The role of MRI after neochemoradiotherapy in predicting pathological tumor regression grade and clinical outcome in patients with locally advanced rectal adenocarcinoma

Final Results of the GRECCAR-6 Trial on Waiting Period Following Neoadjuvant Radiochemotherapy for Locally Advanced Rectal Cancer: 5 Years of Follow-up

BACKGROUND

The potential oncological benefit of extending the waiting period between neoadjuvant radiochemotherapy and surgical resection for rectal cancer is debated.

OBJECTIVE

To evaluate the impact of prolonging this waiting period on the 5-year oncological prognosis and 2-year functional result of locally advanced rectal adenocarcinoma.

DESIGN

Phase III, multicenter, randomized, open-label, parallel-group, controlled trial.

SETTINGS

Patients were enrolled from 24 colorectal centers.

PATIENTS

Patients with nonmetastatic mid or lower cT3/T4Nx or cTxN+ rectal adenocarcinoma who had received radiochemotherapy (45-50 Gy radiation dose with fluorouracil or capecitabine).

INTERVENTION

Patients were randomly assigned to undergo total mesorectal excision either 7 weeks or 11 weeks after radiochemotherapy.

MAIN OUTCOMES MEASURES

Overall survival and disease-free survival at 5-year follow-up and low anterior resection syndrome score assessed after 2 years of follow-up.

RESULTS

Among 265 patients enrolled, 133 were randomized in the 7-week group and 132 in the 11-week group. Twelve patients were excluded because they did not undergo resection. Among 253 patients analyzed, 5-year overall survival was not different between the 2 groups (81.6% in the 7-week group vs 82.6% in the 11-week group, p = 0.827), and neither was the 5-year disease-free survival (70.4% in the 7-week group vs 69.5% in the 11-week group, p = 0.856). No difference was observed between the 2 groups for distant recurrence (27.4% in the 7-week group vs 25.7% in the 11-week group, p = 0.777) or local recurrence (8.4% in the 7-week group vs 10.2% in the 11-week group, p = 0.543). The low anterior resection syndrome score was similar between the 7-week (25.0; interquartile range, 15.0-34.0) and 11-week groups (23.0; interquartile range, 14.2-32.0; p = 0.743).

LIMITATIONS

The response rate to the low anterior resection syndrome questionnaire was only 52%.

CONCLUSIONS

Extending the waiting period between radiochemotherapy and resection from 7 to 11 weeks does not change the 5-year oncological prognosis in rectal cancer or the 2-year low anterior resection occurrence. See Video Abstract.

RESULTADOS FINALES DEL ENSAYO GRECCAR SOBRE EL PERODO DE ESPERA TRAS LA RADIOQUIMIOTERAPIA NEOADYUVANTE PARA EL CNCER DE RECTO LOCALMENTE AVANZADO AOS DE SEGUIMIENTO

ANTECEDENTES:Se debate el posible beneficio oncológico de prolongar el periodo de espera entre la radioquimioterapia neoadyuvante y la resección quirúrgica del cáncer de recto.OBJETIVO:Evaluar el impacto de la prolongación de este periodo de espera sobre el pronóstico oncológico a 5 años y el resultado funcional a 2 años del adenocarcinoma rectal localmente avanzado.DISEÑO:Ensayo controlado de fase III, multicéntrico, aleatorizado, abierto, de grupos paralelos.LUGAR:Se reclutaron pacientes de 24 centros colorrectales.PACIENTES:Pacientes con adenocarcinoma rectal de tercio medio o inferior, no metastásico cT3-4 o TxN+ que habían recibido radioquimioterapia (45 a 50 Gy con fluorouracilo o capecitabina).INTERVENCIÓN:Se asignaron aleatoriamente a los pacientes para ser sometidos a una escisión mesorrectal total 7 semanas (W7) u 11 semanas (W11) después de la radioquimioterapia.MEDIDAS DE RESULTADOS PRINCIPALES:Supervivencia global y supervivencia libre de enfermedad a los 5 años de seguimiento y puntuación del síndrome de resección anterior baja evaluada a los 2 años de seguimiento.RESULTADOS:De los 265 pacientes reclutados, 133 fueron asignados aleatoriamente al grupo de 7 semanas y 132 al grupo de 11 semanas. Doce pacientes fueron excluidos porque no fueron sometidos a resección. Entre los 253 pacientes analizados, la supervivencia global a 5 años no fue diferente entre los dos grupos (81,6% en el grupo de 7 semanas frente a 82,6% en el grupo de 11 semanas, p = 0,827), así como para la supervivencia libre de enfermedad a 5 años (70,4% en el grupo de 7 semanas frente a 69,5% en el grupo de 11 semanas, p = 0,856). No se observaron diferencias entre los dos grupos en cuanto a la recidiva a distancia (27,4% en el grupo de 7 semanas frente a 25,7% en el grupo de 11 semanas, p = 0,777) o la recidiva local (8,4% en el grupo de 7 semanas frente a 10,2% en el grupo de 11 semanas, p = 0,543). La puntuación del síndrome de resección anterior baja fue similar entre los grupos de 7 semanas (25,0 IQR [15,0-34,0]) y 11 semanas (23,0 IQR [14,2-32,0], p = 0,743).LIMITACIONES:La tasa de respuesta al cuestionario LARS fue sólo del 52%.CONCLUSIONES:Ampliar el periodo de espera entre radioquimioterapia y resección de 7 a 11 semanas no modifica el pronóstico oncológico a 5 años en cáncer de recto ni la baja incidencia de resección anterior a 2 años. (Traducción-Dr Osvaldo Gauto ).

Prediction of pathological response and lymph node metastasis after neoadjuvant therapy in rectal cancer through tumor and mesorectal MRI radiomic features

Establishing predictive models for the pathological response and lymph node metastasis in locally advanced rectal cancer (LARC) treated with neoadjuvant chemoradiotherapy (nCRT) based on MRI radiomic features derived from the tumor and mesorectal compartment (MC). This study included 209 patients with LARC who underwent rectal MRI both before and after nCRT. The patients were divided into a training set (n = 146) and a test set (n = 63). Regions of interest (ROIs) for the tumor and MC were delineated on both pre- and post-nCRT MRI images. Radiomic features were extracted, and delta radiomic features were computed. The predictive endpoints were pathological complete response (pCR), pathological good response (pGR), and lymph node metastasis (LNM). Feature selection for various models involved sequentially removing features with a correlation coefficient > 0.9, and features with P-values ≥ 0.05 in univariate analysis, followed by LASSO regression on the remaining features. Logistic regression models were developed, and their performance was evaluated using the area under the receiver operating characteristic curve (AUC). Among the 209 LARC patients, the number of patients achieving pCR, pGR, and LNM were 44, 118, and 40, respectively. The optimal model for predicting each endpoint is the combined model that incorporates pre- and delta-radiomics features for both the tumor and MC. These models exhibited superior performance with AUC values of 0.874 (for pCR), 0.801 (for pGR), and 0.826 (for LNM), outperforming the MRI tumor regression grade (mrTRG) which yielded AUC values of 0.800, 0.715, and 0.603, respectively. The results demonstrate the potential utility of the tumor and MC radiomics features, in predicting treatment efficacy among LARC patients undergoing nCRT.

Prognostic Value of Tumor Volume, Tumor Volume Reduction Rate and Magnetic Resonance Tumor Regression Grade in Rectal Cancer

Background and Objectives: Rectal cancer poses significant treatment challenges, especially in advanced stages. Radiologic assessment, particularly with MRI, is critical for surgeons and oncologists to understand tumor dynamics and tailor treatment strategies to improve patient outcomes. The purpose of this study was to correlate MRI-based tumor volumetric and tumor regression grade analysis in patients with advanced rectal cancer, assessing the impact of preoperative chemotherapy (CT) alone or chemoradiotherapy (CRT) on surgical technique choices. Materials and Methods: Between 2015 and 2022, a prospective study was enrolled, including a cohort of 89 patients diagnosed with rectal cancer at stage II or III. The participants were divided into two distinct therapy groups, ensuring an equal distribution with a ratio of 1:1. The initial group was treated with the contemporary preoperative chemotherapy protocol FOLFOX4. In contrast, the alternative group received conventional preoperative chemoradiotherapy. Before surgery, each patient underwent a rectal MRI scan at 1.5 T, including T2-weighted and diffusion-weighted imaging (DWI) sequences. Results: The CT group showed a 36.52% tumor volume reduction rate (TVRR), and the CRT group showed 54.87%, with varying magnetic resonance and pathological tumor regression grades (mrTRG and pTRG). Analysis revealed a significant interaction between mrTRG and tumor volumetrics (volume and VRR) in both groups, especially CRT, underscoring the complexity of tumor response. Both treatment groups had similar initial tumor volumes, with CRT displaying a higher TVRR, particularly in higher pathological TRG (3/4) cases. This interaction and the strong correlation between mrTRG and pTRG suggest mrTRG's role as a non-invasive predictor for treatment response, highlighting the need for personalized treatment plans. Conclusions: Rectal tumor volume, volume reduction rate, and mrTRG are not just abstract measures; they are concrete indicators that have a direct and practical impact on surgical decision-making, planning, and prognosis, ultimately influencing the quality of care and life expectancy of patients with rectal cancer.