Real life triplet FIr/FOx chemotherapy in first-line metastatic pancreatic ductal adenocarcinoma patients: recommended schedule for expected activity and safety and phase II study

Background Gemcitabine/nab-paclitaxel and FOLFIRINOX demonstrated significantly increased survival compared with gemcitabine in metastatic pancreatic ductal adenocarcinoma (PDAC): objective response rate (ORR) 23 and 31.6%, progression-free survival (PFS) 5.5 and 6.4 months, overall survival (OS) 8.7 and 11.1 months. Present phase II study evaluated recommended first-line triplet FIr/FOx schedule. Methods Simon two-step design: p010%, p130%, power 80%, α5%, β20%. Projected ORR: I step, 1/10; II 5/29. Schedule: 12h-timed-flat-infusion/5-fluorouracil 750-800-900 mg/m2 d1-2,8-9,15-16,22-23; irinotecan 120-140-160 mg/m2 d1,15; oxaliplatin 70-80 mg/m2 d8,22; every 4 weeks, according to clinical parameters (age, comorbidities, performance status (PS), liver function). Activity and efficacy were evaluated, and compared using log-rank; limiting toxicity syndromes (LTS), using chi-square. Results Twenty-nine consecutive patients were enrolled, according to primary/intermediate/secondary Cumulative Illness Rating Scale (CIRS). Median age 62; elderly 13 (44.7%); PS2 3 (10.4%), secondary CIRS 5 (17.2%). Primary endpoint was met: ORR 53% (7/13 patients) as-treated, 50% intent-to-treat. Cumulative G3-4 toxicities: diarrhea 17%, asthenia 14%, hypertransaminasemy 7%, mucositis 7%, vomiting 3%, anemia 3%, thrombocytopenia 3%. LTS were 27.5% overall, 38.4% in elderly. At 3 months median follow-up, PFS 4 months, OS 11 months. PS2 patients showed significantly worse OS (P 0.022). Conclusion Intensive first-line triplet FIr/FOx is tolerable at modulated doses, and confirms high activity/efficacy in metastatic PDAC. Patients’ careful selection, and exclusion of PS2, can maintain safety profile and efficient dose intensity.


INTRODUCTION
Metastatic pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with approximately 6 months median overall survival (OS) [1][2][3]. In the clinical evolution of metastatic PDAC, different combination treatment options have been evaluated, in order to increase clinical outcome. Gemcitabine was the only approved single agent, with median OS 5.7 months and 1-year OS rate 20% [1]. Gemcitabine 1000 mg/m 2 , administered over 30 minutes, weekly for 3 weeks every 28 days, was considered standard treatment schedule. Fixed-dose rate gemcitabine (10 mg/m 2 /minute) maximized intracellular concentrations of the phosphorylated active forms of gemcitabine, and may substitute standard infusion over 30 minutes [4,5].
The association of nab-paclitaxel to gemcitabine reported highest clinical benefit in patients with PDAC, and significantly raised up OS 8.7 months, PFS 5.5 months, and ORR 23%, compared with gemcitabine alone [22,23]. Intensive triplet FOLFIRINOX regimen significantly prolonged OS up to 11.1 months, PFS up to 6.4 months, ORR 31.6%, compared to gemcitabine arm [24].
The most relevant issue limiting the feasibility of addition of more drugs in a chemotherapy combination is the proper design of the schedule assuring the balance between tolerability for individual patients and effective received dose intensity (DI) of each drug in order to obtain the expected efficacy of the combination. Intensive regimens based on triplet chemotherapy in MCRC, and FOLFIRINOX regimen in metastatic PDAC, frequently required proper clinical management of toxicity and treatment modulations due to moderate/severe toxicities [24,25].
Over the last 10 years, we developed triplet chemotherapy regimen according to FIr/FOx schedule, characterized by 12-hour (10 PM to 10 AM ) timed-flatinfusion (TFI) 5-FU (TFI/5-FU), without leucovorin, associated to irinotecan (CPT-11) and OXP, according to a weekly alternating schedule, also added to bevacizumab [26,27]. FIr/FOx showed efficacy equivalent to other triplet schedules, such as FOLFOXIRI [28,29], with a good tolerability profile [30,31], as first-line treatment of metastatic colorectal cancer (MCRC) patients, with increased received 5-FU DI and lower rate of grade 3-4 neutropenia. Intensive triplet chemotherapy plus bevacizumab, according to FIr-B/FOx schedule, was equivalently safe and feasible in young-elderly patients, selected by favourable PS, and comorbidity status. The evaluation of limiting toxicity syndromes (LTS), multiple site (LTS-ms) or single site (LTS-ss), represented an innovative indicator of toxicity of the individual patient [32,33]. More, pharmacogenomic biomarkers of 5-FU, CPT-11 and/or OXP metabolism, could be evaluated to predict gastrointestinal toxicity in individual patients [34][35][36].
To further improve efficacy/tolerability ratio of triplet chemotherapy regimens in metastatic PDAC patients, the present phase II study proposes first-line FIr/FOx association [26,27] in clinical practice.

Patient demographics
From February 2011 to September 2016, 29 consecutive, unselected patients were enrolled (

Activity and efficacy
In the first step, according to two-steps Simon's design [38], assuming as minimal interesting activity an ORR 10% (1 OR among 10 enrolled patients), OR were 3 out of 10 enrolled patients, ORR 30% in the intent-to-treat (ITT) analysis, and 5 out of 10 evaluable patients, ORR 50% in the as-treated analysis.
Recently, phase III trials evaluating more intensive first-line chemotherapy regimen, such as gemcitabine plus nab-paclitaxel and triplet FOLFIRINOX, demonstrated to be much more, and equivalently effective, with significantly increased survival benefit over standard gemcitabine alone in metastatic PDAC patients [24]: ORR 23% and 31.6%, median PFS 5.5 and 6.4 months, OS 8.7 and 11.1 months, respectively. In the FOLFIRINOX study, median OS was significantly prolonged up to 11.1 months, with an increase of 4.3 months, compared with 6.8 months in the gemcitabine arm (hazard ratio for death, 0.57; P < 0.001) [24]. OS rate at 12 months was 48.4%, compared with 20.6% in the gemcitabine arm. In the recently reported phase III trial proposing gemcitabine and nab-paclitaxel association, 12-months OS rate was 35% [23]. Activity and clinical data reported with FIr/FOx in the present study are in the range of those reported with conventional intensive first-line treatment in PDAC patients. Thus, more active first-line treatment of metastatic PDAC can contribute to increase efficacy. FIr/FOx schedule may increase activity and efficacy of metastatic PDAC, with clinical outcome overlapping that reported with other triplet chemotherapy schedules, and evaluated in phase III randomized trials, as previously reported in MCRC setting [26,27].
Our present real life study on consecutive, unselected patients showed that 13 patients (44.8%) were not evaluable in the ITT analysis because they did not received at least 3 cycles of treatment, thus confiming that, even today, the primary challenge of clinical management of metastatic PDAC patients is to start and safely perform at least 3 cycles of intensive chemotherapy treatment, to evaluate activity contributing to increase clinical outcome.
Among patients treated with intensive triplet FIr/FOx regimen, PFS and OS were not significantly different among patients treated with modulated and standard drug dosage, due to clinical parameters requiring treatment modulations. PS 2 significantly affected worse OS (1 compared with 12 months, P = 0.022), thus confirming overall benefit in clinical outcome achieved by metastatic PDAC patients with PS 0-1, treated with gemcitabine-based combinations [17]. In the MPACT trial, PS, presence of liver metastases, age, and number of metastatic sites involved were independent prognostic factors for OS and PFS [39,40]. In our present study, PFS and OS seemed not significantly different according to primary tumor location (head or not), nor according to liver or other metastatic site, even if the small number of enrolled patients limited the relevance of subgroup analyses.
In the present study, LTS were observed in 27.5% of individual patients and in 38.4% of elderly patients treated with FIr/FOx regimen. The innovative clinical evaluation of LTS, consisting of at least the LT associated or not to other G2 or LT, introduced to better evaluate, in the individual patient, the presence of LT alone, LTSss, or the association of major toxicities in different sites, LTS-ms, showed that: overall, they were 3.4% and 24.1%, respectively; among elderly patients, they were all LTS-ms 38.4%. LTS were not significantly represented by LTS-ms compared to LTS-ss, even if the small number of enrolled patients requires further analyses. LTS-ms were mostly represented by diarrhea, mucositis, asthenia, neurotoxicity, thrombocytopenia and/or anemia, associated to nausea, vomiting, anorexia and/or neutropenia, hypokaliemia, hypoalbuminemia, hypertransaminasemia. In the individual patient, limiting and moderate toxicities often characterized LTS, previously observed in 44% MCRC patients treated with FIr-B/FOx, and equally involving single or multiple sites [27,32].
Pharmacogenomic analysis evaluating 5-FU degradation rate (FUDR) and/or detection of a panel of DNA Single Nucleotide Polimorphisms (SNPs) involving different genes, such as DPYD, UGT1A1, ABCB1, CYP3A4, specifically influencing fluoropyrimidines and CPT-11-related adverse events, justifying interpatients variability in safety profile, may help selection of patients fit for triplet chemotherapy, and may predict the occurrence of individual LTS, prevalently gastrointestinal [34-36, 41, 42]. Their predictive role should be prospectively verified, to be used in clinical practice.
Reported data confirmed that intensive regimens, such as FIr/FOx, frequently required proper clinical management of toxicity and treatment modulations due to moderate/severe toxicities. Careful selection of eligible patients, based on age, PS, comorbidity index, and monitoring of individual safety, also according to LTS in individual patients, are major parameters to optimize clinical management of metastatic PDAC. More, close monitoring of patients, expertise with a particular regimen, and toxicity management, remained the physician-related factors, that can guide personalized selection of first-line regimens in individual PDAC patients.
Ineligibility criteria: pregnancy and breastfeeding; uncontrolled severe diseases; cardiovascular disease (uncontrolled hypertension, uncontrolled arrhythmia, ischemic cardiac diseases in the last year); thromboembolic disease, coagulopathy, pre-existing bleeding diatheses; sensory and/or motor polineuropathy; surgery within the previous 28 days; previous adjuvant chemotherapy or radiotherapy completed less than 6 months before. CIRS was used to evaluate the comorbidity status [37]. Primary CIRS stage consisted of: independent Instrumental Activity of Daily Living (IADL), and absent or mild grade comorbidities; intermediate CIRS stage consisted of dependent or independent IADL, and less than 3 mild or moderate grade comorbidities; secondary CIRS stage consisted of more than 3 comorbidities or a severe comorbidity, with or without dependent IADL.
Treatment was approved by Agenzia Italiana del Farmaco (AIFA) for administration in label for metastatic

Schedule
This was a single-arm phase II study evaluating safety and activity of weekly alternating 5-FU, CPT-11, and OXP (FIr/FOx) as first-line treatment of metastatic PDAC.

Study design
Physical examination and routine laboratory studies were performed at baseline and every week on-treatment, including complete blood cell count, electrolytes, liver and renal function tests, urine examination and coagulation function; tumor markers every cycle; electrocardiogram every cycle, and echocardiogram at baseline, and every 3 cycles.
Primary end-point was ORR; secondary end-points were toxicity, PFS, OS. ORR was evaluated according to RECIST criteria [43]; PFS and OS using Kaplan and Meier method [44]. PFS was defined as length of time between the beginning of treatment and disease progression or death (resulting from any cause) or to last contact; OS as length of time between the beginning of treatment and death or to last contact. The log-rank test was used to compare PFS and OS [45]. Clinical evaluation of response was made by computerized tomography (CT)-scan; magnetic resonance imaging (MRI) and/or positron emission tomography (PET) were added based on the investigators' assessment; objective responses were confirmed three months later. Follow-up was scheduled every three months, up to disease progression or death. Toxicity was monitored every week according to National Cancer Institute Common Toxicity Criteria (NCI-CTC, version 4.0). LT was defined as grade 3-4 non-haematological toxicity (mainly represented by diarrhea, mucositis, neurotoxicity, hand-foot syndrome, asthenia, liver functional tests), grade 4 hematologic toxicity, G4 neutropenia, febrile neutropenia, G3-4 thrombocytopenia, or associated with significant clinical bleeding, grade 3-4 anemia, G2-3 neurotoxicity, or any toxicity determining a > 2 weeks treatment delay.
LTS, consisting of at least a LT associated or not to other limiting or G2 toxicities, were evaluated as previously reported [27,32]. These were classified as: LTS-ss, if characterized only by the LT; LTS-ms, if characterized by ≥ 2 LTs or a LT associated to other, at least G2, non-limiting toxicities. Chi-square test was used to compared the rates of LTS-ms and LTS-ss [46].
Correlations between maximum decrease from baseline in CA19.9 level and PFS and OS were analyzed, to assess possible relationships between CA19.9 and clinical outcomes.

Statistical design
This phase II study was planned according to two-steps Simon's design [38]: assuming as minimal interesting activity an ORR 10%, 1 objective response among the first 10 enrolled patients was necessary for the first-step; to verify the alternative hypothesis of ORR 30%, 5 objective responses among the total 29 enrolled patients were necessary; power (1 -β) 80%; error probability α 5%. p 0 was considered as the estimated activity reported with gemcitabine alone (median ORR 10%), and confirmed with the association of gemcitabine plus erlotinib (ORR 8.6%) [1][2][3][4][5]16]; p 1 as the projected ORR using the present intensive triplet combination, according to FIr/FOx schedule, increasing the activity ≥ 20% in metastatic PDAC patients, as reported with FOLFIRINOX (ORR 31.6%), and with the association of gemcitabine and nab-paclitaxel in the phase I/II trial (ORR 46% in the overall population, and 48% in patients treated at the recommended dose of nab-paclitaxel 125 mg/m 2 ; ORR 23% in the more recently reported phase III trial) [22][23][24].

CONCLUSIONS
FIr/FOx intensive triplet chemotherapy in metastatic PDAC patients preliminary showed high activity. Present schedule was feasible in non-elderly and elderly patients, with PS 0-1, with manageable toxicities, at proper CPT-11, OXP, and 5-FU doses. LTS were prevalently characterized by diarrhea, mucositis, asthenia, anemia, neurotoxicity and/or thrombocytopenia, associated to nausea, vomiting, anorexia and/or neutropenia. Elderly patients preliminary showed trendy, but not significantly worse OS. Adequate selection of suitable patients, based on clinical parameters, aimed to maintain safety profile at efficacious DIs, will verify if more intensive approaches, such as triplet chemotherapy regimen could increase OS, compared to historical gemcitabine control, in the clinical practice management of metastatic PDAC patients, and if it could be a treatment option in locally advanced/borderline resectable pancreatic cancer patients.

Author contributions
GB contributed to the conception and design of the study, in the provision of study materials of patients, in the data analysis and interpretation, in the manuscript writing. SM, EC contributed in schedule designing. RM, AVG, SC, ADS contributed in radiological evaluations. ER contributed to the conception and design of the study, in the data analysis and interpretation, in the manuscript writing. GB, SC, ER provided clinical management and data of patients. AG, AR contributed in the data analysis and interpretation. All authors participated in the collection and/or assembly of data. All authors read, revised and approved the final manuscript.