The present invention provides compositions and methods for detecting and/or monitoring a disease state with polyspecific imaging agents. In a particular embodiment, provided methods may be used to assess efficacy of anti-receptor tyrosine kinase and/or anti-cancer treatments. In some embodiments, the present invention provides methods and compositions relating to polyspecific imaging agents that target neurological, tumor-associated and/or intratumoral markers. For example, the present invention provides compositions, including pharmaceutical compositions, comprising anti-receptor tyrosine kinase antibodies, or fragments or characteristic portions thereof. The present invention further provides various therapeutic and/or diagnostic methods of using anti-receptor tyrosine kinase antibodies and/or compositions.
