P-261 Oxaliplatine plus fluoropyrimidine versus fluoropyrimidine monotherapy as adjuvant treatment for stage III resected colorectal cancer (CRC) in older population, a single centre experience

Fluoropyrimidine plus oxaliplatine treatment has proven an increase in survival rates in stage III resected CRC. However, clinical trials, mostly do not include population above 70 years or pool the results with younger patients. It is uncertain if the addition of oxaliplatin is as effective in older patients, having conflicting data from different studies. Oxaliplatine increases treatment related-toxicity being this especially important in this population with more frailty, comorbidities and age-derived organ decline function. Therefore, it is important to study if adding oxaliplatine benefits the older population. We analyzed retrospectively a cohort with 1464 patients diagnosed of colorectal cancer between October/2016 to December/2021. We selected those aged between 70 and 85 years, with stage III resected disease, who completed adjuvant treatment either with fluoropyrimidine monotherapy or fluoropyrimidine plus oxaliplatine. Elected treatment was based on the basal performance status and geriatric integral evaluation. We described baseline tumour characteristics (T4, N2, R1, obstruction and perforation, linfovascular infiltration, perineural infiltracion, high grade tumoral budding and mismatch repair status). We compared the risk of recurrence between both groups with a log-rank test and a Kaplan-Meier survival curve. We had a cohort of 150 patients with a median follow up of 28,7 months. All patients were ECOG 0-1. 91 patients received adjuvant treatment with fluoropyrimidine monotherapy with a median age of 79 (range 71-85). In this group 43 (47,25%) had T4 disease, 34 (37,36%) were N2, 8 (8,79%) were R1, 12 (13,18%) diagnosed with obstruction or perforation, 41 (45,05%) had linfovascular infiltration, 26 (28,57%) had perineural infiltration, 16 (17,58%) had high budding score and 10 (10,99%) were dMMR. 59 patients received oxaliplatine plus fluoropyrimidine with a median age of 74 (71-84). In this group 34 (57,63%) had T4 disease, 23 (38,98%) were N2, 5 (8,47%) were R1, 9 (15,25%) diagnosed with obstruction or perforation, 38 (64,41%) had linfovascular infiltration, 25 (42,37%) had perineural infiltration, 15 (28,81%) had high budding score and 7 (11,86%) were dMMR Overall groups were well balanced. We observed less recurrence rate in the group who received oxaliplatine and fluoropyrimidine treatment with 14 relapses (23,73%) compared to those who received fluoropyrimidine monotherapy with 27 relapses (29,67%), although these differences where not statistically significant (p=0,5893). In our cohort we did not observe an statitistically significant reduction of the risk of relapse with the addition of oxaliplatine to fluoropyrimidines in stage III resected patients elegible for the treatment. These results might be limited by the number of patients. It can also be limited because the group of fluorpyrimide treatment included more frail patients, with risk of relapse being underestimated because of death for other causes before the event or because a less intensive follow-up is done in this group of patients. However, these results are concordant with data published in the literature, suggesting that this population may be treated with fluoropyrimidine monotherapy. There should be more studies conducted in this population to assess the benefit of adding oxaliplatine with more potential toxicity in order to optimize the choice of treatment.