Estrogen Receptor May Play Important Role in Gender Differences of Early-Onset Colorectal Cancer.

Novel, Emerging Risk Factors for Colorectal Cancer Remain Understudied

Background: The causes of the rising incidence of early-onset colorectal cancer (EOCRC), defined as CRC in patients aged <50, remain unknown. In this study, we evaluated tumor genomic differences in patients with EOCRC versus late-onset CRC (LOCRC, age >60). Methods: The international cohort included 13,262 patients diagnosed with stages I-III colon or rectal cancer who had ctDNA testing using a personalized and tumor-informed multiplex PCR assay (Signatera™ 16-plex bespoke mPCR NGS assay), from which whole-exome sequencing (WES) on the surgically resected tumor was performed. Tumor mutational burden (TMB) and microsatellite instability (MSI) status were derived from WES analysis. The prevalence of gene-wide mutations, pathogenic gene variants, and mutations in known oncogenic pathways was compared between EOCRC and LOCRC groups, stratified by TMB and MSI status. Fisher’s exact test was used to test significance between the groups and p-values were adjusted using the FDR method for multiple test correction. Results: A total of 3,093 patients with EOCRC (70.8% colon, 27.4% rectal, 1.9% unknown) and 10,169 patients with LOCRC (79.9% colon, 18.3% rectal, 1.7% unknown) were included, where 9.0%/37.3%/53.7% were AJCC stages I, II, and III, respectively. Early-onset patients compared to late-onset patients had fewer cases of stage II CRC (30.7% vs. 39.3%, p<0.01) and more cases of stage III CRC (60.9% vs 51.6%, p<0.01). Adjusted by stage, patients with EOCRC were less likely to be MSI-H compared to patients with LOCRC (10% vs. 17%, p<0.01), or have high tumor mutational burden (TMB-H) (15% vs. 19%, p<0.01). Genes of the Hippo, NOTCH, WNT, and RTK-RAS oncogenic pathways were less commonly mutated in the EOCRC cohort (p<0.01). The BRAF V600E mutation was less prevalent in the EOCRC group (3% vs. 15%, p<0.01), regardless of TMB and MSI status. In the TMB-low/MSS group, TP53 mutations were more common in EOCRC (8% vs. 5%, p<0.01), but APC gene mutations were less common in EOCRC (56% vs. 66%, p<0.01). When comparing EOCRC and LOCRC in the TMB-H/MSI-H group, BRAF V600E (4% vs. 60%), RNF43 G659V (16% vs. 45%), and WNT1 G619A (6% vs. 20%) mutations were less prevalent in EOCRC (p<0.01 for all mutations); however, patients with EOCRC had more mutations in PIK3CA H1047R (22% vs. 9%), APC R1468* (11% vs. 3%), and KRAS A146T (7% vs. 2%) gene variants (p<0.01 for all mutations). In the TMB-H/MSS group, EOCRC patients were more likely to have driver mutations in the PI3K pathway (74% vs. 56%, p<0.01). Further, POLE P286R mutations were more common in TMB-H/MSS patients with EOCRC compared to LOCRC (38% vs. 13%, p<0.01), whereas ACVR2A K437R was less common (11% vs. 30%, p<0.01). Conclusion: Patients with LOCRC were more likely to have pathogenic gene variants and mutations in established pathways of CRC carcinogenesis. Tumors in EOCRC cases harbored unique genomic alterations that varied between the TMB-low/MSS, TMB-H/MSI-H, and TMB-H/MSS subpopulations. Citation Format: Eric M. Lander, Samuel Rivero-Hinojosa, Vasily N. Aushev, Jesús Izaguirre-Carbonell, Adham Jurdi, Minetta C. Liu, Cathy Eng. Genomic alterations associated with early-onset and late-onset colorectal cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6696.

Evaluation of Early-Life Factors and Early-Onset Colorectal Cancer Among Men and Women in the UK Biobank

3511 Background: The etiology of the rising incidence of early-onset colorectal cancer (EOCRC), defined as CRC in patients aged < 50, remains unknown. In this study, we evaluated tumor genomic differences in patients with EOCRC versus average-onset CRC (AOCRC, age > 60). Methods: The cohort included 13,262 patients diagnosed with stages I-III colon or rectal cancer who had whole exome sequencing as part of their ctDNA testing (Signatera, bespoke mPCR NGS assay). Tumor mutational burden (TMB) and microsatellite instability (MSI) status were derived from tumor whole exome sequencing analysis. The prevalence of somatic variants and mutations in known oncogenic pathways was compared between EOCRC and AOCRC groups, stratified by TMB and MSI status. Fisher’s exact test was used to test significance between the groups and p-values were adjusted using the FDR method for multiple test correction. Results: A total of 3,093 patients with EOCRC (70.8% colon, 27.4% rectal, 1.9% unknown) and 10,169 patients with AOCRC (79.9% colon, 18.3% rectal, 1.7% unknown) were included, where 9.0%/37.3%/53.7% were AJCC stages I, II, and III, respectively. Early-onset patients compared to average-onset patients had fewer cases of stage II CRC (30.7% vs. 39.3%, p < 0.01) and more cases of stage III CRC (60.9% vs 51.6%, p < 0.01). Patients with EOCRC were less commonly MSI-H compared to patients with AOCRC (10% vs. 17%, p < 0.01), or have high tumor mutational burden (15% vs. 19%, p < 0.01). The BRAF V600E mutation and truncated RNF43 mutations were less prevalent in EOCRC (3% vs. 15% and 2% vs. 9%, p < 0.01), regardless of TMB and MSI status. Molecular alterations of the RTK-RAS pathway were less prevalent in the EOCRC cohort (p < 0.01), while TP53 pathway alterations were more frequent in the EOCRC cohort (p < 0.01). In the TMB-low/MSS group, TP53 mutations were more common in EOCRC (8% vs. 5%, p < 0.01), but APC gene mutations were less common in EOCRC (56% vs. 66%, p < 0.01). In the TMB-H/MSI-H group, BRAF V600E (4% vs. 60%), RNF43G659V (16% vs. 45%), and WNT1 G619A (6% vs. 20%) mutations were less prevalent in EOCRC (p < 0.01 for all mutations); however, patients with EOCRC had more PIK3CA H1047R (22% vs. 9%) , APC R1468* (11% vs. 3%), and KRAS A146T (7% vs. 2%) variants (p < 0.01 for all mutations). In the TMB-H/MSS group, EOCRC patients were more likely to have driver mutations in the PI3K pathway (74% vs. 56%, p < 0.01). The POLE P286R mutation was more common in TMB-H/MSS patients with EOCRC (38% vs. 13%, p < 0.01), whereas ACVR2A K437R was less common (11% vs. 30%, p < 0.01). Prevalence of somatic variants and mutated oncogenic pathways did not vary significantly by tumor stage. Conclusions: Patients with AOCRC harbored more somatic variants and mutations in established pathways of CRC carcinogenesis. Tumors in EOCRC cases carried unique genomic alterations that varied across the TMB and microsatellite subpopulations. BRAF V600E and RNF43 truncating mutations were more frequent in AOCRC.

e15520 Background: Colorectal cancer (CRC) is a significant public health concern, with disparities based on race, gender, and socioeconomic status increasingly recognized. The incidence of early-onset CRC (EOCRC) is rising, highlighting the need for detailed examination of disparities in EOCRC compared to late-onset CRC (LOCRC). This study utilizes the NIH All of Us database to explore these disparities. Methods: We conducted a cross-sectional analysis of 266,520 participants from the NIH All of Us Registered Tier Dataset v7. CRC cases were identified based on at least two recorded diagnoses in electronic health records. Participants were categorized into EOCRC if diagnosed before age 50 and LOCRC if diagnosed at age 50 or above. We compared demographic and socioeconomic variables, including gender, race/ethnicity, income, education, and smoking status, between the groups, using questionnaire responses. Statistical analyses were performed using R. Results: The average age at diagnosis was 42.1 years for EOCRC patients and 63.7 years for LOCRC patients. The EOCRC group had a higher proportion of females (57.8%) compared to the LOCRC group (49.2%, p = 0.006). Whites constituted the majority in both categories, but Hispanics were significantly more represented in the EOCRC group (21.1%) compared to the LOCRC group (11.1%, p < 0.001). Individuals with a higher income (more than $100,000 per year) were more prevalent in the EOCRC group (29.9%) than in the LOCRC group (17.7%, p < 0.001). There was no significant difference in education levels between the two groups (p = 0.52). A history of smoking 100 or more cigarettes was less common in EOCRC patients (32.8%) than LOCRC patients (48.1%, p < 0.001). Conclusions: This analysis highlights significant disparities in racial and gender representation as well as income level. Despite observed differences between the two groups, Hispanics, females, and higher income alone may not explain the only influencing factors as other cofounders, like insurance level, may have impacted the result. Cigarette exposure was more prevalent in the LOCRC group, which may represent a stronger environmental influence on CRC within this group. These findings highlight the need for further research to understand the underlying causes of these disparities and to develop targeted interventions. By addressing these disparities, we can move towards more equitable outcomes across all populations. [Table: see text]

The incidence of early-onset colorectal cancer (EOCRC) is rapidly increasing worldwide in decade when screening of colorectal cancer (CRC) is more prevalent. The clinicopathological and molecular characteristics of EOCRC have not yet been clarified. This study aims to evaluate clinicopathological and molecular features among EOCRC and late-onset colorectal cancer (LOCRC) patients according to different tumor locations. We identified CRC patients from a prospectively maintained CRC database between January 2015 and December 2018. The clinicopathological and molecular characteristics including dMMR, mutation of PIK3CA, BRAF and KRAS were compared between EOCRC and LOCRC. The relationships according to different tumor locations were assessed. Totally 4468 patients were analyzed in this study. Compared to LOCRC patients, EOCRC patients were more likely to have status of dMMR (OR, 2.52; P < 0.001), regardless of tumor location. EOCRC patients were more likely to be detected with mutation of PIK3CA (OR, 1.24; P = 0.041), which only tended to exist in the left-side colon (OR, 1.51; P = 0.06), but not in the right-side colon or rectum. No significant difference was found for BRAF or KRAS mutation, but mutation of KRAS was more frequently found in left-side colon (OR, 1.34; P = 0.04) among EOCRC patients. Status of dMMR, mutation of PIK3CA, BRAF and KRAS was different between EOCRC and LOCRC patients according to different tumor locations, which implied that EOCRC might be a unique subgroup of CRC patients. Further investigations of molecular and genetic differences should be performed to help define new diagnosing and therapeutical strategies for EOCRC patients.

Risk Factors for Early Onset Colorectal Cancer: Further Confirmation is Needed

What Is Driving Early-Onset Colorectal Cancer?

With the introduction of early-onset colorectal cancer (EO-CRC), defined as diagnosis before the age of 50, research has increasingly focused on distinguishing it from late-onset colorectal cancer (LO-CRC). However, the majority of these studies have delved deeply into specific aspects of the condition, and there is still a limited number of articles that comprehensively review the overall differences between EO-CRC and LO-CRC. In this review, we conducted literature searches on PubMed, Embase, and ScienceDirect databases using keywords such as "early-onset colorectal cancer", and "late-onset colorectal cancer". The retrieved articles were further screened to select those related to clinical manifestations, pathological features, molecular mechanisms, and prognosis for detailed analysis. Our findings indicate that the potential pathogenesis of EO-CRC is closely associated with lifestyle and environmental changes of the younger population. Compared to LO-CRC, EO-CRC tends to present with more severe initial symptoms, is more often diagnosed at an advanced stage, and primarily affects the left half of the colon. Postoperative pathology shows greater malignancy and invasiveness. At the biomolecular level, PIK3CA mutation and TP53 deletion exhibits a higher mutation rate in EO-CRC compared to LO-CRC, while other common gene mutations such as APC, KRAS, and SMAD4 are relatively less frequent. Additionally, MSI-H is more prevalent in patients with EO-CRC. Differences in transcriptomics and metabolomics profiles have also been observed between EO-CRC and LO-CRC, which may account for their distinct biological characteristics. The prognosis of EO-CRC is a subject of controversy, with varying trends observed across different age groups at onset, as well as between genders and ethnicities. In this study, we aimed to uncover the potential mechanisms behind the continuous rise in EO-CRC incidence and to provide a basis for optimizing standardized screening and treatment strategies for EO-CRC through a comprehensive analysis of the differences between EO-CRC and LO-CRC.

282 Background: Approximately 50% of patients with colorectal cancer develop liver metastases (CRLM). The incidence of early onset colorectal cancer (EOCRC), defined as &lt;50 years of age at time of diagnosis, is increasing. In this study, we aim to explore the prognosis of early vs late onset colorectal cancer patients with CRLM who receive curative-intent treatment. Methods: A retrospective study was conducted to assess clinical outcomes in patients with CRLM presenting with EOCRC compared to those with late onset colorectal cancer (LOCRC). All patients underwent surgical resection and/or ablation between 2009 and 2024 at a tertiary care center. Groups were defined by patient age at the time of diagnosis of the primary tumor &lt; 50 years versus ≥ 50 years. Demographics, tumor characteristics, and treatment modalities were compared between groups using Chi-square, independent samples t-test, and median test. Survival outcomes were assessed using Kaplan-Meier. Results: 342 patients met inclusion criteria. There were 85 (24.9%) EOCRC patients, with a median age at diagnosis of 44 years versus 63 years in the LOCRC group. EOCRC patients had fewer major medical comorbidities. EOCRC patients had a smaller proportion of right-sided (15.9% vs 29.6%, P=0.049) tumors. Rates of synchronous metastases (74.1% in EOCRC vs 72.4%, P=0.781), median size (28cm in EOCRC vs 25cm, P=0.421) median number of metastases (2 in EOCRC vs 2, P=0.385), and initial CEA levels (339.18 + 1276.48 ng/ml vs 328.87 + 2520.59 ng/ml, P=0.482) were similar between groups. However, EOCRC patients had higher rates of node-positive disease (75.6% vs 58.8%, P=0.010) and Fong Clinical Risk Scores 3-5 (57.0% vs 39.7%, P=0.009). Both groups underwent similar operative management with no differences in morbidity, but more EOCRC patients received neoadjuvant therapy (82.4% vs 66.1%, P=0.017). There were no significant differences in RAS/RAF (37.6% in EOCRC vs 34.2%, P=0.669) or TP53 (25.9% vs 34.6%, P=0.98) mutational status or microsatellite instability (stable in 74.1% in EOCRC vs 69.3%, P=0.523). Both intra- (46.5% in EOCRC vs 50.6%, P=0.535) and extra-hepatic (47.7% in EOCRC vs 38.1%, P=0.129) recurrences occurred at similar rates, with no significant differences in post-recurrence treatments received. Patients with CRLM and EOCRC had significantly worse overall survival, with a median time of 80 months versus 116 months (P=0.042). Conclusions: Despite similar clinical, pathologic, and genetic features, fewer medical comorbidities, and receiving similar medical and surgical treatments, EOCRC patients had worse median overall survival than LOCRC patients. High risk Fong Clinical Risk Scores were more common in the EOCRC group, who also received neoadjuvant therapy at higher rates. Additional research is needed to understand the differences in survival.

The incidence of early-onset colorectal cancer (CRC) (age, <50 years) continues to increase globally within high-income countries. To examine and compare rates of synchronous neoplasia found in patients at colonoscopic diagnosis of early-onset CRC with rates found at diagnosis of average-onset CRC. In this multisite retrospective and cross-sectional study conducted at Mayo Clinic sites and in the Mayo Clinic Health System from January 1, 2012, to December 31, 2022, 150 randomly selected patients with early-onset CRC were identified from the electronic health record and matched with 150 patients with average-onset CRC based on sex and colonoscopic indication. Patients with known hereditary syndromes, past history of CRC, or inflammatory bowel disease were excluded. Colonoscopic findings (polyp size, number, site) and related histopathologic findings (adenoma, advanced adenoma, sessile serrated polyp) were analyzed in association with cancer clinicopathologic features and molecular data (mismatch repair status, KRAS, and BRAFV600E). Among 300 patients (156 men [52%]), the median age at diagnosis was 43 years (IQR, 39-47 years) for those with early-onset CRC and 67 years (IQR, 57-76) for those with average-onset CRC. Overall, 85% of patients were symptomatic at CRC diagnosis. Cancer stage, grade, molecular features, body mass index, and family history did not differ significantly between these groups. Among patients with colon cancer, the overall prevalence of synchronous neoplasia was similar, yet advanced adenomas were 3 times more frequent in those with early-onset vs average-onset cancers (31 of 75 [41%] vs 10 of 75 [13%]; P < .001). This difference was not associated with cancer stage or primary location. Among patients with rectal cancer, nonadvanced adenomas were less frequent among the early-onset group than the average-onset group (21 of 75 [28%] vs 36 of 75 [48%]), and although the prevalence of advanced adenomas was similar (11 of 75 [15%] vs 14 of 75 [19%]), they were more commonly located in the rectum (early onset, 5 of 11 [45%] vs average onset, 1 of 14 [7%]). Patients with early-onset cancer of the colon were significantly more likely than those with early-onset cancer of the rectum to have a synchronous advanced adenoma (31 of 75 [41%] vs 11 of 75 [15%]; P < .001). In this cross-sectional study, synchronous advanced adenomas were more commonly found in patients with early-onset colon cancer compared with average-onset colon cancer, and they were distributed throughout the colon. In contrast, advanced adenomas were not increased in patients with rectal cancer and, when detected, were predominantly located in the rectum.

Colorectal cancer (CRC) is the third leading cause of death from cancer in both men and women in the United States. Late onset colorectal cancer (LOCRC) or CRC diagnosed in older adults &amp;gt;50 years old has continued to decline while early onset colorectal cancer (EOCRC) or colorectal cancer in patients under the age of 50 continues to rise at an alarming rate since the mid-1990s. In fact, EOCRC is now the second most common cancer and the third leading cause of cancer mortality in people &amp;lt;50 years of age in the USA. The incidence of EOCRC has been on the rise over the past four decades and is expected to increase by &amp;gt;140% by 2030. Notably, Blacks and Hispanics are disproportionately affected with the EOCRC diagnosis. Despite this, minority patients remain underrepresented in clinical trials and translational research. It has been proposed that environmental exposures including westernized diet, metabolic factors, and the microbiome might be responsible for the rise in incidence of EOCRC. Epigenetic modifications are well-known mechanisms by which the environment can modulate gene expression without changing the DNA sequence. One such modification is DNA methylation, which controls DNA accessibility, chromatin formation, and gene transcriptional activity. Unfortunately, however, little is known about the role of DNA methylation in EOCRC and much less is understood of EOCRC in minority populations. Therefore, we identified a unique cohort of 11 EOCRC patients within the Baylor College of Medicine/Harris Health System which is comprised of majority minority EOCRC population (7- Hispanic, 2 Non-Hispanic (NH) Black, and 1 NH-White EOCRC patients). Using whole-genome bisulfite sequencing, we comprehensively characterized the DNA methylome at single-base resolution in our 11 EOCRC patient samples. Our analyses revealed distinct EOCRC methylation patterns including both global hypomethylation and promoter-specific hypermethylation, which were not previously captured in The Cancer Genome Atlas (TCGA) Analyses. Among the differentially methylated regions (DMRs), we discovered that DNA and RNA transcription pathways were enriched in EOCRCs at advanced stage. Furthermore, we identify differential DMRs patterns among ethnicities. Taken together, our work supports a pathogenic role for DNA methylation in EOCRC. We are the first group to take this comprehensive unbiased approach to analyze the methylome in an underrepresented EOCRC cohort of patients. Citation Format: Karen Riggins, Jason Sheng Li, Benjamin Musher, Li Yang, Patricia Castro, Wedad Alfarkh, Neda Zarrin-Kamah, Michael Scheurer, Chad Creighton, Wei Li, Lanlan Shen. Methylome-wide profiling of early-onset colorectal cancer in underrepresented populations [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr C057.

Incidence rates (IRs) of early-onset colorectal cancer (EOCRC) are increasing, whereas average-onset colorectal cancer (AOCRC) rates are decreasing. However, rural-urban and racial/ethnic differences in trends by age have not been explored. The objective of this study was to examine joint rural-urban and racial/ethnic trends and disparities in EOCRC and AOCRC IRs. Surveillance, Epidemiology, and End Results data on the incidence of EOCRC (age, 20-49 years) and AOCRC (age, ≥50 years) were analyzed. Annual percent changes (APCs) in trends between 2000 and 2016 were calculated jointly by rurality and race/ethnicity. IRs and rate ratios were calculated for 2012-2016 by rurality, race/ethnicity, sex, and subsite. EOCRC IRs increased 35% from 10.44 to 14.09 per 100,000 in rural populations (APC, 2.09; P < .05) and nearly 20% from 9.37 to 11.20 per 100,000 in urban populations (APC, 1.26; P < .05). AOCRC rates decreased among both rural and urban populations, but the magnitude of improvement was greater in urban populations. EOCRC increased among non-Hispanic White (NHW) populations, although rural non-Hispanic Black (NHB) trends were stable. Between 2012 and 2016, EOCRC IRs were higher among all rural populations in comparison with urban populations, including NHW, NHB, and American Indian/Alaska Native populations. By sex, rural NHB women had the highest EOCRC IRs across subgroup comparisons, and this was driven primarily by colon cancer IRs 62% higher than those of their urban peers. EOCRC IRs increased in rural and urban populations, but the increase was greater in rural populations. NHB and American Indian/Alaska Native populations had particularly notable rural-urban disparities. Future research should examine the etiology of these trends.

CRCDB: A comprehensive database for integrating and analyzing multi-omics data of early-onset and late-onset colorectal cancer

3586 Background: The etiology of the rising incidence of early-onset colorectal cancer (EOCRC), defined as in patients aged &lt;50, remains unknown. EOCRC is diagnosed at advanced pathologic stages compared to average-onset colorectal cancer (AOCRC; age &gt;60). We previously reported data for Stages I-III disease. In this analysis, we evaluated tumor genomic differences in stage IV EOCRC versus AOCRC. Methods: The cohort included 3212 patients diagnosed with stage IV colon or rectal cancer who had whole exome sequencing (WES) as part of clinical tumor-informed ctDNA testing (Signatera, bespoke mPCR NGS assay, Natera, Inc.). Tumor mutational burden (TMB) and microsatellite instability (MSI) status were derived from tumor WES analysis. The prevalence of somatic variants, gene mutations and mutational signatures were compared between EOCRC and AOCRC groups, stratified by TMB and MSI status. Fisher’s exact test was used to test significance between age groups and p-values were adjusted using the FDR method for multiple test correction. Results: A total of 1070 patients with EOCRC (75.8% colon, 22.2% rectal, 2% unknown) and 2141 patients with AOCRC (80.2% colon, 18.3% rectal, 1.5% unknown) were included. No significant differences were found in the frequency of MSI and TMB status between age groups. In the TMB-Low/MSS group (EOCRC N=982; AOCRC N=1930), TP53 mutations were more common in EOCRC (62% vs. 54.5%, p=0.0036), but APC gene mutations were less common in EOCRC (59% vs. 65%, p=0.02). In the TMB-High/MSI-H group (EOCRC N=64; AOCRC N=182), BRAFand BEND4 mutations were less common in EOCRC (6.2% vs. 59.3%, p&lt;0.001 and 6.2% vs 31.9%, p=0.036), but KRASgene mutations were more common in EOCRC (54.7% vs. 17%, p&lt;0.001). BRAF V600E was the only significant single variant (0% vs 59.3% p&lt;0.001). No significant differences were found in the TMB-High/MSS group (EOCRC N=24; AOCRC N=29). In the mutational signature analysis for the TMB-Low/MSS group, the clock-like signature was less frequent in EOCRC (76.9% vs. 85.4%, p&lt; 0.001). In the TMB-High/MSI-H group, MMR deficiency signature was the most frequent signature, however no significant differences were found between EOCRC and AOCRC (81.25% vs. 85.71, p=0.42). In the TMB-High/MSS group, POLE exonuclease domain mutations signature was 2.2 times more frequent in EOCRC (62.5% vs. 27.6%, p&lt;0.024). MMR deficiency signature was also less common in EOCRC vs. AOCRC (33.33% vs. 55.17%; p&lt;0.10). Conclusions: Tumors in EOCRC harbored unique genomic alterations that varied between the TMB-Low/MSS, TMB-High/MSI-H, and TMB-High/MSS subpopulations. In TMB-Low/MSS tumors, similar gene mutations and genomic signatures were observed. However, the TMB-High/MSI-H and TMB-High/MSS subgroups harbored gene mutations and signatures that differed between age groups, suggesting that EOCRC may arise from uniquely different mutagenic processes in these subgroups.