Abstract 268P
Background
Rectal cancer is the second most common gastrointestinal (GI) malignancy representing 2-5% of all GI tumors while rectal adenocarcinoma (AC) is the most common subtype of rectal tumors. Although rectal neoplasm has an increasing incidence, the association of second primary GI squamous cell carcinoma (SCC) is poorly discussed in the literature. So, in this study we aimed to assess the risk of GI SCC following the diagnosis of primary rectal adenocarcinoma.
Methods
From the Surveillance Epidemiology and End Results (SEER) database, we used the data of 145,789 patients with rectal adenocarcinoma first primary with sequence (0) or (1). We used MP-SIR session to calculate the standardized incidence ratios (SIR) ratio as observed/Expected (O/E) with latency exclusion period of 0 month, Excess Risk (ER) was calculated per 10.000 and with 95% confidence intervals (CI). The results were significant if P>0.05.
Results
Out of 145,789 patients with rectal adenocarcinoma, 5199 patients developed second primary GI SCC with an O/E of 2.62 (P˂0.05, 95% CI:2.69-2.55, EAR=46.50) with increased risk in 0-11 months interval (O/E = 7.91, P˂0.05, 95% CI 8.25 – 7.59, ER = 180.79). The most common site to develop second primary GI SCC was the rectum (O/E= 5.82; P<0.05, 95% CI: 6.16 - 5.49, ER=14.11), Anus anal canal (O/E= 4.89, P<0.05, 95% CI: 5.67- 4.20, Excess Risk = 2.02). then Descending colon (O/E = 4.60, P<0.05, 95% CI: 5.30-3.96, ER=2.14). But the risk was insignificant for the intrahepatic bile duct (O/E = 1.11, P˃0.05, 95% CI: 1.57 – 0.76, ER = 0.05), Liver (O/E = 1.10, P˃0.05, 95% CI: 1.25 – 0.96, ER = 0.28), gallbladder (O/E = 1, P˃0.05, 95% CI: 1.45 – 0.67, ER = 0) and pancreas (O/E = 0.94, P˃0.05, 95% CI: 1.05 – 0.84, ER = - 0.29).
Conclusions
Patients with Rectal adenocarcinoma had more than two folds increased risk of developing Gastrointestinal SCC Which highlights the necessity to implement a screening program for GI SCC following the diagnosis of rectal adenocarcinoma for a proper management plan and better outcomes epically in the first 11 months after diagnosis.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.