Second Primary Cancers After Liver, Gallbladder and Bile Duct Cancers, and These Cancers as Second Primary Cancers.

BACKGROUND

Second primary cancers (SPCs) are important clinically as they may negatively influence patient survival and they may tell about therapeutic side effects and general causes of cancer. Population-based literature concerning SPCs after hepatobiliary cancers is limited and here we assess risks of SPCs after hepatocellular cancer (HCC), and cancers of the gallbladder, bile ducts and ampulla of Vater. In reverse order, we consider the risk of hepatobiliary cancers as SPCs after any cancer.

METHODS

We used standardized incidence ratios (SIRs) to estimate bidirectional relative risks of subsequent cancers associated with hepatobiliary cancers. Cancer diagnoses were obtained from the Swedish Cancer Registry from years 1990 through 2015.

RESULTS

We identified 9997 primary HCCs, 1365 gallbladder cancers and 4721 bile duct cancers. After HCC, risks of four SPCs were increased: gallbladder (SIR = 4.38; 95% confidence interval 1.87-8.67), thyroid (4.13; 1.30-9.70), kidney (2.92; 1.66-4.47) and squamous cell skin (1.55; 1.02-2.26) cancers. In reverse order, HCC as SPC, in addition to the above cancers, associations included upper aerodigestive tract, esophageal, small intestinal and bladder cancers and non-Hodgkin lymphoma. For gallbladder and bile duct cancers, associations were found with small intestinal and pancreatic cancers.

CONCLUSION

The results suggested that HCC is associated with two types of SPC, one related to shared environmental risk factors, such as alcohol, exemplified by upper aerodigestive tract and esophageal cancer, and the other related to immune dysfunction, exemplified by squamous cell skin cancer. SPCs associated with gallbladder and bile duct cancers suggest predisposition to mutations in the mismatch repair gene MLH1.