Abstract: Disclosed are methods and compositions for the diagnosis and treatment of diseases associated with aberrant expression of a somatostatin receptor (e.g., cancer) or with increased production of a factor regulatable by somatostatin (e.g., acromegaly). The compounds of the invention are of the general formulae: ##STR1## wherein P is a somatostatin peptide analog which binds to a somatostatin receptor,Y is D-tyrosine, L-tyrosine, or desamino-tyrosine,n is an integer from 1 to 32, inclusive,each q, independently, is an integer from 1 to 32, inclusive, and each s, independently, is an integer from 1 to 32, inclusive, where q and s can be the same or different, andX is of the formulaD--NH.sub.2 --CH(CH.sub.2).sub.m NH.sub.2 --CO.sub.2 H orL--NH.sub.2 --CH(CH.sub.2).sub.m NH.sub.2 --CO.sub.2 H,wherein m is an integer from 1 to 10, inclusive.

Abstract: Broadly, the present invention is directed to a method for the detection and differentiation of neoplastic tissue in a patient suspected of having neoplastic tissue. The method includes the administration of a radiolabeled somatostatin congener to the patient and accessing the patient with a radiation detection probe for determining tissue exhibiting elevated levels of radiation, viz., neoplastic tissue. However, before subjecting the patient to such administration, an initial determination preferably is made as to whether the radiolabeled somatostatin congener will bind to the tumor site, i.e., whether somatostatin receptors are associated with the neoplastic tissue. This is conveniently done with a wide variety of endocrine tumors, which release peptides or hormones, referred to as "biochemical markers. " In order to make this determination, initially a biochemical marker-inhibiting dose of unlabeled somatostatin congener is administered to the patient.