Karthik Ganesan1, Shivsamb Jalkote1, Ankit Jain1, Alam Shah1, Slesha Bhalja1, Balaji Ganeshan2, and Swarup Nellore1
1Sir.H.N.Reliance Foundation Hospital & Research Center, Mumbai, India, 2Institute of Nuclear Medicine, University College London, London, United Kingdom
Synopsis
Mucinous adenocarcinoma [MAC] is a histological subtype of colorectal cancer with a poor response to long course chemoradiotherapy [LCCRT] and an overall poor oncologic outcome. In this study, we explored the utility of pre-treatment MR texture analysis as a potential imaging biomarker to differentiate mucinous and non-mucinous variants of rectal cancer. We retrospectively evaluated 39 patients with pathologically proven rectal carcinoma on T2-w images and ADC maps. First order MRTA features including the mean and mpp derived from T2-w images at moderate and coarse texture showed statistically significant difference between mucinous and non-mucinous variants of rectal cancers. The results demonstrate that first order MRTA may help differentiate between mucinous and non-mucinous rectal cancer subtypes and select patients for individualized therapy and also potentially aid in accurate prediction of response to LCCRT.
Introduction
Mucinous adenocarcinoma [MAC] is a histological subtype of colorectal cancer with a reported incidence of 3.9% - 19% [1]. MAC have a poor oncologic outcome vis-a-vis the non-mucinous subtype. Poor response of MAC to long course chemoradiotherapy [LCCRT] is seen as greater residual tumor and nodal disease, higher margin positivity, and, the occurrence of peritoneal dissemination and distant metastases during treatment [2]. In this study we explored the utility of pre-treatment MR texture analysis as potential imaging biomarkers to differentiate mucinous and non-mucinous variants of rectal cancer, which may may help to individualize therapy and potentially predict response to LCCRT [3].
Methods
We retrospectively included 39 patients (24 males and 15 females) with pathologically proven rectal carcinoma (33 non-mucinous tumors and 6 mucinous tumors). Texture analysis was carried out on axial T2-w and ADC images by delineating a 2-D region of interest around the tumour. MR texture analysis [MRTA] comprised of a filtration-histogram technique using a commercially available research software (TexRAD - Feedback Medical Ltd - www.fbkmed.com, Cambridge, UK). Filtration step extracted and enhanced features of different intensity and sizes corresponding to spatial scale filter (SSF) which varied from 0 (without-filtration), 2mm (fine texture scale), 3-5mm (medium texture scale) and 6mm (coarse texture scale). Quantification of texture using statistical and histogram based analysis comprised of mean intensity, standard-deviation, entropy, mean of positive pixels, skewness and kurtosis. Difference in MRTA for non-mucinous and mucinous rectal cancer was assessed using non-parametric Mann Whitney test. Receiver operating characteristic (ROC) curve analysis was performed to assess the discriminatory power of each quantitative parameter to differentiate between non-mucinous and mucinous subtypes.Results
On T2-w images at medium texture [ssf = 3-5mm], the mean [p = 0.07 - 0.012] and mpp [0.012 - 0.031] and at coarse texture [ssf = 6mm] the mean [p = 0.006] and mpp [0.011] showed significant difference between mucinous and non-mucinous tumors. On T2-w images without filtration, the mean [p = 0.012], sd [p = 0.009], entropy [p = 0.039] and mpp [p = 0.012] showed significant difference between non-mucinous and mucinous tumors. On ADCs at medium texture [ssf = 5mm], the skewness [p = 0.035] showed significant difference between mucinous and non-mucinous tumors.
Discussion
First order MRTA features derived from T2-w images at medium and coarse texture can help differentiate between mucinous and non-mucinous variants of rectal cancers.Conclusion
Pre-treatment MR based textural analysis of rectal cancer can help differentiate between mucinous and non-mucinous variants, and, potentially select patients for individualized therapy.Acknowledgements
No acknowledgement found.References
1. Stewart SL, Wike JM, Kato I, et al. A population-based study of colorectal cancer histology in the United States, 1998–2001. Cancer 2006; 107:1128–1141.
2. Simha V, Kappor R, Gupta RG, Bahl A, Nada R. Mucinous adenocarcinoma of the rectum: a poor candidate for neo-adjuvant chemoradiation? J Gastrointest Oncol. 2014 Aug; 5(4): 276–279.
3. De Cecco CN et al. Performance of diffusion-weighted imaging, perfusion imaging, and texture analysis in predicting tumoral response to neoadjuvant chemoradiotherapy in rectal cancer patients studied with 3T MR: initial experience. Abdom Radiol (NY). 2016 Sep;41(9):1728-35.