Role of the status of the mesorectal fascia in the selection of patients with rectal cancer for preoperative radiation therapy: a retrospective cohort study

Identification of patients with locally advanced rectal cancer eligible for neoadjuvant chemotherapy alone: Results of a retrospective study

BACKGROUND AND OBJECTIVES

Neoadjuvant chemotherapy (nCT) appears in a few clinical studies as an alternative to neoadjuvant chemoradiation (nCRT) in selected patients with locally advanced rectal cancer (LARC). We aimed to compare the clinical outcomes of nCT with or without nCRT in patients with LARC and to identify patients who may be suitable for nCT alone.

MATERIALS AND METHODS

A total of 155 patients with LARC who received neoadjuvant treatment (NT) were retrospectively analysed from January 2016 to June 2021. The patients were divided into two groups: nCRT (n = 101) and nCT (n = 54). More patients with locally advanced disease (cT4, cN+ and magnetic resonance imaging-detected mesorectal fascia [mrMRF] positive [+]) were found in the nCRT group. Patients in the nCRT group received a dose of 50 Gy/25 Fx irradiation with concurrent capecitabine, and the median number of nCT cycles was two. In the nCT group, the median number of cycles was four.

RESULTS

The median follow-up duration was 30 months. The pathologic complete response (pCR) rate in the nCRT group was significantly higher than that in the nCT group (17.5% vs. 5.6%, p = 0.047). A significant difference was observed in the locoregional recurrence rate (LRR); 6.9% in the nCRT group and 16.7% in the nCT group (p = 0.011). Among patients with initial mrMRF (+) status, the LRR in the nCRT group was significantly lower than that in the nCT group (6.1% vs. 20%, p = 0.007), but not in patients with initial mrMRF negative (-) (10.5% in each group, p = 0.647). Compared with the nCT group, a lower LRR was observed in patients in the nCRT group with initial mrMRF (+) converted to mrMRF (-) after NT (5.3% vs. 23%, p = 0.009). No significant difference was observed between the two groups regarding acute toxicity and overall and progression-free survivals. Multivariate analysis showed that nCRT and ypN stage were independent prognostic factors for the development of LRR.

CONCLUSION

Patients with initial mrMRF (-) may be suitable for nCT alone. However, patients with initial mrMRF (+) converted to mrMRF (-) after nCT are still at high risk of LRR, and radiotherapy is recommended. Prospective studies are required to confirm these findings.

Predictive value of CT-based extracellular volume fraction in the preoperative pathologic grading of rectal adenocarcinoma: A preliminary study

OBJECTIVE

This study aimed to investigate whether the extracellular volume fraction (ECV) determined using enhanced computed tomography (CT) can predict the pathologic grade of rectal adenocarcinoma.

METHODS

We prospectively analyzed 43 patients with rectal adenocarcinoma confirmed surgically and pathologically and who had undergone preoperative enhanced CT imaging. The plain, arterial, venous, and balance phase values were recorded, and the absolute contrast-enhanced CT differences ΔS1 = HU_{arterial phase}-HU_{plain scan}, ΔS2 = HU_{venous phase}-HU_{plain scan}, ΔS3 = HU_{balance phase}-HU_{plain scan} were obtained. The ECV of the primary lesion was calculated by measuring the CT values of the regions of interest in the plain and balance phases. Patients were allocated to either a low-grade or a high-grade group based on the histologic grading standard for colorectal adenocarcinoma (nonspecial type, World Health Organization 2010 standard). The differences in the parameters between the two groups were evaluated for statistical significance. A receiver operating characteristic (ROC) curve was used to evaluate the diagnostic efficiency.

RESULTS

The 43 enrolled patients [12 in the high-grade group (27.9%) and 31 in the low-grade group (72.1%)] had an average age of 64.47 years. The arterial phase (P = 0.005) as well as ΔS1 (P = 0.006), ΔS3 (P = 0.021), and ECV (P＜ 0.001) differed significantly between the high-grade and low-grade groups, with ECV (P＜ 0.001) and ΔS3 (P = 0.042) being positively correlated with the pathologic grade and arterial phase (P = 0.025) and ΔS1 (P = 0.005) being negatively correlated. The ROC curve demonstrated that the best efficacy in evaluating the pathologic grade of rectal cancer was achieved by ECV, with an area under the curve of 0.892 (95% confidence interval: 0.757-1.000). The diagnostic threshold was 34.42%, sensitivity was 91.7%, and specificity was 83.9%.

CONCLUSION

The use of enhanced CT to obtain ECV is helpful in predicting the pathologic grade of rectal cancer; however, this result has to be confirmed in a study with a larger sample size.