Patients who complete the initial phase (described above) of the study will be eligible to participate in an extension phase. The purpose of the extension phase of the study is to give patients who participated in the phase IIa clinical trial of Gleevec at the Hospital for Special Surgery the opportunity to continue Gleevec treatment if both the treating physicians and the patient are in agreement that Gleevec had acceptable safety and tolerability, as well as possible efficacy during the initial year of therapy.