Thymalfasin, a promising adjuvant therapy in small hepatocellular carcinoma after liver resection

Abstract There is limited information available concerning the effect of thymalfasin (Tα1) as an adjuvant therapy in hepatocellular carcinoma (HCC) patient who received liver resection. The present study aimed to evaluate whether Tα1 can improve the prognosis of small HCC patients after liver resection. A total of 206 patients with small HCC who underwent liver resection were analyzed in our retrospective cohort study. Patients were divided into 2 groups: group A (resection + Tα1, n = 44) and group B (resection, n = 162). Clinical data, overall survival (OS), and recurrence-free survival (RFS) were compared. Prognostic factors were identified using multivariate analysis. After a median follow-up of 47.0 months, 134 patients (65%) had recurrence, and 62 patients (30.09%) died. The 1, 3, and 5-year OS rate of patients in group A was 97.7%, 90.6%, and 82.9%, respectively, and 95.1%, 80.5%, and 62.9%, respectively, for patients in group B (P = .014). The 1, 3, and 5-year RFS rate of patients in group A was 70.5%, 56.8%, and 53.3%, respectively, and 65.8%, 41.3%, and 32.1%, respectively, for patients in group B (P = .015). Multivariate analysis indicated that Tα1 was an independent prognostic factor for both OS (P = .015, hazard ratio 0.349, 95% confidence interval 0.149–0.816) and RFS (P = .019, hazard ratio 0.564, 95% confidence interval 0.349–0.910). Tα1 as an adjuvant therapy after liver resection may improve the prognosis of small HCC patients after liver resection.


Introduction
Hepatocellular carcinoma (HCC) is 5th common malignancies and the 3rd-leading cause of cancer-related death worldwide. Because of high hepatitis B virus (HBV) infection, China alone accounts for about 50% of the total number of cases and deaths. [1,2] Although surgical techniques and perioperative management have improved, survival remains very poor in HCC patients. Therefore, continuing efforts to explore new approaches to impede recurrence and improve the outcome of HCC is necessary. Immunotherapy has been shown to have potential benefit but evidence is not strong enough. [3,4] Thymalfasin (thymosin a1, Ta1, commercial name: ZADAXIN) is a naturally occurring thymic polypeptide of 28 amino acids. [5] The mechanism of this drug is related to its immune-modulating activities, and Ta1 has been widely used in various diseases, including some infection disease and malignances. [6] Previous investigations have shown that Ta1 may improve the outcomes of HCC patients who underwent transarterial chemoembolization (TACE). [7,8] However, whether Ta1 can improve the prognosis of small HCC patients who received liver resection has not been confirmed and the underlying mechanisms remains unclear. The present study was designed to evaluate the efficacy of Ta1 as an adjuvant therapy in patients with small HCC who underwent liver resection.

Patients
This study was approved by the Ethics Committee of West China Hospital, Sichuan University. The HCC patients who underwent liver resection in the Department of Liver Surgery and Liver Transplantation Center of West China Hospital between February 2007 and February 2013 were identified from our prospectively maintained database. During the period, 283 small HCC patients (within Milan criteria) received curative resection in our department. Diagnoses of HCC were confirmed by postoperative histopathologic examination. Microvascular invasion (MVI) was identified under a light microscope by pathologists. HCC was histologically classified using the Edmondson-Steiner classification. Clinical data, follow-up data, recurrence, and survival data were retrieved from our prospectively maintained database. In our study, inclusion criteria were as follows: primary HBV-related small HCC (solitary tumor <5 cm in diameter or 3 nodules, each of them <3 cm in diameter, without major vascular invasion or distant metastasis); receiving liver resection as initial therapy in our hospital; and liver reserve function Child-Pugh grade A. Exclusion criteria included the following: extra-hepatic malignancies; previous resection, TACE, ablative therapies, or liver transplantation; loss to follow-up within 3 months after liver resection; poor liver reserve function with a Child-Pugh grade B or C; rupture of HCC; coinfection with hepatitis C virus; simultaneous splenectomy; and previously treated with Ta1. Based on our inclusion and exclusion criteria, 77 patients were excluded. Excluded patients were as follows: 8 had recurrent HCC, 9 had a preoperative Child-Pugh grade of B, 4 had a rupture of HCC, 5 had a history of therapy before resection, 8 lost to follow-up within 3 months after operation, 4 coinfected with hepatitis C virus, and 39 had poor data integrity. Finally, a total of 206 patients were included in the analysis. Patients were divided into 2 groups based on whether they received Ta1 adjuvant therapy: group A (liver resection plus Ta1, n = 44), group b (liver resection only, n = 162). Details about patient selection are shown in Fig. 1. Current regimen of Ta1 (ZADAXIN): 1.6 mg subcutaneously twice per week for at least 26 weeks.

Follow-up visit
All the 206 patients were regularly followed up at the 1st, 3rd, and 6th months in the 1st half year after surgery, every 3 months during the following 3 years, and every 6 months in the subsequent years. Antiviral therapy was administered to patients with positive hepatitis B DNA before and after operation. Physical examination, blood cell and differential counts, alpha fetoprotein level, liver function test and HBV-DNA, and radiology examination were included in the follow-up examinations. Tumor recurrence was diagnosed according to positive imaging findings and arising of tumor marker (alpha fetoprotein) or pathologic report of biopsy or resection. Once identified, patients were advised to receive additional treatment. For example, liver transplantation, resection, ablative therapy, TACE, or sorafenib. The last follow-up date was the end of June 2016.

Statistical analysis
We used SPSS software version 20.0 (SPSS Company, Chicago, IL) for windows to perform statistical analysis. The continuous variables are expressed as the mean ± the standard deviation. The categorical variables are presented as numbers (percentages). Categorical data were compared by the chi-square test or Fisher exact test. Continuous variables were compared by independent t test for normal distributed data or Mann-Whiney U test for skewness-distributed data. The overall survival (OS) and recurrence-free survival (RFS) were analyzed by the Kaplan-Meier method, and the differences were analyzed by a log-rank test. Multivariate Cox proportional hazards regression analysis was used to evaluate the prognostic factors. Calculated P values were 2sided, and a P value <.05 was considered statistically significant.
Neutrophil to lymphocyte ratio (NLR) was defined as absolute neutrophil counts divided by lymphocyte counts. For group A, NLR0 was defined as NLR in the first follow-up visit. AS for group B, NLR0 was defined as NLR before administration of Ta1. dNLR1, dNLR2, and dNLR3 were defined as the NLR of 2nd, 3rd, and 4th follow-up visit minus NLR0. Data of NLR were excluded if there was clinical symptoms or signs of sepsis at the time of blood sampling for NLR, or white blood cell counts >10^109/L.

Baseline characteristics
In the present research, a total of 206 patients were included in the analysis. As described in Table 1. There were 178 males (86.4%) and 28 females (14.6%), with the mean age of 50.2 ± 11.8 (range from 21 to 78) year. The median follow-up time 47.0 months (range from 21.00 to 78.00). A total of 174 patients (84.5%) had 1 nodule, and 32 (15.5%) patients had 2 or 3 nodules; 78 patients (37.9%) had a nodule <3 cm in diameter, and 128 (62.1%) had a nodule 3 to 5 cm in diameter. A total of 178 (86.4%) patients had cirrhosis, 108 (52.4%) patients had HBV-DNA levels higher than 10^3 IU/L. The baseline characteristics of patients in the 2 groups are described in Table 1. There was no significant difference between the 2 groups in the baseline characteristics and the number of patients who received adjuvant therapy after recurrence ( Table 2). In group A, all of the 44 patients were administrated Ta1 with a median treatment time of 33.9 months (range from 6 to 93 months).         Table 3.

Univariate and multivariate analysis
To identify the prognostic factors for OS and RFS of small HCC after liver resection, 17 potential variables were analyzed. As shown in

Discussion
Liver resection has been widely accepted as standard treatment for HCC patients. However, recurrence rate is high as 70% at 5 years. [3] Risk factors for recurrence are multiple and prevalent. Consistent with previous research, our research confirmed MVI, tumor number, and cirrhosis were independent risk factors for small HCC recurrence. In small HCC, about 15% to 35% cases are with MVI, [9] about 60% to 90% cases are with cirrhosis, [10,11] and about 15% to 45% cases are multifocal. [10,12,13] Therefore, even in small HCC, 5-year RFS rate is only about 40%, [14,15] improvements in preventing recurrence and prolonging OS are essential. However, methods to prevent recurrence are limited. Adjuvant therapy, such as TACE and sorafenib, although are generally used for HCC patients who have risk factors of recurrence, remains controversial. [8,16] TACE is restricted by invasive nature, possibility of severe complications. As for sorafenib, its application is mainly compromised by high cost which is not affordable for most HCC patients. Immunotherapy has shown some potential efficacy, but evidence is not strong enough. [3,17] Previous investigations have shown Ta1 may improve the outcome of unresectable HCC patients who received TACE. [7,18,19] However, little is known about its efficacy in HCC patients who received liver resection. Shuqun et al [20] report that Ta1 plus lamivudine postoperatively compared to lamivudine In group A, NLR0 = NLR in the 1st follow-up visit. In group B, NLR0 = NLR before administration of Ta1. dNLR1, dNLR2, dNLR3 = NLR of 2nd, 3rd, and 4th follow-up minus NLR0. NLR = neutrophil to lymphocyte ratio, Ta1 = thymalfasin.  In recent years, accumulated evidence suggest that the systemic inflammatory response plays a significant role in various malignancies including HCC. NLR is one of the systemic inflammation markers, high postoperative NLR has been shown to be related to poor prognosis of HCC, and reduction of postoperative NLR is associated better prognosis. [15] Our research first reports that Ta1 can reduce postoperative NLR. The decline of NLR was associated with reduction of neutrophils and increment of lymphocytes. As lymphocytes have pivotal roles in inhibiting proliferation and metastatic activity of tumor cells. A relative lymphopenia may reflect deficient immune response to malignances. On the other hand, increased neutrophils can increase the level of circulating vascular endothelial growth factor, angiopoietin-1, and matrix metalloproteinase-9 which are major contributors to tumor-related angiogenesis. [21,22] Second, the immune response against tumor is weakened in HCC patients. [23,24] Ta1 can stimulate both adaptive and innate immune system against tumor by various paths. For instance, augmenting T-cell function, modulating cytokine and chemokine production, and augmenting the function of macrophages and other immune cells involving innate immune system. [6,25] Furthermore, Ta1 even suppress proliferation and induce apoptosis of tumor cells. [26] Third, postoperative active HBV replication has been proved to be associated with early HCC recurrence and shortened OS. Several studies have proved that combination of antivirus therapy and Ta1 postoperatively may be more effective in control HBV infection, and thus improve the prognosis of HCC. Therefore, Ta1 may improve the prognosis of HBV-related HCC by inhibiting HBV active replication. [20,27] There are several limitations in our study. First, this is a retrospective analysis from our single institution, and the sample size is relatively small. Second, the analysis of the dynamic change of NLR did not incorporate all the recruited patients, because of lacking the integrity of the follow-up blood cell data and patients had clinical symptoms or signs of sepsis at the time of blood sampling for NLR. Therefore, the result of dynamic NLR change must be tested in prospective research. Third, the present study only investigates the effect of Ta1 in small HCC patients who underwent liver resection, it is uncertain its effect in other stages of HCC, or other modalities of treatment.
In conclusion, our study demonstrated that Ta1 as adjuvant therapy in small HCC after liver resection may delay recurrence and prolong OS. It is rational for small HCC patients who have high risk for recurrence after resection to receive Ta1 adjuvant therapy.