The impact of neoadjuvant therapy in patients with left-sided resectable pancreatic cancer: an international multicenter study.

Purpose: To assess the association between neoadjuvant therapy and overall survival (OS) in patients with left-sided resectable pancreatic cancer (RPC) compared to upfront surgery.
Background: Left-sided pancreatic cancer is associated with worse OS compared to right-sided pancreatic cancer. Although neoadjuvant therapy is currently seen as not effective in patients with RPC, current randomized trials included mostly patients with right-sided RPC.
Methods: International multicenter retrospective study including consecutive patients after left-sided pancreatic resection for pathology-proven RPC, either after neoadjuvant therapy or upfront surgery in 76 centers from 18 countries on 4 continents (2013-2019). Primary endpoint is OS from diagnosis. Time-dependent Cox regression analysis was performed to investigate the association of neoadjuvant therapy with OS, adjusting for confounders at time of diagnosis. Adjusted OS probabilities were calculated.
Results: Overall, 2,282 patients after left-sided pancreatic resection for RPC were included of whom 290 patients (13%) received neoadjuvant therapy. The most common neoadjuvant regimens were (m)FOLFIRINOX (38%) and gemcitabine-nab-paclitaxel (22%). After upfront surgery, 72% of patients received adjuvant chemotherapy, mostly a single-agent regimen (74%). Neoadjuvant therapy was associated with prolonged OS compared to upfront surgery (adjusted HR=0.69 [95%CI 0.58-0.83]) with an adjusted median OS of 53 vs. 37 months (P=0.0003) and adjusted 5-year OS rates of 47% vs. 35% (P=0.0001) compared to upfront surgery. Interaction analysis demonstrated a stronger effect of neoadjuvant therapy in patients with a larger tumor (P _interaction =0.003) and higher serum CA19-9 (P _interaction =0.005). In contrast, the effect of neoadjuvant therapy was not enhanced for splenic artery (P _interaction =0.43), splenic vein (P _interaction =0.30), retroperitoneal (P _interaction =0.84), and multivisceral (P _interaction =0.96) involvement.
Conclusions: Neoadjuvant therapy in patients with left-sided RPC was associated with improved OS compared to upfront surgery. The impact of neoadjuvant therapy increased with larger tumor size and higher serum CA19-9 at diagnosis. Randomized controlled trials on neoadjuvant therapy specifically in patients with left-sided RPC are needed.
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