1 Introduction

Cervical cancer ranks as the fourth most prevalent malignancy among women worldwide and stands as the leading cause of cancer-related mortality in develo** countries [1, 2]. The treatment of cervical cancer is based on the FIGO staging system outlined in the 2018 edition. Radiotherapy combined with platinum-based chemotherapy is the standard treatment approach for stage IB3 and IIA2-IVA cervical cancer. Additionally, this therapeutic modality can be employed for patients with early to mid-stage cervical cancer who are not suitable candidates for hysterectomy [3]. However, due to its localized effect, radiotherapy alone fails to yield satisfactory curative outcomes. Conversely, the curative effect of radiotherapy combined with synchronous chemotherapy is better than that of radiotherapy alone, significantly enhancing the overall survival rate and local control rate of cervical cancer patients [4,5,6]. Concurrent chemoradiotherapy builds upon precision radiotherapy combined with chemotherapy by effectively targeting hidden metastatic cells throughout the body while simultaneously shrinking tumors and eradicating distant metastases. Consequently, this comprehensive treatment strategy offers improved therapeutic benefits and prognostic outcomes for patients. However, since both radiation and drugs exert inhibitory effects on bone marrow function, toxicity superimposition will increase the probability of blood toxicity in patients [7,8,9,23]. PEG-rhG-CSF is a long-acting preparation of granulocytic stimulating factor that exhibits similar efficacy to the short-acting preparation. PEG-rhG-CSF acts on hematopoietic cells after binding to the surface receptors of hematopoietic cells to promote cell proliferation, differentiation, and activation. It possesses a long half-life and long-lasting effect, and has the advantages of "self-regulation" and less toxic side effects [24,25,26,27]. Several studies have demonstrated the significant benefits of PEG-rhG-CSF in preventing and treating chemotherapy-induced leukopenia/neutropenia [28,29,30,31]. However, whether it can be utilized for primary prevention of concurrent chemoradiotherapy-induced leukopenia/neutropenia remains unexplored.

The recommended dose of PEG-rhG-CSF approved for primary and secondary prophylaxis of leukopenia/neutropenia after chemotherapy alone is 100 μg/kg once per chemotherapy cycle, with an interval between subsequent chemotherapies of ≥ 14 days. However, there is no standard for the dose used in concurrent chemoradiotherapy for cervical cancer. Currently, the commonly used dose of PEG-rhG-CSF during concurrent chemoradiotherapy is 100 μg/kg, which aligns with the recommended dose used in chemotherapy. The relatively expensive price of PEG-rhG-CSF contributes to difficult clinical promotion and poor patient compliance. Since the myosuppression effect of radiotherapy is weaker than that of chemotherapy, concurrent chemoradiotherapy enhances the efficacy, while the dose of chemotherapy when radiotherapy is combined with chemotherapy is mostly lower than that of chemotherapy alone. Therefore, the recommended dose of PEG-rhG-CSF for post-chemotherapy leukopenia/neutropenia is not necessarily appropriate for concurrent chemoradiotherapy, which remains to be explored. The purpose of this study was to investigate the effect of different doses of PEG-rhG-CSF on the prevention of leukopenia/neutropenia during concurrent chemoradiotherapy of cervical cancer, especially low dose (50 μg/kg) for primary prevention, aiming to provide a more rational treatment plan for the prevention of leukopenia/neutropenia of cervical cancer during concurrent chemoradiotherapy.

2 Data and methods

2.1 Research design

This study was a single-center prospective clinical study. Patients with cervical cancer who received initial radical radiotherapy combined with platinum-based chemotherapy every 3 weeks in the Affiliated Cancer Hospital of Dalian University of Technology (Liaoning Cancer Hospital) from June 2020 to January 2023 were enrolled. This prospective clinical study focused on the efficacy of different doses of PEG-rhG-CSF on the prevention of leukopenia/neutropenia.

The sample size was determined as follows. In the pre-trial, the effect size (f) of the primary outcome measure (reduced values of leukocytes & neutrophils) was all close to low, and in the formal trial, the one-way random ANOVA test was employed to calculate the study sample size, effect size f = 0.15, α=0.05, β=0.85, and N=3, yielded a sample size of 163 cases per group. Considering a potential maximum sample loss of 20%, a total of 204 cases per group were deemed necessary. However, in clinical practice (the real world), on the premise of respecting the wishes of patients, we found that the proportion of patients who chose the P 0, P 50, and P 100 regimens was about 3/2/2. To ensure greater clinical relevance in our study population distribution, we increased the sample size for the P0 group to 306 cases (i.e., P 0=204*1.5=306 cases), while maintaining P 50 and P 100 groups at 204 cases each; resulting in a total cohort of 714 cases.

Randomization was performed according to allocation rules as follow. Three table tennis balls with the number "1", two balls with the number "2", and two balls with the number "3" were put in a closed and opaque cloth bag. Whenever a patient was enrolled to be assigned, the person responsible for randomization randomly took out a table tennis ball, read out the number on the ball. The numbers 1, 2, 3 on the balls indicated that the patient correspondingly joined the P 0, P 50, P 100 group. When all seven table tennis balls were removed, they were put back together until all 714 patients in this study were enrolled.

Eligible participants were randomly allocated into the control group (P 0) and experimental groups. The experimental groups were further categorized based on the dose of PEG-rhG-CSF, including the low-dose group (P 50, 50 μg/kg) and the high-dose group (P 100, 100 μg/kg). All participants were enrolled voluntarily and signed an informed consent form, which was reviewed and approved by the hospital ethics committee.

2.2 Inclusion and exclusion criteria

2.2.1 Inclusion criteria

(1) Locally advanced cervical squamous cell carcinoma, adenocarcinoma, and adenosquamous cell carcinoma diagnosed by histological pathology (2) Age: 18~75 years (3) Patients with stage IB3 or IIA 2-IVA according to FIGO stage (International Union of Obstetrics and Gynecology) 2018 clinical stage criteria (4) Receiving concurrent chemoradiotherapy treatment (5) The estimated survival period of 8 months; Physical strength status (KPS) score of 80 points; The ECOG score less than 2 points (6) Normal bone marrow hematopoiesis, white blood cell count (WBC )≥ 3.5×109 /L, neutrophil (ANC) ≥ 1.8×109/L, Platelet count (PLT)≥ 90×109/L; hemoglobin (HB)≥ 90g/L (7) During concurrent chemoradiotherapy, no other drugs that raise leukocytes/neutrophils were used except PEG-rhG-CSF and rhG-CSF.

2.2.2 Exclusion criteria

(1) Serious heart, lung, liver, kidney, and other vital organ diseases (2) Patients with abnormal coagulation function, bleeding tendency, or receiving thrombolysis or anticoagulation therapy (3) Combined with an uncontrollable infection, body temperature ≥38°C (4) Combined with other site malignancies or hematological diseases (5) Radiotherapy is preceded by chemotherapy/targeting/immunotherapy (6) A history of chemotherapy and/or radiation therapy.

2.2.3 Study groups

The study was divided into experimental groups and a control group. The control group, designated as P 0, did not receive any drugs for the prevention of leucopenia/neutropenia during chemoradiotherapy, while the experimental group received PEG-rhG-CSF treatment after each chemotherapy session to prevent leucopenia/neutropenia. The drug dosage administered was calculated as 50 μg/kg and 100 μg/kg, respectively.

2.3 Chemoradiotherapy regimen

Chemotherapy regimen: Cisplatin 50-60 mg/m2 (or carboplatin AUC 4-5), IV, day 1; paclitaxel 135 mg/m2, IV, day 1; repeated every 3 to 4 weeks for a total of 2 cycles of chemotherapy.

Radiation therapy protocol: external irradiation with conformal intensity modulated radiation therapy (IMRT) at the prescribed dose of 50 Gy (25 times, once a day, five times a week) in the planned target area (PTV), 2 Gy per time; for paraintrauterine invasion, 10 to 14 Gy (5-7 times) can be added locally; and enlarged pelvic lymph nodes, 12 to 14 Gy (5-7 times) can be added locally. Brachytherapy was performed after the end of external irradiation. The brachytherapy source was Iridium 192, prescribed to administer more than 90% of the volume of the high-risk clinical target area (HR-CTV), at a dose of 30 Gy (5 times), twice a week. The schematic diagram of radical concurrent chemoradiotherapy is shown in Fig. 1.

Fig. 1
figure 1

Schematic diagram of radical concurrent chemoradiotherapy

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2.4 Administration and monitoring protocol of PEG-rhG-CSF, rhG-CSF

Patients in the test group were injected with PEG-rhG-CSF 24 h to 48 h after each chemotherapy [Shiyao Group (Shandong) Biopharmaceutical Co., LTD., S20110014, specification: 3mg / dose: 1 ml (pre-filling)]. The dosages of P 50 group and P 100 group were calculated at 50 μg/kg and 100 μg/kg each time and were injected subcutaneously, once per chemotherapy cycle, twice in total. PEG-rhG-CSF was administered more than 14 days before the next chemotherapy. Control patients will not receive PEG-rhG-CSF injections after chemotherapy. Patients with ANC <1.0×109 / L or WBC < 2.0×109 / L in the three groups could be injected 100 μ g rhG-CSF [Qilu Pharmaceutical Co., Ltd., S19990049; Specification: 6.0106 IU (100 μ g): 0.6 mL] subcutaneously once daily until ANC≥ 1.8×109 / L or WBC 3.5×109 / L. The normal reference value of ANC was between 1.8×109 / L and 6.3×109 / L, and the normal reference value of WBC was between 3.5×109 / L and 9.5×109 / L.

2.5 Observation method

Maximum body temperature was recorded after chemotherapy or on the day of trial drug administration and daily thereafter. Venous blood was collected at 3, 7, 10, 14, and 17 days after chemotherapy or PEG-rhG-CSF administration. If grade 3 or higher leukopenia/neutropenia occurred, blood routine changes were monitored the next day.

2.6 Efficacy and safety evaluation indicators

2.6.1 Efficacy evaluation index

Several indexes were compared in all three groups during concurrent chemoradiotherapy, such as the lowest values, incidence and recovery time of neutropenia and leukopenia, FN incidence, and time of radiotherapy interruption due to leukopenia/neutropenia.

2.6.2 Evaluation of adverse reactions

NCI Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 was used to evaluate major adverse events, including osteoarticular myalgia and drug-induced fever.

2.6.3 Total cost of treatment

The total cost of in-patient/out-patient treatment with concurrent chemoradiotherapy was calculated, and the difference of total cost of treatment among the three groups was compared.

2.7 Statistical analysis

The Kolmogorov-Smirnov test (K-S method) was used for normality testing, and Levene's test was used for homogeneity of variance. The measurement data conforming to the normal distribution were described by means and standard deviation, analyzed by one-way ANOVA and the LSD method for pairwise comparison in groups, while the measurement data and rank data that did not follow the normal distribution were described by median (P 25, P 75) and analyzed by the median test or K test and pairwise comparison between groups. The counting data were described by frequency and composition ratio, and the Pearson χ2 test was used, and the P value was not corrected for pairwise comparison. Binary logsitic regression was used to analyze the OR of grade 3-4 leukopenia/neutropenia between different treatment protocols. All statistical analyses were performed using IBM SPSS 23.0 statistical software, using a two-sided test, with a P < 0.05 representing a statistically significant difference.

3 Results

3.1 Baseline characteristics of the patients

According to the inclusion and exclusion criteria, a total of 714 patients were enrolled, with 306 in the control group and 204 in each experimental group. Due to side effects or other reasons, random loss occurred, to be exact, 37 cases (12.1%) in the P 0 group, 16 cases (7.8%) in the P 50 group and 17 cases (8.3%) in the P 100 group. Ultimately, there were 188 cases in the P 50 group, 187 cases in the P 100 group, and 269 cases in the P 0 group (control group). There were no significant differences observed among the three groups regarding age, tumor stage, and tumor type (P > 0.05) as shown in Table 1.

Table 1 Comparison of general data between the two groups
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3.2 Efficacy evaluation

3.2.1 Minimum values of leukocytes and neutrophils

There were significant differences in leukocyte and neutrophil reduction values among the three groups (F=12.768, P<0.001; F=11.282, P<0.001). Pairwise comparison (LSD) showed that the lowest WBC value in the P 50 group (2.97±1.66×109/L, P < 0.001) and the P 100 group (3.05±1.62±1.26×109/L, P < 0.001) was markedly higher than that in P0 group. The lowest neutrophils in the P 50 group (1.99±1.40×109/L, P < 0.001) and the P 100 group (2.02±1.26×109/L, P < 0.001) were significantly higher than that in the P 0 group (1.56±0.93×109/L). There was no significant difference between the P 50 group and the P 100 group in the lowest value of leukocytes and neutrophils (P > 0.05; P > 0.05) (Table 2, Fig. 2).

Table 2 Comparison between groups with reduced values of leukocytes & neutrophils (×10-9/L,‾x ± s)
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Fig. 2
figure 2

Results of the study

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3.2.2 The occurrence of grade 3-4 leukopenia and neutropenia

There were significant differences in the occurrence of grade 3-4 leukocytes and neutrophilia among the three groups (χ2=14.594, P=0.001; χ2=7.782, P=0.020). Pairwise comparison between groups revealed that grade 3-4 leukopenia in the P 0 group (110/269,40.9%)was observably higher than that in the P 50 group ((52/188,27.7%, P=0.004) and the P 100 group (48/187,25.7%, P=0.001). The grade 3-4 neutropenia in the P 0 group (81/269,30.1%) was remarkably higher than that in the P 50 group ((38/188,20.2%, P=0.018) and the P 100 group (39/187,20.9%, P=0.027). There was no statistical difference between the P 50 group and the P 100 group in the occurrence of grade 3-4 leukopenia and neutropenia (P > 0.05; P > 0.05) (Table 3, Fig. 2).

Table 3 Comparison between groups with reduced grade III-IV leukocytes & neutrophils [n, (%)]
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3.3 Clinical indicators

3.3.1 Recovery time of grade 3-4 leukopenia and neutropenia

Significant differences were recorded between the three groups in the recovery time of grade 3-4 leukopenia and neutropenia (F=77.567, P<0.001; F=31.113, P<0.001). The pairwise comparison (LSD) indicated that the recovery time of grade 3-4 leukopenia in the P 0 group (9.70±2.51 days) was notably higher than that in the P 50 group (5.85±2.31 days, P<0.001) and the P 100 group (5.46±1.99 days, P<0.001). The recovery time of grade 3-4 neutropenia in the P 0 group (9.05±3.32 days) was noticeably higher than that of the P 50 group (5.71±2.45 days, P<0.001) and the P 100 group (5.23±2.11 days, P<0.001). There was no difference in the recovery time of grade 3-4 leukopenia and neutropenia between the P 50 and the P 100 group (P > 0.05; P > 0.05) (Table 4).

Table 4 Comparison between groups of recovery time for reduced grade III-IV leukocytes & neutrophils (d, ‾x ± s)
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3.3.2 Comparison of the occurrence of the FN

There was no significant difference in FN occurrence (P 0 group: 6/269, 2.2%; P 50 group: 2/188, 1.1; P 100 group: 4/187, 2.1%) between the three groups (χ2=0.924, P=0.630) (Table 5).

Table 5 Comparison between groups of grade III-IV myelosuppression, moderate to severe bone pain, and drug-induced fever [n (%)]
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3.3.3 Grade 3-4 leukopenia / neutropenia and adverse reactions

The incidence of grade 3-4 leukopenia / neutropenia was significantly different among the three groups (χ2=16.729, P<0.001). The comparison showed that the occurrence of grade 3-4 leukopenia / neutropenia in the P 0 group (118/269,43.9%) was significantly higher than that in the P 50 group (57/188, 30.3%, P=0.003) and the P 100 group (50/187, 26.7%, P<0.001). There was no difference between the P 50 group and the P 100 group in the occurrence of grade 3-4 reduction of leukocytes/neutrophils (P > 0.05; P > 0.05). There were significant differences between the three groups in the occurrence of moderate to severe osteoarticular myalgia (χ2=6.492, P=0.039). The comparison showed that the occurrence of severe osteoarticular myalgia in the P 0 group (120/269, 44.6%) was significantly higher than that in the P 50 group (57/188, 42.0%, P=0.039) and the P 100 group (65/187, 34.8%, P<0.035). There was no statistical difference in the occurrence of bone pain between the P 50 group and the P 100 group (P > 0.05; P > 0.05). There was no statistical significant difference in the occurrence of drug-induced fever between the three groups (P 0 group:10/269, 3.7%; P 50 group: 11/188, 5.9%; P 100 group:16/187, 8.6%, χ2=4.775, P=0.092) (Table 5).

3.3.4 Radiotherapy interruption time

There was a significant difference in the duration of radiotherapy interruption between the three groups (Z=27.056, P<0.001). The pairwise comparison showed that the interruption time of radiotherapy in the P 0 group [0(0, 10) d] was conspicuously higher than that in the P 50 group ([0(0,7) d] P<0.001) and the P 100 group ([0(0,7) d], P<0.001). There was no significant difference between the P 50 group and the P 100 group (P > 0.05; P > 0.05) (Table 6, Fig. 2).

Table 6 Comparison between groups of radiotherapy interruption time in patients with grade III-IV myelosuppression
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3.4 Medical expenses

There was no significant difference in medical expenses (including outpatient) between the three groups (χ2=3.751, P=0.153) (Fig. 2).

3.5 Comparison of the efficacy of high and low dose PEG-rhG-CSF in the prevention of leukopenia/neutropenia

In Binary logsitic regression analysis, the severity of leukopenia / neutropenia (non-grade 3-4 = 0, grade 3-4 = 1) was considered as the dependent variable, whereas the diagnosis and treatment regimen (P 0 group, P 50 group, P 100 group) were the independent variables. In addition, age, tumor classification, and tumor stage were the control variables. In contrast to the P0 group, the risk of grade 3-4 leukopenia/neutropenia in the P50 group was OR (95% CI)=0.557(0.376, 0.825), P=0.004, while that in the P100 group was OR (95% CI) = 0.467 (0.312, 0.699), P< 0.001. On the other hand, compared with the P100 group, the risk of grade 3-4 leukopenia/neutropenia in the P50 group was OR(95%CI)=1.192 (0.761, 1.868), P=0.443. Namely, there was no significant difference in the prevention effect of grade 3-4 leukopenia/neutropenia between the two groups (Fig. 2).

4 Discussion

Concurrent chemoradiotherapy is the standard treatment for patients with advanced cervical cancer and inoperable early cervical cancer. Compared with radiotherapy or chemotherapy alone, it offers significant advantages and is an important measure to improve the long-term survival of patients. Although the acute side effects of concurrent chemoradiotherapy can be tolerated, more than 50% of proliferative bone marrow is located in cervical cancer radiotherapy areas such as pelvis and lumbar vertebrae [23, 35,36,42].

Moreover, PEG-rhG-CSF with a high dose of 100 μg/kg or a low dose of 50 μg/kg for the prevention of leukopenia/neutrophilia during concurrent chemoradiotherapy for cervical cancer exhibited similar efficacy. The results of binary logsitic regression analysis in this study showed that compared with the P 0 group, both the P 50 group and the P 100 group could significantly cut down the risk of grade 3-4 leukopenia/neutropenia, and compared with the P 100 group, the P 50 group had similar preventive effect, OR=1.192 (0.761,1.868), P=0.443. It is suggested that PEG-rhG-CSF with a dose of 50 μg/Kg could sufficiently achieve the efficacy of preventing leukopenia/neutrophilia of cervical cancer with concurrent chemoradiotherapy, which can actually decline the medical cost, improve the treatment compliance and satisfaction of patients, and be used safely. Moreover, it may be feasible to initially administer a low dose of PEG-rhG-CSF for prevention before considering an overall increase in dosage after grade 3-4 leukopenia/neutrophilia occurs.

It cannot be denied that there were some limitations in this study. In the first place, due to the limitations of research conditions, this study was conducted as a single-center clinical trial and could not be designed as a double-blind trial, potentially leading to selection bias. Therefore, further multi-center, double-blind trials are anticipated to yield more robust results. In addition, the analysis of efficacy and safety regarding prophylactic use of PEG-rhG-CSF did not include further stratification based on different radiotherapy methods (such as pelvic irradiation field or pelvic irradiation field and extended field etc.). Moreover, future data should be collected and analyzed in order to summarize the observed differences in thrombocytopenia between the PEG-rhG-CSF prophylaxis group and the non-prophylaxis group. Furthermore, the effect of the other two types of bone marrow suppression (thrombocytopenia and hemoglobin reduction) on treatment outcomes was not included in the analysis, which may have influenced the study results. Besides, one of the limitations of this study is that the baseline values of white blood cells and neutrophils were not recorded, neglecting their potential influence on bias. This aspect will receive greater attention and supplementation in future studies. Finally, it should be noted that this study exclusively focused on cervical cancer patients undergoing concurrent chemoradiotherapy; therefore, its applicability to all patients receiving concurrent chemoradiotherapy cannot be confirmed.

In conclusion, the prophylactic application of PEG-rhG-CSF in the course of concurrent chemoradiotherapy for cervical cancer is safe and effective. PEG-rhG-CSF could remarkably reduce the incidence of ≥ grade 3 leukopenia/neutrophilia, shorten the recovery time of leukopenia/neutrophilia, and reduce the occurrence of interruption of radiotherapy without increasing treatment costs. A low dose (50 μg/kg) of PEG-rhG-CSF was equipped with the potential to achieve similar preventive effects as a high dose (100 μg/kg), reducing medical costs while increasing patient adherence to treatment, although further studies are essential for the use of low doses to screen more suitable populations.