DOES LOSS OF ARID1A EXPRESSION AFFECT NEOADJUVANT CHEMORADIOTHERAPY RESPONSE IN RECTAL CARCINOMAS?

This study evaluated the difference of ARID1A protein immunoexpression between responders and non-responders to neoadjuvant chemoradiotherapy in locally advanced rectal cancers. The biopsies before neoadjuvant chemoradiotherapy and resection materials after mesorectal excision were re-examined for conventional prognostic parameters, tumour regression score was determined, and survival data were evaluated. All parameters were statistically compared. Of the 117 cases, most (93%) were adenocarcinoma, 88% were moderately differentiated and no response was seen in 28%. Before neoadjuvant therapy, low nuclear expression of ARID1A was noted in 49 (41.9%), while high expression was observed in 68 cases (58.1%). After neoadjuvant therapy, low expression was observed in 12 (10.7%) cases, while high expression was seen in 90 cases (80.3%). After neoadjuvant therapy a statistically lower ARID1A expression was noted in the absence of distant organ metastasis (p = 0.033). No statistically significant relationship was observed between ARID1A expression and overall survival or progression-free survival. ARID1A expression before neoadjuvant treatment had no statistically significant effect on response to neoadjuvant treatment and was not significantly associated with survival. More patients had significantly higher ARID1A expression in the post-treatment period than the pretreatment period. This may suggest that tumour cells with low ARID1A expression are more sensitive to neoadjuvant therapy.