"Poker" association of weekly alternating 5-fluorouracil, irinotecan, bevacizumab and oxaliplatin (FIr-B/FOx) in first line treatment of metastatic colorectal cancer: a phase II study

Background This phase II study investigated efficacy and safety of weekly alternating Bevacizumab (BEV)/Irinotecan (CPT-11) or Oxaliplatin (OHP) associated to weekly 5-Fluorouracil (5-FU) in first line treatment of metastatic colorectal carcinoma (MCRC). Methods Simon two-step design: delta 20% (p0 50%, p1 70%), power 80%, α 5%, β 20%. Projected objective responses (ORR): I step, 8/15 patients (pts); II step 26/43 pts. Schedule: weekly 12 h-timed-flat-infusion/5-FU 900 mg/m2, days 1-2, 8-9, 15-16, 22-23; CPT-11 160 mg/m2 plus BEV 5 mg/kg, days 1,15; OHP at three dose-levels, 60-70-80 mg/m2, days 8, 22; every 4 weeks. Results Fifty consecutive, unselected pts < 75 years were enrolled: median age 63; young-elderly (yE) 24 (48%); liver metastases (LM) 33 pts, 66% Achieved OHP recommended dose, 80 mg/m2. ORR 82% intent-to-treat and 84% as-treated analysis. Median progression-free survival 12 months. Equivalent efficacy was obtained in yE pts. Liver metastasectomies were performed in 26% of all pts and in 39% of pts with LM. After a median follow-up of 21 months, median overall survival was 28 months. Cumulative G3-4 toxicities per patient: diarrhea 28%, mucositis 6%, neutropenia 10%, hypertension 2%. They were equivalent in yE pts. Limiting toxicity syndromes (LTS), consisting of the dose-limiting toxicity, associated or not to G2 or limiting toxicities: 44% overall, 46% in yE. Multiple versus single site LTS, respectively: overall, 24% versus 20%; yE pts, 37.5% versus 8%. Conclusion Poker combination shows high activity and efficacy in first line treatment of MCRC. It increases liver metastasectomies rate and can be safely administered. Trial registration Osservatorio Nazionale sulla Sperimentazione Clinica dei Medicinali (OsSC) Agenzia Italiana del Farmaco (AIFA) Numero EudraCT 2007-004946-34

A major problem concerning the addition of more drugs in a chemotherapy combination is designing a proper schedule assuring the balance between dose intensity (DI) of each drug and tolerability. We previously showed that 12-hour (10 PM to 10 AM ) timed-flatinfusion (TFI) of 5-FU associated to CPT-11 can be safely administered at high 5-FU/DI without Leucovorin; ORR was 40%, median PFS 10 months, median OS 21 months [19]. The 12-hour (10 PM to 10 AM ) TFI/5-FU infusion traces the 12-hour circadian-timed infusion of 5-FU [3,20,21]. Recently, we designed the triplet schedule FIr/FOx by splitting TFI/5-FU weekly with alternating CPT-11 or OHP: ORR was 66.7%, median PFS was 12 months, median OS 20 months [22].
This present phase II study proposes FIr-B/FOx or "Poker" association (so called because it represents the combination of four drugs), adding Bevacizumab to this triplet chemotherapeutic schedule, in order to assess its activity, efficacy and safety.

Patient Eligibility
Pts were eligible if they had histologically confirmed diagnosis of measurable MCRC; age 18-75 years; World Health Organization (WHO) performance status ≤ 2; adequate hematological, renal and hepatic functions; life expectancy more than 3 months.
Ineligibility criteria: pregnancy and breast-feeding; uncontrolled severe diseases; cardiovascular disease (uncontrolled hypertension, uncontrolled arrhythmia, ischemic cardiac diseases in the last year); thromboembolic disease, coagulopathy, preexisting bleeding diatheses; proteinuria > 1 g/24 h urine; surgery within the previuos 28 days before; previous adjuvant chemotherapy or radiotherapy completed less than 6 months before.
The study was approved by the Local Ethical Committee (Comitato Etico, Azienda Sanitaria Locale n.4 L'Aquila, Regione Abruzzo, Italia) and conducted in accordance with the Declaration of Helsinki. All patients provided written, informed consent.

Methods Schedule
This was a single-arm, multicenter phase II study evaluating activity of weekly alternating 5-FU, CPT-11, BEV and OHP (FIr-B/FOx) as first-line treatment of MCRC.

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 two weeks and echocardiogram at baseline, and every 3 cycles.
Primary end-point was ORR; secondary end-points were PFS, toxicity, OS. ORR was evaluated according to RECIST criteria [23]; PFS and OS using Kaplan and Meier method [24]. 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.
Clinical evaluation of response was planned by CTscan; PET was added based on investigators' assessment; objective responses were confirmed three months later. Follow-up was scheduled every three months up to disease progression or death. Toxicity was registered every week according to National Cancer Institute Common Toxicity Criteria (NCI-CTC, version 3.0). DLT was defined as grade 3-4 non-haematological toxicity (mainly represented by diarrhea, mucositis, neurotoxicity, handfoot syndrome, asthenia), grade 4 hematologic toxicity, febrile neutropenia, or any toxicity determining a > 2 weeks treatment delay.
The concept of limiting toxicity syndromes (LTS), consisting of at least a dose-limiting toxicity (DLT) associated or not to other limiting or G2 toxicities, was established. These were classified as: LTS in single site (LTS-ss), if characterized only by the DLT; LTS in multiple sites (LTS-ms), if characterized by ≥ 2 DLTs or a DLT associated to other, at least G2, non-limiting toxicities.

Statistical design
This phase II study was planned according to two-steps Simon's design [25]: assuming as minimal interesting activity an ORR 50%, 8 objective responses among the first 15 enrolled pts were necessary for the first-step; to verify the alternative hypothesis of ORR 70%, 26 objective responses among the total 43 pts enrolled were necessary; power (1 -β) 80%; error probability α 5%. p 0 was considered as the activity of triplet combinations in MCRC (CPT-11/OHP/5-FU or BEV/CPT-11/5-FU) [17,18,20,11]; p 1 as the projected ORR using the present Poker combination, increasing the activity ≥ 20%.

Dose finding
In the first step of the study, a concomitant dose-finding was conducted in order to assess the recommended OHP dose. At the first dose-level, 9 pts were enrolled and 12 cycles were administered; a DLT, G3 diarrhea, was observed in 1 out of 9 pts (11%). At the second dose level, 11 pts were treated (3 new pts); no DLT was observed. At the third dose level, 14 pts were treated (3 new pts); a DLT (7%) was observed, characterized by G3 mucositis (G3 stomatitis and G2 diarrhea, associated with G2 hypoalbuminemia). Thus, 2 DLTs were observed out of 15 pts (13%) and out of 37 cycles of treatment (5%). The OHP dose-finding established that the maximum tolerated dose (MTD) was not reached at the third dose level [Additional file 1: Supplemental Table S1]; thus, the recommended dose of OHP was 80 mg/m 2 day 8 and 22, every 4 weeks.

Discussion
The present phase II study proposing FIr-B/FOx association in first line treatment of consecutive, unselected MCRC pts, reached the primary endpoint: ORR 82% in the ITT and 84% in the as-treated analysis. After a median follow-up of 21 months, median PFS was 12 months and 24% of pts were progression-free > 12 months; median OS was 28 months and 80% of pts (40 pts) were alive > 12 months. The subsequent generations of randomized studies [8,10,11,13,14,17,18] showed increased activity and efficacy starting from ORR ≤ 20%, PFS 5 months and OS ≤ 14 months of 5-FU alone. Doublets consisting of CPT-11, or OHP, or BEV associated to 5-FU or Capecitabine gained ORR 20.0-47.0%, PFS 5.9-9.0 months and OS 15.1-21.5 months, without demonstrating differences between 5-FU/BEV associations compared to 5-FU or Capecitabine with CPT-11 or OHP. Triplets consisting of chemotherapeutic drugs or doublets plus BEV obtained ORR 39.0-66.0%, PFS 8.3-10.6 months and OS 20.3-26.1 months. In particular, the addition of a third drug, either BEV or OHP, equivalently increased the efficacy of doublet combination associating 5FU/CPT-11; 5-FU or Capecitabine and OHP plus BEV shows OS 20.4-26.1 months [13,14]. Based on these data, a phase II study of four drug association, adding BEV to FOL-FOXIRI, was recently proposed [27].
We previously showed that doublet and triplet chemotherapy using TFI/5-FU, without Leucovorin, according to the present schedule [19,20], obtained equivalent    [19,20,28]. In this scenario, Poker combination, adding BEV to FIr-FOx association, in first line treatment of MCRC, increased activity compared to triplet associations and it also increased efficacy; the 48% young elderly pts enrolled showed equivalent activity and efficacy.
Randomized studies of doublets (5-FU plus CPT-11 or OHP) adding Cetuximab (an EGFR-inhibitor) in EGFRoverexpressing pts, showed equivalent efficacy to other triplet combinations [29,30]; in these studies, k-ras wildtype status was reported as a statistically relevant predictive biomarker of higher activity and efficacy. Preliminary data of a phase III trial may also confirm this with Panitumumab plus FOLFOX4 [31]. The effectiveness of BEVcontaining treatments was maintained in k-ras wild-type as it was in k-ras mutated pts [32].
Liver metastasectomies were performed in 26% of MCRC pts and 39% of pts with liver metastases. Moreover, 54% of pts with liver-only metastases and 50% of pts with initially unresectable liver metastases underwent surgical resection. Liver metastasectomies were reported in 8-11% of pts treated with triplet chemotherapy (36% in liver-only pts) [17,18] and in 7.6% of pts in BEV-containing associations (15.2% in liver-only pts) [16]; in pts with potentially curable liver metastases, they were 92.8% [15]. In Cetuximab-containing associations [29,30], metastasectomies were performed in 7% and 4.7% of overall pts [29,30]; 9.8% of KRAS wt pts [30]. More, using neoadjuvant Cetuximab with either FOLFOX6 or FOLFIRI for unresectable colorectal liver metastases, metastasectomies were performed in 38% and 30% of pts, respectively [33]. Our data show that more active first line treatment of MCRC [34], such as Poker combination, contribute to increase efficacy also by raising surgical resection of liver metastases.
Cumulative G3-4 toxicities in young-elderly pts were prevalently represented by diarrhea (25%), hypertransaminasemy (4%), neutropenia 12.5%, stomatitis/mucositis (12.5%), asthenia (12.5%). Souglakos et al reported a significantly higher incidence of G3-4 diarrhea in elderly versus non-elderly pts either in the FOLFIRI or in the FOLFOXIRI arm [18]. In our study, DLT was observed in 44% of pts and in 46% of young-elderly pts, with no differences of cumulative G3-4 toxicities by pts and by cycles. The innovative clinical evaluation of LTS, consisting of at least the DLT associated or not to other G2 or limiting toxicities, was introduced to better evaluate, in the individual patient, the presence of DLT alone, LTS-ss, or the association of major toxicities in different sites, LTS-ms: overall, they were 20% and 24% respectively; among young-elderly pts, they were 8% and 37.5%, respectively. Most LTS-ms (2 double DLTs and 7 out of 10 DLT associated to other, at least G2, nonlimiting toxicities) were observed in this subgroup. LTSms were mostly represented by diarrhea and/or stomatitis/mucositis associated to nausea, vomiting and/or asthenia.

Conclusions
Randomized trials will confirm if intensive chemotherapy approaches, such as Poker association, increase efficacy, also by raising surgical resection of liver metastases, as first line treatment of MCRC. The present schedule is feasible, also in young-elderly pts, with manageable toxicity. Young-elderly pts show equivalent efficacy and cumulative toxicity, with a prevalence of LTSms associating the DLT with other moderate/severe toxicities.

Additional material
Additional file 1: Oxaliplatin dose-finding, activity in the first step of the study (Simon's design) and Limiting Toxicity Syndromes (LTS). Supplemental Table S1 reports results of the dose-finding planned in order to assess the recommended Oxaliplatin dose. Supplemental Table S2 describes preliminary data of activity, in the first step of the study (Simon's two-step design). Supplemental Table S3 describes toxicities characterizing Limiting Toxicity Syndromes (LTS) in individual patients.