Background <p>Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal cancers, usually diagnosed at late stages, at which point the best option is palliative chemotherapy. Several treatment sequences are currently used in the clinic, but the optimal sequence is unknown.</p> Methods <p>Retrospectively, 168 PDAC patients treated at a Spanish hospital (single-center study) with either FOLFIRINOX, Gemcitabine (GEM) or Gemcitabine plus nab-paclitaxel (GEM-NABP) as first-line of chemotherapy were studied. Of them, 80 patients received second-line treatment with either GEM- or 5FU-based drugs. Survival analysis was calculated by Kaplan-Meier curves, log-rank test and hazards ratios by univariate and multivariate Cox regression.</p> Results <p>GEM-NABP and FOLFIRINOX presented similar survival outcomes for first-line treatment, and both were better than GEM alone, although FOLFIRINOX presented higher toxicity than GEM-NABP. However, the best second-line option was application of GEM-based drugs after FOLFIRINOX first-line, which offered a better survival and lower toxicity than 5FU-based treatments after GEM-NABP. Specifically, within the most frequent second-line therapies in our cohort, GEM-NABP outperformed FOLFOX6. Thus, individuals that received FOLFIRINOX followed by GEM-NABP treatment presented better outcomes.</p> Conclusions <p>In patients deemed eligible for multiple lines of chemotherapy, initiating treatment with FOLFIRINOX followed by a GEM-NABP regimen may represent a beneficial therapeutic sequence for metastatic PDAC, as opposed to the alternative approach of starting with GEM-NABP followed by a 5FU-based regimen.</p>