FDG-PET/CT imaging predicts histopathologic treatment responses after the initial cycle of neoadjuvant chemotherapy in high-grade soft-tissue sarcomas.
OBJECTIVE
In patients with soft-tissue sarcoma (STS), the early assessment of treatment responses is important. Using positron emission tomography/computed tomography (PET/CT) with [(18)F]fluorodeoxyglucose (FDG), we determined whether changes in tumor FDG uptake predict histopathologic treatment responses in high-grade STS after the initial cycle of neoadjuvant chemotherapy.


METHODS
From February 2006 to March 2008, 50 patients with resectable high-grade STS scheduled for neoadjuvant therapy and subsequent tumor resection were enrolled prospectively. FDG-PET/CT before (baseline), after the first cycle (early follow-up), and after completion of neoadjuvant therapy (late follow-up) was done. Tumor FDG uptake and changes were measured by standardized uptake values. Histopathologic examination of the resected specimen provided an assessment of treatment response. Patients with > or = 95% pathologic necrosis were classified as treatment responders. FDG-PET/CT results were compared with histopathologic findings.


RESULTS
At early follow-up, FDG uptake decreased significantly more in 8 (16%) responders than in the 42 (84%) nonresponders (-55% versus -23%; P = 0.002). All responders and 14 of 42 nonresponders had a > or = 35% reduction in standardized uptake value between baseline and early follow-up. Using a > or = 35% reduction in FDG uptake as early metabolic response threshold resulted in a sensitivity and specificity of FDG-PET for histopathologic response of 100% and 67%, respectively. Applying a higher threshold at late follow-up improved specificity but not sensitivity. CT had no value at response prediction.


CONCLUSIONS
A 35% reduction in tumor FDG uptake at early follow-up is a sensitive predictor of histopathologic tumor response. Early treatment decisions such as discontinuation of chemotherapy in nonresponding patients could be based on FDG-PET criteria.
Ahmanson Biological Imaging Division, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095-1782, USA.
Matthias R
MR
Benz
Johannes
J
Czernin
Martin S
MS
Allen-Auerbach
William D
WD
Tap
Sarah M
SM
Dry
David
D
Elashoff
Kira
K
Chow
Vladimir
V
Evilevitch
Jeff J
JJ
Eckardt
Michael E
ME
Phelps
Wolfgang A
WA
Weber
Fritz C
FC
Eilber
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000627:therapeutic use; D004317:Doxorubicin / Q000627:therapeutic use; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D005500:Follow-Up Studies; D006801:Humans; D007069:Ifosfamide / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D012509:Sarcoma / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000473:pathology; D012680:Sensitivity and Specificity; D012983:Soft Tissue Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000473:pathology; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D000093542:Gemcitabine
D003841:Deoxycytidine; D019788:Fluorodeoxyglucose F18; D004317:Doxorubicin; D007069:Ifosfamide; D000093542:Gemcitabine