Objective:

To investigate the relationship between mesorectal fat area (MFA) and metachronous liver metastasis (MLM) in mid-to-lower rectal cancer.

Methods:

A total of 260 patients with mid-to-lower rectal cancer who underwent high- resolution magnetic resonance imaging (HR-MRI) in Nantong Tumor Hospital from December 2016 to December 2019 were retrospectively included in the study. The starting time of follow-up was the radical resection of rectal cancer of the enrolled patients

and the follow-up deadline was December 31

2022. The average follow-up period was (51.5±13.9) months. During the follow- up period

31 patients had MLM and 229 patients had no MLM. HR-MRI findings were reinterpreted independently by two readers

and MFA was obtained by outlined along the mesorectal fascia (MRF) on oblique axial T2-weighted imaging (T2WI) images of the largest cross-section of the rectal tumor. The differences of clinical baseline data

HR-MRI imaging findings and MFA between the two groups were calculated by t test

rank sum test

χ

2

test and Fisher’s exact test. COX proportional hazards regression models wereused to identify risk factors for MLM in patients with mid-to-lower rectal cancer. Kaplan-Meier survival curves were used to analyze the prognostic effects of risk factors for MLM.

Result:

Compared with non-MLM group

the MLM group patients had higher rate of carcinoembryonic antigen (CEA) abnormality ［17 (54.8%)

vs

83(36.2%)

P

=0.046］

higher rate of HR-MRI reported N stage (mrN stage) ［17 (54.8%)

vs

81 (35.4%)

P

=0.036］

higher positive rate of HR-MRI reported extramural vascular invasion (mrEMVI) ［14 (45.2%)

vs

54 (23.6%)

P

=0.010］

and lower MFA (9.34±3.77

vs

11.43±5.13

P

=0.008). COX regression analysis showed that mrN stage positive

mrEMVI positive

MFA＜14.6 cm

2

and without preoperative neoadjuvant chemoradiotherapy (nCRT) were independent risk factors for MLM after radical resection of rectal cancer. Kaplan-Meier survival curves showed that the non-MLM free survival rate was significantly lower in mrN stage positive group

mrEMVI positive group and MFA＜14.6 cm 2 group than in their corresponding groups

but there was no statistical difference in non-MLM free survival rate between the two groups receiving nCRT or not.

Conclusion:

MrN stage positive

mrEMVI positive

low MFA

and without preoperative nCRT were independent risk factors for MLM after radical resection of mid-to-lower rectal cancer.