P-403 Rectal cancer in young patients – single center experience

Colorectal cancer (CRC) is the third most common cancer worldwide and the second most common cause of cancer-related death. The incidence of early-onset CRC in those younger than 50 years is rising globally. In this group, in the absence of high-risk features screening is not standard of care. There is strong evidence that development of CRC is related to diet and lifestyle. Retrospective, unicentric, cohort analysis of patients with rectal cancer diagnosed between January 2018 and August 2022 with ≤ 50 years old at diagnosis. Data was collected from electronic medical records regarding clinical and demographic parameters (including weight), preoperative assessment, treatment, tumor response and pattern of disease recurrence. Obesity and overweight were determined with body mass index (BMI) tables. There were 27 patients meeting inclusion criteria. Median age was 44 years, and 14 (52%) were female. All patients had symptoms that motivated further evaluation at the time of diagnosis. The most common was hematochezia in 12 (44%) of patients. All tumors were adenocarcinomas. The most frequent tumor location was the lower rectum, in 14 (52%) patients. Only 11 (41%) patients had a family history of cancer. Two patients had previously treated gastric and thyroid cancer. Six (22%) patients had moderate alcohol consumption and 10 (37%) had tobacco consumption. Regarding risk factors, 5/27 had obesity grade I and 3/27 patients were overweight. There were 3 patients with hereditary syndromes related to colorectal cancer: being 2 with familial adenomatous polyposis and 1 with Lynch syndrome. Clinical staging at diagnosis was: II in 1 (4%), III in 20 (74%) and IV in 6 (22%) patients. Curative treatment was done in 23 patients (74%). Neoadjuvant treatment was delivered to 21 (91%): mostly chemoradiotherapy based on capecitabine in 17 (81%). Two patients completed chemotherapy with capecitabine and oxaliplatin (CAPOX) based regimen. 1/23 had total mesorectal excision and 1/23 had complete response with MRI and considered for a watch and wait strategy. In the curative treatment setting, six patients had completed pathologic response. The majority were grade 2 tumors (59%), and 41% had neural invasion. Six (27%) patients had pathologic complete response. Median time of follow up was 26,7 months, and recurrence rate was 22,2%, with median 15,8 months to recurrence. In our experience, young-onset rectal cancer frequently presents with locally advanced and/or metastatic disease. High BMI seems to have high prevalence, showing a possible impact of microbiome and inflammation in the pathogenesis of rectal cancer (although this can’t be demonstrated conclusively in a cohort study). Due to the small sample size, we aim to perform a multicentric analysis, in order to assess possible risk factors and perhaps reappraise the current screening strategies of colorectal cancer in our country.