Objective:

To quantitatively detect fatty acid composition of various adipose tissue depots using chemical shift- encoded magnetic resonance imaging (CSE-MRI) in patients with rectal cancer

and to explore the application value in evaluating fatty acid effects on rectal carcinogenesis and progression.

Methods:

Patients with surgically pathologically confirmed rectal adenocarcinoma underwent preoperative routine MRI and multi-echo gradient-echo CSE-MRI in Huadong Hospital

Fudan University from October 2021 to December 2022. The saturated fatty acid (fSFA)

monounsaturated fatty acid (fMUFA) andpolyunsaturated fatty acid (fPUFA) fractions of adipose tissue from rectal mesentery

ileal mesentery

and gluteal subcutaneous area were detected. Twenty age- and sex-matched controls with non-rectal cancer were enrolled at the same time. Changes in fatty acid fractions of adipose tissue at various sites were analyzed between the rectal cancer group and the control group as well as among rectal cancer patients to evaluate the role of fatty acids in tumorigenesis; changes in fatty acid fractions of adipose tissue at various sites were analyzed between the lymph vascular invasion (LVI) and peripheral nerve invasion (PNI) positive and the negative rectal cancer groups to evaluate the effect of fatty acids on tumor aggressiveness. Interobserver agreement of fatty acid fraction parameter measurements was assessed by intra-group correlation coefficient (ICC). Differences between two groups were analyzed by independent samples

t

-test or Mann-Whitney

U

-test; differences between multi

ple groups were analyzed by one-way ANOVA (One- Way ANOVA) or Kruskal-Wallis H (

K

) test.

Results:

A total of 56 patients with rectal adenocarcinoma were included

including 36 males and 20 females

with a mean age of (65.1±10.1) years. There were 11 (19.6%) rectal adenocarcinomas with LVI and 10 (17.9%) patients with PNI; and 20 cases in the control group

including 12 males and 8 females

with a mean age of (66.3±8.8) years. Measurements of each fatty acid fraction at each site correlated well between observers

with ICC＞0.60. The SFA fraction of rectal mesenteric adipose tissue was higher in the rectal cancer group than in the control group (37.2±4.2 vs 35.0±2.7

P

=0.035); The fMUFA (37.5±2.4

37.3±8.1 and 40.6±8.7

respectively

P

=0.003) and fPUFA (24.9±4.1

26.3±4.9 and 21.5±4.7

respectively

P

0.001) of adipose tissue from rectal mesentery

ileal mesentery

and gluteal subcutaneous area in patients with rectal cancer were statistically significant. The fMUFA of rectal mesenteric adipose tissue was higher in the LVI (+) rectal cancer than in the LVI (-) group (38.8±1.5

vs

37.1 ± 2.5

P

=0.035); none of the differences in the fractions of each fatty acid in adipose tissue of each site were statistically significant between the PNI (+)/(-) rectal cancer groups (

P

0.05).

Conclusion:

① Differences were found between the SFA fractions of rectal mesenteric fat in rectal cancer patients and normal controls; ② Differences were found between the fMUFA and fPUFA of rectal mesenteric and mesenteric fat of rectal cancer and subcutaneous adipose tissues; ③ Associations were found between the fMUFA of rectal mesenteric fat of rectal cancer and LVI.