Differential Association Between Circulating Lymphocyte Populations With Outcome After Radiation Therapy in Subtypes of Liver Cancer

Hypofractionated Radiotherapy-Related Lymphopenia Is Associated With Worse Survival in Unresectable Intrahepatic Cholangiocarcinoma

OBJECTIVE

The aim of this study was to evaluate the incidence of radiotherapy (RT)-related lymphopenia, its predictors, and association with survival in unresectable intrahepatic cholangiocarcinoma (ICC) treated with hypofractionated-RT (HF-RT).

METHODS

Retrospective analysis of 96 patients with unresectable ICC who underwent HF-RT (median 58.05 Gy in 15 fractions) between 2009 and 2022 was performed. Absolute lymphocyte count (ALC) nadir within 12 weeks of RT was analyzed. Primary variable of interest was severe lymphopenia, defined as Grade 3+ (ALC <0.5 k/μL) per CTCAE v5.0. Primary outcome of interest was overall survival (OS) from RT.

RESULTS

Median follow-up was 16 months. Fifty-two percent of patients had chemotherapy pre-RT, 23% during RT, and 40% post-RT. Pre-RT, median ALC was 1.1 k/μL and 5% had severe lymphopenia. Post-RT, 68% developed RT-related severe lymphopenia. Patients who developed severe lymphopenia had a significantly lower pre-RT ALC (median 1.1 vs. 1.5 k/μL, P=0.01) and larger target tumor volume (median 125 vs. 62 cm3, P=0.02). In our multivariable Cox model, severe lymphopenia was associated with a 1.7-fold increased risk of death (P=0.04); 1-year OS rates were 63% vs 77% (P=0.03). Receipt of photon versus proton-based RT (OR=3.50, P=0.02), higher mean liver dose (OR=1.19, P<0.01), and longer RT duration (OR=1.49, P=0.02) predicted severe lymphopenia.

CONCLUSIONS

HF-RT-related lymphopenia is an independent prognostic factor for survival in patients with unresectable ICC. Patients with lower baseline ALC and larger tumor volume may be at increased risk, and use of proton therapy, minimizing mean liver dose, and avoiding treatment breaks may reduce RT-related lymphopenia.

The Correlation Between Low-Dose Radiotherapy Area of the Mediastinum and CD8+T Cells and the Efficacy of Radiotherapy for Non-Small Cell Lung Cancer

Background

Radiation therapy (RT) can cause changes in peripheral blood immune cells. The relationship between the efficacy of radiation therapy for non-small cell lung cancer (NSCLC) and immune cell changes and the study of how mediastinal radiation dose parameters affect immune cell changes is still unclear. This study aims to analyze the relationship between immune cell changes induced by radiotherapy and the efficacy of NSCLC radiotherapy, as well as the relationship between radiotherapy dose parameters and immune cell changes.

Materials and Methods

We retrospectively analyzed the data of NSCLC patients receiving mediastinal radiation therapy from 2020 to 2022. Collect lymphocytes and circulating immune cells within one week before and after radiotherapy and collect the dose-volume parameters of the whole mediastinum in the patient's RT planning system. Analyze the changes in lymphocytes and radiotherapy effects after radiotherapy, and explore the relationship between radiotherapy dose parameters and immune cell changes.

Results

A total of 72 patients were enrolled. Compared with before radiotherapy, the proportion of CD3+T cells, CD8+T cells, and CD8/Treg in peripheral blood significantly increased after radiotherapy (P<0.05). The increase in CD8+T cells and CD8/Treg after radiotherapy was correlated with Objective response rate (ORR) (P<0.05). Based on binary logistic univariate and multivariate regression analysis, an increase in CD8+T cells after radiotherapy is an independent predictor of objective tumor response after radiotherapy (OR=12.71, 95% CI=3.64-44.64, P=0.01), and Volume of 200 cGy irradiation (V2) is an independent positive predictor of an increase in CD8+T lymphocyte ratio after radiotherapy (high group, OR=3.40, 95% CI=1.13-10.36, P=0.03).

Conclusion

The increase in CD8+T cells after radiotherapy can positively predict the short-term efficacy of radiotherapy. Mediastinal low-dose radiation therapy can increase CD8+T cells, thereby improving the short-term efficacy of radiotherapy. These potentially related mechanisms are worth further verification and exploration.

Mitigating Radiotoxicity in the Central Nervous System: Role of Proton Therapy

OPINION STATEMENT

Central nervous system (CNS) radiotoxicity remains a challenge in neuro-oncology. Dose distribution advantages of protons over photons have prompted increased use of brain-directed proton therapy. While well-recognized among pediatric populations, the benefit of proton therapy among adults with CNS malignancies remains controversial. We herein discuss the role of protons in mitigating late CNS radiotoxicities in adult patients. Despite limited clinical trials, evidence suggests toxicity profile advantages of protons over conventional radiotherapy, including retention of neurocognitive function and brain volume. Modelling studies predict superior dose conformality of protons versus state-of-the-art photon techniques reduces late radiogenic vasculopathies, endocrinopathies, and malignancies. Conversely, potentially higher brain tissue necrosis rates following proton therapy highlight a need to resolve uncertainties surrounding the impact of variable biological effectiveness of protons on dose distribution. Clinical trials comparing best photon and particle-based therapy are underway to establish whether protons substantially improve long-term treatment-related outcomes in adults with CNS malignancies.

Advances in radiotherapy and immunity in hepatocellular carcinoma

Primary liver cancer is one of the most common malignant tumours worldwide; it caused approximately 830,000 deaths in 2020. Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, accounting for over 80% of all cases. Various methods, including surgery, chemotherapy, radiotherapy, and radiofrequency ablation, have been widely used in the treatment of HCC. With the advancement of technology, radiotherapy has become increasingly important in the comprehensive treatment of HCC. However, due to the insufficient sensitivity of tumour cells to radiation, there are still multiple limitation in clinical application of radiotherapy. In recent years, the role of immunotherapy in cancer has been increasingly revealed, and more researchers have turned their attention to the combined application of immunotherapy and radiotherapy in the hope of achieving better treatment outcomes. This article reviews the progress on radiation therapy in HCC and the current status of its combined application with immunotherapy, and discusses the prospects and value of radioimmunotherapy in HCC.

Effect of Lymphopenia on Tumor Response and Clinical Outcomes Following Chemoradiotherapy in Stage III Non-Small Cell Lung Cancer

Background

Prior studies suggest lymphopenia, systemic immune-inflammatory index, and tumor response all impact clinical outcomes in Stage III NSCLC. We hypothesized that tumor response after CRT would be associated with hematologic metrics and might predict clinical outcomes.

Materials and Methods

Patients with stage III NSCLC treated at a single institution between 2011 and 2018 were retrospectively reviewed. Pre-treatment gross tumor volume (GTV) was recorded then reassessed at 1-4 months post-CRT. Complete blood counts before, during and after treatment were recorded. Systemic immune-inflammation index (SII) was defined as neutrophil × platelet/lymphocyte. Overall survival (OS) and progression free survival (PFS) were calculated using Kaplan-Meier estimates, and compared with Wilcoxon tests. A multivariate analysis of hematologic factors impacting restricted mean survival was then performed using pseudovalue regression, accounting for other baseline factors.

Results

106 patients were included. After median follow-up of 24 months, median PFS and OS were 16 and 40 months, respectively. Within the multivariate model, baseline SII was associated with OS (p = 0.046) but not PFS (p = 0.09), and baseline ALC correlated with both PFS and OS (p = 0.03 and p = 0.02, respectively). Nadir ALC, nadir SII, and recovery SII were not associated with PFS or OS.

Conclusion

In this cohort of patients with stage III NSCLC, baseline hematologic factors were associated with clinical outcomes including baseline ALC, baseline SII and recovery ALC. Disease response was not well correlated with hematologic factors or clinical outcomes.

The current understanding of the immune landscape relative to radiotherapy across tumor types

Radiotherapy is part of the standard of care treatment for a great majority of cancer patients. As a result of radiation, both tumor cells and the environment around them are affected directly by radiation, which mainly primes but also might limit the immune response. Multiple immune factors play a role in cancer progression and response to radiotherapy, including the immune tumor microenvironment and systemic immunity referred to as the immune landscape. A heterogeneous tumor microenvironment and the varying patient characteristics complicate the dynamic relationship between radiotherapy and this immune landscape. In this review, we will present the current overview of the immunological landscape in relation to radiotherapy in order to provide insight and encourage research to further improve cancer treatment. An investigation into the impact of radiation therapy on the immune landscape showed in several cancers a common pattern of immunological responses after radiation. Radiation leads to an upsurge in infiltrating T lymphocytes and the expression of programmed death ligand 1 (PD-L1) which can hint at a benefit for the patient when combined with immunotherapy. In spite of this, lymphopenia in the tumor microenvironment of 'cold' tumors or caused by radiation is considered to be an important obstacle to the patient's survival. In several cancers, a rise in the immunosuppressive populations is seen after radiation, mainly pro-tumoral M2 macrophages and myeloid-derived suppressor cells (MDSCs). As a final point, we will highlight how the radiation parameters themselves can influence the immune system and, therefore, be exploited to the advantage of the patient.

Selective Internal Radiotherapy Changes the Immune Profiles of Extracellular Vesicles and Their Immune Origin in Patients with Inoperable Cholangiocarcinoma

The incidence of cholangiocellular carcinoma (CCA) is rising worldwide. As there are no specific early symptoms or specific markers of CCA, it is often diagnosed in later inoperable stages. Accumulating evidence underlines the importance of radiation therapy in the induction of antitumor immunity. The surface protein composition on extracellular vesicles (EVs) relates to originating cells and thus may play a role in vesicle function. We assessed immune profiles of EVs and their immune origin in patients with inoperable CCA prior and after selective internal radiotherapy (SIRT). A total of 47 CCA patients receiving SIRT and 12 healthy volunteers (HV) were included. Blood was withdrawn before therapy (pre T) and after T. EVs were purified from plasma by cluster of differentiation (CD)9-, CD63-, and CD81-immunobead isolation. To detect differently abundant surface markers, dynamic range and EVs input quality were assessed. A total of 37 EVs surface markers were measured by flow cytometry and correlated either with the administered activity dose (MBq) or with the interval until death (month). EVs phenotyping identified lymphocytes, B cells, NK cells, platelets, endothelial cells, leukocyte activation, B cell activation, T and B cell adhesion markers, stem/progenitor cells, and antigen-presenting cells (APC) as EVs-parenteral cells. CD4 and CD8 significantly declined, while other markers significantly increased in CCA patients pre T vs. HV. Platelets-deriving EVs significantly decreased, normalizing to levels of HV but still significantly increasing vs. HV post SIRT. B cells-deriving EVs significantly increased pre T vs. HV, positively correlating with administered activity dose. MHCII and CD40 EVs significantly increased pre SIRT and negatively correlated with administered activity dose, while EVs from antigen presenting cells and CD49e pre SIRT positively correlated with survival time after therapy. Increased levels of CD24 and CD44 in cancer pre T were significantly decreased post T. Among the heterogeneity of EVs that was demonstrated, in particular, B cells-deriving, MHCII, and CD40 positive or APC-deriving EVs need to be further studied for their diagnostic or prognostic relevance in clinical scenarios.

Reshaping the systemic tumor immune environment (STIE) and tumor immune microenvironment (TIME) to enhance immunotherapy efficacy in solid tumors

The development of combination immunotherapy based on the mediation of regulatory mechanisms of the tumor immune microenvironment (TIME) is promising. However, a deep understanding of tumor immunology must involve the systemic tumor immune environment (STIE) which was merely illustrated previously. Here, we aim to review recent advances in single-cell transcriptomics and spatial transcriptomics for the studies of STIE, TIME, and their interactions, which may reveal heterogeneity in immunotherapy responses as well as the dynamic changes essential for the treatment effect. We review the evidence from preclinical and clinical studies related to TIME, STIE, and their significance on overall survival, through different immunomodulatory pathways, such as metabolic and neuro-immunological pathways. We also evaluate the significance of the STIE, TIME, and their interactions as well as changes after local radiotherapy and systemic immunotherapy or combined immunotherapy. We focus our review on the evidence of lung cancer, hepatocellular carcinoma, and nasopharyngeal carcinoma, aiming to reshape STIE and TIME to enhance immunotherapy efficacy.

Leveraging Blood-Based Diagnostics to Predict Tumor Biology and Extend the Application and Personalization of Radiotherapy in Liver Cancers

While the incidence of primary liver cancers has been increasing worldwide over the last few decades, the mortality has remained consistently high. Most patients present with underlying liver disease and have limited treatment options. In recent years, radiotherapy has emerged as a promising approach for some patients; however, the risk of radiation induced liver disease (RILD) remains a limiting factor for some patients. Thus, the discovery and validation of biomarkers to measure treatment response and toxicity is critical to make progress in personalizing radiotherapy for liver cancers. While tissue biomarkers are optimal, hepatocellular carcinoma (HCC) is typically diagnosed radiographically, making tumor tissue not readily available. Alternatively, blood-based diagnostics may be a more practical option as blood draws are minimally invasive, widely availability and may be performed serially during treatment. Possible blood-based diagnostics include indocyanine green test, plasma or serum levels of HGF or cytokines, circulating blood cells and genomic biomarkers. The albumin–bilirubin (ALBI) score incorporates albumin and bilirubin to subdivide patients with well-compensated underlying liver dysfunction (Child–Pugh score A) into two distinct groups. This review provides an overview of the current knowledge on circulating biomarkers and blood-based scores in patients with malignant liver disease undergoing radiotherapy and outlines potential future directions.

Single-cell immune signature for detecting early-stage HCC and early assessing anti-PD-1 immunotherapy efficacy

Background

The early diagnosis of hepatocellular carcinoma (HCC) can greatly improve patients’ 5-year survival rate, and the early efficacy assessment is important for oncologists to harness the anti-programmed cell death protein 1 (PD-1) immunotherapy in patients with advanced HCC. The lack of effective predicting biomarkers not only leads to delayed detection of the disease but also results in ineffective immunotherapy and limited clinical survival benefit.

Methods

We exploited the single-cell approach (cytometry by time of flight (CyTOF)) to analyze peripheral blood mononuclear cells from multicohorts of human samples. Immune signatures for different stages of patients with HCC were systematically profiled and statistically compared. Furthermore, the dynamic changes of peripheral immune compositions for both first-line and second-line patients with HCC after anti-PD-1 monotherapy were also evaluated and systematically compared.

Results

We identified stage-specific immune signatures for HCC and constructed a logistic AdaBoost-SVM classifier based on these signatures. The classifier provided superior performance in predicting early-stage HCC over the commonly used serum alpha-fetoprotein level. We also revealed the treatment stage-specific immune signatures from peripheral blood and their dynamical changing patterns, all of which were integrated to achieve early discrimination of patients with non-durable benefit for both first-line and second-line anti-PD-1 monotherapies.

Conclusions

Our newly identified single-cell peripheral immune signatures provide promising non-invasive biomarkers for early detection of HCC and early assessment for anti-PD-1 immunotherapy efficacy in patients with advanced HCC. These new findings can potentially facilitate early diagnosis and novel immunotherapy for patients with HCC in future practice and further guide the utility of CyTOF in clinical translation of cancer research.

Trial registration numbers

NCT02576509 and NCT02989922.

Normal Tissue Injury Induced by Photon and Proton Therapies: Gaps and Opportunities

Despite technological advances in radiation therapy (RT) and cancer treatment, patients still experience adverse effects. Proton therapy (PT) has emerged as a valuable RT modality that can improve treatment outcomes. Normal tissue injury is an important determinant of the outcome; therefore, for this review, we analyzed 2 databases: (1) clinical trials registered with ClinicalTrials.gov and (2) the literature on PT in PubMed, which shows a steady increase in the number of publications. Most studies in PT registered with ClinicalTrials.gov with results available are nonrandomized early phase studies with a relatively small number of patients enrolled. From the larger database of nonrandomized trials, we listed adverse events in specific organs/sites among patients with cancer who are treated with photons and protons to identify critical issues. The present data demonstrate dosimetric advantages of PT with favorable toxicity profiles and form the basis for comparative randomized prospective trials. A comparative analysis of 3 recently completed randomized trials for normal tissue toxicities suggests that for early stage non-small cell lung cancer, no meaningful comparison could be made between stereotactic body RT and stereotactic body PT due to low accrual (NCT01511081). In addition, for locally advanced non-small cell lung cancer, a comparison of intensity modulated RTwith passive scattering PT (now largely replaced by spot-scanned intensity modulated PT), PT did not provide any benefit in normal tissue toxicity or locoregional failure over photon therapy. Finally, for locally advanced esophageal cancer, proton beam therapy provided a lower total toxicity burden but did not improve progression-free survival and quality of life (NCT01512589). The purpose of this review is to inform the limitations of current trials looking at protons and photons, considering that advances in technology, physics, and biology are a continuum, and to advocate for future trials geared toward accurate precision RT that need to be viewed as an iterative process in a defined path toward delivering optimal radiation treatment. A foundational understanding of the radiobiologic differences between protons and photons in tumor and normal tissue responses is fundamental to, and necessary for, determining the suitability of a given type of biologically optimized RT to a patient or cohort.

Circulating Lymphocyte Counts Early During Radiation Therapy Are Associated With Recurrence in Pediatric Medulloblastoma

PURPOSE

Decreased peripheral lymphocyte counts are associated with survival after radiation therapy (RT) in several solid tumors, although they appear late during or after the radiation course and often correlate with other clinical factors. Here we investigate if absolute lymphocyte counts (ALCs) are independently associated with recurrence in pediatric medulloblastoma early during RT.

METHODS AND MATERIALS

We assessed 202 patients with medulloblastoma treated between 2000 and 2016 and analyzed ALC throughout therapy, focusing on both early markers (ALC during week 1 - ALCwk1; grade 3+ Lymphopenia during week 2 - Lymphopeniawk2) and late markers (ALC nadir). Uni- and multivariable regressions were used to assess association of clinical and treatment variables with ALC and of ALC with recurrence.

RESULTS

Thirty-six recurrences were observed, with a median time to recurrence of 1.6 years (range, 0.2-10.3) and 7.1 years median follow-up. ALC during RT was associated with induction chemotherapy (P < .001), concurrent carboplatin (P = .009), age (P = .01), and high-risk status (P = .05). On univariable analysis, high-risk disease (hazard ratio = 2.0 [1.06-3.9]; P = .03) and M stage≥1 (hazard ratio = 2.2 [1.1-4.4]) were associated with recurrence risk, as was lower ALC early during RT (ALCwk1, hazard ratio = 0.28 [0.12-0.65]; P = .003; Lymphopeniawk2, hazard ratio = 2.27 [1.1-4.6]; P = .02). Neither baseline ALC nor nadir correlated with outcome. These associations persisted when excluding carboplatin and pre-RT chemotherapy patients, and in the multivariable analysis accounting for confounders lymphocyte counts remained significant (ALCwk1, hazard-ratio = 0.23 [0.09-0.57]; P = .002; Lymphopeniawk2, hazard-ratio = 2.3 [1.1-4.8]; P = .03).

CONCLUSIONS

ALC during weeks 1 and 2 of RT was associated with recurrence, and low ALC is an independent prognostic factor in medulloblastoma. Strategies to mitigate the risk of radiation-induced lymphopenia should be considered.

The effects of stereotactic body radiotherapy on peripheral natural killer and CD3+CD56+ NKT-like cells in patients with hepatocellular carcinoma

BACKGROUND

Both natural killer (NK) and CD3⁺CD56⁺natural killer T (NKT)-like cells play critical roles in the antitumor response. This study aimed to explore the effects of stereotactic body radiotherapy (SBRT) on peripheral NK and NKT-like cells in patients with hepatocellular carcinoma (HCC), and to identify possible surface markers on these cells that correlate with the prognosis.

METHODS

Twenty-five HCC patients were prospectively enrolled in our study, and 10 healthy individuals were served as healthy controls. Flow cytometry was used to determine the counts and the percentages of peripheral NK and NKT-like cells, cells with certain receptors, and cells with intracellular interferon-γ and TNF-α secretion at different time points, including time points of prior to SBRT, at post-SBRT, and 3-month and 6-month after treatment. The Kaplan-Meier method with the log-rank test was applied for survival analysis.

RESULTS

The peripheral NKT-like cells was increased at post-SBRT. Meanwhile, elevated levels of inhibitory receptors and reduced levels of activating receptors of NK cells were also observed in NK cells at post-SBRT, but the levels was not significantly different at 3-month and 6-month as compared with the baseline levels. Lower percentage of NKp30⁺NK cells before SBRT and higher percentage of CD158b⁺NK cells after SBRT were associated with poor progression-free survival. In addition, higher percentage of CD3⁺CD56⁺ NKT-like cells was associated with a higher overall survival rate in HCC patients.

CONCLUSIONS

SBRT has an apparent effect on both peripheral NK and CD3⁺CD56⁺NKT-like cells. Lower percentage of NKp30⁺NK cells before SBRT and higher percentage of CD158b⁺NK cells after SBRT are correlated with poor patients' PFS. Higher percentage of CD3⁺CD56⁺ NKT-like cells is associated with higher OS in HCC patients.

Efficacy of Stereotactic Body Radiotherapy in Patients With Hepatocellular Carcinoma Not Suitable for Transarterial Chemoembolization (HERACLES: HEpatocellular Carcinoma Stereotactic RAdiotherapy CLinical Efficacy Study)

The aim of this prospective observational trial was to evaluate the efficacy, toxicity and quality of life after stereotactic body radiation therapy (SBRT) in patients with hepatocellular carcinoma (HCC) and to assess the results of this treatment in comparison to trans-arterial chemoembolization (TACE). Patients with HCC, treated with TACE or SBRT, over a period of 12 months, enrolled in the study. The primary endpoint was feasibility; secondary endpoints were toxicity, quality of life (QOL), local progression (LP) and overall survival (OS). Between 06/2016 and 06/2017, 19 patients received TACE and 20 SBRT, 2 of whom were excluded due to progression. The median follow-up was 31 months. The QOL remained stable before and after treatment and was comparable in both treatment groups. Five patients developed grade ≥ 3 toxicities in the TACE group and 3 in the SBRT group. The cumulative incidence of LP after 1-, 2- and 3-years was 6, 6, 6% in the SBRT group and 28, 39, and 65% in the TACE group (p = 0.02). The 1- and 2- years OS rates were 84% and 47% in the TACE group and 44% and 39% in the SBRT group (p = 0.20). In conclusion, SBRT is a well-tolerated local treatment with a high local control rates and can be safely delivered, while preserving the QOL of HCC patients.

Radiation-Associated Lymphopenia and Outcomes of Patients with Unresectable Hepatocellular Carcinoma Treated with Radiotherapy

Background

The immune system plays a crucial role in cancer surveillance. Previous studies have shown that lymphopenia associated with radiotherapy (RT) portends a poor prognosis. We sought to differentiate the effects of proton and photon RT on changes in absolute lymphocyte count (ALC) for patients with hepatocellular carcinoma (HCC).

Patients and Methods

Patients with HCC treated with definitive RT from 2006 to 2016 were studied. Serial ALCs were graded according to CTCAE v4.0. Overall survival (OS), disease-free survival, and distant metastasis-free survival were analyzed using the Kaplan-Meier method. Univariable and multivariable Cox-proportional hazards analyses were used to identify predictors of OS. A cohort analysis matched for treatment volume was performed to investigate differences in ALC dynamics between photon and proton therapy.

Results

Of 143 patients identified, the median age was 66 (range, 19-90) years. The treatment modality was photon in 103 (72%) and proton in 40 (28%). Median follow-up was 17 months (95% confidence interval, 13-25 months). The median time to ALC nadir after initiation of RT was 17 days with a median relative decrease of 67%. Those who received proton RT had a higher median ALC nadir (0.41 vs 0.32 k/µL, p=0.002) and longer median OS (33 vs 13 months, p=0.002) than those who received photon RT. Matched cohort analyses revealed a larger low-dose liver volume in the photon group, which correlated with lower ALC. On multivariable Cox analysis, Grade 3 or higher lymphopenia prior to or after RT, portal venous tumor thrombus, larger planning target volumes, Child-Pugh (CP) Class B, and increased CP score after RT were associated with a higher risk of death, whereas the use of proton therapy was associated with lower risk.

Conclusion

Grade 3 or higher lymphopenia may be associated with poorer outcomes in patients receiving RT for HCC. Protons may mitigate lymphopenia compared with photons, potentially due to reduced dose exposure of sites of lymphopoiesis.

Proton therapy reduces the likelihood of high-grade radiation-induced lymphopenia in glioblastoma patients: phase II randomized study of protons vs photons

BACKGROUND

We investigated differences in radiation-induced grade 3+ lymphopenia (G3+L), defined as an absolute lymphocyte count (ALC) nadir of <500 cells/µL, after proton therapy (PT) or X-ray (photon) therapy (XRT) for patients with glioblastoma (GBM).

METHODS

Patients enrolled in a randomized phase II trial received PT (n = 28) or XRT (n = 56) concomitantly with temozolomide. ALC was measured before, weekly during, and within 1 month after radiotherapy. Whole-brain mean dose (WBMD) and brain dose-volume indices were extracted from planned dose distributions. Univariate and multivariate logistic regression analyses were used to identify independent predictive variables. The resulting model was evaluated using receiver operating characteristic (ROC) curve analysis.

RESULTS

Rates of G3+L were lower in men (7/47 [15%]) versus women (19/37 [51%]) (P < 0.001), and for PT (4/28 [14%]) versus XRT (22/56 [39%]) (P = 0.024). G3+L was significantly associated with baseline ALC, WBMD, and brain volumes receiving 5‒40 Gy(relative biological effectiveness [RBE]) or higher (ie, V5 through V40). Stepwise multivariate logistic regression analysis identified being female (odds ratio [OR] 6.2, 95% confidence interval [CI]: 1.95‒22.4, P = 0.003), baseline ALC (OR 0.18, 95% CI: 0.05‒0.51, P = 0.003), and whole-brain V20 (OR 1.07, 95% CI: 1.03‒1.13, P = 0.002) as the strongest predictors. ROC analysis yielded an area under the curve of 0.86 (95% CI: 0.79-0.94) for the final G3+L prediction model.

CONCLUSIONS

Sex, baseline ALC, and whole-brain V20 were the strongest predictors of G3+L for patients with GBM treated with radiation and temozolomide. PT reduced brain volumes receiving low and intermediate doses and, consequently, reduced G3+L.

MRI-guided Radiation Therapy: An Emerging Paradigm in Adaptive Radiation Oncology

Radiation therapy (RT) continues to be one of the mainstays of cancer treatment. Considerable efforts have been recently devoted to integrating MRI into clinical RT planning and monitoring. This integration, known as MRI-guided RT, has been motivated by the superior soft-tissue contrast, organ motion visualization, and ability to monitor tumor and tissue physiologic changes provided by MRI compared with CT. Offline MRI is already used for treatment planning at many institutions. Furthermore, MRI-guided linear accelerator systems, allowing use of MRI during treatment, enable improved adaptation to anatomic changes between RT fractions compared with CT guidance. Efforts are underway to develop real-time MRI-guided intrafraction adaptive RT of tumors affected by motion and MRI-derived biomarkers to monitor treatment response and potentially adapt treatment to physiologic changes. These developments in MRI guidance provide the basis for a paradigm change in treatment planning, monitoring, and adaptation. Key challenges to advancing MRI-guided RT include real-time volumetric anatomic imaging, addressing image distortion because of magnetic field inhomogeneities, reproducible quantitative imaging across different MRI systems, and biologic validation of quantitative imaging. This review describes emerging innovations in offline and online MRI-guided RT, exciting opportunities they offer for advancing research and clinical care, hurdles to be overcome, and the need for multidisciplinary collaboration.

Splenic Hematopoietic and Stromal Cells in Cancer Progression

Tumor-derived secretory factors orchestrate splenic hematopoietic and stromal cells to fuel metastasis. The spleen acts as a reservoir site for hematopoietic stem and progenitor cells, which are rapidly exploited as myeloid-derived suppressor cells at the cost of tumor-reactive lymphoid cells. Splenic erythroid progenitor cells and mesenchymal stromal cells contribute directly and indirectly to both tumor immune escape and the metastatic cascade. Animal models provide valuable mechanistic insights, but their translation to a clinical setting highlights specific challenges and open issues. In this review, we envision the exploitation of the spleen as a source for novel biomarkers and therapeutic approaches.

A tumor-immune interaction model for hepatocellular carcinoma based on measured lymphocyte counts in patients undergoing radiotherapy

PURPOSE

The impact of radiation therapy on the immune system has recently gained attention particularly when delivered in combination with immunotherapy. However, it is unclear how different treatment fractionation regimens influence the interaction between the immune system and radiation. The goal of this work was to develop a mathematical model that quantifies both the immune stimulating as well as the immunosuppressive effects of radiotherapy and simulates the effects of different fractionation regimens based on patient data.

METHODS AND MATERIALS

The framework describes the temporal evolution of tumor cells, lymphocytes, and inactivated dying tumor cells releasing antigens during radiation therapy, specifically modeling how recruited lymphocytes inhibit tumor progression. The parameters of the model were partly taken from the literature and in part extracted from blood samples (circulating lymphocytes: CLs) collected from hepatocellular carcinoma patients undergoing radiotherapy and their outcomes. The dose volume histograms to circulating lymphocytes were calculated with a probability-based model.

RESULTS

Based on the fitted parameters, the model enabled a study into the depletion and recovery of CLs in patients as a function of fractionation regimen. Our results quantify the ability of short fractionation regimens to lead to shorter periods of lymphocyte depletion and predict faster recovery after the end of treatment. The model shows that treatment breaks between fractions can prolong the period of lymphocyte depletion and should be avoided.

CONCLUSIONS

This study introduces a mathematical model for tumor-immune interactions using clinically extracted radiotherapy patient data, which can be applied to design trials aimed at minimizing lymphocyte depleting effects in radiation therapy.

Immune status and the efficacy of radiotherapy on overall survival for patients with localized Merkel cell carcinoma: An analysis of the National Cancer Database

BACKGROUND

Immunosuppressed (IS) patients with Merkel cell carcinoma (MCC) have worse outcomes compared to immunocompetent (IC) patients, and it is unclear if adjuvant radiotherapy (RT) is beneficial for these patients. We sought to determine the effect of immune status on adjuvant RT efficacy regarding overall survival (OS) for patients with localized MCC.

METHODS

This was an observational study of National Cancer Database (NCDB) identifying patients with stage I/II or III MCC with known immune status diagnosed from 2010 to 2014. The median follow-up time was 29 months. OS was described using Kaplan-Meier methods and compared for subgroups by immune status and adjuvant RT using log-rank tests, multivariable Cox regression and interaction effect testing.

RESULTS

A total of 2049 IC and 255 IS patients were included. Adjuvant RT was associated with decreased hazard of death for stage I/II MCC (HR 0.65, CI 0.54-0.78) adjusting for factors including immune status. Interaction effect testing did not demonstrate a significant difference in the effect of adjuvant RT on OS between IC and IS status in either stage I/II or III MCC (both P values > 0.05).

CONCLUSIONS

In this observational study, adjuvant RT was associated with decreased hazard of death for patients with stage I/II MCC regardless of immune status. Adjuvant RT should be considered for both IS and IC patients with localized MCC.

Lymphocyte-Sparing Radiotherapy: The Rationale for Protecting Lymphocyte-rich Organs When Combining Radiotherapy With Immunotherapy

There is now strong clinical and preclinical evidence that lymphocytes, for example, CD8+ T cells, are key effectors of immunotherapy and that irradiation of large blood vessels, the heart, and lymphoid organs (including nodes, spleen, bones containing bone marrow, and thymus in children) causes transient or persistent lymphopenia. Furthermore, there is extensive clinical evidence, across multiple cancer sites and treatment modalities, that lymphopenia correlates strongly with decreased overall survival. At the moment, we lack quantitative evidence to establish the relationship between dose-volume and dose-rate to critical normal structures and lymphopenia. Therefore, we propose that data should be systematically recorded to characterise a possible quantitative relationship. This might enable us to improve the efficacy of radiotherapy and develop strategies to predict and prevent treatment-related lymphopenia. In anticipation of more quantitative data, we recommend the application of the principle of As Low As Reasonably Achievable to lymphocyte-rich regions for radiotherapy treatment planning to reduce the radiation doses to these structures, thus moving toward "Lymphocyte-Sparing Radiotherapy."

Assessing the interactions between radiotherapy and antitumour immunity

Immunotherapy, specifically the introduction of immune checkpoint inhibitors, has transformed the treatment of cancer, enabling long-term tumour control even in individuals with advanced-stage disease. Unfortunately, only a small subset of patients show a response to currently available immunotherapies. Despite a growing consensus that combining immune checkpoint inhibitors with radiotherapy can increase response rates, this approach might be limited by the development of persistent radiation-induced immunosuppression. The ultimate goal of combining immunotherapy with radiotherapy is to induce a shift from an ineffective, pre-existing immune response to a long-lasting, therapy-induced immune response at all sites of disease. To achieve this goal and enable the adaptation and monitoring of individualized treatment approaches, assessment of the dynamic changes in the immune system at the patient level is essential. In this Review, we summarize the available clinical data, including forthcoming methods to assess the immune response to radiotherapy at the patient level, ranging from serum biomarkers to imaging techniques that enable investigation of immune cell dynamics in patients. Furthermore, we discuss modelling approaches that have been developed to predict the interaction of immunotherapy with radiotherapy, and highlight how they could be combined with biomarkers of antitumour immunity to optimize radiotherapy regimens and maximize their synergy with immunotherapy.

Association Between Circulating Lymphocyte Populations and Outcome After Stereotactic Body Radiation Therapy in Patients With Hepatocellular Carcinoma

Background and Objective: Radiation-induced lymphopenia has a tangible impact on overall survival (OS) in multiple solid tumors. We investigated the association between circulating lymphocyte populations (CLPs) before and after stereotactic body radiation therapy (SBRT) and OS in patients with hepatocellular carcinoma (HCC).

Materials and Methods: Seventy-eight HCC patients treated with SBRT between January 2013 and June 2017 were retrospectively analyzed. Baseline and post-treatment total peripheral lymphocyte counts (TPLCs) and values of different CLPs were obtained and analyzed for clinical outcomes. Univariate and multivariate Cox regression analyses were used to explore the independent prognostic factors for patient survival.

Results: The one-, two- and three-year OS rates were 94.8, 75.9, and 63.3%, respectively. The mean TPLCs before and 10 days after SBRT were 1.4 × 10⁹/L and 0.7 × 10⁹/L, respectively. The TPLC recovered to its baseline value 1 year after SBRT. Multivariate analysis results revealed that variables, including tumor necrosis factor-alpha (TNF-α) level <5.5 ng/mL and post-treatment TPLC <0.45 × 10⁹/L were independent factors for inferior OS. Further analysis showed that the values of CLPs, including CD3⁺, CD4⁺, CD8⁺, CD19⁺, and CD16⁺56⁺ cells dropped profoundly 10 days after SBRT, among which CD19⁺ B cell count was mostly depleted and gradually recovered after 2 months. Univariate analysis showed that both baseline and post-treatment TPLC and CLP (except post-treatment B cell) counts were significantly associated with patient OS (p < 0.05 for each). Further stratified analysis performed according to OS at 2 years demonstrated that the CD16⁺CD56⁺ NK cell counts remained significantly elevated in patients with better survival (OS > 2 years) compared to those in short-term survivors at 10 days, 1 month, and 2 months after SBRT (p < 0.05 for each). In addition, there were significant differences in TPLC and CD8⁺ T cell counts in patients with long-term and short-term OS at 2 months after SBRT (p < 0.05).

Conclusions: Peripheral lymphopenia after SBRT might be an independent prognostic factor for poorer outcome in HCC patients. Post-treatment lymphocyte subsets, including CD8⁺ T cell and NK cell counts were also associated with 2-year OS rates.