Cancer survivors are at a high risk to develop second primary malignancy (SPM) which constitutes a serious threat for them. Radiotherapy is the cornerstone for the management of many cancers as a locoregional treatment modality. Due to the low liver tolerance, cirrhotic patients are at a high risk of developing radiation-induced liver toxicities despite the modern safe radiation delivery techniques. Radiation damages cells through direct energy deposition and reactive free radical generation. Recent studies demonstrated a potential risk of SPMs following radiotherapy with further investigations for strategies to decrease radiation-induced SPMs. However, it is insufficiently addressed if developing liver SPMs is a serious adverse event following radiotherapy for cirrhotic patients. The aim of this study was to quantitatively assess the risk of gastrointestinal (GI) and liver SPMs following radiotherapy in patients with chronic liver disease.

The SEER.stat software version 8.4.3 was used to obtain and analyze the data of patients with chronic liver disease diagnosed from 2010 to 2021. Using Ishak fibrosis score: F0-4 no to moderate fibrosis and F5-6 advanced or severe cirrhosis. patients were subgrouped according to the history of receiving radiotherapy for prior cancer treatment in two groups and excluded patients with unknown radiotherapy administration history. An MP-SIR session was used to calculate the Standardized Incidence Ratio (SIR) as Observed/Expected (O/E) with 95% confidence interval (CI). Significance was achieved at 0.05.

Inclusion Criteria:

• Cancer patients were classified according to fibrosis severity using the Ishak fibrosis score: F0-F4 (no to moderate fibrosis) and F5-F6 (advanced or severe cirrhosis) from 2010 to 2021.

Exclusion Criteria:

• Patients with unknown radiotherapy history or unknown fibrosis score or missing age data

Using the Surveillance, Epidemiology and End Results (SEER) database (17 Registries, 2000-2021, November 2023 Submission), maintained by the National Cancer Institute (NCI) containing a population-based cancer incidence and survival data from 17 registries covering approximately 28% of the U.S. population to extract the data of cancer patients with chronic liver disease diagnosed from 2010 to 2021. Patients were classified according to fibrosis severity using the Ishak fibrosis score: F0-F4 (no to moderate fibrosis) and F5-F6 (advanced or severe cirrhosis) from 2010 to 2021. Patients were stratified based on previous radiotherapy exposure into two groups; who received radiotherapy including beam radiation, radioactive implants, radioisotopes, combinations, or unspecified radiotherapy methods and patients who received no radiotherapy.