Effectiveness and Safety of Intensive Triplet Chemotherapy Plus Bevacizumab, FIr-B/FOx, in Young-Elderly Metastatic Colorectal Cancer Patients

Four-drug regimens, such as FIr-B/FOx schedule, can improve efficacy of first-line treatment of metastatic colorectal cancer (MCRC) patients. The present study specifically evaluates feasibility of FIr-B/FOx first-line intensive regimen in fit young-elderly MCRC patients, representing approximately 40% of overall MCRC patients. Activity, efficacy, and safety were equivalent to overall MCRC patients, not significantly different according to KRAS genotype. Clinical outcome was significantly prolonged in liver-limited compared to other/multiple metastatic disease. Safety evaluation of the individual young-elderly patient showed that limiting toxicity syndromes (LTS) in multiple sites were significantly increased, compared to LTS in single site, with respect to non-elderly patients.

Older patients are usually underrepresented in clinical trials, despite the increased incidence with age, and often undertreated in clinical practice. Retrospective studies showed similar safety and efficacy in fit elderly compared to younger patients [9][10][11]. Elderly patients require a decisionmaking process including functional, nutritional, and comorbidity status to discriminate fitness and tailor medical treatment [12]. Fit patients ≥70 years benefit from 5fluorouracil (5-FU) as younger patients: ORR 23.9%, PFS 5.5 months, and OS 10.8 months [13]. A retrospective review and a pooled analysis reported no different activity and efficacy [14,15]. The same benefit was reported from irinotecan (CPT-11) containing chemotherapy in fit older ≥70 years [16]; age was not an independent prognostic factor for OS [17]. The significantly improved relative benefit of FOLFOX did not differ by age [18]. In the OPTIMOX1 trial, ORR 59%, median PFS 9.0 months, and median OS 20.7 months were comparable in old-elderly patients [19]. In the FOCUS2 trial, specifically designed to evaluate first line reduced-dose (80%) of 5-FU or capecitabine with or without oxaliplatin (OXP), in old-elderly and/or frail patients, addition of OXP significantly improved ORR, and trendly PFS, but not OS [20]. Treatment efficacy was consistent across subgroups, 2 BioMed Research International including age, when BEV was combined with CPT-11-based therapy [21]. In fit elderly patients, addition of BEV to 5-FU based chemotherapy significantly prolonged PFS (9.2-9.3 months) and OS (17.4-19.3 months) [22,23]. In BRiTE and BEAT studies, no different PFS was observed; median OS decreased with age [24,25]. No impact on PFS and OS was observed by age and/or comorbidities in patients treated with FOLFOX or FOLFIRI added or not to cetuximab [26]. Addition of panitumumab to FOLFOX showed no clear benefit in PFS in elderly and performance status 2 patients [27].
In the randomized phase III trial comparing FOLFOXIRI with FOLFIRI, age was not a significant factor for activity and efficacy; elderly patients showed median OS 16.9 and 19.9 months with FOLFIRI or FOLFOXIRI, respectively [28,29]. ORR was significantly lower in older patients treated with FOLFOXIRI [29]; no differences were reported in PFS and OS. Patients underwent metastasectomies without increased morbidity or mortality, irrespective of age.
Here, we report a retrospective analysis evaluating activity, efficacy, and safety of first-line FIr-B/FOx intensive regimen and the prognostic value of extension of metastatic disease [4,5] in fit young-elderly MCRC patients enrolled in a previously reported phase II study [1] and in the expanded clinical program proposing first-line FIr-B/FOx treatment.

Patient Eligibility.
Present retrospective analysis evaluated consecutive young-elderly patients 65 to 75 years enrolled in a previously reported phase II study [1] and in the expanded clinical program proposing first-line FIr-B/FOx treatment. Patients who were eligible were with histologically confirmed diagnosis of measurable MCRC, performance status ≤2, adequate hematological, renal, and hepatic functions, and life expectancy >3 months. Patients were not eligible if they showed uncontrolled severe diseases; cardiovascular disease (uncontrolled hypertension, uncontrolled arrhythmia, and ischemic cardiac diseases in the last year); thromboembolic disease, coagulopathy, and preexisting bleeding diatheses; proteinuria >1 g/24 h urine; surgery within the previous 28 days before. Cumulative Index Rating Scale (CIRS) was used to evaluate the comorbidity status, and only patients with primary and intermediate CIRS stage were enrolled [12]. 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. Patients with secondary CIRS stage, consisting of more than 3 comorbidities or a severe comorbidity, with or without dependent IADL, were not enrolled. 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.

Mutational
Analysis. Genetic analyses were performed on paraffin-embedded tissue blocks from the primary tumor and/or metastases, as previously reported [5]. Genotype status was assessed for KRAS codon 12, 13, and BRAF c.1799 T>A (V600E) mutations by SNaPshot multiplex assay in 17 samples, as elsewhere reported [32,33]. Briefly, KRAS exon 2 and BRAF exon 15 were simultaneously PCR-amplified and analyzed for KRAS c.34G, c.35G, c.37G, c.38G, and BRAF c.1799T mutations using the ABI PRISM SNaPshot Multiplex kit (Applied Biosystems, Foster City, CA, USA). KRAS exon 2 direct sequencing was performed using the Big Dye V3.1 Terminator Kit (Applied Biosystems, Foster City, CA, USA). Labelled products were separated in ABI Prism 3130xl Genetic Analyzer (Applied Biosystems, Foster City, CA, USA) and analysed using the GeneMapper Analysis Software version 4.0 (Applied Biosystems, Foster City, CA, USA).

Study Design.
Response was evaluated by computed tomography scan; positron emission tomography was added based on investigators' assessment. Follow-up was scheduled every three months up to progression or death. Resectability, defined according to reported categories [3], was evaluated in patients with L-L metastases every three cycles by a multidisciplinary team, consisting of a medical oncologist, liver surgeon, and radiologist, and recommended >4 weeks after BEV discontinuation. Liver metastasectomies were defined as R0, if radical surgery, R1, if radioablation was added.
Toxicity was registered according to the National Cancer Institute Common Toxicity Criteria (version 3.0). Limiting toxicity (LT) was defined as grade 3-4 non-hematological toxicity, grade 4 hematologic toxicity, febrile neutropenia, or any toxicity determining >2 weeks treatment delay. To discriminate individual safety, limiting toxicity syndromes (LTS), consisting of at least an LT associated or not to other limiting or G2 toxicities, were evaluated, as previously reported [1]. LTS were classified as limiting toxicity syndromes single site (LTS-ss), characterized only by the LT, and limiting toxicity syndromes multiple sites (LTS-ms), ≥2 LTs or an 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 [34].
Clinical criteria of activity and efficacy were ORR, PFS and OS. ORR was evaluated according to RECIST criteria [35]; pathologic complete response was defined as absence of residual cancer cells in surgically resected specimens. PFS
Retrospective analysis of doublets CPT-11, or OXP, associated to 5-FU or capecitabine in older patients reported ORR 18-59.4%, PFS 4.9-10.0 months, and OS 8.5-20.7 months [13-20, 29, 40]. The addition of BEV to 5-FU-based chemotherapy in elderly patients significantly increased PFS 9.2-9.3 and OS 17.4-19.3 months [22,23]. Triplet chemotherapy or doublet plus BEV obtained ORR 34.9-45.9%, PFS 7.9-9.3 months, and OS 17.4-20.5 months [23][24][25]. In the HORG-FOLFOXIRI trial, no different clinical outcome was observed in elderly patients; significantly lower PFS and OS were reported in patients with performance status 2 [28,29]. Liver metastasectomies were reported in 1.3% and 4.2% patients treated with FOLFIRI and FOLFOXIRI, respectively, [29] and can achieve OS 43 months, not significantly different from younger patients [41]. Morbidity and/or mortality after liver surgery were significantly higher in elderly patients (8%) [42]. Our present retrospective data show that intensive FIr-B/FOx treatment of young-elderly MCRC patients, carefully selected according to comorbidity and functional status, may achieve increased activity and clinical outcome than that reported. The high activity is correlated with 18% liver resection rate, 37.5% in L-L patients, and 40% pathologic CR, without increased morbidity and/or mortality.
FOLFOXIRI plus BEV and FIr-B/FOx schedules may increase activity and efficacy in patients with KRAS wildtype and mutant genotypes [5,38]. Median OS of patients treated with FIr-B/FOx was different in KRAS wild-type and mutant patients (38 months and 21 months, resp.), but not significantly different [5]. Similarly, FIr-B/FOx clinical outcome was not significantly different according to KRAS genotype, in young-elderly patients. Our previous reports of significantly different clinical outcome of L-L compared to multiple metastatic disease [3], particularly in KRAS wildtype patients, while not in KRAS mutant [5], were confirmed in young-elderly patients and should be prospectively verified.
FIr-B/FOx in young-elderly patients was feasible at median rDI 80%. Cumulative G3-4 toxicities were prevalently represented by diarrhea (21%), stomatitis/mucositis (11%), asthenia (11%), and neutropenia (11%). Individual LTS were reported in 46% young elderly patients, mainly including diarrhea (69.2%), and significantly more represented by LTSms compared to LTS-ss (chi-square 3.832, = 0.05), with respect to non-elderly patients. Published studies showed that grade 3/4 toxicities were not significantly different in elderly patients treated with 5-FU or CPT-11 [14][15][16], slightly increased with FOLFOX [19], and significantly increased by capecitabine (40%), while not by the addition of OXP [20]. Limiting diarrhea was significantly higher with FOLFIRI and FOLFOXIRI [28,29]. Performance status 2 was significantly associated with increased grade 3/4 neutropenia, febrile neutropenia, diarrhea, and fatigue, compared with performance status 0-1 [28,29,40]. In elderly patients, BEV addition to chemotherapy was significantly associated with increased arterial thromboembolism [43], while not to other adverse events [22][23][24][25]. The present retrospective, exploratory analysis in a small cohort of MCRC patients, showed that intensive FIr-B/FOx schedule is equivalently safe and feasible, without severe adverse events related to BEV, in young-elderly patients, selected by favourable performance status and functional and comorbidity status, with a rate of LTS-ms significantly increased compared to LTS-ss, with respect to non-elderly patients. Young-elderly MCRC patients suitable for FIr-B/FOx intensive treatment should be carefully selected based on comorbidity and functional status and monitored for individual safety in clinical practice.

Conclusions
In fit young-elderly patients, FIr-B/FOx intensive regimen is safe, with toxicity characterized by LTS-ms, high activity, efficacy, and liver metastasectomies, particularly in L-L, KRAS wild-type, compared to O/MM. Present findings would be prospectively verified in a larger cohort of young-elderly MCRC patients.