Multi-parametric MR Evaluation of Post Neo-adjuvant Chemo-radiation Cases of Rectal Cancer

Abstract

Introduction: In India as per ICMR|NCDIR newly diagnosed rectal cancer cases in 20211 were 15,782. Among these new cases, more cases were registered in males (9506) than females (6276). MRI is the imaging modality of choice for staging and restaging after chemo radiotherapy. Multi-parametric MRI implies addition of multiple parameters including diffusion weighted imaging, dynamic contrast enhancement, conventional MRI and specific sequences tailored to rectal cancer. As such Dynamic contrast enhanced MRI and Diffusion weighted imaging remains an active area of ongoing research. Characterization of lymph nodes based on morphologic criteria helps in diagnosing metastatic lymph nodes. Objectives: Primary objective is to establish the role of novel MRI pulse sequences and protocols in patients with rectal cancer post-treatment (neo-adjuvant chemo-radiation). Secondary objective is to evaluate post-treatment morphological components of tumour on MRI and its correlation with treatment response. Methods: Present prospective study was conducted in the Department of Radio-diagnosis of a tertiary level care. Results: Total 40 patients were enrolled in this study. Dynamic contrast enhanced and diffusion weighted sequences gave most significant results, where the exact localization of tumour was done, however in DCE MRI and DWI MRI there were 1 (97.5%) and 2 (95%) patients respectively, showed inconclusive results in T staging after post NACRT. As per the study, conventional sequences in post NACRT patients are less sensitive in T staging due to the post NACRT fibrosis and necrosis. Conclusion: Among conventional sequences oblique axial T2 weighted imaging with minimal spacing and slice thickness along with post contrast T1 images allow the most accurate assessment of residual tumor. In novel sequences DWI and dynamic contrast imaging also shows accurate results and should be added to routine sequences if possible.

Keywords

• magnetic resonance imaging
• dynamic contrast enhanced
• chemo radiation therapy
• diffusion weighted imaging