Rationale and Objectives
To retrospectively assess the value of spectral presaturation by inversion-recovery (SPIR) magnetic resonance (MR) imaging sequence after gadolinium injection to differentiate fibrotic scar tissue and tumoral infiltration within the mesorectal fat in patients with rectal carcinoma undergoing MR restaging after neoadjuvant chemo- and radiation therapy (CRT).
Materials and Methods
Forty-three consecutive patients (mean age, 65.8 years; range, 46–85 years; male:female, 29:14) with locally advanced rectal carcinoma underwent CRT followed by surgery. MR imaging was performed before and after completion of CRT by using T2-weighted turbo spin-echo and T1-weighted SPIR sequences before and after gadolinium injection, and MR images were assessed by two radiologists in consensus. Logistic regression was conducted to test the significance of the MR image findings with histology.
Results
After CRT the disease was either limited to the rectal wall ( n = 18 patients) or presented perirectal infiltration ( n = 25) on histology. In 21 patients, mesorectal enhancing strands were observed. Reticular-shaped enhancing strands reaching the mesorectal fascia presented the highest correlation with tumor infiltration of the mesorectal fat (OR 130.33, 95% CI: 4.1–4220.29; logistic regression), whereas linear-shaped enhancing strands either reaching or not reaching the mesorectal fascia (OR 0.25 or 0.1, 95% CI: 0.024–2.6 or 0.01–1.07) revealed the lowest correlation.
Conclusions
Reticular-shaped enhancing strands on SPIR MR imaging after gadolinium injection are associated with tumor infiltration of the mesorectal fat.
Total mesorectal excision is widely accepted as standard surgical practice for rectal cancer , and it provides the best chance of a tumor-free circumferential resection margin . Local recurrence is directly related to incomplete resection of the tumor and the most important parameter related to local recurrence is the distance between the tumor and the mesorectal fascia . Locally advanced rectal cancer with extramural spread (T3 tumor) has high frequency of local recurrence and metastasis. Nowadays, the standard treatment for locally advanced rectal cancer consists of preoperative neoadjuvant concomitant radiation and chemotherapy (CRT) followed by standard resection of the rectum and resection of the surrounding organs .
The classic approach of defining the T stage of the tumor is based on magnetic resonance (MR) imaging or endoscopic ultrasound and may lead to staging failures in the differentiation of T2 and borderline T3 tumors . The measurement of tumor extent relative to the mesorectal fascia and the prediction of tumor-free resection margins on the basis of MR imaging may be more feasible than defining the T stage . MR imaging has an accuracy of 66% in predicting resection margin involvement during restaging of irradiated rectal cancers (sensitivity, 100%; specificity, 35%; positive predictive value, 58%; negative predictive value, 100%) . The reported overall accuracy of MR imaging in predicting the pathologic stage of nonirradiated rectal cancer is 71%–91% (mean, 85%) for T staging, and 43%–85% (75%) for N staging . However, the reported overall accuracy of MR imaging in the restaging of irradiated rectal cancer is much lower being 47%–54% (50%) for T staging and 64%–68% (65%) for N staging , and it is even worse for mucin-producing tumors.
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Materials and methods
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Patients
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Neoadjuvant Treatment
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MR Imaging
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Consensual Analysis
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Table 1
T Stage Before and After Neoadjuvant Therapy
Tumor Before CRT ∗ After CRT † T0/T2 0 18 ‡ T3 38 23 T4 5 2
Note:–Neoadjuvant treatment refers to radiation therapy with concomitant chemotherapy.
CRT, neoadjuvant chemo- and radiation therapy.
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Surgery and Histopathologic Evaluation
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Statistical Analysis
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Results
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Table 2
Patient-by-Patient MR Imaging Findings
Patient Number Sex Age (y) T/N Stage ∗ Enhancing Nodules Reticular Enhancing Strands Linear-shaped Enhancing Strands Mesorectal Fat Infiltration on Histology 1 M 60 T3/N0 − − − + 2 M 74 T2/N1 − − − − 3 F 71 T2/N0 − − + − 4 M 70 T3/N2 − + − + 5 M 71 T2/N0 − − + − 6 F 64 T3/N0 − − − + 7 M 62 T2/N0 − − + − 8 F 78 T2/N0 − − + − 9 M 64 T3/N1 − − − + 10 M 60 T3/N2 + + − + 11 M 68 T3/N1 − + − + 12 F 60 T3/N0 − + − + 13 M 72 T1/N0 − + − − 14 F 77 T1/N0 − − − − 15 F 56 T3/N0 − − − + 16 M 78 T3/N1 − + − + 17 M 66 T3/N0 − − − + 18 F 80 T3/N2 − − − + 19 F 52 T3/N1 − + − + 20 M 69 T2/N1 − − − − 21 M 63 T3/N1 − − − + 22 M 74 T3/N0 − − + + 23 M 56 T0/N0 − − − − 24 M 85 T3/N2 − + − + 25 M 73 T2/N1 − − − − 26 M 52 T1/N0 + − + − 27 M 60 T4/N1 − + − + 28 M 68 T3/N1 − − − + 29 F 67 T1/N0 − − + − 30 F 61 T3/N0 − − − + 31 M 60 T2/N0 + + − − 32 F 46 T2/N0 − − − − 33 M 56 T3/N0 − + − + 34 M 63 T4/N1 − − − + 35 F 63 T3/N0 − − − + 36 M 65 T2/N0 − − − − 37 F 65 T3/N0 − + − + 38 M 60 T3/N0 − + − + 39 M 79 T3/N0 − − − + 40 M 74 T2/N0 − − − − 41 M 60 T2/N0 − − − − 42 M 74 T3/N0 − − + + 43 F 71 T2/N0 − − − −
Note:–Correlation of MR imaging features and presence of mesorectal fat infiltration after neoadjuvant chemo- and radiation therapy. +, present; −, absent; F, female; M, male; MR, magnetic resonance.
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![Figure 2, A 55-year-old woman with a rectal cancer. (a,b) Magnetic resonance (MR) imaging before radiation therapy with concomitant chemotherapy. (a) Turbo spin-echo T2-weighted sequence (repetition time [TR]/echo time [TE], 4947/130) and (b) spectral presaturation by inversion recovery T1-weighted sequence (TR/TE, 598/27) after gadolinium injection. Transverse plane. Rectal cancer of the left wall ( large arrow ) without evidence of mesorectal strands. (c,d) MR imaging after radiation therapy with concomitant chemotherapy. (c) Turbo spin-echo T2-weighted sequence (TR/TE, 4947/130) and (d) spectral presaturation by inversion recovery T1-weighted sequence (TR/TE, 598/27) after gadolinium injection. Transverse plane. There is a clear reduction of the tumor volume after neoadjuvant chemo- and radiation therapy with evidence of reticular enhancing strands within the mesorectal fat ( small arrows ).](https://storage.googleapis.com/dl.dentistrykey.com/clinical/SpectralPresaturationInversionRecoveryMRImagingSequenceafterGadoliniumInjectiontoDifferentiateFibroticScarTissueandNeoplasticStrandsintheMesorectalFatinPatientsUndergoingRestagingofRectalCarcinomaafterNeoadjuvantChemoandRadiationTherapy/1_1s20S1076633211003576.jpg)
![Figure 3, A 60-year-old woman with a rectal cancer treated by radiation therapy with concomitant chemotherapy. Tumor infiltration of the perirectal fat. (a,b) Turbo spin-echo T2 weighted sequence (repetition time [TR]/echo time [TE], 4947/130) and (c,d) spectral presaturation by inversion recovery T1-weighted sequence (TR/TE, 598/27) after gadolinium injection. Transverse plane. Reticular enhancing strands ( arrows ) within the mesorectal fat. (e) The corresponding transversely sliced pathologic specimen shows residual tumor in the rectal wall ( large black arrow ) and perirectal strands extending into the perirectal fat as ( small black arrows ). (f,g) Histologic evaluation showed perirectal fibrotic strands extending within the mesorectal fat with evidence of tumoral infiltration ( small black arrows ). Hematoxylin-eosin stain; original magnification, ×35. L: rectal lumen.](https://storage.googleapis.com/dl.dentistrykey.com/clinical/SpectralPresaturationInversionRecoveryMRImagingSequenceafterGadoliniumInjectiontoDifferentiateFibroticScarTissueandNeoplasticStrandsintheMesorectalFatinPatientsUndergoingRestagingofRectalCarcinomaafterNeoadjuvantChemoandRadiationTherapy/2_1s20S1076633211003576.jpg)
Table 3
Univariate Logistic Regression Analysis
MR Imaging Findings Odds Ratio (95% CI)P Enhancing nodules .295 (.024–3.58) > .05 Enhancing strands 1.33 (.4–4.43) > .05 Reticular enhancing strands reaching the mesorectal fascia 5.95 (1.09–32.57)
28.52 (1.34–604.1) < .05
< .05 Separate enhancing strands reaching the mesorectal fascia .08 (.009–.76)
.18 0 (.019–1.78) > .05
> .05
Note:–Odds ratio according to the different MR imaging parameters.
Enhancing nodules or strands were defined as focal or linear enhancing areas appearing more intense than the surrounding mesorectal fat.
CI, confidence intervals; MR, magnetic resonance.
Table 4
Multivariate Logistic Regression Analysis
MR Imaging Findings Odds Ratio (95% CI)P Enhancing nodules .095 (.003–2.87) > .05 Enhancing strands .16 (.017–1.58) > .05 Reticular enhancing strands reaching the mesorectal fascia 62.14 (3.34–1154.26)
130.33 (4.1–4220.29) < .05
< .05 Separate enhancing strands reaching the mesorectal fascia .1 (.01–1.07)
.25 (.024–2.6) > .05
> .05
Note:–Odds ratio according to the different MR imaging parameters.
Enhancing nodules or strands were defined as focal or linear enhancing areas appearing more intense than the surrounding mesorectal fat.
CI, confidence intervals; MR, magnetic resonance.
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![Figure 4, A 55-year-old woman with a rectal cancer treated by radiation therapy with concomitant chemotherapy. Fibrotic reaction of the perirectal fat after neoadjuvant radiochemotherapy. (a) Turbo spin-echo T2-weighted sequence (repetition time [TR]/echo time [TE], 4947/130) and (b) spectral presaturation by inversion recovery T1-weighted sequence (TR/TE, 598/27) after gadolinium injection. Transverse plane. Linear-shaped enhancing strands ( arrows ) traveling separately within the mesorectal fat. (c) Histologic evaluation showed fibrotic strands ( arrows ) extending within the mesorectal fat without evidence of tumoral infiltration. Hematoxylin-eosin stain; original magnification, ×35. L: rectal lumen. There is reactive hypertrophy of the muscular layer of the rectal wall.](https://storage.googleapis.com/dl.dentistrykey.com/clinical/SpectralPresaturationInversionRecoveryMRImagingSequenceafterGadoliniumInjectiontoDifferentiateFibroticScarTissueandNeoplasticStrandsintheMesorectalFatinPatientsUndergoingRestagingofRectalCarcinomaafterNeoadjuvantChemoandRadiationTherapy/3_1s20S1076633211003576.jpg)
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![Figure 5, A 60-year-old man with a rectal cancer. (a-d) Magnetic resonance imaging examination after radiation therapy with concomitant chemotherapy. (a,b) Turbo spin-echo T2 weighted sequence (repetition time [TR]/echo time [TE], 4947/130) and (c,d) spectral presaturation by inversion recovery T1-weighted sequence (TR/TE, 598/27) after gadolinium injection. Transverse plane. Reticular enhancing strands ( black arrows ) within the mesorectal fat associated with concomitant enhancing nodules ( white arrows ) projecting from the rectal wall toward the mesorectal fat. (e) Histologic evaluation showed perirectal fibrotic strands extending within the mesorectal fat with tumoral infiltration ( black arrows ). Hematoxylin-eosin stain; original magnification, ×35. There is reactive hypertrophy of the muscular layer of the rectal wall.](https://storage.googleapis.com/dl.dentistrykey.com/clinical/SpectralPresaturationInversionRecoveryMRImagingSequenceafterGadoliniumInjectiontoDifferentiateFibroticScarTissueandNeoplasticStrandsintheMesorectalFatinPatientsUndergoingRestagingofRectalCarcinomaafterNeoadjuvantChemoandRadiationTherapy/4_1s20S1076633211003576.jpg)
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Discussion
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