Somatostatin receptor incidence and distribution in breast cancer using receptor autoradiography: Relationship to egf receptors

Somatostatin receptors (SS‐R) were measured with in vitro receptor autoradiography using the SS analog 125I‐[Tyr3]‐SMS 201‐995 as radioligand in 342 breast‐tumor samples. In a group of 158 “small” tumor samples (mean section surface: 14 mm2 ± 0.4; mean ± SEM), 34 tumors (21%) were SS‐R positive. In a group of 72 “large” tumor samples (mean size: 180 mm2 ± 8; mean ± SEM), 33 tumors (46%) were SS‐R positive. In this second group, more than half of the tumors had a non‐homogeneous distribution of SS‐R, i. e., tumor regions within SS‐R positive tumors were SS‐R negative. In a group of 48 additional patients, we could show that primaries and their metastases, or double primaries from right and left breasts, or 2 primaries resected consecutively, could both occasionally be SS‐R positive. Finally, in 71 SS‐R‐positive primary tumors, 18 tumor samples were found to have simultaneously Epidermal Growth Factor receptors (EGF‐R); in 12 of these 18 cases, the 2 receptor types were not topographically overlapping. Whereas SS‐R were located on tumor tissue, EGF‐R were often seen on adjacent normal lobules and ducts. These results show that a subgroup of breast tumors contain SS‐R, in several cases non‐homogeneously distributed. Their location does not coincide with that of EGF‐R. Metastasis of SS‐R‐positive primaries may be SS‐R‐positive, as are sometimes second primaries. For evaluation of SS‐R incidence and distribution, autoradiography is of advantage, specially if it is performed on large tumor samples, since it allows precise identification of the tissue elements containing these receptors.