F-Tryptophan PET/CT in Human Cancers

Inclusion Criteria: * Age ≥18 years. * Targeted lesion (tumor) is at least 1 cm in diameter as shown by clinical imaging. * Patient is able to lie in the PET/CT scanner for at least 70 minutes while undergoing scanning. * Women of childbearing potential must not be pregnant or breastfeeding. * Recent anatomic imaging with visible disease (tumor) for comparison with the PET/CT. . * Physical exam within 28 days of PET imaging, CBC and Multiphasic (including electrolytes, BUN, creatinine, total bilirubin, AST and ALT) within 14 days. * Patients must sign an informed consent indicating that they are aware of the investigational nature of this study. Inclusion Criteria Specific for Intracranial Tumors \- Clinical and MRI diagnosis of an intracranial lesion suspicious for a brain tumor, including gliomas or metastatic brain tumors; primary, residual, or recurrent brain tumors (judged by clinical imaging) will qualify. Inclusion Criteria Specific for Extracranial Neuroendocrine Tumors: * Histopathologically confirmed, well-differentiated metastatic neuroendocrine tumor. * ECOG performance status of 2 or better. * Patients receiving stable-dose somatostatin analogs (SSAs, long-acting release \[LAR\], depot) for \>3 months before enrollment may be enrolled on the study, but such treatment is not required. Inclusion Criteria specific for Extracranial Primary Breast tumors: * Clinical and radiological diagnosis of a breast cancer * ECOG performance status of 2 or better. Inclusion Criteria specific for Rectal tumors: * Histologically confirmed colorectal cancer, which is located in the rectum. * ECOG performance status of 2 or better. Exclusion Criteria: * Patients who are pregnant or lactating are excluded. Exclusion Criteria Specific for Intracranial Tumors: * Severe increased intracranial pressure, status epilepticus, or other symptoms requiring emergency or urgent intervention. * Tumor surgery or radiation within 1 month prior to the PET scan Exclusion Criteria Specific for Extracranial Neuroendocrine Tumors: * Tumor-directed therapy within 3 months to the area of planned imaging. * Ongoing treatment with a targeted agent (e.g., sunitinib or everolimus) or receiving cytotoxic chemotherapy (e.g., capecitabine or temozolomide). * Use of telotristat ethyl (a tryptophan-hydroxylase inhibitor) within one month. Exclusion Criteria for Extracranial Primary Breast tumors: -Recent (within 1 month) tumor resection or radio-chemotherapy (acute/subacute post-treatment inflammatory changes may cause false positive increases on PET). Exclusion Criteria for Rectal tumors: -Active inflammatory bowel disease (Crohn's or Ulcerative colitis) involving the rectum.