Clinical utility of PEG-G-CSF for preventing severe neutropenia in metastatic colorectal cancer patients treated with FOLFOXIRI plus bevacizumab: A single centor retrospective study

Background: This study aimed to evaluate in clinical practice the efficacy and safety of polyethylene glycol conjugated granulocyte colony-stimulating factor (PEG-G-CSF) for preventing neutropenia in metastatic colorectal cancer (mCRC) patients that received fluorouracil, leucovorin, oxaliplatin, and irinotecan (FOLFOXIRI) plus bevacizumab (Bev). Methods: We retrospectively analyzed mCRC patients who received FOLFOXIRI plus Bev between December 2015 and December 2017. We evaluated the efficacy of PEG-G-CSF for treating neutropenia, the overall response rate (ORR) according to the Response Evaluation Criteria in Solid Tumors version 1.1, progression free survival (PFS), overall survival (OS), and adverse events of FOLFOXIRI plus Bev based on the Common Terminology Criteria for Adverse Events version 4.0. Results: A total of 26 patients (median age 53.5 years) were included. The ORR rate was 65.3%, the median PFS was 9.6 months (7.2–16.9), and the median OS was 24.2 months (13.6–NA). Grade 3 or 4 neutropenia occurred in 53.8% of the patients and febrile neutropenia occurred in 7.7%. PEG-G-CSF was given to 77.0% of the patients, including prophylactically (n = 9) and after the development of grade 3 or 4 neutropenia (n = 11). No patients experienced grade 3 or higher neutropenia after the administration of PEG-G-CSF. In seven of the nine patients who received PEG-G-CSF prophylactically (77.7%), no dose adjustment was required. Conclusions: PEG-G-CSF was useful in preventing severe neutropenia in mCRC patients treated with FOLFOXIRI plus Bev.

factor antibody and anti-epidermal growth factor antibody have extended the overall survival (OS) of patients with metastatic colorectal cancer (mCRC) 1 . The efficacy of fluorouracil, leucovorin, oxaliplatin, and irinotecan (FOLFOXIRI) for mCRC patients in terms of overall response rate (ORR), progression free survival (PFS), and OS was confirmed by several studies 2 . The benefit of adding bevacizumab (Bev) to the FOLFOXIRI regimen has also been demonstrated and the use of FOLFOXIRI plus Bev as an upfront treatment for mCRC patients is currently widely used 3,4 . In the Pan-Asian adopted European Society for Medical Oncology (ESMO) consensuses guidelines, FOLFOXIRI plus Bev is recommended as a first-line cytoreduction chemotherapy in "fit" mCRC patients with right sided primary tumor location or for those with the BRAF V600E mutation 5 . FOLFOXIRI plus Bev is also one of the alternative treatment options of first-line chemotherapy of mCRC listed in another treatment guidelines including the Japanese Society for Cancer of the Colon and Rectum Guidelines 2019 6,7 . Furthermore, the MEBGEN RASKET™-B kit was recently approved in Japan for detecting mCRC patients with the BRAF V600E mutation 8 .
Therefore, it is expected that the number of patients treated with FOLFIXIRI plus Bev will increase.
With regard to adverse events of FOLFOXIRI plus Bev, grade 3 or higher neutropenia or febrile neutropenia (FN) frequently occur. Several studies have shown that approximately 50% of patients experience grade 3 or higher neutropenia 3,[9][10][11][12] . In a Japanese phase 2 trial of FOLFOXIRI plus Bev for mCRC, grade 3 or higher neutropenia and FN occurred in 72.5% and 21.7%, respectively 13 . The American Society of Clinical oncology practice guidelines recommend the prophylactic use of granulocyte colony stimulating factor (G-CSF) when the risk of FN in approximately 20% or higher 14 . Thus, we consider prophylactic G-CSF to be suitable for Japanese patients treated with FOLFOXIRI plus Bev.
However, a dose adjustment of the chemotherapy is often required, and the management of neutropenia is often inadequate, even if G-CSF is administered. Polyethylene glycolconjugated G-CSF (PEG-G-CSF), which is characterized as having an increased circulating half-life, has the potential to shorten the duration and severity of neutropenia. However, while the addition of PEG-G-CSF with FOLFOXIRI plus Bev may be useful in preventing severe neutropenia or FN, there are currently few reports evaluating the efficacy of the PEG-G-CSF for neutropenia in mCRC patients administered FOLFOXIRI plus Bev and in the safety of PEG-G-CSF in a every 2-week cycle of use. The current study aimed to evaluate the efficacy and safety of the PEG-G-CSF for preventing neutropenia in mCRC patients treated with FOLFOXIRI plus Bev.

Patients
Patients diagnosed with mCRC and that received FOLFOXIRI plus Bev between December 2015 and December 2017 at the Cancer Institute Hospital, Tokyo, Japan were included in the study based on the following eligibility criteria: 1) histologically confirmed colorectal adenocarcinoma; 2) unresectable or recurrent disease; 3) no previous chemotherapy except for adjuvant chemotherapy completed more than 6 mo prior to the starting date of FOLFOXIRI plus Bev treatment. The protocol summary was described on the hospital website and the subjects were provided with the opportunity to opt out. Therefore, no new consent for this study was required from the patients.

Data collection
All data were collected by reviewing medical records and imaging results. We confirmed the patient age, sex, and Eastern Cooperative Oncology Group Performance Status (ECOG-PS). Data regarding the primary tumor site, the histological type of primary site tumor, whether primary resection was performed, the metastatic sites, and the number of metastatic sites were also considered. Any previous adjuvant chemotherapy, the tumor maker level before chemotherapy, RAS and UGT1A1 status, the number of chemotherapy cycles, tumor response (objective response and early tumor shrinkage (ETS)), toxicity, conversion surgery, the date of disease progression, and the date of the last follow-up were also evaluated.

Treatment and evaluation
Bev was administered as a 5 mg/kg intravenous dose. week eight (± 4 weeks compared to that of the baseline (cutoff: 20%). PEG-G-CSF (3.6 mg) starting at day four was administered every 2 weeks until progression. Whether PEG-G-CSF was used as primary preventative treatment for neutropenia or as a secondary treatment after a patient experienced grade 4 neutropenia or FN was decided by the treating physician.
PFS and OS rates were estimated using the Kaplan-Meier method. All statistical analyses were performed using EZR software (Saitama Medical Center, Jichi Medical University, Saitama, Japan), which is a graphical user interface for R (The R Foundation for Statistical Computing, Vienna, Austria).

Patient characteristics
The demographics and clinical characteristics of the 26 patients before the initiation of FOLFOXIRI plus Bev therapy are summarized in Table 1 Adverse events and efficacy and safety of PEG-GCSF in mCRC patients treated with FOLFOXIRI plus Bev The most common adverse event was hematological toxicity with grade 3 or higher neutropenia observed in 14 patients (53.8%). Grade 3 FN was observed in two patients (7.7%). Other hematological or non-hematological toxicities were less frequent such as diarrhea being observed in two patients (7.7%). No treatment-related deaths occurred. In the 26 patients, 20 (77%) received PEG-G-CSF. Eleven patients (55%) received it secondarily to treat neutropenia. Among these 11 patients, two had previously been treated prophylactically with conventional G-CSF. Nine patients (45%) were administrated PEG-G-CSF prophylactically (Fig. 1). None of the patients developed grade 3 or higher neutropenia after receiving PEG-G-CSF. Ten of 26 patients (38%) received a reduction in their dose of FOLFOXIRI plus Bev. Six of 11 patients (54.5%) who received PEG-G-CSF secondarily to treat neutropenia were able continue treating with FOLFOXIRI plus Bev without the need for a dose adjustment. On the other hand, in the nine patients given PEG-G-CSF prophylactically, two (22.2%) required the dose adjustment due to nonhematological adverse events. There were no severe adverse events associated with the PEG-G-CSF treatment.

Treatment outcomes
Treatment outcomes and adverse events are shown in Table 2 and Table 3, respectively.

Discussion
In the current study, we evaluated the efficacy and safety of the PEG-G-CSF for preventing neutropenia in mCRC patients treated with FOLFOXIRI plus Bev. Despite the high ratio of poorly differentiated adenocarcinoma and patients with RAS mutant type, the ORR was relatively high. PEG-G-CSF prevented the development of severe neutropenia without any increases in adverse events.
FN is one of the life-threatening adverse events of chemotherapy. In the 1990's, G-CSF was widely used in the clinic as a leading supportive therapy for FN. There is substantial data regarding the effectiveness of G-CSF for cancer chemotherapy 15,16 . Compared to conventional G-CSF, the number of visits to a hospital by patients and the work load of the medical staff both decreased when we used PEG-G-CSF. This demonstrates a great benefit for the outpatient clinic. There are several reports regarding the efficacy of PEG-G-CSF for neutropenia and FN in both mCRC and other cancers.
A Japanese double-blind placebo-controlled randomized phase 3 trial of PEG-G-CSF in 343 breast cancer patients receiving docetaxel and cyclophosphamide chemotherapy showed that the incidence of FN was significantly lower in the PEG-G-CSF group compared to that in the placebo group (1.2% vs. 68.8 %, P < 0.001) 17 . A Japanese retrospective study also showed that the incidence of FN was significantly lower in a group of non small cell lung cancer patients pretreated with PEG-G-CSF compared to that in the placebo group [0/52 (0%) vs 3/9 (33%), respectively] 18 .
Regarding mCRC patients, in a phase 3 double-blind trial that evaluated the efficacy of PEG-G-CSF compared to a placebo in reducing the incidence of grade 3 or 4 FN in patients with advanced CRC receiving Bev combined with first-line chemotherapy, PEG-G-CSF significantly reduced the incidence of grade 3 and grade 4 FN in the first four treatment cycles (PEG-G-CSF 2.4%, placebo, 5.7%, P = 0.014) 19 . Another randomized placebocontrolled phase II study examined PEG-G-CSF efficacy and safety in patients with CRC that received chemotherapy every two weeks. Results from this study showed that PEG-G-CSF significantly reduces the incidence of grade 3 and grade 4 FN (PEG-G-CSF, 2.0%; placebo, 8.0%; P < 0.001) 20 . Notably, this study demonstrated that PEG-G-CSF could prevent severe neutropenia in patients receiving FOLFOXIRI plus Bev on a two-week cycle without an increase of adverse events, consistent with previous reports. However, the safety of PEG-G-CSF had not been established when administered within 14 days before the start of chemotherapy. It is recommended that the administration interval of PEG-G-CSF should be 2 weeks or longer.
In addition, UGT1A1 polymorphism was detected in this study in eight (30.7%) of the patients (*6 in six patients, *28 in two patients). Among these patients with UGT1A1 polymorphism, six had been administered PEG-G-CSF, two after the development of grade 3 neutropenia and four prophylactically. In Japan, the incidence of UGT1A1 *6 polymorphism is higher than that in the US and European countries [21][22][23] . In a Japanese phase 2 trial of FOLFOXIRI plus BV in mCRC patients, the frequency of neutropenia in patients with UGT1A1 *6 or *28 polymorphism is higher than that in patients with wildtype UGT1A1 13 . However, in the current study, no patients experienced severe neutropenia after the administration of PEG-G-CSF, even in those patients with UGT1A1 *6 or *28 polymorphisms. Furthermore, five of 6 patients were able continue treating with FOLFOXIRI plus Bev without the need for a dose adjustment. These data suggest that the administration of PEG-G-CSF in two-week cycle may be safe and that PEG-G-CSF is able to prevent severe neutropenia in patients with UGT1A1 *6 or *28 polymorphisms.
There were several limitations to our study. For instance, it was a retrospective study with a relatively small sample size. A further large-scale study to validate the results of this study and to compare PEG-G-CSF with G-CSF in mCRC patients treated with FOLFOXIRI plus which is the most common adverse events in patients being treated with FOLFOXIRI plus Bev, could be prevented using PEG-G-CSF.

Conclusion
PEG-G-CSF was useful in preventing severe neutropenia in mCRC patients treated with FOLFOXIRI plus Bev without any increases in adverse events.

Ethics approval and informed consent
The study was performed in accordance with the Declaration of Helsinki and was approved by the Cancer Institute Hospital Institutional Review Board (Registry no: 2018-1014).

Availability of data and materials
All data generated or analysed during this study are included in this published article.

Funding
The author reports no any funding about this analysis.

Competing interests
The author reports no conflicts of interest in this work.   Progression free survival and overall survival rates of the study cohort.

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