Correlation of MR based textural analysis parameters with MR tumor regression score and its potential role in predicting response to long course chemoradiotherapy in patients with locally advanced rectal cancers [LARC].

Treatment of locally advanced rectal cancers (cT3/4, cN1/2) with neoadjuvant chemoradiotherapy leads to a reduction in tumor size and enhances the likelihood of tumor resectability and sphincter preservation with low local recurrence rates. In this study we attempted to correlate first order MR textural parameters with the MR tumor regression [TRG] score determined on the post-treatment MRI and to also predict response to long course chemoradiotherapy in locally advanced rectal cancers. We retrospectively included 20 patients with pathologically proven rectal carcinoma who underwent long course chemoradiotherapy [LCCRT] following a pre-treatment MRI. All 20 patients had a post-treatment MRI after a 6-week interval at which MR tumor regression [TRG] scores were determined based on the T2-w and DW-ADC maps. TRG was represented as MR_TRG [TRG 1,2 - Complete Response [CR] = 7; TRG 3 - Partial Response [PR] = 11; TRG 4,5 - Minimal / No response [NR] = 2). Texture analysis was carried out on axial T2-w and ADC images by delineating a 2-D region of interest around the tumour. The results showed that First order MRTA features derived from the post-treatment MR T2-w and ADC images can help differentiate between responders [TRG 1 and 2] and non-responders [TRG 3, 4 and 5] in patients with locally advanced rectal cancers who underwent long course chemoradiotherapy.