Use of molecular imaging to predict clinical outcome in patients with rectal cancer after preoperative chemotherapy and radiation.

PURPOSE

To correlate changes in 2-deoxy-2-[18F]fluoro-d-glucose (18-FDG) positron emission tomography (PET) (18-FDG-PET) uptake with response and disease-free survival with combined modality neoadjuvant therapy in patients with locally advanced rectal cancer.

METHODS AND MATERIALS

Charts were reviewed for consecutive patients with ultrasound-staged T3x to T4Nx or TxN1 rectal adenocarcinoma who underwent preoperative chemoradiation therapy at Fox Chase Cancer Center (FCCC) or Robert H. Lurie Comprehensive Cancer Center of Northwestern University with 18-FDG-PET scanning before and after combined-modality neoadjuvant chemoradiation therapy . The maximum standardized uptake value (SUV) was measured from the tumor before and 3 to 4 weeks after completion of chemoradiation therapy preoperatively. Logistic regression was used to analyze the association of pretreatment SUV, posttreatment SUV, and % SUV decrease on pathologic complete response (pCR), and a Cox model was fitted to analyze disease-free survival.

RESULTS

A total of 53 patients (FCCC, n = 41, RLCCC, n = 12) underwent pre- and postchemoradiation PET scanning between September 2000 and June 2006. The pCR rate was 31%. Univariate analysis revealed that % SUV decrease showed a marginally trend in predicting pCR (p = 0.08). In the multivariable analysis, posttreatment SUV was shown a predictor of pCR (p = 0.07), but the test results did not reach statistical significance. None of the investigated variables were predictive of disease-free survival.

CONCLUSIONS

A trend was observed for % SUV decrease and posttreatment SUV predicting pCR in patients with rectal cancer treated with preoperative chemoradiation therapy. Further prospective study with a larger sample size is warranted to better characterize the role of 18-FDG-PET for response prediction in patients with rectal cancer.