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Resecting residual gastrointestinal stromal tumors improved survival



Major Finding: Time to tumor progression was 88 months in 42 patients who had surgery for residual disease and 42 months in 92 patients given imatinib alone. Metastases in the peritoneum were present in 41% of the imatinib-and-surgery group and 61% of the imatinib-only group.

Data Source: Retrospective study of 134 patients with metastatic or recurrent gastrointestinal tumors who showed at least 6 months of disease stabilization or response to imatinib, 42 of whom had residual tumors resected.

Disclosures: Dr. Park reported having no financial disclosures.

SAN FRANCISCO – Surgically removing residual gastrointestinal stromal tumors in patients who respond to imatinib therapy significantly increased time to tumor progression to 88 months, compared with 43 months using imatinib alone, based on findings from a retrospective study of 134 patients.

After controlling for the effects of other risk factors, the surgery decreased threefold the likelihood of disease progression and decreased fivefold the risk of death, Dr. Seong Joon Park reported in a press briefing sponsored by the American Society of Clinical Oncology (ASCO). The press conference was held in advance of at a meeting on gastrointestinal cancers sponsored by ASCO and three other cancer organizations.

The findings support the widely adopted practice of removing residual tumors in these patients, despite the retrospective and observational design of the study, Dr. Park said. A prospective European study of similar design to this one terminated early due to poor patient enrollment. "It’s really hard to conduct a prospective study of this design," said Dr. Park of Asan Medical Center, Seoul, South Korea.

He and his associates reviewed the records of patients who showed at least 6 months of disease stabilization or response to imatinib (Gleevec) treatment, 92 of whom got the drug treatment alone and 42 of whom underwent surgery to remove residual tumors after a median of 19 months of imatinib therapy. The imatinib therapy was restarted after surgery. Median follow-up for the cohort as a whole was 59 months.

"This treatment strategy is worth trying as a clinical practice if the medical center is large enough to have an experienced multidisciplinary team and to have low morbidity and mortality associated with surgery," he said.

Each year, approximately 5,000 new cases of gastrointestinal stromal tumors are diagnosed in the United States, most often in the stomach and small intestine, though they can occur anywhere in or near the GI tract. Imatinib typically is first-line therapy, and 80%-85% of patients will respond to the treatment, he said. A majority of patients who respond to imatinib will have residual tumors, however, which are believed to contribute to the development of drug resistance, leading to the hypothesis that removing the residual tumors would improve survival.

In general, one-third of patients are candidates for surgical removal of residual lesions, depending on the tumor size and other tumor and patient characteristics, Dr. Park said.


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Surgery adds to targeted molecular therapy

GI stromal tumors are an uncommon type of gastrointestinal tumor that can arise at many different places within the GI tract. This disease is notable because it’s really been a triumph of molecularly targeted therapy with imatinib (Gleevec), a drug that targets a particular molecular abnormality present in GI stromal tumors. Because of this, there is an extremely high response rate in patients with GI stromal tumors and drug therapy can control the disease for years.

Unfortunately, resistance ultimately develops to imatinib. This study provides provocative evidence that taking an aggressive approach surgically in addition to medical treatment with imatinib may result in longer survival of patients with GI stromal tumors.

Dr. Neal J. Meropol is chief of hematology and oncology at Case Western Reserve University, Cleveland. He gave these comments as moderator of the press briefing. He has been a consultant or advisor to Precision Therapeutics.

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