Currently, no consensus exists regarding the definition of oligometastatic pancreatic ductal adenocarcinoma, its necessary diagnostic measures, and potential treatment approaches. To address these knowledge gaps, the OligoPanc project brought together an interdisciplinary group of experts to establish consensus using a modified Delphi process and clinical vignettes. Participants agreed that the number of metastatic lesions and the number of affected organs are key elements in defining oligometastatic pancreatic ductal adenocarcinoma. Specifically, up to three lesions in a single organ, either the liver or the lung, define oligometastatic pancreatic ductal adenocarcinoma and could be either synchronous or metachronous. Necessary diagnostics include a triple-phase contrast-enhanced CT scan of the chest and abdomen and MRI of the liver with a hepatocyte-specific contrast agent. In unclear cases, [18F]fluorodeoxyglucose-PET CT or MRI can be considered. A multidisciplinary tumour board is essential. Patient-intrinsic factors, including age, do not define oligometastatic disease but should be considered for any treatment decision. Systemic treatment before any local consolidative treatment, including surgery, stereotactic ablative radiotherapy, or other locally ablative techniques, is mandatory. The proposed definition should be incorporated into future trials to improve comparability and enable validation.

BACKGROUND:Data on the prognostic value of dMMR/MSI-H in locally advancer rectal cancer (LARC) are inconsistent and mostly from patients treated with conventional neoadjuvant therapy. We sought to evaluate oncological outcomes by mismatch repair/microsatellite (MMR/MS) status in LARC patients treated with total neoadjuvant therapy (TNT). METHODS:Patients from the International Real-World Study of TNT in Rectal Cancer tested for dMMR/MSI-H by immunohistochemistry and/or molecular testing were included. Pathological complete response (pCR), complete response (CR, pCR + clinical complete response), event-free survival (EFS) and overall survival (OS) were assessed by MMR/MS status in the overall and matched populations. For the latter, variable-ratio matching according to nine variables (age, year of diagnosis, tumour location, staging modality, cT stage, cN stage, presence of lateropelvic lymphadenopathy, distance from the mesorectal fascia, TNT regimen) was applied. RESULTS:Of 1911 patients, 1320 (69.1%) (09/2012-09/2025) had information on the MMR/MS status, 46 (3.5%) having dMMR/MSI-H tumours. No outcome differences were found by MMR/MS status in the overall population. In the matched population (n = 372), pCR was 14.2% among patients with pMMR/MSS tumours versus 12.5% among those with dMMR/MSI-H tumours (adjusted OR 1.07, 95%CI 0.39-2.91, p = 0.899), while CR was 18.9% and 16.7%, respectively (adjusted OR 0.95, 95%CI 0.35-2.58, p = 0.917). 3-year EFS and 5-year OS were 65.8% and 79.2%, and 67.6% and 93.5% in patients with pMMR/MSS and in those with dMMR/MSI-H tumours, respectively (adjusted HR EFS 1.30, 95%CI 0.57-2.89, p = 0.527; adjusted HR OS 2.52, 95%CI 0.67-9.42, p = 0.171). CONCLUSIONS:In this study, the dMMR/MSI-H phenotype did not hold prognostic value in LARC patients treated with TNT.

Colorectal cancer predominantly affects older adults (ie, those aged 70 years or older). Along with shifting demographic trends, the number of patients with colorectal cancer in this age group is estimated to sharply increase globally over the next few decades. During the past decade, new treatment modalities and systemic therapeutic options have been introduced through well conducted clinical trials that shaped and fundamentally redefined the treatment landscape. However, older adults with reduced physiological reserves, functional impairment, comorbidities, and geriatric syndromes are under-represented in such studies. Yet, for this population, growing evidence for geriatric assessment and management shows patient-centred benefits with the potential to further improve outcomes, parallel to the broadening armamentarium of medical innovations. The purpose of this Review is to summarise the evidence base of the current therapeutic landscape of colorectal cancer and guide management of older adults in daily clinical practice through pragmatic decision making.

Background: Breast, colorectal, lung and prostate cancers are the most frequent malignancies in Cyprus. This study estimated the incidence rate and 5-year net survival (NS) trends for these cancers, by sex, age, and tumor stage at diagnosis Methods: We analyzed data from the Cyprus Cancer Registry for adults diagnosed between 2004 and 2017, with follow-up until 2019. Tumor stage was classified into localized, regional, distant and unknown categories. We estimated the annual percentage change (APC) in incidence rates using Joinpoint regression. NS was estimated using flexible parametric models, adjusting for sex, age, stage and period of diagnosis. Multiple imputation was used to address unknown cancer stage. Results: During 2004-2017, the incidence significantly increased for breast and lung cancer (APC: 1.1 % and 2.6 %, respectively), mainly among the elderly (70 +). A decreasing trend was identified for prostate cancer only among individuals aged 80 +. No temporal variations were identified for colorectal cancer incidence. A positive time trend was identified for localized breast cancer between 2006 and 2017 (APC: 2.8 %). Conversely, a significant increase was noted at more advanced stages for lung (APC distant : 4.1 %) and prostate (APC regional : 7.6 %) cancers. NS improved for all cancers, ranging between 80 % and 90 % for regional and all stages of breast cancer, localized colorectal cancer, and all stages of prostate cancer, surpassing 95 % for localized breast cancer, localized and regional prostate cancer. Conclusion: The study observed increased (breast and lung) or stable (colorectal and prostate) cancer incidence and substantial improvements in 5-years NS trends for all cancer types, despite differences by sex and stage. Efforts should be intensified to reduce incidence by addressing cancer risk factors, and to improve survival by implementing and increasing the uptake of screening programs.

Background Approved treatments for colorectal cancer (CRC) patients pretreated with two lines of therapy are of limited efficacy. Anti-epidermal growth factor receptor (EGFR) re-challenge might represent an option in RAS wild-type tumours. This study aimed to evaluate the efficacy of anti-EGFR re-challenge strategies (panitumumab/chemotherapy). Materials and methods RAS wild-type metastatic CRC patients following first-line chemotherapy + anti-EGFR agent and second-line chemotherapy ± anti-vascular endothelial growth factor agent were eligible. Panitumumab with irinotecan or oxaliplatin-based chemotherapy was used. The primary objective was response rate (RR). Secondary objectives were safety, progression-free survival and overall survival. Next-generation sequencing-based genotyping in archived tissue and plasma was carried out to identify prognostic factors. Results The study closed prematurely, due to poor accrual, with 23 patients included. Most patients had primary tumours in the left colon/rectum, and the liver was the most common metastatic site. Treatment modifications were required in 74% of patients due to side-effects primarily, neutropenia and acneiform rash. One patient died from hepatic failure. The objective RR in the intention-to-treat population was 13%, and the disease control rate (DCR) was 52%. Forty-eight percent of patients tested via liquid biopsy had RAS mutations before re-challenge with panitumumab despite a median interval from previous anti-EGFR therapy of 12 months. Control of disease did not correlate with the results of liquid biopsy. RR and DCR in patients without RAS mutations in liquid biopsies were 18.2% and 54.5%, respectively. Conclusion Panitumumab/chemotherapy as an anti-EGFR re-challenge strategy had modest activity in our patient cohort.

Importance:This was a clinical study of total neoadjuvant therapy (TNT) for rectal cancer. Objective:To assess the use and outcomes of TNT in routine practice. Design, Setting, and Participants:This international, multicenter study was conducted at 61 centers across 21 countries and included consecutive patients treated off trial with TNT for stage II/III rectal adenocarcinoma from September 2012 to December 2023. Data were analyzed between August and October 2024. Exposure:TNT, defined as the delivery of radiotherapy and nonradiosensitizing chemotherapy before surgery or watch and wait. Main Outcomes and Measures:The primary outcome was type of TNT administered. Secondary outcomes were patient characteristics, treatment adherence, safety, and efficacy overall and by type of TNT in the entire population and after propensity vector matching. Results:A total of 1585 patients (588 female [37.1%]; median [IQR] age, 61 [53-68] years) were included, 1260 (79.5%) of whom had 1 or more high-risk features (eg, cT4, cN2, extramural venous invasion, threatened/involved mesorectal fascia, and lateropelvic lymphadenopathy). Patients were treated with the PRODIGE 23-like regimen (FOLFIRINOX/FOLFOXIRI followed by long-course chemoradiotherapy) (271 [17.7%]), RAPIDO-like regimen (short-course radiotherapy followed by consolidation FOLFOX/CAPOX) (529 [33.4%]), OPRA induction-like (induction FOLFOX/CAPOX followed by long-course chemoradiotherapy) (190 [12.0%]), OPRA consolidation-like (long-course chemoradiotherapy followed by consolidation FOLFOX/CAPOX) (257 [16.2%]), and other regimens (360 [22.7%]). After TNT, 192 (12.1%) underwent watch and wait, and 30 (1.9%) underwent local excision. Pathological or clinical complete response was reported in 23.2% of cases. At treatment failure, 8.5% was local and 16.4% was distant progression. Three-year event-free survival (EFS) was 68% (95% CI, 64%-71%), and 5-year overall survival (OS) was 79% (95% CI, 75%-83%). In the overall population, patients treated with the PRODIGE 23-like regimen were most likely to have serious adverse events (61 [23.5%]) but had better local control and survival outcomes than those treated with the RAPIDO-like (EFS: hazard ratio [HR], 0.68; 95% CI, 0.49-0.95; P = .03; OS: HR, 0.51; 95% CI, 0.27-0.97; P = .04), OPRA induction-like (EFS: HR, 0.66; 95% CI, 0.44-0.98; P = .04; OS: HR, 0.35; 95% CI, 0.18-0.70; P = .003), and OPRA consolidation-like (EFS: HR, 0.64; 95% CI, 0.44-0.93; P = .02; OS: HR, 0.50; 95% CI, 0.25-1.00; P = .05) regimens. In the matched population (928 patients [58.5%]), no differences in survival outcomes were observed between the TNT regimens. Conclusions and Relevance:The findings of this case series study show substantial variation in the choice of the TNT regimen and were overall aligned with those reported in clinical trials, suggesting the efficacy of TNT in a clinical setting regardless of the specific regimen.

INTRODUCTION:The rising incidence of early-onset gastrointestinal (GI) cancer has made the impact of treatments on fertility of high significance. While there is abundant evidence on oncofertility outcomes in breast cancer and hematological malignancies, data regarding these perspectives in GI cancers is lacking. We sought to evaluate current practices of fertility preservation (FP) among GI oncologists across Europe. METHODS:A cross-sectional survey was distributed through the Gastrointestinal Tract Cancer Group (GITCG) of the EORTC network and affiliated cooperative groups and cancer centers using a 10-item electronic survey regarding oncofertility practices. The target population was oncologists who routinely treat GI cancers. A statistical analysis was performed based on country, patient volume, and tumor type. RESULTS:Two hundred and twenty-six GI oncologists from 27 countries completed the survey, the majority from high volume cancer centers. Fifty seven percent of the participating oncologists routinely discuss the impact of treatment on fertility in any patient <40 years, while 36% discuss this only in the curative setting. Fifty-nine percent refer female patients to standard FP options (embryo/oocyte preservation), while 24% chose to refer to ovarian cryopreservation. Of note, 17% indicated they would not refer a curative patient for FP at all due to time or resource issues. Sixty five percent routinely refer male patients to sperm preservation. Use of Gonadotropin Releasing Hormone analogues (GnRHa) in CRC patients is recommended by 34% of oncologists. In the setting of pelvic radiation, 65% refer a female patient for ovarian transposition before pelvic irradiation; 32% would consider uterine transposition. Sixty one percent would consider a nonradiation protocol as perioperative chemotherapy as a valid option for young female patients. We observed heterogeneity upon country but not upon physician gender. CONCLUSION:Our study indicates a substantial diversity in current practices in Europe with regard to FP in young cancer patients with GI malignancies, which is not always aligned with current guidelines. There is a need to disseminate and educate GI oncologists on oncofertility perspectives and contemporary data. Additionally, there is a need to establish evidence on the utility of fertility preservation options for patients with GI cancers.

Older adults are underrepresented in clinical trials, and studies specifically focused on older cancer patients are uncommon. By screening PubMed, EMBASE and proceedings from international meetings, we searched for trials testing systemic therapies in solid cancer patients aged ≥70 years. We identified age-unselected trials testing the same intervention in the same setting. The primary objective was to assess the proportion of older-age-selected trials meeting the target accrual. Secondary objectives included the analysis of the use of geriatric assessment (GA) tools and quality of life (QoL) questionnaires, and the comparison between older-age-selected and matching age-unselected trials. We included 313 trials (10.9 % phase I, 78.6 % phase I/II-II, and 10.5 % phase III). 7.7 % were published in 1990-2000, 40.3 % in 2001-2011, and 52.1 % in 2012-2023. Of 234 evaluable trials, 77.8 % enrolled ≥90 % of the required patients. Premature study discontinuation occurred in 50 cases (5.9 % phase I, 14.2 % phase II, 39.4 % phase III). Among 232 evaluable trials, 60.3 % met the primary endpoint (63.7 % phase I/II-II, 35.5 % phase III). GA and QoL analyses were carried out in 28.1 % and 23 % of trials, respectively. Corresponding age-unselected trials were identified for 154 older-age-selected trials. Compared with age-unselected trials, a lower proportion of older-age-selected trials met the target accrual (83.5 % vs 94.8 %, p = 0.035) or the primary endpoint (63.9 % vs 81.5 %, p = 0.022). In conclusion, older-age-selected trials are increasingly performed but rarely include GA and QoL analyses. Effective strategies to meet target accrual should be implemented especially for phase III trials, which suffer from high rates of premature discontinuation.

PURPOSE A number of studies suggest that older patients may have reduced or no benefit from the addition of oxaliplatin to fluoropyrimidines as adjuvant chemotherapy for stage III colon cancer (CC). MATERIALS AND METHODS We studied the prognostic impact of age, as well as treatment adherence/toxicity patterns according to age, in patients with stage III CC who received 3 or 6 months of infusional fluorouracil, leucovorin, and oxaliplatin/capecitabine and oxaliplatin (CAPOX) on the basis of data collected from trials from the ACCENT and IDEA databases. Associations between age and time to recurrence (TTR), disease-free survival (DFS), overall survival (OS), survival after recurrence (SAR), and cancer-specific survival (CSS) were assessed by a Cox model or a competing risk model, stratified by studies and adjusted for sex, performance status, T and N stage, and year of enrollment. RESULTS A total of 17,909 patients were included; 24% of patients were age older than 70 years (n = 4,340). Patients age ≥70 years had higher rates of early treatment discontinuation. Rates of grade ≥3 adverse events were similar between those older and younger than 70 years, except for diarrhea and neutropenia that were more frequent in older patients treated with CAPOX (14.2% v 11.2%; P = .01 and 12.1% v 9.6%; P = .04, respectively). In multivariable analysis, TTR was not significantly different between patients <70 years and those ≥70 years, but DFS, OS, SAR, and CSS were significantly shorter in those patients ≥70 years. CONCLUSION In patients ≥70 years with stage III CC fit enough to be enrolled in clinical trials, oxaliplatin-based adjuvant chemotherapy was well tolerated and led to similar TTR compared with younger patients, suggesting similar efficacy. TTR may be a more appropriate end point for efficacy in this patient population.

With the aging population, older adults constitute a growing proportion of the new cancer cases. Given the heterogeneous health status among older adults and their susceptibility to aging-related vulnerabilities, understanding their diversity and its implications becomes increasingly crucial for prognostication and guiding diagnostics, treatment decisions, and follow-up, as well as informing supportive care interventions. Geriatric assessment and management (GAM) refers to the comprehensive evaluation of an older individual’s health status with subsequent management plans focusing on both oncologic and non-oncologic interventions. In 2019, the European Society for Medical Oncology (ESMO) and the International Society of Geriatric Oncology (SIOG) established the ESMO/SIOG Cancer in the Elderly Working Group. This position paper reflects the recommendations of the working group. Our paper summarizes the existing evidence with a focus on recent key trials and based on this, we propose several recommendations and future directions.

AIM:Multiple neoadjuvant therapy strategies have been used and compared for rectal cancer and there has been no true consensus as to the optimal neoadjuvant therapy regimen. The aim is to identify and compare the neoadjuvant therapies available for stage II and III rectal cancer.DESIGN:A systematic literature review was performed, from inception to August 2022, of the following databases: MEDLINE, EMBASE, Science Citation Index Expanded, Cochrane Library. Only randomized controlled trials comparing neoadjuvant therapies for stage II and III rectal cancer were considered. Stata was used to draw network plots, and a Bayesian network meta-analysis was conducted through models utilizing the Markov Chain Monte Carlo method in WinBUGS.RESULTS:A total of 58 articles were included based on 41 randomised controlled trials, reporting on 12,404 participants that underwent 15 neoadjuvant treatment regimens. No significant difference was identified between treatments for major or total postoperative complications, anastomotic leak rates, or sphincter-saving surgery. Straight to surgery (STS) ranked as best treatment for preoperative toxicity but ranked worst treatment for positive resection margins and complete response. STS had significantly increased positive resection margins compared to long-course chemoradiotherapy with short-wait (LCCRT-SW) or long-wait (LCCRT-LW) to surgery, or short-course radiotherapy with short-wait (SCRT-SW) or immediate surgery (SCRT-IS). LCCRT-SW or LCCRT-LW resulted in significantly increased complete response rates compared to STS. LCCRT-LW significantly improved 2-year overall survival compared to STS, SCRT-IS, SCRT-SW. Total neoadjuvant therapy regimes with short-course radiotherapy followed by consolidation chemotherapy (SCRT-CT-SW), induction chemotherapy followed by long-course chemoradiotherapy (CT-LCCRT-S), long-course chemoradiotherapy followed by consolidation chemotherapy (LCCRT-CT-S), significantly improved positive resection margins, complete response, and disease-free survival compared to STS. Chemotherapy with monoclonal antibodies followed by long-course chemoradiotherapy (CT+MAB-LCCRT+MAB-S) significantly improved complete response and positive resection margins compared to STS, and 2-year disease-free survival compared to STS, SCRT-IS, SCRT-SW, SCRT-CT-SW, LCCRT-SW, LCCRT-LW. CT+MAB-LCCRT+MAB-S ranked as best treatment for disease-free survival and overall survival.CONCLUSIONS:Conventional neoadjuvant therapies with short-course radiation or long-course chemoradiotherapy have oncological benefits compared to no neoadjuvant therapy without increasing perioperative complication rates. Prolonged wait to surgery may improve oncological outcomes. Total neoadjuvant therapies provide additional benefits in terms of complete response, positive resection margins, and disease-free survival. Monoclonal antibody therapy may further improve oncological outcomes but currently is only applicable to a small subgroup of patients and requires further validation.

PURPOSE: In a previous study of treatment for advanced colorectal cancer, the LV5FU2 regimen, comprising leucovorin (LV) plus bolus and infusional fluorouracil (5FU) every 2 weeks, was superior to the standard North Central Cancer Treatment Group/Mayo Clinic 5-day bolus 5FU/LV regimen. This phase III study investigated the effect of combining oxaliplatin with LV5FU2, with progression-free survival as the primary end point. PATIENTS AND METHODS: Four hundred twenty previously untreated patients with measurable disease were randomized to receive a 2-hour infusion of LV (200 mg/m2/d) followed by a 5FU bolus (400 mg/m2/d) and 22-hour infusion (600 mg/m2/d) for 2 consecutive days every 2 weeks, either alone or together with oxaliplatin 85 mg/m2 as a 2-hour infusion on day 1. RESULTS: Patients allocated to oxaliplatin plus LV5FU2 had significantly longer progression-free survival (median, 9.0 v 6.2 months; P = .0003) and better response rate (50.7% v 22.3%; P = .0001) when compared with the control arm. The improvement in overall survival did not reach significance (median, 16.2 v 14.7 months; P = .12). LV5FU2 plus oxaliplatin gave higher frequencies of National Cancer Institute common toxicity criteria grade 3/4 neutropenia (41.7% v 5.3% of patients), grade 3/4 diarrhea (11.9% v 5.3%), and grade 3 neurosensory toxicity (18.2% v 0%), but this did not result in impairment of quality of life (QoL). Survival without disease progression or deterioration in global health status was longer in patients allocated to oxaliplatin treatment (P = .004). CONCLUSION: The LV5FU2-oxaliplatin combination seems beneficial as first-line therapy in advanced colorectal cancer, demonstrating a prolonged progression-free survival with acceptable tolerability and maintenance of QoL.

OBJECTIVE:To analyze the factors associated with overall survival (OS) and progression-free survival (PFS) in patients with ovarian cancer in Cyprus. METHODS:We retrospectively analyzed data from patients with histologically confirmed epithelial ovarian cancer (EOC) and primary peritoneal cancer (PPC). RESULTS:A total of 106 women diagnosed with ovarian cancer were included, with a median age at diagnosis of 58 years. The Kaplan-Meier survival analysis showed a median OS of 41 months (95% C.I = 36.9, 45.1), and the FIGO stage (p < 0.001), type of surgery (p < 0.001) and performance status (p < 0.001) were identified as statistically significant prognostic factors for OS. PFS analysis revealed the FIGO stage (p = 0.006) and the performance status (p < 0.001) as significant prognostic factors. Additionally, a Cox regression analysis for median OS was performed for patients with high-grade serous carcinoma, identifying the performance status, FIGO stage, and type of surgery as prognostic factors in univariate analysis. However, in the subsequent multivariate analysis, the performance status and the FIGO stage were confirmed to be the only statistically significant prognostic factors for OS (p < 0.05). CONCLUSIONS:This study confirms that the FIGO stage, performance status, and surgery type were considered as prognostic factors for OS in ovarian cancer.

PURPOSE Oxaliplatin-based adjuvant chemotherapy in patients with stage III colon cancer (CC) for 6 months remains a standard in high-risk stage III patients. Data are lacking as to whether early discontinuation of all treatment (ETD) or early discontinuation of oxaliplatin (EOD) could worsen the prognosis. MATERIALS AND METHODS We studied the prognostic impact of ETD and EOD in patients with stage III CC from the ACCENT/IDEA databases, where patients were planned to receive 6 months of infusional fluorouracil, leucovorin, and oxaliplatin or capecitabine plus oxaliplatin. ETD was defined as discontinuation of treatment and EOD as discontinuation of oxaliplatin only before patients had received a maximum of 75% of planned cycles. Association between ETD/EOD and overall survival and disease-free survival (DFS) were assessed by Cox models adjusted for established prognostic factors. RESULTS Analysis of ETD and EOD included 10,447 (20.9% with ETD) and 7,243 (18.8% with EOD) patients, respectively. Compared with patients without ETD or EOD, patients with ETD or EOD were statistically more likely to be women, with Eastern Cooperative Oncology Group performance status ≥ 1, and for ETD, older with a lower body mass index. In multivariable analyses, ETD was associated with a decrease in disease-free survival and overall survival (hazard ratio [HR], 1.61, P < .001 and HR, 1.73, P < .001), which was not the case for EOD (HR, 1.07, P = .3 and HR, 1.13, P = .1). However, patients who received < 50% of the planned cycles of oxaliplatin had poorer outcomes. CONCLUSION In patients treated with 6 months of oxaliplatin-based chemotherapy for stage III CC, ETD was associated with poorer oncologic outcomes. However, this was not the case for EOD. These data favor discontinuing oxaliplatin while continuing fluoropyrimidine in individuals with significant neurotoxicity having received > 50% of the planned 6-month chemotherapy.

In this study of 400 patients with early-onset rectal cancer, 12.5 per cent demonstrated microsatellite instability (MSI). MSI was associated with a reduced likelihood of nodal positivity, an increased rate of pathological complete response, and improved disease-specific survival.

Background The molecular profile of early-onset colonic cancer is undefined. This study evaluated clinicopathological features and oncological outcomes of young patients with colonic cancer according to microsatellite status. Methods Anonymized data from an international collaboration were analysed. Criteria for inclusion were patients younger than 50 years diagnosed with stage I-III colonic cancer that was surgically resected. Clinicopathological features, microsatellite status, and disease-specific outcomes were evaluated. Results A total of 650 patients fulfilled the criteria for inclusion. Microsatellite instability (MSI) was identified in 170 (26.2 per cent), whereas 480 had microsatellite-stable (MSS) tumours (relative risk of MSI 2.5 compared with older patients). MSI was associated with a family history of colorectal cancer and lesions in the proximal colon. The proportions with pathological node-positive disease (45.9 versus 45.6 per cent; P = 1.000) and tumour budding (20.3 versus 20.5 per cent; P = 1.000) were similar in the two groups. Patients with MSI tumours were more likely to have BRAF (22.5 versus 6.9 per cent; P < 0.001) and KRAS (40.0 versus 24.2 per cent; P = 0.006) mutations, and a hereditary cancer syndrome (30.0 versus 5.0 per cent; P < 0.001; relative risk 6). Five-year disease-free survival rates in the MSI group were 95.0, 92.0, and 80.0 per cent for patients with stage I, II, and III tumours, compared with 88.0, 88.0, and 65.0 per cent in the MSS group (P = 0.753, P = 0.487, and P = 0.105 respectively). Conclusion Patients with early-onset colonic cancer have a high risk of MSI and defined genetic conditions. Those with MSI tumours have more adverse pathology (budding, KRAS/BRAF mutations, and nodal metastases) than older patients with MSI cancers. Data on 650 patients aged less than 50 years diagnosed with stage I-III colonic cancer and undergoing surgery with curative intent were collected, and the impact of microsatellite instability (MSI) on clinicopathological features and disease-specific outcomes was assessed. Patients with early-onset disease had a high risk of MSI and defined genetic conditions. Those with MSI tumours had more adverse pathology (budding, KRAS/BRAF mutations, and nodal metastases) than older patients with MSI cancers.