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Impact Of Rectal Cancer On Bowel Dysfunction Before Treatment And Its Relationship With Post-treatment Function
*Stephan Robitaille, *Anna Wang, *Sender Liberman, *Patrick Charlebois, *Barry Stein, Liane S Feldman, *Julio F Fiore, Jr., Lawrence Lee
McGill University Health Center, Montreal, QC, Canada

OBJECTIVE(S):
Rectal cancer treatments can cause significant bowel dysfunction(BD) in up to 80% of cases, and the decision for sphincter preservation or permanent colostomy often depends on baseline function. However, there are few data on pre-treatment function, and there is also a high proportion of the general population that have baseline BD. Therefore, we sought to evaluate pre-treatment bowel function and its relationship with post-treatment function.
METHODS:
A prospective functional outcomes database of adult patients evaluated for new primary rectal cancer at a single university-affiliated colorectal referral center from 08/2018-12/2021 was queried. Patients were excluded if they received any treatment prior to their consultation. Bowel function was measured using the Low Anterior Resection Syndrome(LARS) score(range 0-42) before treatment and at ≥6months following restoration of bowel continuity. Patients were categorized as no(0-20), minor(21-29), and major(30-42) LARS. Predicted LARS scores were obtained from published normative data for age and sex. Results were analyzed using one-sample z-test, Pearson chi-square and multiple regression.
RESULTS:
Overall, 94 patients were included with mean age 61.8years(SD11.9), 74% male, mean tumour height 8.4cm(SD5.3) and size 3.7cm(SD2.2). Mean observed LARS score was 18.1(SD13.1), with 46% categorized as no, 31% minor, and 22% major LARS. Male sex and high-risk age group was associated with worse than predicted LARS categories(table). Larger tumour size (β +2.1 per cm, 95%CI 0.7,3.5) and tumour height (β-0.6, 95%CI -1.2,-0.1) were independently associated with a larger mean difference between observed and predicted LARS. In the 63 patients with post-surgery LARS scores, LARS improved in 13%(95%CI 4%,21%), worsened in 33%(95%CI 21%,45%) and remained unchanged in 54%(95%CI 42%,66%) following treatment. There were significantly more patients with major LARS post-treatment compared to pre-treatment(table).
CONCLUSIONS:
Pre-treatment BD in rectal cancer patients can be significantly worse than normative values and largely does not improve after treatment. This suggests that patientsí pre-treatment bowel function can be used to predict postsurgical function and may aid in the decision-making process regarding sphincter preservation vs. permanent colostomy.

*p-values using the one-sample z-test **p-value using chi-squared test
Male(n=70)High-risk (50-80 years)(n=71)Treatment category(n=63)
LARS CategoryObservedPredictedP*ObservedPredictedP*Pre-treatmentPost-treatmentP**
No30 (43%)72%<0.00134(48%)69%<0.00133(52%)26(41%)
Minor21(30%)18%<0.00120(28%)17%0.01122(35%)17(27%)
Major19 (27%)10%<0.00117(24%)14%0.0188(13%)20(32%)<0.037


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