Gemcitabine and Pemetrexed in Primary Unknown Adenocarcinoma

Inclusion Criteria: * Histologically proven adenocarcinoma * No obvious primary on routine history, physical examination, and investigations * Patients greater than or equal to 18 years of age * ECOG Performance Status 0-1 * Patients requiring opioids for pain control must be on a fixed analgesic regimen aimed to provide adequate pain control with no more than 3 breakthrough (supplemental) doses of analgesics per day to control pain; Additional inclusion criteria due apply, but not are not listed here. Exclusion Criteria: * Have received treatment within the last 30 days with a drug that has not received regulatory approval for any indication at the time of study entry * Unable to stabilize pain and analgesics for a period of 7 days prior to starting study treatment * Prior treatment with chemotherapy * Bilirubin greater than or equal to 40 mol/L * AST or ALT greater than or equal to 5 times the upper limit of normal (ULN); Additional exclusion criteria due apply, but not are not listed here.