1954P - The risk of second primary gastrointestinal tract GIT malignancy after primary retroperitoneal liposarcoma

Background

Gastrointestinal tract (GIT) retroperitoneal sarcomas are rare tumors representing 1-2% of all solid malignancies and 20% of sarcomas and the most common subtype is liposarcoma. As reported in the literature, the occurrence of multiple primary tumors in a different site than the first primary site is a rare event in the literature, and there are very limited data about retroperitoneal liposarcoma (RPLS) with only a few case reports and case series, so this study aimed to assess the risk of multiple GIT malignancies after primary RPLS.

Methods

Data of RPLS patients was extracted from Surveillance, Epidemiology, and End-Results (SEER) database diagnosed in 2000-2020. We used an MP-SIR session to calculate the standardized Incidence Ratio (SIR) as Observed/Expected (O/E) with 95% Confidence Intervals (CI) showed significance at P<0.05 and the Excessive Absolute Risk (EAR) per 10,000.

Results

In 2257 patients, we observed an increased risk of synchronous and metachronous retroperitoneal malignancy after primary RPLS with EAR of 56.34 (O/E=213.24, 95%CI: 271.30-164.92, P<0.05). There was an increased risk for small intestinal cancer in the 0-11 months after primary RPLS with O/E of 31.76 (95%CI: 81.32-8.65; P<0.05, EAR=5.31) and appendicular cancer (O/E=45.14, 95%CI: 163.05-5.47; P<0.05, EAR=9.86). The overall risk to develop 2nd primary gastric carcinoma (O/E= 1.49, 95%CI: 3.81-0.41; P>0.05, EAR =1.13), colorectal cancer (O/E=1,44, 95%CI: 2.30-0.84; P>0.05, EAR=4.44), hepatocellular carcinoma (O/E=2.08, 95%CI: 4.52-0.76; P>0.05, EAR=2.67), and pancreatic cancer (O/E=1.61, 95%CI: 3.17-0.69; P>0.05, EAR=2.60). While there was slightly decreased risk in esophageal carcinoma (O/E=0.56; P>0.05, EAR= -0.68) and gall bladder cancer (O/E= 0.00; P>0.05, EAR= -0.37).

Conclusions

These results show a significantly increased risk of synchronous and metachronous retroperitoneal cancer by 213-fold through ten years while the peak increase of small intestinal cancer and appendicular cancer as 2^nd primary malignancies is during the first-year interval. This highlights the importance of regular screening for tumors of the retroperitoneum, small intestine, and appendix after RPLS diagnosis for early detection and better management plan.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.