Some patients that don’t have metastatic disease will have large or difficult to remove tumors at the time of diagnosis. In cases where surgery seems likely to cause significant loss of function, medical treatment with Gleevec can be considered prior to surgery.
Such cases might include total removal of the stomach. Other areas that are good candidates for neoadjuvant Gleevec include tumors of the esophagus and rectal tumors. Gleevec has a high response rate, with about 2/3 of patients experiencing significant shrinkage.
Patients must be monitored closely to ensure that they are not progressing.
According to the current treatment guidelines (JCCN), “The role of preoperative imatinib for treating primary localized GIST is a matter of surgical and medical discretion. In many patients with very large localized GISTs, the disease can reasonably be considered unresectable without risk for unacceptable morbidity or functional deficit. Therefore, using imatinib as the first-line therapy to downstage the tumor is possible. Preoperative imatinib is recommended for both large tumors and poorly positioned small GISTs that are considered marginally resectable on technical grounds. Patients with primary localized GIST whose tumors are deemed unresectable should also start imatinib. Two randomized phase II trials have evaluated the safety and efficacy of imatinib as preoperative therapy for primary GIST.”
Caution: Tissue taken after surgery from patients treated with neoadjuvant Gleevec cannot be used to estimate risk of recurrence. The mitotic rate may be lower (due to effective Gleevec treatment) and tumor size may be smaller. Tissue taken from a core needle biopsy prior to neoadjuvant treatment may also be problematic as the needle sample may not contain tissue with the highest mitotic rate (and it may thus underestimate risk).