Efficacy of Pegamotecan (PEG-Camptothecin) in Localized or Metastatic Cancer of the Stomach or Gastroesophageal Junction

Inclusion Criteria: * Pathologically confirmed diagnosis of adenocarcinoma of the stomach or gastroesophageal junction. * Disease measurable in at least one dimension. * Target tumors outside of prior radiation field(s). * An Eastern Cooperative Oncology Group (ECOG) performance scale score of 0 or 1 * Adequate hematologic profile, as determined by hemoglobin, platelet, and neutrophil count. * Adequate renal function, as determined by serum creatinine and serum albumin measurements. * Adequate liver function, as determined by total bilirubin and transaminases levels. Transaminases may be \<= 5.0x ULN if due to metastatic disease in the liver. * Fully recovered from prior surgery. * No history of hemorrhagic cystitis. * No microscopic hematuria (\>10 RBC/hpf) unless documented to be due to an infection or non-bladder origin. * Capable of understanding the protocol requirements and risks and providing written informed consent. Exclusion Criteria: * Concurrent serious medical illness unrelated to tumor within the past 6 months. * Known chronic infectious disease, such as AIDS or hepatitis (screening for hepatitis and HIV will not be performed). * Positive screening pregnancy test or is breast-feeding. * Female or male subject of reproductive capacity who is unwilling to use methods appropriate to prevent pregnancy during the course of this study. * Receiving concurrent chemotherapy, investigational agents, radiotherapy, surgery, or has received wide field radiation within the previous 4 weeks. * History of another malignancy (except basal and squamous cell carcinomas of the skin and carcinoma in situ of the cervix) within the last 5 years. * Known or clinically suspected brain metastases. * Received more than one prior regimen of chemotherapy for locally advanced or metastatic adenocarcinoma of the stomach or GE junction. * Received prior neoadjuvant and/or adjuvant cytotoxic chemotherapy * Received any investigational drug within the last 30 days. * Not fully recovered from any prior, and from any reversible side effects related to the administration of cytotoxic chemotherapy, investigational agents, or radiation therapy. * Prior treatment with a camptothecin analog.