A retrospective analysis of Selective Internal Radiation Therapy (SIRT) and chemotherapy for metastatic pancreatic adenocarcinoma.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is a major cause of cancer-related deaths in Australia, with a 5-year survival rate of less than 13%. The liver is the most common site of PDAC metastasis, and is observed in over 50% of cases. Standard chemotherapy, including regimens such as FOLFIRINOX or nab-paclitaxel plus gemcitabine, offer limited survival benefits, with median survival rates typically below one year. Selective internal radiation therapy (SIRT) with Yttrium-90 (90Y) microspheres is used to target liver metastases, but the optimal chemotherapy companion for SIRT in metastatic PDAC remains unknown.

METHODS: We conducted a retrospective audit of 32 patients with metastatic PDAC treated with SIRT and chemotherapy, and evaluated the clinical outcomes associated with platinum-based versus non-platinum-based regimens.

RESULTS: Patients who received platinum-based chemotherapy alongside SIRT had a median PFS of 10 months, compared to 2 months in those treated with non-platinum-based regimens. Stratified analysis revealed that patients receiving platinum-based chemotherapy in the first-line setting achieved a median post-SIRT survival of 16 months, compared to 4 months for those treated in later lines. For non-platinum-based regimens, median post-SIRT survival was 9 months in the first-line and 6 months in later lines. Median OS from Stage IV diagnosis was 17 months for patients with liver-only metastases and 15 months for those with additional extra-hepatic disease, suggesting that liver disease burden remains a dominant driver of outcomes.

CONCLUSIONS: These findings describe survival outcomes among patients treated with SIRT and chemotherapy for metastatic PDAC in a real-world setting. Longer observed survival was seen in patients who received platinum-based chemotherapy alongside SIRT, particularly in the first-line setting. Given the descriptive design and small sample size, these findings should be interpreted as hypothesis-generating and may inform future prospective evaluation of SIRT-chemotherapy combinations.