[Hormone receptor contents and tumor growth in a series of transplantable human breast carcinoma during and after radiotherapy].

The influence of radiotherapy on tumor growth and hormone receptor concentration (estrogen-, progesteron-receptor) in xenotransplanted human breast cancer is observed. Tumor growth significantly is delayed under therapy during the first 35 days after radiation. Renewed growth follows after that time. After the first days of treatment the ER and PR concentration decreases considerably and finally reaches 40% respectively 30% of the pretreatment level for a period of approximately 35 days after the end of radiotherapy. In general radiation therapy seems to affect the PR stronger than the ER. After this period ER and PR levels increase again with the regrowing tumor. The results point out that radiotherapy reduces the concentration of ER and PR in human breast cancer. Therefore the assay of steroid receptors in human breast cancer after radiation therapy is useful in predicting hormone dependency and prognosis only when receptor concentrations are positive.