505 Background: Pathologic complete response (pCR) after neoadjuvant chemoradiation has been observed in 15% to 30% of patients with locally advanced rectal cancer. The utility of FDG PET/CT scans in the management of patients with stage II or III rectal cancer is not well defined. The objective of this study is to determine if FDG PET/CT can be used to predict pCR and disease-free survival in patients receiving neoadjuvant chemoradiation with locally advanced rectal cancer. Methods: A retrospective chart review was conducted in patients with endorectal ultrasound-staged T3 to T4 rectal tumors who underwent preoperative and postoperative FGD PET/CT imaging. All patients were treated with neoadjuvant chemoradiotherapy (CRT). Maximum standardized uptake value (SUV) of each tumor was recorded. Logistic regression was used to analyze the association of pre-CRT SUV, post-CRT SUV, % SUV change, and time between therapy and surgery in comparison to pathological complete response. Kaplan-Meier estimation was used to look for significant predictors of survival. Results: Seventy patients (mean age 62; 42M:28F) with preoperative stage T3Nx (n = 60) and T4Nx (n = 10) underwent pre-CRT and post-CRT FDG PET/CT scans between November 2002 and March 2009. All patients underwent definitive surgery after therapy with standard pathologic evaluation.The pCR rate was 26%. Median pre-CRT SUV was 10.5 while the median post-CRT SUV was 4.05. Patients with pCR had a lower mean post-CRT SUV compared to those without pCR (2.7 vs. 4.5, p = 0.02). Median SUV decrease was 61% (range 6% to 95%) and was significant in predicting pCR (p = 0.004). Patients with a pCR had a greater time interval between neoadjuvant therapy and surgery (median 57 days vs. 50 days) than those without (p = 0.05). Furthermore, patients with post-CRT SUV < 4 had a lower local recurrence rate compared to those with post-CRT SUV > 4 (p = 0.03). Patients with SUV decrease > 61% had improved overall survival at mean follow-up of 39 months than those without (p = 0.01). Conclusions: PET/CT can predict response to neoadjuvant chemoradiation in patients with locally advanced rectal cancer. Pre-CRT SUV was the only predictor of disease-free survival. No significant financial relationships to disclose.
Early prediction of pathological response in locally advanced rectal cancer based on sequential 18F-FDG PET
