<italic id="italic-ea2f6076d9e1397c2b3d919f2514e933">Age<italic id="italic-5de3b62f46cfcb397c3202473b046776"/></italic>
The mean age of the patients in the current study was 44.17±13.4 years and the age varied from 16 to 70 years, with males commonly affected by rectal cancer more than females. The mean age of the patients with rectal cancer found in a study on 978 patients at a tertiary care center in India was 45.7 years, with a range of ages from 11 to 85 years. Also, 517 (65%) males were seen as affected predominantly with CRC over 283 (35%) females, out of 978 patients assessed in one year.33% of the participants in their study were under the age of 40, while 44% were in the 40 to 60 age range [2]. The median age at diagnosis in research by Hussain et al [22] 2013, in central India, on 233 patients over 8 years, was reported to be 43 years; 39% of the study participants were identified with CRC at 40 years or below [3]. In a study from eastern India, the mean age was reported to be 47.01 years, while in a retrospective examination of 220 patients, it was 58.4 years [4,5]. Similar results with CRC at younger ages have also been found in other trials [6,7]. In contrast, the data from western nations shows higher ages. 90% of newly diagnosed CRC cases in the USA are over 50 at the time of diagnosis, and 58% of newly diagnosed CRC cases are over 65 years of age [8].
Our findings are consistent with other researches done in India, which found that rectal cancer occurs more frequently in the younger age group and is most common in people in their fourth decade of life. Although the precise cause is unknown, the increasing prevalence may be related to changes in lifestyle since a sizable section of the world’s population is made up primarily of young and middle-aged people [9]. Younger people are more likely to access medical care than older ones, therefore it could represent a referral bias. Due to the anatomical proximity and continuity of the colon and rectum, there is also a chance of misclassification with over diagnosis. The greater accessibility of diagnostic colonoscopies could be another factor contributing to the rise in rectal cancer incidence that we observed [3].
<italic id="italic-3f67e284b1574f5d6dbd7cc95885a52c">Role of Dwi-Mri and Dce-Mri in Rectal Cancer<italic id="italic-924e58638c8056d84af9325360141622"/></italic>
Now, in the current study, the diagnosis of rectal cancer was conclusive in 95% of patients with DWI and 97.5% with contrast-enhanced MRI. A study by Rao SX et al [14] 2008 on 45 patients with rectal cancer showed that the sensitivity in detecting the primary lesion improved from 82–84% to 93%–96% by adding the DWI technique together with T2-weighted imaging [14]. In 2014, Attenbergeret al. demonstrated that multi-parametric MRI in rectal cancer in 54 patients showed a significant difference between cT2 and cT3 tumours and also predicted tumour grade using perfusion MRI [15]. A study by Sun H et al [16] 2018 showed that DWI MRI is useful in tumour grading and staging as well as the detection of extramural vascular invasion. Albert et al. 2013 reported DCE MRI as a useful tool for nodal staging but not for tumour staging, CRM involvement, or complete response detection [17]. High nodal staging performance has been reported for DCE MRI with lymph node-specific contrast agents [18]. In contrast to our study, a previous report reported that DWI is less useful for the detection of mucinous rectal tumours because the high mucin content of these tumours shows less restricted diffusion, and the evaluation is limited by T2 effects [19]. After treatment with neo-adjuvant therapy, in our study, we noted improved results in 15% of patients in the T2 stage, 28 patients with no lymph nodal metastasis, a significant difference in the craniocaudal length, extramesorectal lymph nodal involvement in only 1 patient as against 4 patients before treatment. 77.5% of patients showed tumour downgrading. However, the study noted disease progression in 22.5% of patients. Even after treatment, the inconclusive diagnosis according to T2, DWI, and CE MRI was 30%, 17.5%, and 10% respectively of the study population. The results of our study are consistent with those of previous rectal cancer studies [20-23] in which the addition of DWI to conventional MR sequences helped to detect viable tumours after neo-adjuvant CRT. Previous literature supports the addition of DWI to conventional MRI in local restaging after NCRT [24-28]. In a meta- analysis by van der Paardt et al [29] 2013, the pooled sensitivity for predicting response (defined as either ypT0, ypT0-2 or T-down staging compared to primary staging) was significantly higher in studies that included DWI in the MR protocol compared to studies, which did not (83.6% vs. 50.4%). Oberholzer et al. [30] 2013, demonstrated in a large prospective study that DCE curves and semi quantitative perfusion parameters were able to distinguish between good responders and poor responders. In contrast to our results, previous reports suggest that DWI-MRI is futile in predicting nodal response [25,26]. Nie et al [37] 2016, evaluated the pathologic response of rectal cancer after neo-adjuvant treatment in 48 patients using multi-parametric MRI (DWI and DCE) and found better predictive value compared to conventional imaging metrics through a systematic analysis of multi-parametric MRI features. Hotker et al [31] 2016, performed a study on 24 patients using multi-parametric MRI and observed a significant association between histo-pathological grades of tumor regression with DEC and DWI volumetry. However, they did not find an association between functional parameters (ADC, Ktrans) and tumor regression. Attenberger et al’s [32] 2017, research on multi-parametric MRI evaluation of rectal cancer response to treatment after NCRT found significant differences in ADC values about tumor regression with no statistically significant difference in perfusion parameters [32]. Sun et al [16] 2018, observed good interobserver agreement with diffusion and perfusion parameters using multi-parametric MRI. However, it should be noted that the authors did not perform a contrast perfusion technique, which in our opinion is the main limitation of their study [16].
Our study showed that CE-MRI is more conclusive in staging, after treatment than DWI MRI. Similar results were also reported in a study of 51 patients evaluating the value of (DCE-MRI) for predicting pathologic response in rectal cancer. The study reported 100% PPV for ΔK trans DCE-MRI, which was better than DW-MRI PPV. However, the sensitivity of 67% was significantly lower when using DCE-MRI. The lower sensitivity has been attributed to differences in the biological/physiological background of the two imaging techniques, with DW-MRI showing cell density while DCE-MRI reflects tumour vasculature [33]. High nodal staging performance has been reported for DCE MRI with lymph node-specific contrast agents [18]. A retrospective analysis of 328 patients also showed that the contrast-enhanced MRI protocol in predicting the pathologic stage of ypT0-1 tumours was 0.81 (95% CI: 0.77, 0.85), better than the T2-weighted DWI protocol (0.66; 95 % CI: 0.60, 0.71; P < 0.001) and concluded that CE MRI provides accurate discrimination of ypT0-1 from ypT2-4 tumours after NCRT. In 2015, Petrillo et al. [35] investigated the predictive role of MRI volumetry based on signal intensity characteristics on DCE to differentiate between complete and incomplete responders. They showed that the diagnostic performance associated with the volumetric change of DCE-MRI was superior to that of T2-weighted volumes and DW-MRI.
Despite the obvious use of DWI, image interpretation requires a certain level of experience due to certain pitfalls such as suboptimal sequential angulation, misinterpretation of low ADC signal from fibrosis, sensitivity effects, and fluid translucency in the rectal lumen. These hinder the diagnostic performance of inexperienced radiologists [36]. The better results with CEMRI could also be due to the higher artefacts seen in DWMRI, for which a previous study suggested performing a micro-enema before performing rectal MRI in the setting of tumour restaging to reduce the amount of rectal gas to reduce artefacts in DWI MRI [29-37].
In conclusion, oblique axial T2 weighted imaging with minimal spacing and slice thickness along with post contrast T1 images allow the most accurate assessment of residual tumour. Current guidelines do not routinely recommend contrast study but we strongly recommend in all cases. DWI and dynamic contrast imaging also shows accurate results and should be added to routine sequences if possible. Several morphological responses like fibrosis and tumour necrosis are well demonstrated on MRI and are extremely useful for tumour chemo-radiotherapy response. Multi-parametric MRI correlates well with pathological responses and offers superior soft tissue characteristics, that allows for detection of recurrence/ residual tumour and restaging of post-NACRT patients. It plays a crucial role in the staging of rectal cancer post NACRT. Multi-parametric novel pulse sequences aid in predicting the extent of involvement of mesorectal fascia in pre and post treatment, being more sensitive in differentiating post treatment remnant lesion from post treatment fibrosis. The advent in multi-parametric sequences and introduction of techniques like CE-MRI have improved the quality of detection of lymph node positivity.