Four weeks after the completion of radiotherapy, patients are re-evaluated*. Beginning within 4-7 weeks after the completion of chemotherapy and radiotherapy, patients receive gemcitabine hydrochloride alone or in combination with another cytotoxic agent or gemcitabine hydrochloride combined with a targeted drug (e.g., erlotinib or bevacizumab) at the discretion of the oncologist. NOTE: *Patients whose imaging studies suggest potential curative resection are referred for a surgical evaluation before initiating gemcitabine hydrochloride therapy. Cohorts of 3-6 patients receive escalating doses of flavopiridol until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 3 or 2 of 6 patients experience dose-limiting toxicity. Once the MTD is determined, 10 additional patients are treated at the recommended phase II dose.