Locoregional staging using magnetic resonance imaging in rectal cancer: influence of diffusion-weighted imaging in the diagnostic accuracy.

OBJECTIVE: To assess whether the accuracy in locoregional staging using magnetic resonance imaging (MRI) in rectal cancer (primary or post-chemoradiotherapy) improves by adding diffusion-weighted imaging, according to the radiologist's degree of experience. METHOD: Retrospective study on 100 MRI records (1.5 T, 2011-2016) from patients with rectal cancer (reference standard: histology of surgical specimens). Ten radiologists (three experienced in rectal cancer, three specialized in other areas and four residents) individually reviewed each case twice: first, evaluating just high-resolution T2-weighted sequences; second, evaluation of diffusion-weighted plus high-resolution ones. The analysis focused on the differentiation between early (0-I) and advanced (II-IV) stages. Accuracy, sensitivity/specificity and predictive values were calculated. RESULTS: Experienced radiologists showed some worsening by adding diffusion-weighted imaging, mainly at primary staging (accuracy: 0.769 to 0.701). Inexperienced radiologists presented a post-chemoradiotherapy improvement (accuracy: 0.574 to 0.642; specificity of 19.1 to 29.8%), although with no other remarkable changes. Residents demonstrated a worsening at primary staging by adding diffusion (accuracy: 0.670 to 0.633; specificity: 45.8 to 39.6%), but post-chemoradiotherapy improvement (sensitivity: 80.6 to 87%). The differences between both reviews were not statistically significant. CONCLUSIONS: No significant differences were found in the distinction between early and advanced rectal tumors secondary to adding diffusion-weighted imaging to high-resolution T2-weighted sequences.

OBJETIVO: Evaluar si la eficacia en la estadificación locorregional por resonancia magnética (RM) del cáncer de recto (primaria o posneoadyuvancia) mejora al añadir imágenes potenciadas en difusión, según la experiencia previa del radiólogo. MÉTODO: Estudio retrospectivo sobre 100 RM de 1.5 T (2011-2016) de pacientes con cáncer rectal (estándar de referencia: estadiaje histológico de pieza quirúrgica). Diez radiólogos (tres con experiencia en cáncer rectal, tres inexpertos y cuatro residentes) evaluaron individualmente cada caso dos veces: primero, solo secuencias T2 de alta resolución; segundo, valoración conjunta con difusión. Se analizó la diferenciación entre estadios precoces (0-I) y avanzados (II-IV), y se calcularon la precisión, la sensibilidad y la especificidad, y los valores predictivos. RESULTADOS: Al agregar la difusión, los radiólogos experimentados presentaron peores resultados, sobre todo en estadiaje primario (precisión: 0.769 a 0.701). Los inexpertos mostraron mejoría posneoadyuvancia (precisión: 0.574 a 0.642; especificidad: 19.1 a 29.8%), sin otros cambios destacables. Los residentes manifestaron peores resultados en estadiaje primario (precisión: 0.670 a 0.633; especificidad: 45.8-39.6%), pero mejoría posneoadyuvancia (sensibilidad: 80.6 a 87%). Las diferencias entre ambas revisiones no fueron estadísticamente significativas. CONCLUSIONES: No se encontraron diferencias significativas en la distinción entre tumores rectales precoces y avanzados al añadir secuencias de difusión al uso de secuencias T2 de alta resolución.

Primary and post-chemoradiotherapy MRI detection of extramural venous invasion in rectal cancer: the role of diffusion-weighted imaging.

OBJECTIVE: To assess the added value of diffusion-weighted imaging (DWI) to high-resolution T2-weighted sequences (HRT2w) in MRI detection of extramural venous infiltration (EMVI), according to the previous experience of radiologists. METHODS: A cross-sectional study of a retrospective database including 1.5 T MRI records from 100 patients with biopsy-proven rectal cancer (2011-2016; 75 male/25 female, average 63 y/o), which included primary staging (54) and post-chemoradiotherapy follow-up MRIs (46). The reference standard was histology of surgical specimens. All cases were individually blindly reviewed by ten radiologists: three specialists in abdominal radiology, three specialized in different areas and four residents. In each case, the presence of EMVI was assessed twice: first, using just HRT2w; second, with DWI added to HRT2w. The results were pooled by experience, analyzing sensitivity, specificity, accuracy (area under ROC curve), likelihood ratios, predictive values and overstaging/understaging. RESULTS: Addition of DWI improved diagnostic performance by specialists radiologists, particularly post-chemoradiotherapy (accuracy 0.74-0.84; positive likelihood ratio 3.9-9.1; overstaging 16-8%), less so at primary staging (specificity 76-87.2%; overstaging 21-11%). Non-specialist radiologists also improved, but only at primary staging (accuracy 0.59-0.63). Residents showed small changes, except for notably increased sensitivity in both primary staging (35.7-43%) and post-chemoradiotherapy (41.7-58.3%) staging, at the expense of increased overstaging. CONCLUSIONS: The addition of DWI improved the diagnostic performance of EMVI by experienced radiologists, downgrading overstaging, especially in post-chemoradiotherapy follow-up. It resulted in fewer changes for inexperienced radiologists (enhanced primary staging) and residents (increased sensitivity).

Primary and post-chemoradiotherapy staging using MRI in rectal cancer: the role of diffusion imaging in the assessment of perirectal infiltration.

PURPOSE: To analyze changes in MRI diagnostic accuracy in main rectal tumor (T) evaluation resulting from the use of diffusion-weighted imaging (DWI), according to the degree of experience of the radiologist. METHODS: This is a cross-sectional study of a database including one hundred 1.5 T MRI records (2011-2016) from patients with biopsy-proven rectal cancer, including primary staging and post-chemoradiotherapy follow-up. All cases were individually blindedly reviewed by ten radiologists: three experienced in rectal cancer, three specialized in other areas, and four residents. Each case was assessed twice to detect perirectal infiltration: first, evaluating just high-resolution T2-weighted sequences (HRT2w); second, evaluation of DWI plus HRT2w sequences. Results were pooled by experience, calculating accuracy (area under ROC curve), sensitivity and specificity, predictive values, likelihood ratios, and overstaging/understaging. Histology of surgical specimens provided the reference standard. RESULTS: DWI significantly improved specificity by experienced radiologists in primary staging (63.2% to 75.9%) and, to a lesser extent, positive likelihood ratio (2.06 to 2.87); minimal changes were observed post-chemoradiotherapy, with a slight decrease of accuracy (0.657 to 0.626). Inexperienced radiologists showed a similar pattern, but with slight enhancement post-chemoradiotherapy (accuracy 0.604 to 0.621). Residents experienced small changes, with increased sensitivity/decreased specificity in both primary (69% to 72%/67.2% to 64.7%) and post-chemoradiotherapy (68.1% to 73.6%/47.3% to 44.6%) staging. CONCLUSIONS: Adding DWI to HRT2w significantly improved specificity for the detection of perirectal infiltration at primary staging by experienced radiologists and also by inexperienced ones, although to a lesser extent. In the post-neoadjuvant treatment subgroup, only minimal changes were observed.