Introduction: Chemotherapy is one of the modalities of systemic therapy. It is not tumor-specific and is linked to the occurrence of toxicities in healthy tissues. Chemotherapy also impairs the immune system, reducing the number of immune cells and weakening its function.

Aim: This study evaluated immune system parameters among solid tumor patients that underwent chemotherapy before and after three cycles. Parameters that were evaluated here were neutrophil count, lymphocyte count, and CD4 and CD8 pre- and post-three cycles of chemotherapy.

Materials and methods: This was a pre- and post-study that took place in the Hematology Medical Oncology Clinic between June 2023 and May 2024. A total of 36 subjects were recruited for this study.

Results: Most subjects were female (58.3%) with a mean age of 46.69±16.30 years. Body mass index (BMI) fell primarily into the normal weight range (38.9%), with underweight and overweight coming in second and third, respectively, at 33.3% and 27.8%. Most subjects had stage IV disease (61.1%) and head and neck cancer (30.6%). We evaluated four immune parameters after three rounds of chemotherapy and found that the neutrophil count (p=0.035), lymphocyte count (0.032), CD4 (0.027), and CD8 (0.020) had decreased. A correlation between neutrophils and ECOG score (p=0.021) and a decreased lymphocyte count with weight loss greater than 3 kg (p=0.038) was found in the analysis of clinical characteristics and immune parameters following chemotherapy. CD8 levels were lower in people over 40 (p=0.027).

Conclusions: Immune markers such as neutrophils, lymphocytes, and CD4 cells have been shown to decrease as a result of chemotherapy. Following chemotherapy, patients with solid tumors who are older than 40, have an ECOG score of 1 or higher, and have lost at least 3 kg of weight typically exhibit lower immune parameters.

CD4, CD8, chemotherapy, neutrophil, lymphocyte, solid cancer

Conventional chemotherapy using cytostatic agents is one of the modalities of systemic cancer therapy, which is the first therapy used to kill cancer cells.^[1] Some classes of cytostatic drugs, including antimetabolites, anti-microtubules, and alkylating agents, have been developed in recent decades.^[1] Cytostatic chemotherapy is generally not tumor-specific, and its administration is associated with toxicity to healthy tissues.^[1]

Solid tumors are abnormal tissue masses that typically lack cysts or fluid-filled areas.^[2] They are categorized according to the cell types that give rise to them; sarcomas, carcinomas, and lymphomas are typical examples.^[2] Unlike leukemias, which are blood cancers and usually do not form solid masses, solid tumors can influence immune system parameters and are often associated with changes in immune function.^[2]

One of the defenses against cancer cells is the immune system. Both tumor growth and antitumor responses are impacted by the immune system. As is widely acknowledged, immune system dysfunction in cancer fosters the proliferation and metastasis of cancer cells^[3] CD4 and CD8 T cells are impaired in producing IL6 and IFN-γ. In addition, the response of CD4 cells to IL6 has decreased. The number of polymorphonuclear cells (PMN) will increase due to the presence of a tumor mass.^[3]

Cytostatic agents will attack cells that have a high proliferation rate, both cancer cells and healthy cells, including the immune system cells. Administration of cytostatic agents will cause lymphocyte and CD8 cell depletion, which will recover within one year after chemotherapy. CD4 cells will change their nature to become inflammatory effectors due to chemotherapy.^[3] The mechanism of immune system suppression due to chemotherapy is like the cytotoxic effect of chemotherapy agents on immune cells such as T lymphocytes and neutrophils that will decrease in number. ^[4] Chemotherapy will also alter the proliferation, differentiation, and evolution of the immune system, resulting in dysfunction of the immune response.^[4] Recent studies have also reported chemotherapy can increase immunogenic cell death (ICD) of cancer cells. Chemotherapy-induced cancer cell damage causes some cancer cell proteins to be exposed to the immune system, so they can be recognized and increase cancer cell death due to immune system activation.^[5]

Chemotherapy can disrupt and weaken the immune system. This will almost certainly be associated with treatment-related side effects. Chemotherapy-induced neutropenia can result in potentially fatal infections. Meanwhile, decreased expression of Toll-like receptors impairs the ability to recognize pathogens.^[4] Better understanding about changes in the immune system during chemotherapy is important to obtain maximum therapeutic results and minimal toxicity.

This study will evaluate changes in the immune system, including neutrophils, lymphocytes, CD4, and CD8, in solid cancer patients undergoing chemotherapy.

There was a pre- and post-research study that enrolled solid tumor patients who have undergone three cycles of chemotherapy at the Hematology and Medical Oncology Clinic, Cipto Mangunkusumo Hospital, Indonesia. This research was conducted between June 2023 and May 2024. Patients over the age of 18, male and female, of Asian descent, diagnosed with a solid tumor, who had completed three cycles of chemotherapy and had not received radiotherapy in the previous six months, were eligible for inclusion. Exclusion criteria included patients with hematologic malignancies and those with a history of radiotherapy within six months or injection of G-CSF within three days before blood collection. Patients will undergo blood tests to measure CD4, neutrophil, lymphocyte, and CD8 before starting the first cycle and after completing three cycles of chemotherapy. Blood samples are collected between days 14 and 21, after the third chemotherapy cycle but before the next cycle. Blood was drawn from the brachial vein using a 3-cc syringe and immediately sent to the laboratory.

Data from this study were processed using SPSS version 28.0. Bivariate analysis was performed on the data from the actual sample to examine the relationships between variables. This study took into account subject characteristics such as sex, age, body mass index (BMI), stadium, Eastern Cooperative Oncology Group Performance Status, and cancer type. The Faculty of Medicine Ethical Commission granted ethical approval for this study (KET-1391/UN2.F1/ETIK/PPM.00.02/2022). All patients provided informed consent.

This study included 36 subjects in total. Prior to chemotherapy, there were 58 patients, with 17 dying during three cycles of chemotherapy and 5 lost to follow-up. The majority of subjects were female (58.3%), with a mean age of 46.69±16.30 years. Nutritional status was determined by pre-treatment BMI, with the majority falling into the normoweight category (38.9%), followed by underweight and overweight (33.3% and 27.8%, respectively). The majority of subjects had stage IV cancer, accounting for up to 61.1% of the total sample. Table 1 presents subject characteristics.

Table 2 shows the immune profiles prior to and after chemotherapy. Bivariate statistics were then used to compare pre- and post-chemotherapy results. This study found that four parameters, lymphocyte and CD8, differed significantly between pre- and post-chemotherapy levels.

A subgroup analysis was conducted based on age (<40 vs. ≥40), post-chemotherapy ECOG score (0 vs. ≥1), post-treatment BMI (normal weight vs. malnourished), reduced body weight after chemotherapy (<3 kg vs. ≥3 kg), and chemotherapy regimen. Table 3 displayed the results of the analysis.

The analysis showed that post-chemotherapy neutrophils decreased in ECOG ≥1 (p=0.029), and lymphocyte count decreased in subjects with weight loss >3 kg after chemotherapy (p=0.039). CD8 levels are lower among people over the age of 40 (p=0.032). Meanwhile, there was no correlation between the type of cytostatic agent used and the frequency of immune parameters.

The immune system was evaluated before and after three cycles of chemotherapy, and it was discovered that there was a significant decrease in neutrophil count, lymphocytes count, CD4 and CD8 cells. This is consistent with previous research suggesting that chemotherapy can cause lymphodepletion. Cytostatic agents have direct cytotoxic effects on immune cells, including all types of T lymphocytes. Verma et al.^[6] found that breast cancer patients who received chemotherapy had fewer NK cells and B and T lymphocytes. Aldarouish et al.^[7] also found a decrease in post-chemotherapy CD8 levels compared to pre-chemotherapy levels among lung cancer patients receiving platinum-pemetrexed, which is consistent with the findings of this study. The decrease in lymphocyte cells was observed as early as two weeks after the initial chemotherapy. Lymphodepletion can last up to 3-6 months.^[6] This study found a significant decrease in neutrophils. Neutropenia is a common chemotherapy side effect that occurs on days 10-14 after treatment.^[8,9] Neutropenia can occur after the first cycle of chemotherapy.^[8] Routine G-CSF prophylaxis has also been demonstrated to reduce the incidence of neutropenia following chemotherapy.^[8] However, in this center, G-CSF is only administered in cases where the absolute neutrophil count (ANC) is less than 500/µL. We do not routinely provide secondary prophylaxis because it is not covered by national health insurance.^[10] Previous studies have found that chemotherapy lowers CD4 levels in both solid and blood cancers.^[6,11] Meanwhile, CD4 cell recovery can take more than 9 months.^[6]

In this study, an analysis was conducted based on clinical characteristics of post-chemotherapy immune parameters. In the group of patients with ECOG ≥1, there was a significant relationship with post-chemotherapy neutrophil levels. This is in line with other studies reporting that ECOG 2-4 is associated with neutropenia and mortality.‌^[4,12] Neutrophils are important in host defense against infection, particularly bacterial and fungal infections. The risk of infection increases with the depth and length of neutropenia, with the highest risk in patients that experience prolonged neutropenia.^[13] Neutropenia is also related to delay in treatment delivery and dose reduction.^[13]

In this study, an analysis was conducted based on clinical characteristics of post-chemotherapy immune parameters. In the group of patients with ECOG ≥1, there was a significant relationship with post-chemotherapy neutrophil levels. This is in line with other studies reporting that ECOG 2-4 is associated with neutropenia and mortality. ^[4,12] Neutrophils are important in host defense against infection, particularly bacterial and fungal infections. The risk of infection rises with the depth and duration of neutropenia, with the highest risk in patients with prolonged neutropenia.^[13] Neutropenia is also related to delay in treatment delivery and dose reduction.

A subgroup analysis was also performed by assessing post-chemotherapy immune parameters after the cytostatic agent was administered. The analysis in this study revealed that there was no correlation between the chemotherapy agents used and post-chemotherapy immune parameters. There have been studies that show that each class has a different effect on immune parameters.^[6–21] The discrepancy in the results of this study could be attributed to the small sample size when analyzing each chemotherapy drug.

The advantage of this study is that it compares immune parameters to simple clinical parameters like weight change, BMI, and ECOG. This can be done at a variety of cancer centers throughout Indonesia. The study’s limitation is that there were insufficient samples for each class of cancer drugs. Future studies on specific chemotherapy regimens will provide a more complete picture of how each cytostatic agent affects immune parameters.

Chemotherapy reduces immune markers like neutrophils, lymphocytes, and CD4 cells. Patients with solid tumors over the age of 40, with an ECOG score of 1 or higher, and a weight loss of 3 kg or more tend to have lower immune parameters following chemotherapy.

This study was funded by the Publikasi Terindeks Internasional (PUTI) Prosiding Grant 2022 from Universitas Indonesia (Contract Number NKB‐199/ UN2.RST/HKP. 05.00/2022).

There are no conflicts of interest.

The authors express gratitude for the support and assistance provided by nurses in the Hematology and Medical Oncology clinic, as well as the clinical pathology unit at Cipto Mangunkusumo Hospital, during the course of this study.