Avinash Kambadakone R MD, FRCR, Presenter: Nothing to Disclose

Anna Galuzzo MD, Abstract Co-Author: Nothing to Disclose

Lawrence Blaszkowsky MD, Abstract Co-Author: Nothing to Disclose

Christopher G. Willett MD, Abstract Co-Author: Nothing to Disclose

Dushyant V. Sahani MD, Abstract Co-Author: Researcher, General Electric Company

To evaluate and compare tumor vascularity changes on perfusion CT with metabolic changes on 18FDG PET in patients with advanced rectal cancer and their correlation with clinical outcome at surgery.

In this IRB approved clinical trial, 16 patients (12M: 4F, mean age 56 years; age range, 37-69 years) with advanced rectal cancer (T3N0/N1-N2M0) were included. The CTp and whole body FDG PET was performed at baseline, at 2 weeks after start of treatment and at 6 weeks after completion of treatment. For CTp, iodinated CM was injected at 7cc/sec and cine acquisition performed for 45 sec to include 2 cm of tumor. Using CTp-3 software (GE), perfusion parameters (BF, BV, MTT and PS) were estimated. Tumor SUV values were also estimated. Response to treatment was indicated by downstaging of the tumor at pathologic analysis compared to preoperative stage. The change in CTp parameters and tumor SUV at 2 week after start of treatment and after completion (6 weeks) were compared. Baseline perfusion and tumor SUV was compared between responders (R) and non-responders (NR) and their correlation with long term outcome was assessed.

At 2 weeks following antiangiogenic treatment, there was reduction in tumor perfusion (mean CTp change 22-33%, p=0.001) while no significant change in tumor SUV [mean SUV change: 11%,(6.4±3.7 vs 5.6±1.2), p=0.9] was noted. After completion of C-XRT, tumors showed significant reduction in perfusion (mean CTp change 41-72%, p<0.001) and metabolic activity [mean SUV change: 59%,(6.4±3.7 vs 2.6±1.2), p=0.005]. Tumors in responders at surgery showed a greater change in perfusion (mean change 55-82%) and metabolic activity [mean SUV change: 73.8%, (7.83±4.3 vs 2±0.8)] compared to change in perfusion (mean change 33-68%) and metabolic activity [mean SUV change: 44%, (5.24±2.3 vs 3±1.2)] in non responders (p=0.1).

CT perfusion is a more robust surrogate to evaluate early antiangiogenic activity in advanced rectal cancer while both CT perfusion and FDG PET can be used as reliable indicators to measure late tumor response following completion of treatment.

Early treatment effects to antiangiogenic drug manifest with changes in tumor perfusion on CT without substantial metabolic effects on 18-FDG PET.

Kambadakone R, A, Galuzzo, A, Blaszkowsky, L, Willett, C, Sahani, D, Tumor Perfusion or Metabolism for Predicting Early and Late Treatment Response in Advanced Rectal Cancer?.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8014162.html