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Tumor Shrinkage Doesn't Predict Response to Imatinib Therapy in Patients With Gastrointestinal Stromal Tumors: Presented at ESMO
By Charlene Laino
VIENNA, AUSTRIA -- November 4, 2004 -- Lack of progression is the most clinically significant predictor of a patient's response to imatinib in patients with gastrointestinal stromal tumours (GIST), a new analysis shows.
While clinicians traditionally use tumour shrinkage to assess the anticancer activity of a given therapy, the new study suggests that, at least in this instance, the paradigm does not fit, said co-investigator Stan N. Finkelstein, MD, a senior research scientist at Massachusetts Institute of Technology Sloan School of Management in Cambridge, Massachusetts, United States.
"If you have a patient with GIST on imatinib and the disease is not progressing, it is worth keeping therapy up -- even if you don't see tumour shrinkage on radiological scans," Dr. Finkelstein said. "Patients with so-called stable disease do just as well as those who have a partial or complete response."
The study, led by George Demetri, MD, an oncologist at the Dana-Farber Cancer Institute in Boston, Massachusetts, United States, was presented here on November 1st at the 29th European Society for Medical Oncology Congress.
The analysis, which utilised data from the American-Finnish phase 2 trial comparing 2 doses of imatinib in patients with inoperable or unresectable GIST, included a total of 147 patients. One patient achieved a complete response, 67% attained a partial response, and 16% demonstrated prolonged stable disease. The drug failed to control the disease in 12% of patients with progressive disease, and 5% were not evaluable for response, Dr. Finkelstein said.
At 21 months follow-up, 92% of patients with stable disease were still alive, compared with 95% of those with a partial response – a nonsignificant difference, he said. The patients with progressive disease had a significantly lower survival rate of 24%.
While the overall median survival has not yet been observed in the trial, an exponential survival curve fitted to the data suggests that it will be about 69 months, he added. In comparison, the median survival of GIST patients never treated with imatinib has historically been estimated at 12 months to 19 months, Dr. Finkelstein concluded.
[Presentation title: Lack of Progression is the Most Clinically Significant Measure of a Patient's Clinical Benefit: Correlating the Effects of Imatinib Mesylate Therapy in Gastrointestinal Stromal Tumor (GIST) With Survival Benefits. Abstract 764P]
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