a specific radioimmunoassay. The disappearance rates for both LH and HCG appear to follow a double exponential curve although there may be a possible additional exponential. The initial disappearance involves a fast process (t½ about 21 min for LH, t½ about 11 hr for HCG) followed by a slower process of disappearance (t½ about 235 min for LH, t½ about 23 hr for HCG), which probably reflects the distribution of these hormones in at least 2 compartments.

The presence of estrogen receptors in breast cancers is now accepted as a predictor of extended disease-free survival, but the relative value of progesterone receptors for this purpose has not been established. We have examined both receptors along with other risk factors in 189 patients receiving adjuvant therapy for Stage II breast cancer. The presence of either estrogen receptors or progesterone receptors was positively correlated with disease-free survival when analyzed separately, whether or not the adjuvant regimen included an endocrine component. However, when estrogen receptors and progesterone receptors were analyzed together in multivariate models, the presence of progesterone receptors was more significant than that of estrogen receptors for predicting time to recurrence, regardless of what other variables were included in the model. These data suggest that determination of the progesterone-receptor concentration is of equal or greater value than determination of the estrogen-receptor concentration for predicting the disease-free survival of patients with breast cancer. Future trials should include measurement of progesterone receptors.

We report an incidence of thrombosis of 17.6% in 159 patients treated with a five-drug chemotherapy regimen (cyclophosphamide, methotrexate, 5-fluorouracil, vincristine, and prednisone) for Stage IV breast carcinoma. Chi-squared analysis of risk factors for thrombosis (ambulatory status, obesity, family history, smoking, diabetes mellitus, hypertension, liver dysfunction, thrombocytosis, and previous endocrine therapy) showed no difference between the patients who had a thromboembolic event and those who did not. Statistical analysis revealed that a significantly higher incidence of thrombosis occurred during the chemotherapy regimen than when off this regimen (P less than 0.05). Detailed coagulation studies done prospectively on 10 patients receiving the five-drug chemotherapy regimen compared with 10 control patients showed a significantly elevated Factor VIII antigen:activity ratio in the group receiving the chemotherapy regimen compared with the control group and normals. These results implicate the chemotherapeutic regimen in the pathogenesis of the increased incidence of thrombosis. The pathophysiology of thrombosis in settings such as this awaits better in vitro tests defining the "hypercoagulable state."