Background: Although surgical resection is the only potentially curative treatment for pancreatic cancer (PC), long-term outcomes of this treatment remain poor. The aim of this study is to describe the feasibility of a neoadjuvant treatment with induction polychemotherapy (IPCT) followed by chemoradiation (CRT) in resectable PC, and to develop a machine-learning algorithm to predict risk of relapse. Methods: Forty patients with resectable PC treated in our institution with IPCT (based on mFOLFOXIRI, GEMOX or GEMOXEL) followed by CRT (50 Gy and concurrent Capecitabine) were retrospectively analyzed. Additionally, clinical, pathological and analytical data were collected in order to perform a 2-year relapse-risk predictive population model using machine-learning techniques. Results: A R0 resection was achieved in 90% of the patients. After a median follow-up of 33.5 months, median progression-free survival (PFS) was 18 months and median overall survival (OS) was 39 months. The 3 and 5-year actuarial PFS were 43.8% and 32.3%, respectively. The 3 and 5-year actuarial OS were 51.5% and 34.8%, respectively. Forty-percent of grade 3-4 IPCT toxicity, and 29.7% of grade 3 CRT toxicity were reported. Considering the use of granulocyte colony-stimulating factors, the number of resected lymph nodes, the presence of perineural invasion and the surgical margin status, a logistic regression algorithm predicted the individual 2-year relapse-risk with an accuracy of 0.71 (95% confidence interval [CI] 0.56–0.84, p = 0.005). The model-predicted outcome matched 64% of the observed outcomes in an external dataset. Conclusion: An intensified multimodal neoadjuvant approach (IPCT + CRT) in resectable PC is feasible, with an encouraging long-term outcome. Machine-learning algorithms might be a useful tool to predict individual risk of relapse. A small sample size and therapy heterogeneity remain as potential limitations.

e20553 Background: NSCLC therapeutic paradigm has changed with immune checkpoint blockers. Biomarkers predicting clinical benefit are still lacking. As previously shown in melanoma, changes in absolute lymphocytes and neutrophils count (ALC and ANC) during IT (PD-1/PD-L1 inhibitors) may be related to response in NSCLC (Nakamuta et al, Oncotarget 2016). TTF1 expression has been associated with PD-L1 expression (Vieira et al, Lung Cancer 2016). We aimed to investigate TTF1 expression and changes in ALC and ANC after 2 cycles and their potential association with clinical outcomes to IT. Methods: We retrospectively analyzed 26 consecutive patients with stage IV NSCLC treated with IT at Clínica Universidad de Navarra (Spain) during 2016. Radiological response was evaluated according to RECIST v1.1. The potential correlation between ALC and ANC changes during the first two cycles and response to treatment [disease control rate (DCR) vs progression] was evaluated using Student’s T-test. Fisher’s exact test was used to study the association between changes in ALC ( < 1,000 vs > 1,000) and ANC ( < 4,000 vs > 4,000) after 2 cycles and response to IT. TTF-1 expression was correlated with treatment response. Overall survival (OS) was assessed with Kaplan-Meier analysis and Log-rank test according to ALC and ANC. Results: An ALC increase after 2 cycles was significantly associated with DCR compared to progression (192 vs -155; p = 0.043). ALC > 1,000 after 2 cycles was more frequent among patients experiencing DCR compared to progression (87% vs 50%; p = 0.07). ALC > 1,000 after 2 cycles was more frequently observed among patients with TTF1+ tumors (93% vs 55%; p = 0.03). Patients with ANC < 4,000 showed a longer median OS (NR vs 19.25 months; p = 0.03). TTF1 expression in adenocarcinoma (n = 18) was associated with response to IT (83% vs 16%, p = 0.01). Conclusions: Despite this retrospective small series’ limitations, our results show that ALC and ANC changes during IT and TTF1 expression may act as early predictors of clinical benefit in stage IV NSCLC patients treated with PD1/PD-L1 blockers. Our results warrant further investigation in larger prospective series.

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4636 Background: Neoadjuvant therapy is an increasingly used approach in patients with resectable pancreatic cancer (PC). A positive link between chemotherapy dose intensity and patients’ outcome has been suggested in PC. The aim of this study was to rule out whether 5-FU pharmacokinetic (PK) parameters correlate with outcome in resectable PC patients treated with preoperative FOLFOXIRI. Methods: Patients with resectable and borderline resectable PC treated with Oxaliplatin (85mg/m2), Leucovorin (400mg/m2), Irinotecan (150 mg/m2) and 5-FU (initial dose of 3200 mg/m2 in 46h infusion and subsequent doses based on PK-guided dose adjustements targeting an AUC of 25-30 mcg*h/ml) were included. 5-FU PK analysis was performed taking two plasma samples during 5-FU infusion in at least two cycles. Drug concentrations were analysed by High-Perfomanced Liquid Chromatography. After induction polychemotherapy (IPCT), patients with no progressive disease received chemoradiation (CRT) (50.4 Gy with concurrent Capecitabine and Oxaliplatin) followed by surgical resection 4 to 6 weeks after the completion of CRT. Subsequent follow-up until disease progression was remained. An exploratory analysis with Log-Rank test was performed to assess progression free survival (PFS) based on 5-FU AUC values. Results: From November 2012 to October 2018, 29 patients were retrospectively assessed: median age 63 (46-75); M/F rate 20/9; R0 resection rate of 90% in the intention-to-treat analysis. The pathological response according to CAP classification was 0, 1, 2 and 3 in 14, 58, 19.5 and 8.5%, respectively; and median number of resected lymph nodes was 11 (2-22), with lymph node infiltration (ypN1) in 14% of patients. Grade 3-4 IPCT related toxicities and grade 3 CRT related toxicities were reported in 40 and 30% of patients, respectively. Median PFS was 723 days (24 months) and median 5-FU AUC 28.5 mcg*h/ml (23-53). Median PFS for patients with 5-FU AUC ≥27 mcg*h/ml was 29 months versus 15 months in patients with 5-FU AUC < 27 mcg*h/ml (adjusted hazard ratio for disease progression 0.223; 95% CI = 0.059-0.848; p = 0.028; in a model controlled by age, sex and irinotecan dose intensity). Conclusions: 5-FU pharmacokinetic parameters achieving a target of AUC ≥ 27 mcg*h/ml seem to correlate with longer PFS in this subset of patients.

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