The PRISMA flow diagram below summarizes the results of the search (Fig. 1). Web of Science Core Collection, Scopus and PubMed retrieved 170, 167 and 43 articles respectively. Of the 380 articles, 98 duplicates were manually removed, and 111 articles were removed by the automated filters (111 non-English articles, of which 98 were also marked as non-articles). Manual first pass screening excluded 55 articles and full text screening removed another 19 articles. 19 studies were included in the final analysis.

Summary of the systematic search in accordance with PRISMA guidelines

Of the 19 included studies, 13 (68%) and 6 (32%) of them were case series and cohort studies respectively. All included studies were retrospective, published between 2016 to 2024 and had varying sample sizes (5–168), with a total of 1027 patients analyzed in this review. These studies were from USA (n = 5, 26%), South Korea (n = 4, 21%), UK (n = 3, 16%), Japan (n = 4, 21%), India (n = 3, 16%), France (n = 1, 5%), Ireland (n = 1, 5%), Turkey (n = 1, 5%), Italy (n = 1, 5%), Norway (n = 1, 5%) and Australia (n = 1, 5%) (Table 2).

Age was reported in all 19 studies, though the statistical formats varied, including combinations of medians, means, interquartile ranges (IQR), ranges, and standard deviations (SD). Median age, reported in 15 studies [6, 7, 20, 22, 25,26,27,28,29, 32, 34,35,36,37, 39], ranged from 51 to 68 years. The overall mean age from four studies was 61.3 years [30, 31, 33, 39]. Reported IQRs commonly overlapped between 50 and 60 years [6, 7, 20, 26, 28, 31, 32, 36, 39], with the widest range being 44–71 years in one study [6]. Six studies reported cumulative age ranges spanning from 27 to 85 years [25, 27, 33,34,35]. Gender was described in all but one study [30], with males comprising the majority in 14 studies (73.7%) [6, 22, 25,26,27, 29, 30, 32,33,34,35,36,37, 39].

BMI was reported using different measures. Median values ranged between 21.1–28.6 kg/m2 [6, 7, 20, 26, 29, 30, 36, 39], while means ranged from 22.7–27.1 kg/m2 [22, 31, 33, 38]. The narrowest and widest IQRs were 24.4–27.7 kg/m2 [7] and 20.15–28.35 kg/m2 [36], respectively. Six studies reported BMI ranges spanning from 16.7–40.8 kg/m2 [25, 27, 33,34,35, 37]. One study [28] did not report BMI data, and another [32] identified BMI ≥ 30 kg/m2 without providing summary statistics.

ASA classification was described in 15 studies [6, 7, 20, 22, 25,26,27, 29,30,31,32, 34, 36,37,38,39], of which 13 reported distributions for individual scores [6, 7, 20, 22, 26, 27, 29,30,31,32, 34, 36,37,38]. Across these, 182 (20.5%) patients were ASA 1, 471 (53.1%) ASA 2, 202 (22.8%) ASA 3, 10 (1.1%) ASA 4, and 22 (2.5%) had missing ASA data.

Tumor location was commonly reported by distance from the anal verge [6, 22, 25, 27, 30,