The Predictive Value of F18 FDG PET/CT and Diffusion Weighted MRI Derived Functional Parameters in Prediction of Response to Neoadjuvant Therapy in Patients with Locally Advanced Colorectal Cancer

Background: Rectal cancer is one of the most common malignancies globally, when it comes to locally advanced cases typically a patient undergoes neoadjuvant treatment fol-lowed by surgery with curative aim. But, in the new era of more customised care, tailored medicine and treatment, it is necessary to study the possibilities for assessing response ac-curately before surgery in order to provide the optimum treat-ment for each patient especially with the rise of a wait and see strategy and less intrusive surgery. Aim of Study: The purpose of this prospective study was to investigate and compare the ability of different PET CT and DWMRI functional parameters in assessing response to neoad-juvant treatment in patients with locally advanced rectal cancer (LARC). Patients and Methods: A total 30 patients with proven LARC in the national cancer institute (NCI) underwent both pre- and post-neoadjuvant therapy FDG PET/CT and pelvic DW-MRI scans. For each patient initial and post therapy SUV-max, MTV, TLG, ADC as well as ΔSUVmax, ΔMTV, ΔTLG and ΔADC were calculated, post therapy pathological results were assessed and results were correlated. Results: In post neoadjuvant therapy scans the SUVmax, SUVpeak, SUL in PET/CT and ADC values were significant-ly correlated with pathological response. Regarding % change in all functional parameters the % ΔSUV max was the sole parameter that owes a statistically significant correlation with pathological response. The final MRI tumour length and thick-ness as well as % changes in tumour length showed statistical significance in predicting response to neoadjuvant therapy. The initial ADC value is the only factor that could predict response in initial assessment. Conclusion: Both F18 FDG and DW-MRI diagnostic im-aging modalities with their functional parameters can predict neoadjuvant therapy response (p<0.05) in patients with ad-vanced colorectal cancer, however overall DW-MRI showed a relatively better specificity, positive predictive value and over-all accuracy in predicting response to neoadjuvant therapy.