Reduction of glucose metabolic activity is more accurate than change in size at predicting histopathologic response to neoadjuvant therapy in high-grade soft-tissue sarcomas.
OBJECTIVE
Change in tumor size as classified by Response Evaluation Criteria in Solid Tumors poorly correlates with histopathologic response to neoadjuvant therapy in patients with soft-tissue sarcomas. The aim of this study was to prospectively evaluate whether positron emission tomography with (18)F-fluorodeoxyglucose (FDG-PET) allows for a more accurate evaluation of histopathologic response.


METHODS
From January 2005 to January 2007, 42 patients with resectable biopsy-proven high-grade soft-tissue sarcoma underwent a FDG-PET/computed tomography scan before and after neoadjuvant treatment. Relative changes in tumor FDG uptake and size from the baseline to the follow-up scan were calculated, and their accuracy for assessment of histopathologic response was compared by receiver operating characteristic curve analysis. Histopathologic response was defined as > or =95% tumor necrosis.


RESULTS
In histopathologic responders (n = 8; 19%), reduction in tumor FDG uptake was significantly greater than in nonresponders (P < 0.001), whereas no significant differences were found for tumor size (P = 0.24). The area under the receiver operating characteristic curve for metabolic changes was 0.93, but only 0.60 for size changes (P = 0.004). Using a 60% decrease in tumor FDG uptake as a threshold resulted in a sensitivity of 100% and a specificity of 71% for assessment of histopathologic response, whereas Response Evaluation Criteria in Solid Tumors showed a sensitivity of 25% and a specificity of 100%.


CONCLUSIONS
Quantitative FDG-PET was significantly more accurate than size-based criteria at assessing histopathologic response to neoadjuvant therapy. FDG-PET should be considered as a modality to monitor treatment response in patients with high-grade soft-tissue sarcoma.
Evilevitch
Vladimir
V
Abteilung Nuklearmedizin (University of Freiburg), Freiburg, Germany.
Weber
Wolfgang A
WA
Tap
William D
WD
Allen-Auerbach
Martin
M
Chow
Kira
K
Nelson
Scott D
SD
Eilber
Fredrick R
FR
Eckardt
Jeffery J
JJ
Elashoff
Robert M
RM
Phelps
Michael E
ME
Czernin
Johannes
J
Eilber
Fritz C
FC
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000627:therapeutic use; D003131:Combined Modality Therapy; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007890:Leiomyosarcoma / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D008080:Liposarcoma / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012509:Sarcoma / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology* / Q000532:radiotherapy; D014057:Tomography, X-Ray Computed
D000970:Antineoplastic Agents; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18