Association between unintentional splenic radiation and lymphopenia and high neutrophil/lymphocyte ratio after radiotherapy in patients with esophageal cancer

Lymphopenia after palliative radiotherapy for vertebral metastases

Lymphopenia is a well-known side effect of radiotherapy and has been shown to have a negative impact on patient outcomes. However, the extent of lymphopenia caused by palliative radiotherapy and its effect on patient prognosis has not been clarified. The aim of this study was to determine the incidence and severity of lymphopenia after palliative radiotherapy for vertebral metastases and to determine their effects on patients' survival outcomes. We conducted a retrospective analysis for patients who underwent palliative radiotherapy for vertebral metastases and could be followed up for 12 weeks. Lymphocyte counts were documented at baseline and throughout the 12-week period following the start of radiotherapy and their medians and interquartile ranges (IQRs) were recorded. Exploratory analyses were performed to identify predictive factors for lymphopenia and its impact on overall survival (OS). A total of 282 cases that met the inclusion criteria were analyzed. The median baseline lymphocyte count was 1.26 × 103/μl (IQR: 0.89-1.72 × 103/μl). Peak lymphopenia occurred at a median of 26 days (IQR: 15-45 days) with a median nadir of 0.52 × 103/μl (IQR: 0.31-0.81 × 103/μl). Long-term analysis of patients surviving for 1 year showed that lymphopenia persisted at 1 year after radiotherapy. The main irradiation site, radiation field length and pretreatment lymphocyte count were significantly related to grade 3 or higher lymphopenia. Lymphopenia was identified as a significant predictor of OS by multivariate Cox regression analysis. This study demonstrated the incidence of lymphopenia after palliative radiotherapy for vertebral metastases and its effect on patients' OS.

Platelet-to-albumin ratio and radiation-induced lymphopenia-prognostic biomarker for carcinoma esophagus

BACKGROUND

Esophageal cancer has a poor survival outcome with 5-year OS at 16.7% despite treatment. Some inflammation-based prognostic indicators like the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) have been previously studied as potential biomarker for predicting outcome in esophageal cancer. Recently, platelet-to-albumin ratio (PAR) has been reported as a promising prognostic factor in gastrointestinal malignancies.

METHODS

We performed a retrospective analysis of prospectively treated patients of carcinoma esophagus to evaluate the prognostic significance of inflammation-based prognostic indicators-neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and a composite inflammation-nutrition index: platelet-to-albumin ratio (PAR) in esophageal cancer. Based on previous studies, the optimal cut-off value of PAR was kept at 5.7 × 10^9, and 2.62 for NLR.

RESULTS

A total of 71 patients of locally advanced esophageal cancer treated between 2019 and 2022, with either neoadjuvant or definitive chemoradiotherapy, were included. Median follow-up time was 19 months [range: 7-44 months]. Median OS and PFS in our study cohort were 11.3 months [range: 7-23 months] and 7.8 months [range: 3-17 months], respectively. In univariate analysis, lower PAR was found to be significantly correlated with shorter survival time (HR = 2.41; 1.3-4.76; p = 0.047). There was no association found between the OS and the NLR [HR = 1.09; 0.95-1.26; p = 0.222]. Univariate and multivariate linear and logistic regressions found no association between V15, V10, V5, or V2 of spleen and nadir lymphocyte count or between Dmax or Dmean and nadir lymphocyte counts.

CONCLUSION

Present analysis found a trend toward an inverse association between PAR and OS. PAR, in the not-so-distant future, may evolve as a novel, convenient, and inexpensive prognostic indicator in esophageal cancer.

Acute hematologic toxicity of radiation therapy - a comprehensive analysis and predictive nomogram

To investigate radiation-induced cytopenia and establish predictive nomograms for hematological toxicity, we reviewed 3786 patients aged 18 or older who received radiation monotherapy between 2010 and 2021 for non-hematologic malignancies. We collected data on patient background, treatment content and hematologic toxicities for 12 weeks after the start of radiotherapy. The patients were randomly divided into training and test groups in 7:3 ratio. In the training group, we conducted ordered logistic regression analysis to identify predictive factors for neutropenia, lymphocytopenia, anemia and thrombocytopenia. Nomograms to predict Grade 2-4 cytopenia were generated and validated in the test group. Grade 3 or higher hematologic toxicities were observed in 9.7, 44.6, 8.3 and 3.1% of patients with neutropenia, lymphocytopenia, anemia and thrombocytopenia, respectively. We identified six factors for neutropenia grade, nine for lymphocytopenia grade and six for anemia grade with statistical significance. In the analysis of thrombocytopenia, the statistical model did not converge because of a small number of events. Nomograms were generated using factors with high predictive power. In evaluating the nomograms, we found high area under the receiver operating characteristic curve values (neutropenia; 0.75-0.85, lymphopenia; 0.89-0.91 and anemia; 0.85-0.86) in predicting Grade 2-4 cytopenia in the test group. We established predictive nomograms for neutropenia, leukocytopenia and anemia and demonstrated high reproducibility when validated in an independent cohort of patients.

[Radiation-induced lymphopenia: Lymphocytes as a new organ at risk]

Taking the immune system into account in the fight against tumors has upset the cancer treatment paradigm in the 21st century. Combination treatment strategies associating radiotherapy with immunotherapy are being increasingly implemented in clinical practice. In this context, lymphocytes, whether lymphocytes infiltrating the tumour, circulating blood lymphocytes or lymphocytes residing within the lymph nodes, are key players in cellular and humoral anti-tumor immunity. The significant radiosensitivity of lymphocytes was demonstrated in the early 1990s. Along with the cells of the digestive mucosa, lymphocytes are thus among the most radiosensitive cell types in the body. Compared to the old practices of external radiotherapy, current intensity modulated treatments have allowed a considerable improvement in acute and late toxicity, at the cost of a significant increase in the volume irradiated at low doses. This is not without consequence on the incidence of radiation-induced lymphopenia, with prognostic implications for many tumor types. Thus, in order not to hinder the action of antitumor immunity and the efficacy of immunotherapy, it is essential to consider lymphocytes as a new organ at risk in its own right. In this development, based on current data from the literature, we will begin by justifying the necessary prevention of radiation-induced lymphopenia, before providing the tools currently known to apprehend lymphocytes as a new multicompartments. Finally, we will broaden the perspective by outlining ways to develop research in this area.

Emerging evidence for adapting radiotherapy to immunotherapy

Immunotherapy has revolutionized the clinical management of many malignancies but is infrequently associated with durable objective responses when used as a standalone treatment approach, calling for the development of combinatorial regimens with superior efficacy and acceptable toxicity. Radiotherapy, the most commonly used oncological treatment, has attracted considerable attention as a combination partner for immunotherapy owing to its well-known and predictable safety profile, widespread clinical availability, and potential for immunostimulatory effects. However, numerous randomized clinical trials investigating radiotherapy-immunotherapy combinations have failed to demonstrate a therapeutic benefit compared with either modality alone. Such a lack of interaction might reflect suboptimal study design, choice of end points and/or administration of radiotherapy according to standard schedules and target volumes. Indeed, radiotherapy has empirically evolved towards radiation doses and fields that enable maximal cancer cell killing with manageable toxicity to healthy tissues, without much consideration of potential radiation-induced immunostimulatory effects. Herein, we propose the concept that successful radiotherapy-immunotherapy combinations might require modifications of standard radiotherapy regimens and target volumes to optimally sustain immune fitness and enhance the antitumour immune response in support of meaningful clinical benefits.

Higher aorta dose increased neutrophil-to-lymphocyte ratio resulting in poorer outcomes in stage II-III non-small cell lung cancer

BACKGROUND

This study focused on the relationship between the neutrophil-to-lymphocyte ratio (NLR) and the dose of organs at risk in patients with stage II-III non-small cell lung cancer (NSCLC) receiving intensity-modulated radiotherapy.

METHODS

The clinical characteristics and dosimetric parameters of 372 patients were collected retrospectively. A high NLR was defined as that ≥1.525. Survival analysis was conducted using the Kaplan-Meier and Cox regression analysis. Least absolute shrinkage and selection operator (LASSO) analysis was conducted to select appropriate dosimetric parameters. The risk factors of NLR were evaluated using univariate and multivariate logistic regression analyses.

RESULTS

Patients with a high NLR had poorer progression-free survival (PFS) (p = 0.011) and overall survival (OS) (p = 0.061). A low NLR (<1.525) predicted better PFS (hazard ratio [HR] 0.676, 95% confidence interval [CI]: 0.508-0.900, p = 0.007) and OS (HR 0.664, 95% CI: 0.490-0.901, p = 0.009). The aorta dose differed between the low and high NLR groups (all <0.1) in the univariate analysis. An aorta V10 was confirmed as a significant risk factor for a high NLR (odds ratio [OR] 1.029, 95% CI: 1.011-1.048, p = 0.002). Receiving chemotherapy before (OR 0.428, 95% CI: 0.225-0.813, p = 0.010) and during (OR 0.491, 95% CI: 0.296-0.815, p = 0.006) radiotherapy were predictive factors of a low NLR.

CONCLUSION

The aorta dose was significantly associated with a high NLR. Patients with stage II-III NSCLC with a high NLR had poorer prognosis. Receiving chemotherapy before and/or during radiotherapy predicted a low NLR.

Functional plasticity of neutrophils after low- or high-dose irradiation in cancer treatment - A mini review

Over the last several decades, radiotherapy has been considered the primary treatment option for a broad range of cancer types, aimed at prolonging patients' survival and slowing down tumor regression. However, therapeutic outcomes of radiotherapy remain limited, and patients suffer from relapse shortly after radiation. Neutrophils can initiate an immune response to infection by releasing cytokines and chemokines to actively combat pathogens. In tumor immune microenvironment, tumor-derived signals reprogram neutrophils and induce their heterogeneity and functional versatility to promote or inhibit tumor growth. In this review, we present an overview of the typical phenotypes of neutrophils that emerge after exposure to low- and high-dose radiation. These phenotypes hold potential for developing synergistic therapeutic strategies to inhibit immunosuppressive activity and improve the antitumor effects of neutrophils to render radiation therapy as a more effective strategy for cancer patients, through tumor microenvironment modulation.

Lymphocyte sparing normal tissue effects in the clinic (LymphoTEC): A systematic review of dose constraint considerations to mitigate radiation-related lymphopenia in the era of immunotherapy

BACKGROUND

Radiation-related lymphopenia has been associated with suboptimal tumor control rates leading to inferior survival outcomes. To date, no standardized dose constraints are available to limit radiation dose to resident and circulating lymphocyte populations. We undertook this systemic review of the literature to provide a synopsis of the dosimetric predictors of radiation-related lymphopenia in solid malignancies.

METHODOLOGY

A systematic literature review of PubMed (National Institutes of Health), Cochrane Central (Cochrane collaboration), and Google Scholar was conducted with the following keywords: "radiation", "lymphopenia", "cancer", "dosimetric predictors" with an inclusion deadline of May 31, 2022. Studies that met prespecified inclusion criteria were designated either Good, Fair, or Poor Quality based on the Newcastle-Ottawa quality assessment. The dosimetric parameters derived from Good Quality studies were tabulated as LymphoTEC dose constraints. Dosimetric parameters derived from Fair and Poor-quality studies were grouped as optional.

RESULTS

An initial systematic search of the literature yielded 1,632 articles. After screening, a total of 48 studies met inclusion criteria and were divided into the following categories: central nervous system (CNS, 6), thoracic (11), gastrointestinal (26), gynecologic (2), head and neck, breast, and genitourinary (one each) cancers. Lung mean dose, heart mean dose, brain V25, spleen mean dose, estimated dose to immune cells, and bone marrow V10 were among the strongest predictors for severe lymphopenia related to radiotherapy.

CONCLUSION

Optimizing the delivery of radiation therapy to limit dose to lymphocyte-rich structures may curb the negative oncologic impact of lymphocyte depletion. The dose constraints described herein may be considered for prospective validation and future use in clinical trials to limit risk of radiation-related lymphopenia and possibly improve cancer-associated outcomes.

Splenic irradiation contributes to grade ≥ 3 lymphopenia after adjuvant chemoradiation for stomach cancer

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Severe lymphopenia occurs commonly after adjuvant chemoradiation for gastric cancer.

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High splenic radiation doses increase the chances of severe lymphopenia.

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Severe lymphopenia predicts a poorer overall survival and higher risk of infections.

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The spleen is not routinely considered an organ-at-risk with dosimetric constraint.

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Applying dose constraints to the spleen might lower the risk of severe lymphopenia.

Introduction

Adjuvant chemoradiation therapy (CRT) in gastric cancer inevitably results in an unintentional spleen radiation dose. We aimed to determine the association between the spleen radiation dose and the observed severity of lymphopenia which may affect the clinical outcomes (survival time and infection risk).

Methods

Patients who received adjuvant CRT for gastric cancer between January 2015 and December 2020 were analyzed. The splenic dose-volume histogram (DVH) parameters were reported as mean splenic dose (MSD) and percentage of splenic volume receiving at least × Gray (Gy). Peripheral blood counts were recorded pre- and post-CRT. The development of severe (Common Terminology Criteria for Adverse Events, version 5.0, grade ≥ 3) post-CRT lymphopenia (absolute lymphocyte count [ALC] < 0.5 K/μL) was assessed by multivariable logistic regression using patient and dosimetric factors. Overall survival (OS), recurrence-free survival (RFS), and cumulative incidence of infectious events were estimated and analyzed using the Cox model or competing risk analysis.

Results

Eighty-four patients with a median follow-up duration of 42 months were analyzed. Pre- and post-CRT median ALC values were 1.8 K/μL (0.9–3.1 K/μL) and 0.9 K/μL (0.0–4.9 K/μL), respectively (P < 0.001). MSD > 40 Gy (odds ratio [OR], 1.13; 95 % confidence interval [CI], 1.01–1.26; P = 0.041), sex (OR for male to female, 0.25; 95 % CI, 0.09–0.70; P = 0.008), and baseline absolute neutrophil count (OR per 1 unit increase, 1.61; 95 % CI, 1.02–2.58; P = 0.040) were associated with the development of severe post-CRT lymphopenia, which was a risk factor for poorer OS (hazard ratio [HR] = 2.47; 95 % CI, 1.24–4.92; P = 0.010) and RFS (HR = 2.27; 95 % CI, 1.16–4.46; P = 0.017). The cumulative incidence of infections was higher among severe post-CRT lymphopenia patients (2.53, 95 % CI, 1.03–6.23, P = 0.043).

Conclusion

High splenic radiation doses increase the odds of severe post-CRT lymphopenia, an independent predictor of lower OS and higher risks of recurrence and infections in gastric cancer patients receiving adjuvant CRT. Therefore, optimizing the splenic DVH parameters may decrease the risk of severe post-CRT lymphopenia.