Radiologic assessment of earliest, best, and plateau response of gastrointestinal stromal tumors to neoadjuvant imatinib prior to successful surgical resection.
BACKGROUND
To determine the timing of earliest, best and plateau response to neoadjuvant imatinib in patients with GIST.


METHODS
In this IRB-approved retrospective study, we included all 20 patients (10 women; mean age 61 years, range 30-83 years) with KIT-positive primary GIST who received neoadjuvant imatinib and underwent surgery between January 2001 and December 2012. Earliest (earliest time to partial response), best (percentage reduction in longest axial diameter [LAD] and volume correlated with RECIST 1.1 and volumetric criteria) and plateau (time point when there was <10% change in treatment response between two consecutive scans beyond best response) responses were analyzed on review of imaging.


RESULTS
Median tumor size at baseline was 7.2 cm (range, 3.0-31.4 cm). Median duration of neoadjuvant imatinib was 32 weeks (IQR, 16-36 weeks). Partial response was noted in 16/20 patients (median interval = 16 weeks; IQR, 7-26 weeks); 4/20 had stable disease. Median time to earliest PR was 16 weeks (IQR, 7-26 weeks). At best response, median decrease in LAD and volume were 43% (IQR, 31-48%) and 83% (IQR, 63-87%), (median interval = 28 weeks; IQR, 18-37 weeks), at which point 10 tumors were resected. Plateau response (45% [IQR, 35-45%] LAD reduction) was noted in the remaining 10 patients (median interval = 34 weeks; IQR, 26-41 weeks) before resection. Tumor size, location or risk category did not correlate with best response or time to best response.


CONCLUSIONS
Best response to neoadjuvant imatinib was seen at 28 weeks irrespective of tumor size and location. Plateau response was seen at 34 weeks, beyond which further treatment may not be beneficial.
Department of Imaging, Dana-Farber Cancer Institute, Harvard Medical School, 450 Brookline Ave, Boston, MA 02215, USA; Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA. Electronic address: stirumani@partners.org.
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Tirumani
Department of Imaging, Dana-Farber Cancer Institute, Harvard Medical School, 450 Brookline Ave, Boston, MA 02215, USA; Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA. Electronic address: ashinagare@partners.org.
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Shinagare
Department of Imaging, Dana-Farber Cancer Institute, Harvard Medical School, 450 Brookline Ave, Boston, MA 02215, USA; Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA. Electronic address: jjagannathan@partners.org.
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Jagannathan
Department of Imaging, Dana-Farber Cancer Institute, Harvard Medical School, 450 Brookline Ave, Boston, MA 02215, USA; Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA. Electronic address: kmkrajewski@partners.org.
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Krajewski
Department of Imaging, Dana-Farber Cancer Institute, Harvard Medical School, 450 Brookline Ave, Boston, MA 02215, USA; Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA. Electronic address: nramaiya@partners.org.
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Ramaiya
Department of Surgery, Division of Surgical Oncology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02215, USA; Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA. Electronic address: craut@partners.org.
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Raut
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001549:Benzamides / Q000627:therapeutic use*; D017024:Chemotherapy, Adjuvant; D013505:Digestive System Surgical Procedures / Q000009:adverse effects / Q000379:methods; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000601:surgery*; D046152:Gastrointestinal Stromal Tumors / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000601:surgery*; D006801:Humans; D000068877:Imatinib Mesylate; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy / Q000379:methods*; D010879:Piperazines / Q000627:therapeutic use*; D011743:Pyrimidines / Q000627:therapeutic use*; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate
Gastrointestinal stromal tumor; Imaging; Neoadjuvant imatinib; RECIST; Surgery