Pancreatic metastases after surgery for renal cell carcinoma: survival and pathways of progression.

Purpose: Metastatic ccRCC has peculiar tropism in the pancreas. We describe the characteristics and pathways of progression of patients with PM in a large multi-institutional consortium and compare them to patients with metastases from ccRCC at other sites.

Methods: Detailed clinical and histopathological data were collected. To account for differences in baseline characteristics between the two groups, IPTW was used to compare the two groups in terms of PFS and OS.

Results: Of the 182 patients, 33 (18%) had pancreatic, 94 (52%) pulmonary, 30 (16%) bone, 13 (7%) hepatic, and 12 (7%) brain metastases. Patients with PM had less aggressive ccRCC at baseline compared to those with progression at other sites in terms of tumour stage and grade. Median time from ccRCC surgery to PM was 8 (95%CI 5-10) vs. 1 year (95%CI 1-2) for progression to other sites (p < 0.001). Median IPTW-weighted time to second progression was 4.3 years (95%CI 2.4-not reached) for patients with PM vs 1.1 year (95%CI 0.8-2.3) for those with progression in other sites (p < 0.001). The most frequent second progression sites were pancreas (24%) and liver (15%) in patients with PM, while progression to the pancreas was rare (4%) in those with a different first progression site. Surgery alone (55%) or in combination with medical therapy (30%) was more frequent in the PM group than in other sites (p < 0.001). Median IPTW-OS time was longer for patients with PM [8.8 years (95%CI 6.5-not reached)] compared to those with first progression in other sites [2.8 years (95%CI 1.9-4.3), p < 0.001].

Conclusion: Pancreatic tropism is typical of ccRCC tumours with more indolent behaviour than those progressing to other sites. A long follow-up period is necessary to distinguish PM from ccRCC.