Prediction of Severe Lymphopenia During Chemoradiation Therapy for Esophageal Cancer: Development and Validation of a Pretreatment Nomogram

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.

Prognostic value of lymphocytes in patients with breast cancer receiving radiotherapy after breast-conserving surgery: A post hoc analysis of a phase III randomized trial

PURPOSE

To evaluate the prognostic value of peripheral lymphocyte count (PLC) in the breast cancer patients after breast-conserving surgery (BCS) with radiotherapy (RT).

METHODS AND MATERIALS

This post hoc analysis was performed using data of 628 patients from a phase III, randomized controlled trial comparing hypofractionated RT (HFRT) with conventional fractionated RT (CFRT) after BCS. PLCs were obtained before, during, and after RT until the 1-year follow-up. The optimal cut-off PLCs were determined using the maxstat package in R. Survival rates were estimated using the Kaplan-Meier method and compared with the log-rank test.

RESULTS

A total of 275 (46.1 %) patients developed lymphopenia during RT, among them, 17 (2.8 %) had grade 3 lymphopenia and no one developed grade 4 lymphopenia. With a median follow-up of 110.8 months, patients with pre-RT PLCs of < 1.77 × 109/L had a significantly lower 10-year breast cancer-specific survival (BCSS) rate (P = 0.013) and overall survival (OS) rate (P = 0.026). Patients with a nadir PLC of < 1.35 × 109/L had a significantly poorer 10-year OS rate (P = 0.048). Multivariate analysis showed that a pre-RT PLC of < 1.77 × 109/L was an independent factor influencing BCSS and OS, while the effect of the nadir PLC did not remain significant. Neither PLC nor lymphopenia recovery at post-RT 1, 3, and 6 months and 1 year was associated with survival.

CONCLUSIONS

Radiation-induced lymphopenia in patients with breast cancer after BCS tends to be mild. The lower pre-RT PLC predicted poorer survival.

Personalized Composite Dosimetric Score-Based Machine Learning Model of Severe Radiation-Induced Lymphopenia Among Patients With Esophageal Cancer

PURPOSE

Radiation-induced lymphopenia (RIL) is common among patients undergoing radiation therapy (RT)' Severe RIL has been linked to adverse outcomes. The severity and risk of RIL can be predicted from baseline clinical characteristics and dosimetric parameters. However, dosimetric parameters, e.g. dose-volume (DV) indices, are highly correlated with one another and are only weakly associated with RIL. Here we introduce the novel concept of "composite dosimetric score" (CDS) as the index that condenses the dose distribution in immune tissues of interest to study the dosimetric dependence of RIL. We derived an improved multivariate classification scheme for risk of grade 4 RIL (G4RIL), based on this novel RT dosimetric feature, for patients receiving chemo RT for esophageal cancer.

METHODS AND MATERIALS

DV indices were extracted for 734 patients who received chemo RT for biopsy-proven esophageal cancer. Nonnegative matrix factorization was used to project the DV indices of lung, heart, and spleen into a single CDS; XGBoost was employed to explore significant interactions among predictors; and logistic regression was applied to combine the resultant CDS with baseline clinical factors and interaction terms to facilitate individualized prediction of immunotoxicity. Five-fold cross-validation was applied to evaluate the model performance.

RESULTS

The CDS for selected immune organs at risk (ie, heart, lung, and spleen) (OR 1.791; 95 CI [1.350, 2.377]) was a statistically significant risk determinant for G4RIL. Pearson correlation coefficients for CDS versus G4RIL risk for individual immune organs at risk were greater than any single DV indicx. Personalized prediction of G4RIL based on CDS and 4 clinical risk factors yielded an area under the curve value of 0.78. Interaction between age and CDS revealed that G4RIL risk increased more sharply with increasing CDS for patients aged ≥65 years.

CONCLUSIONS

Risk of immunotoxicity for patients undergoing chemo RT for esophageal cancer can be predicted by CDS. The CDS concept can be extended to immunotoxicity in other cancer types and in dose-response models currently based on DV indices. Personalized treatment planning should leverage composite dosimetric scoring methods rather than using individual or subsets of DV indices.

The relationship between splenic dose and radiation-induced lymphopenia

Lymphocytes, which are highly sensitive to radiation, play a crucial role in the body's defense against tumors. Radiation-induced lymphopenia has been associated with poorer outcomes in different cancer types. Despite being the largest secondary lymphoid organ, the spleen has not been officially designated as an organ at risk. This study hypothesizes a connection between spleen irradiation and lymphopenia and seeks to establish evidence-based dosage limits for the spleen. We retrospectively analyzed data from 96 patients with locally advanced gastric cancer who received postoperative chemoradiotherapy (CRT) between May 2010 and May 2017. Complete blood counts were collected before, during and after CRT. We established a model for predicting the minimum absolute lymphocyte count (Min ALC) and to investigate potential associations between spleen dosimetric variables and Min ALC. The median follow-up was 60 months. The 5-year overall survival (OS) and disease-free survival (DFS) were 65.2% and 56.8%, respectively. The median values of pre-treatment ALC, Min ALC and post-treatment ALC were 1.40 × 109, 0.23 × 109 and 0.28 × 109/L, respectively. Regression analysis confirmed that the primary tumor location, number of fractions and spleen V5 were significant predictors of Min ALC during radiation therapy. Changes in ALC (ΔALC) were identified as an independent predictor of both OS and DFS. Spleen V5 is an independent predictor for Min ALC, and the maximum dose of the spleen is associated with an increased risk of severe lymphopenia. Therefore, these doses should be restricted in clinical practice. Additionally, ΔALC can serve as a prognostic indicator for adjuvant radiotherapy in gastric cancer.

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.

Severe Lymphopenia During Chemoradiation Therapy for Esophageal Cancer: Comprehensive Analysis of Randomized Phase 2B Trial of Proton Beam Therapy Versus Intensity Modulated Radiation Therapy

PURPOSE

Lymphocytes play an important role in antitumor immunity; however, they are also especially vulnerable to depletion during chemoradiation therapy (CRT). The purpose of this study was to compare the incidence of grade 4 lymphopenia (G4L) between proton beam therapy (PBT) and intensity modulated photon radiation therapy (IMRT) in patients with esophageal cancer treated with CRT in a completed randomized trial and to ascertain patient heterogeneity to G4L risk based on treatment and established prognostic factors.

METHODS AND MATERIALS

Between April 2012 and March 2019, a single-institution, open-label, nonblinded, phase 2 randomized trial (NCT01512589) was conducted at the University of Texas MD Anderson Cancer Center. Patients were randomly assigned to IMRT or PBT, either definitively or preoperatively. This secondary analysis of the randomized trial was G4L during concurrent CRT according to Common Terminology Criteria for Adverse Events version 5.0.

RESULTS

Among 105 patients evaluable for analysis, 44 patients (42%) experienced G4L at a median of 28 days after the start date of concurrent CRT. Induction chemotherapy (P = .003), baseline absolute lymphocyte count (P < .001), radiation therapy modality (P = .002), and planning treatment volume (P = .033) were found to be significantly associated with G4L. Multivariate classification analysis partitioned patients into 5 subgroups for whom the incidence of G4L was observed in 0%, 14%, 35%, 70%, and 100% of patients. The benefit of PBT over IMRT was most pronounced in patients with an intermediate baseline absolute lymphocyte count and large planning treatment volume (P = .011).

CONCLUSIONS

This is the first prospective evidence that limiting dose scatter by PBT significantly reduced the incidence of G4L, especially in the intermediate-risk patients. The implication of this immune-sparing effect of PBT, especially in the context of standard adjuvant immunotherapy, needs further examination in the current phase 3 randomized trials.

Severe radiation-induced lymphopenia during concurrent chemoradiotherapy for stage III non-small cell lung cancer: external validation of two prediction models

Background

Severe radiation-induced lymphopenia (RIL) in patients undergoing chemoradiotherapy (CRT) for non-small cell lung cancer (NSCLC) is associated with decreased immunotherapy efficacy and survival. At The Christie and MD Anderson Cancer Center (MDACC), prediction models for lymphopenia were developed in lung and esophageal cancer patients, respectively. The aim of this study was to externally validate both models in patients with stage III NSCLC.

Methods

Patients who underwent concurrent CRT for stage III NSCLC in 2019-2021 were studied. Outcomes were grade ≥3 and grade 4 lymphopenia during CRT. The Christie model predictors for grade ≥3 lymphopenia included age, baseline lymphocyte count, radiotherapy duration, chemotherapy, mean heart and lung doses, and thoracic vertebrae V20Gy. MDACC predictors for grade 4 lymphopenia were age, baseline lymphocyte count, planning target volume (PTV), and BMI. The external performance of both models was assessed.

Results

Among 100 patients, 78 patients (78%) developed grade ≥3 lymphopenia, with grade 4 lymphopenia in 17 (17%). For predicting grade ≥3 lymphopenia, the Christie and MDACC models yielded c-statistics of 0.77 and 0.79, respectively. For predicting grade 4 lymphopenia, c-statistics were 0.69 and 0.80, respectively. Calibration for the Christie and MDACC models demonstrated moderate and good agreement, respectively.

Conclusion

The PTV-based MDACC prediction model for severe RIL demonstrated superior external performance in NSCLC patients compared to the dosimetry-based Christie model. As such, the MDACC model can aid in identifying patients at high risk for severe lymphopenia. However, to optimize radiotherapy planning, further improvement and external validation of dosimetry-based models is desired.

[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.

Pretreatment absolute lymphocyte count is an independent predictor for survival outcomes for esophageal squamous cell carcinoma patients treated with neoadjuvant chemoradiotherapy and pembrolizumab: An analysis from a prospective cohort

BACKGROUND

The aim of the study was to analyze the relationship between pretreatment inflammatory biomarkers (IBs) and survival outcomes for patients with esophageal squamous cell carcinoma (ESCC) treated with neoadjuvant chemoradiotherapy (neo-CRT) and pembrolizumab.

METHODS

Clinical variables and IBs (absolute monocyte count [AMC], absolute lymphocyte count [ALC], platelet count [PLT], neutrophil-to-lymphocyte ratio [NLR], platelet-to-lymphocyte ratio [PLR], lymphocyte-to-monocyte ratio [LMR], pan-immune inflammation value [PIV], systemic immunoinflammatory index [SII], systemic immunoreactivity index [SIRI] and prognostic nutritional index [PNI]) were collected. Univariate and multivariate analysis were performed to identify the independent factors for outcomes of ESCC.

RESULTS

A total of 51 patients were included. Of these, 35 patients achieved pathological complete response (pCR) after neo-CRT and pembrolizumab (pCR: 68.6%). With a median follow-up of 20 months, the two-year PFS and OS of the cohort was 64% and 91%, respectively. Multivariate logistic regression analysis indicated that ALC (overall response [OR] 4.4, p = 0.051) and PLT (OR 6.7, p = 0.023) were two independent predictors for achieving pCR among ESCC treated with neo-CRT and pembrolizumab. Multivariate Cox regression analysis showed that ALC (HR 0.27, p = 0.028) and SIRI (HR 3.13, p = 0.048) were two independent predictors associated with PFS. Kaplan Meier analysis demonstrated that the PFS of ESCC with high baseline ALC was significantly better than those with low ALC (2-year PFS: 77% vs. 47%, p = 0.027), but not for overall survival (2-year OS: 96% vs. 87%, p = 0.46).

CONCLUSIONS

This retrospective analysis based on a prospective cohort for the first time demonstrates that pretreatment ALC is an independent predictor for achieving pCR and favorable outcomes of ESCC treated with neo-CRT and pembrolizumab.

Analysis of the prognostic factors of simultaneous integrated boost-intensity modulated radiation therapy (SIB-IMRT) in 220 cases of locally advanced squamous esophageal cancer: a retrospective cohort study

Background

Esophageal cancer is one of the most common malignant tumors in China. Patients with advanced esophageal cancer often cannot be treated by surgery; in these cases, radiation therapy is usually applied. However, there are currently few studies on the clinical efficacy of this treatment method. The present study aimed to investigate and observe the clinical efficacy and related prognostic factors of simultaneous integrated boost-intensity modulated radiation therapy (SIB-IMRT) in esophageal squamous carcinoma, and to provide a reference for clinicians in radiotherapy (RT) departments.

Methods

The clinical and follow-up data of 220 patients with esophageal squamous carcinoma admitted to the First Affiliated Hospital of Bengbu Medical College from January 2017 to December 2018 were retrospectively analyzed to assess the relevant prognostic factors and analyze their effects on 3-year overall survival (OS) and progression-free survival (PFS). The prognostic influencing factors were analyzed using the log-rank test and Cox multi-factor regression analysis.

Results

The median follow-up time was 56.0 months (3.0 to 66.0 months). The 1-, 2-, and 3-year survival rates were 68.6%, 49.1%, and 36.3%, respectively, for the entire cohort, and the 1-, 2-, and 3-year PFS rates were 52.3%, 37.7%, and 25.5%, respectively. The median OS time was 24 months [95% confidence interval (CI): 19.16-28.84 months] and the median PFS time was 15 months (95% CI: 11.04-18.96 months). The multifactorial analysis results showed that gender, RT dose, treatment modality, absolute lymphocyte count (ALC), and gross tumor volume (GTV) were independent prognostic factors affecting 3-year OS (P<0.05); while gender, N-stage, RT dose, and GTV were independent prognostic factors affecting 3-year PFS (P<0.05).

Conclusions

In the SIB-IMRT era, the survival of esophageal squamous cell carcinoma (ESCC) patients treated with radical (chemo)radiotherapy is relatively satisfactory. As a single-institution study on radiation therapy for esophageal cancer, this study yielded accurate results that help to provide references for subsequent related studies and clinicians' selection of treatment options.

Effect of intensity modulated radiotherapy on lymphocytes in patients with esophageal squamous cell carcinoma and its clinical significance

Background

Radiotherapy usually leads to a decrease in the total number of lymphocytes in patients with esophageal cancer. The factors that causing lymphopenia and the clinical significance of lymphopenia are studied in this article.

Patients and methods

110 patients with esophageal squamous cell carcinoma who had undergo intensity-modulated radiation therapy were enrolled. Statistical methods were used to analyze the correlation between lymphopenia and total survival in patients with esophageal cancer during radiotherapy, and analyze the correlations between nutritional factors and lymphopenia.

Results

There were 11 patients with the lowest lymphocyte value with level 1-2 during radiotherapy, accounting for 10% of all the patients, and 110 patients with level 3-4, accounting for 90% of all the patient. In all the enrolled patients, the incidence of lymphocyte nadir G1, G2, G3 and G4 MinALC during radiotherapy accounted for 0.91%, 9.09%, 62.73% and 27.27%, respectively.KM survival analysis showed that the overall survival of patients in the group (MinALC ≤ 0.41×10⁹/L) was significantly lower than that of the patients in the other group (MinALC>0.43×10⁹/L). Nutritional indicators were positively correlated with the decline degree of lymphocytes. The minimal value of lymphocyte can predict the occurrence of grade 3-4 radiation pneumonitis.

Conclusion

Lymphopenia induced by radiotherapy can predict survival and radiation pneumonitis. Nutritional factors such as hemoglobin and albumin were positively correlated with total lymphocytes numbers induced by radiotherapy.

Radiotherapy as a means to increase the efficacy of T-cell therapy in solid tumors

Chimeric antigen receptor (CAR)-T cells have demonstrated significant improvements in the treatment of refractory B-cell malignancies that previously showed limited survival. In contrast, early-phase clinical studies targeting solid tumors have been disappointing. This may be due to both a lack of specific and homogeneously expressed targets at the surface of tumor cells, as well as intrinsic properties of the solid tumor microenvironment that limit homing and activation of adoptive T cells. Faced with these antagonistic conditions, radiotherapy (RT) has the potential to change the overall tumor landscape, from depleting tumor cells to reshaping the tumor microenvironment. In this article, we describe the current landscape and discuss how RT may play a pivotal role for enhancing the efficacy of adoptive T-cell therapies in solid tumors. Indeed, by improving homing, expansion and activation of infused T cells while reducing tumor volume and heterogeneity, the use of RT could help the implementation of engineered T cells in the treatment of solid tumors.

Meta-analysis and Critical Review: Association Between Radio-induced Lymphopenia and Overall Survival in Solid Cancers

Purpose

Immune system modulation, with the use of immune checkpoint inhibitors, has drastically changed the field of oncology. Strong preclinical data indicate that radiation therapy (RT) may enhance the response rate to such drugs via in situ vaccination, although these data do not consider immune radiotoxicity. This meta-analysis investigates whether radio-induced lymphopenia (RIL) is associated with overall survival (OS).

Methods and Materials

A systematic literature search and quantitative analysis were planned, conducted, and reported per the Preferred Reporting Items for Systematic Reviews and Meta-analyses and Quality of Reporting of Meta-analyses checklists. The literature from January 1990 to March 2021 was searched to identify clinical studies with OS data in patients treated with RT and presenting with lymphopenia. A random-effect model was employed for the meta-analysis. Heterogeneity was assessed using the I² statistic. Publication bias was estimated using a P-curve analysis.

Results

A total of 56 studies with 13 223 patients and 11 types of cancers were selected. The mean follow-up time was 35.9 months. Over a third of patients had RIL (37.25%). After removing outlying studies (n = 14), the between-study heterogeneity variance was estimated at t² = 0.018 (P = .01) with an I² value of 36.0% (95% confidence interval, 6%-56%). The results showed that RIL was significantly associated with worse OS (hazard ratio: 1.70; 95% confidence interval, 1.55-1.86; P < .01; 95% prediction interval, 1.27-2.26). A subgroup analysis was performed based on the type of primary tumor, and a difference between the subgroups was found (P < .01). Based on the P-curve analysis, a significant evidential value was found, and no significant publication bias was identified among the studies.

Conclusions

RIL is a significant prognostic factor for mortality in virtually all solid cancers. Pooled-effect estimates indicate a significantly reduced risk of death in patients without RIL. Tailoring RT regimens to spare the immune system and updating dosimetric constraints for new organs at risk, such as major blood vessels, organs with rich blood supplies, bones, and all lymph node areas, may improve prognoses.

Spleen as an organ at risk in adjuvant chemoradiotherapy for gastric cancer: a retrospective dosimetric study

Introduction:

This study aimed to determine the radiation dose to the spleen in adjuvant chemoradiotherapy for gastric cancer, resulting in haematological toxicities.

Methods:

This retrospective analysis of a prospectively maintained database was conducted at a tertiary referral cancer centre. All patients with biopsy-proven non-metastatic gastric adenocarcinoma planned for adjuvant chemoradiotherapy from January 2017 to December 2021 were included. The mean dose to the spleen (Dmean) was estimated and correlated with the development of haematological toxicities.

Results:

The mean spleen volume was 186·65 cc. The Dmean to the spleen was 35·35 Gy (20–42 Gy). Grade 3 leukopenia was observed in 67%, grade 4 in 15%, and grade 3 thrombocytopenia was noted in 41% of patients. Radiotherapy (RT) dose > 35·5 Gy to the spleen resulted in ≥ grade 3 leukopenia. RT dose ≥ 36·5 Gy resulted in grade 3 thrombocytopenia. The occurrence of leukopenia and thrombocytopenia was also affected by the location of the primary gastric cancer (higher incidence in distal than in proximal tumours).

Conclusion:

The spleen should be considered as an important organs at risk during adjuvant RT for gastric cancer. Dmean to the spleen should be < 35·5 Gy to prevent major haematological toxicities.

A machine learning model for grade 4 lymphopenia prediction during pelvic radiotherapy in patients with cervical cancer

Background/purpose

Severe lymphopenia during pelvic radiotherapy (RT) predicts poor survival in patients with cervical cancer. However, the risk of severe lymphopenia has not been well predicted. We developed a machine learning model using clinical and dosimetric information to predict grade 4 (G4) lymphopenia during pelvic RT in patients with cervical cancer.

Methods

This retrospective study included cervical cancer patients treated with definitive pelvic RT ± induction/concurrent chemotherapy. Clinical information and a set of dosimetric parameters of external beam radiotherapy plan were collected. G4 lymphopenia during RT, which was also referred to as G4 absolute lymphocyte count (ALC) nadir, was defined as ALC nadir <0.2 × 10⁹ cells/L during RT according to Common Terminology Criteria for Adverse Events (CTCAE) v4.03. Elastic-net logistic regression models were constructed for the prediction of G4 lymphopenia during pelvic RT using a repeated cross-validation methodology.

Results

A total of 130 patients were eligible, and 43 (33.1%) patients had G4 lymphopenia during RT. On multivariable analysis, G4 ALC nadir was associated with poor overall survival (OS) [hazard ratio (HR), 3.91; 95% confidence interval (CI), 1.34–11.38, p = 0.01]. Seven significant factors [Eastern Cooperative Oncology Group (ECOG) performance score, pre-RT hemoglobin, pre-RT lymphocytes, concurrent chemotherapy, gross tumor volume of regional lymphadenopathy (GTV_N volume), body volume, and maximum dose of planning target volume receiving at least 55 Gy (PTV_5500 Dmax)] were obtained by elastic-net logistic regression models and were included in the final prediction model for G4 ALC nadir. The model’s predicting ability in test set was area under the curve (AUC) = 0.77 and accuracy = 0.76. A nomogram of the final predicting model was constructed.

Conclusions

This study developed and validated a comprehensive model integrating clinical and dosimetric parameters by machine learning method, which performed well in predicting G4 lymphopenia during pelvic RT for cervical cancer and will facilitate physicians to identify patients at high risk of G4 lymphopenia who might benefit from modified treatment approaches.

Severe radiation-induced lymphopenia during postoperative radiotherapy or chemoradiotherapy has poor prognosis in patients with stage IIB-III after radical esophagectomy: A post hoc analysis of a randomized controlled trial

Objective

To investigate whether radiation-induced lymphopenia (RIL) affects survival and identify the predictors of RIL in postoperative esophageal cancer.

Materials and methods

Post hoc analysis was conducted on data from 116 patients with esophageal cancer from a randomized controlled trial comparing adjuvant therapy with surgery alone. Doses of 54 Gy in 27 fractions was delivered in the postoperative radiotherapy (PORT) group and 50.4 Gy in 28 fractions combined with chemotherapy was delivered in postoperative concurrent chemoradiotherapy (POCRT) group. Blood counts were obtained before, during, and at first follow-up after treatment. Lymphopenia was graded per version 4.03 of the Common Terminology Criteria for Adverse Events. Disease-free survival (DFS) and overall survival (OS) were analyzed using the Kaplan-Meier method, and compared between groups using the log-rank test. Receiver operating characteristic curves identified thresholds for preventing grade 4 (G4) lymphopenia.

Results

Median follow-up duration was 56.0 months. During treatment, 16 patients (13.8%) had G4 lymphopenia. All cases of G4 lymphopenia occurred in group PORT (30.2% vs 0.0%, p<0.001). Baseline absolute lymphocyte count was comparable between G1-3 and G4 patients (2.0 ± 0.8 *10⁹/L vs 1.7 ± 0.5 *10⁹/L; p=0.101). The 3-year DFS was significantly lower in group G4 lymphopenia than that in group G1-3 (31.3% vs 57.6%, p=0.036). The 3-year OS was comparable between both groups (50.0% vs 66.5%, p=0.095). Logistic regression analysis revealed that exposed more thoracic marrow (TM V20 ≥75%; TVB V20 ≥71%), heart (V15 ≥40%) and PTV (volume ≥507 ml) were associated with G4 lymphopenia (p<0.05).

Conclusions

G4 RIL had poor disease-free survival, which may be related to more dose exposure of thoracic marrow and heart due to larger PTV. Reasonably reducing the radiation field combined with concurrent chemotherapy, or radiation dose constraints for these normal tissues may be sufficient to decrease the incidence of G4 lymphopenia, but further prospective trials are needed to verify the results.

Clinical Trial Registration

clinicaltrials.gov, identifier NCT02279134

Severe Radiation-Induced Lymphopenia Attenuates the Benefit of Durvalumab After Concurrent Chemoradiotherapy for NSCLC

Introduction

Durvalumab after concurrent chemoradiation (CCRT) for NSCLC improves survival, but only in a subset of patients. We investigated the effect of severe radiation-induced lymphopenia (sRIL) on survival in these patients.

Methods

Outcomes after CCRT (2010–2019) or CCRT followed by durvalumab (2018–2019) were reviewed. RIL was defined by absolute lymphocyte count (ALC) nadir in samples collected at end of CCRT; sRIL was defined as nadir ALC less than 0.23 × 10⁹/L (the lowest tertile). Progression-free survival (PFS) and overall survival (OS) were calculated by the Kaplan-Meier method. Cox proportional hazard modeling evaluated associations between clinical variables and survival.

Results

Of 309 patients, 192 (62%) received CCRT only and 117 (38%) CCRT plus durvalumab. Multivariable logistic regression analysis indicated that sRIL was associated with planning target volume (OR = 1.002, p = 0.001), stage IIIB disease (OR = 2.77, p = 0.04), and baseline ALC (OR = 0.36, p < 0.01). Durvalumab extended median PFS (23.3 versus 14.1 mo, p = 0.003) and OS (not reached versus 30.8 mo, p < 0.01). sRIL predicted poorer PFS and OS in both treatment groups. Among patients with sRIL, durvalumab did not improve survival (median = 24.6 mo versus 18.1 mo CCRT only, p = 0.079). On multivariable analyses, sRIL (OR = 1.81, p < 0.01) independently predicted poor survival.

Conclusions

Severe RIL compromises survival benefits from durvalumab after CCRT for NSCLC. Measures to mitigate RIL after CCRT may be warranted to enhance the benefit of consolidation durvalumab.

Prediction and clinical impact of delayed lymphopenia after chemoradiotherapy in locally advanced non-small cell lung cancer

Introduction

The dosimetric factors of radiotherapy have an acute impact on the host immune system during chemoradiotherapy (CRT) in locally advanced non-small cell lung cancer (NSCLC). However, even after CRT, a substantial number of patients remain immunosuppressed with delayed lymphopenia. Therefore, we aimed to evaluate clinical and dose-volumetric predictors of delayed lymphopenia after CRT in locally advanced NSCLC.

Materials and methods

We retrospectively reviewed 272 patients with locally advanced NSCLC who received definitive CRT from January 2012 to August 2020. Differential blood count data, including serum albumin values, were obtained at baseline, during and at first follow up after CRT. Acute and delayed lymphopenia events were defined as grade III/IV lymphopenia developed during or 4-12 weeks after CRT completion, which accounted for 84% and 10% of cases, respectively. Dose-volume histogram parameters for planned target volume, whole body, heart, lung, great vessels, spleen, esophagus and thoracic vertebral bodies were evaluated.

Results

Multivariate analysis revealed that patients with delayed lymphopenia were associated with inferior overall survival (HR 2.53, P = 0.001) and progression-free survival (HR 1.98, P = 0.006). However, there was no significant survival difference between groups stratified by acute lymphopenia. On multivariable logistic regression models, lung V5, baseline ALC, during-CRT ALC, and albumin nadir were significant predictors for delayed lymphopenia. Furthermore, the nomogram for delayed lymphopenia based on these variables had good discrimination (area under the curve, 0.905).

Conclusions

In this study, we investigated the prognostic significance of delayed lymphopenia and identified clinico-dosimetric parameters to predict delayed lymphopenia.

Modeling of radiation effects to immune system: a review

Cancer metastasis is the major cause of cancer mortality and accounts for about 90% of cancer death. Although radiation therapy has been considered to reduce the localized cancer burden, emerging evidence that radiation can potentially turn tumors into an in situ vaccine has raised significant interest in combining radiation with immunotherapy. However, the combination approach might be limited by the radiation-induced immunosuppression. Assessment of radiation effects on the immune system at the patient level is critical to maximize the systemic antitumor response of radiation. In this review, we summarize the developed solutions in three different categories for systemic radiation therapy: blood dose, radiation-induced lymphopenia, and tumor control. Furthermore, we address how they could be combined to optimize radiotherapy regimens and maximize their synergy with immunotherapy.

Reflections on beam configuration optimization for intensity-modulated proton therapy

Presumably, intensity-modulated proton radiotherapy (IMPT) is the most powerful form of proton radiotherapy. In the current state of the art, IMPT beam configurations (i.e. the number of beams and their directions) are, in general, chosen subjectively based on prior experience and practicality. Beam configuration optimization (BCO) for IMPT could, in theory, significantly enhance IMPT’s therapeutic potential. However, BCO is complex and highly computer resource-intensive. Some algorithms for BCO have been developed for intensity-modulated photon therapy (IMRT). They are rarely used clinically mainly because the large number of beams typically employed in IMRT renders BCO essentially unnecessary. Moreover, in the newer form of IMRT, volumetric modulated arc therapy, there are no individual static beams. BCO is of greater importance for IMPT because it typically employs a very small number of beams (2-4) and, when the number of beams is small, BCO is critical for improving plan quality. However, the unique properties and requirements of protons, particularly in IMPT, make BCO challenging. Protons are more sensitive than photons to anatomic changes, exhibit variable relative biological effectiveness along their paths, and, as recently discovered, may spare the immune system. Such factors must be considered in IMPT BCO, though doing so would make BCO more resource intensive and make it more challenging to extend BCO algorithms developed for IMRT to IMPT. A limited amount of research in IMPT BCO has been conducted; however, considerable additional work is needed for its further development to make it truly effective and computationally practical. This article aims to provide a review of existing BCO algorithms, most of which were developed for IMRT, and addresses important requirements specific to BCO for IMPT optimization that necessitate the modification of existing approaches or the development of new effective and efficient ones.

A hybrid deep learning model for forecasting lymphocyte depletion during radiation therapy

PURPOSE

Recent studies have shown that severe depletion of the absolute lymphocyte count (ALC) induced by radiation therapy (RT) has been associated with poor overall survival of patients with many solid tumors. In this paper, we aimed to predict radiation-induced lymphocyte depletion in esophageal cancer patients during the course of RT based on patient characteristics and dosimetric features.

METHODS

We proposed a hybrid deep learning model in a stacked structure to predict a trend toward ALC depletion based on the clinical information before or at the early stages of RT treatment. The proposed model consisted of four channels, one channel based on long short-term memory (LSTM) network and three channels based on neural networks, to process four categories of features followed by a dense layer to integrate the outputs of four channels and predict the weekly ALC values. Moreover, a discriminative kernel was developed to extract temporal features and assign different weights to each part of the input sequence which enabled the model to focus on the most relevant parts. The proposed model was trained and tested on a dataset of 860 esophageal cancer patients who received concurrent chemoradiotherapy.

RESULTS

The performance of the proposed model was evaluated based on several important prediction metrics and compared to other commonly used prediction models. The results showed that the proposed model outperformed off-the-shelf prediction methods with at least a 30% reduction in the mean squared error (MSE) of weekly ALC predictions based on pretreatment data.Moreover, using an extended model based on augmented first-week treatment data reduced the MSE of predictions by 70% compared to the model based on the pretreatment data.

CONCLUSIONS

In conclusion, our model performed well in predicting radiation-induced lymphocyte depletion for RT treatment planning. The ability to predict ALC will enable physicians to evaluate individual RT treatment plans for lymphopenia risk and to identify patients at high risk who would benefit from modified treatment approaches. This article is protected by copyright. All rights reserved.

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

Background

Unintentional irradiation of the spleen may reduce absolute lymphocyte count (ALC), which can affect tumor immunity. Therefore, in the present study, we evaluated spleen dose-volume parameters associated with ALC and neutrophil/lymphocyte ratio (NLR) in patients with esophageal cancer.

Methods

This retrospective study evaluated patients who were diagnosed with stage I–IV esophageal cancer and who received radiotherapy at Nihon University Itabashi Hospital between January 2015 and March 2020. Spleen V5, V10, V20, and V30 and mean spleen dose, which are dose-volume histogram parameters correlated with ALC and NLR, were analyzed.

Results

In total, 89 esophageal cancer patients with a median age of 72 years (range, 51–92 years) were included in this research. Results showed that spleen V5, V10, and V20 and mean splenic dose were significantly correlated with a low ALC. Meanwhile, a significant association was observed between spleen V5 and V10 and a high NLR (P<0.05). In the linear regression analysis, spleen V5 and V10 were remarkably associated with a low ALC (P=0.006 and 0.008). Further, a correlation was noted between spleen V5 and a high NLR (P=0.019). Spleen V5 and V10 were remarkably associated with greater than grade 3 lymphopenia (P=0.024 and P=0.031).

Conclusions

A correlation was observed between the irradiated volume of the spleen and ALC and NLR in patients with esophageal cancer. Furthermore, the spleen should be regarded as a high-risk organ, and the use of techniques in reducing spleen V5, V10 for the preservation of tumor immunity may be beneficial.

Shortened Radiation Time Promotes Recovery From Radiation-induced Lymphopenia in Early-Stage Non-small Cell Lung Cancer Patients Treated With Stereotactic Body Radiation Therapy

Background: To evaluate the potential impact of radiation time on radiation-induced lymphopenia (RIL) and subsequently recovery after stereotactic body radiation therapy (SBRT) and to examine the associations between radiation time and with patient outcomes in early-stage non-small cell lung cancer (NSCLC). Methods: Clinical and laboratory records of subjects consisted of 115 patients who had received SBRT for early-stage NSCLC. Clinical and laboratory records were retrospective reviewed to assess the changes in total lymphocyte counts (TLCs) following SBRT. Associations of TLCs kinetics with the clinical and treatment features, and outcomes were analyzed. Results: Most patients (100/115, 86.96%) experienced significantly decreased median TLCs following SBRT (1700 vs 1100 cells/µL; P < .001), and 52 patients (45.21%) met the criteria for lymphopenia. Six months after SBRT, 44 patients (38.26%) had recovered. A negative correlation between TLCs reduction and radiation time was observed (r = −0.381, P < .001). According to the receiver-operating characteristic curve analysis, the optimal cut-off value for radiation time to was 3950 s to predict lymphocyte count recovery (LR) following RIL was 3950 s (P < .001). Multivariate analyses demonstrated that radiation time was significantly associated with LR (odds ratio [OR], 0.113; 95% confidence interval [CI], 0.029-0.432; P = .001) but not TLCs reduction (P = .575). LR within 6 months after SBRT was associated with improved progression-free survival in patients without non-lymphopenia (P = .034), but had little effect in patients with lymphopenia (P = .405). Conclusion: A longer radiation time was associated with a lower rate of LR within 6 months after SBRT in patients with early-stage NSCLC. Given the association of severe and persistent RIL with survival in NSCLC, further study of the effect of radiation time on immune status is warranted.

Radiation-Induced Lymphopenia Risks of Photon Versus Proton Therapy for Esophageal Cancer Patients

Purpose

To assess possible differences in radiation-induced lymphocyte depletion for esophageal cancer patients being treated with the following 3 treatment modalities: intensity-modulated radiation therapy (IMRT), passive scattering proton therapy (PSPT), and intensity-modulated proton therapy (IMPT).

Methods and Materials

We used 2 prediction models to estimate lymphocyte depletion based on dose distributions. Model I used a piecewise linear relationship between lymphocyte survival and voxel-by-voxel dose. Model II assumes that lymphocytes deplete exponentially as a function of total delivered dose. The models can be fitted using the weekly absolute lymphocyte counts measurements collected throughout treatment. We randomly selected 45 esophageal cancer patients treated with IMRT, PSPT, or IMPT at our institution (15 per modality) to demonstrate the fitness of the 2 models. A different group of 10 esophageal cancer patients who had received PSPT were included in this study of in silico simulations of multiple modalities. One IMRT and one IMPT plan were created, using our standards of practice for each modality, as competing plans to the existing PSPT plan for each patient. We fitted the models by PSPT plans used in treatment and predicted absolute lymphocyte counts for IMRT and IMPT plans.

Results

Model validation on each modality group of patients showed good agreement between measured and predicted absolute lymphocyte counts nadirs with mean squared errors from 0.003 to 0.023 among the modalities and models. In the simulation study of IMRT and IMPT on the 10 PSPT patients, the average predicted absolute lymphocyte count (ALC) nadirs were 0.27, 0.35, and 0.37 K/μL after IMRT, PSPT, and IMPT treatments using Model I, respectively, and 0.14, 0.22, and 0.33 K/μL using Model II.

Conclusions

Proton plans carried a lower predicted risk of lymphopenia after the treatment course than did photon plans. Moreover, IMPT plans outperformed PSPT in terms of predicted lymphocyte preservation.

Current status and application of proton therapy for esophageal cancer

Esophageal cancer remains one of the leading causes of death from cancer across the world despite advances in multimodality therapy. Although early-stage disease can often be treated surgically, the current state of the art for locally advanced disease is concurrent chemoradiation, followed by surgery whenever possible. The uniform midline tumor location puts a strong importance on the need for precise delivery of radiation that would minimize dose to the heart and lungs, and the biophysical properties of proton beam makes this modality potential ideal for esophageal cancer treatment. This review covers the current state of knowledge of proton therapy for esophageal cancer, focusing on published retrospective single- and multi-institutional clinical studies, and emerging data from prospective clinical trials, that support the benefit of protons vs photon-based radiation in reducing postoperative complications, cardiac toxicity, and severe radiation induced immune suppression, which may improve survival outcomes for patients. In addition, we discuss the incorporation of immunotherapy to the curative management of esophageal cancers in the not-too-distant future. However, there is still a lack of high-level evidence to support proton therapy in the treatment of esophageal cancer, and proton therapy has its limitations in clinical application. It is expected to see the results of future large-scale randomized clinical trials and the continuous improvement of proton radiotherapy technology.

Cytomegalovirus reactivation in esophageal cancer patients receiving chemoradiotherapy: A retrospective analysis

Background

Although rare, cytomegalovirus (CMV) reactivation can be lethal in patients with cancer. However, the criteria for the prevention of cytomegalovirus reactivation during cancer treatment are unclear. This study aimed to identify factors associated with CMV reactivation in patients with esophageal cancer who were receiving chemoradiotherapy.

Methods

This retrospective study included esophageal cancer patients receiving definitive or palliative chemoradiotherapy during April 2013–March 2020. Patients with fever during chemoradiotherapy underwent a systemic work‐up to detect the primary focus of infection, and CMV antigenemia was assessed in cases of unidentifiable infection.

Results

Among 132 patients (80.3% male, median age 69 years [range, 39–86 years]), 124 received 5‐fluorouracil plus cisplatin and 8 received oxaliplatin–5‐fluorouracil–levofolinate chemotherapy. Overall, 19 patients had CMV reactivation, 37 had other infections, and 76 had no identified infection (groups 1, 2, and 3, respectively). Median minimum lymphocyte counts were 81.0/µl (interquartile range: 52.0–144.0/µl), 120.0/µl (81.0–162.5/µl), and 185.5/µl (120.5–328.0/µl) in groups 1, 2, and 3, respectively, with counts being significantly lower in groups 1 and 2 than in group 3 (p < 0.001). In multiple logistic regression analysis, the minimum lymphocyte count was associated with CMV reactivation (odds ratio 0.983, 95% confidence interval: 0.973–0.994, p = 0.002).

Conclusion

CMV reactivation is not rare in patients with esophageal cancer who were receiving chemoradiotherapy and is associated with the minimum lymphocyte counts. CMV reactivation should be considered during differential diagnosis for patients with a severe decline in lymphocyte counts when receiving chemoradiotherapy.

Identifying Individualized Risk Profiles for Radiotherapy-Induced Lymphopenia Among Patients With Esophageal Cancer Using Machine Learning

PURPOSE

Radiotherapy (RT)-induced lymphopenia (RIL) is commonly associated with adverse clinical outcomes in patients with cancer. Using machine learning techniques, a retrospective study was conducted for patients with esophageal cancer treated with proton and photon therapies to characterize the principal pretreatment clinical and radiation dosimetric risk factors of grade 4 RIL (G4RIL) as well as to establish G4RIL risk profiles.

METHODS

A single-institution retrospective data of 746 patients with esophageal cancer treated with photons (n = 500) and protons (n = 246) was reviewed. The primary end point of our study was G4RIL. Clustering techniques were applied to identify patient subpopulations with similar pretreatment clinical and radiation dosimetric characteristics. XGBoost was built on a training set (n = 499) to predict G4RIL risks. Predictive performance was assessed on the remaining n = 247 patients. SHapley Additive exPlanations were used to rank the importance of individual predictors. Counterfactual analyses compared patients' risk profiles assuming that they had switched modalities.

RESULTS

Baseline absolute lymphocyte count and volumes of lung and spleen receiving ≥ 15 and ≥ 5 Gy, respectively, were the most important G4RIL risk determinants. The model achieved sensitivitytesting-set 0.798 and specificitytesting-set 0.667 with an area under the receiver operating characteristics curve (AUCtesting-set) of 0.783. The G4RIL risk for an average patient receiving protons increased by 19% had the patient switched to photons. Reductions in G4RIL risk were maximized with proton therapy for patients with older age, lower baseline absolute lymphocyte count, and higher lung and heart dose.

CONCLUSION

G4RIL risk varies for individual patients with esophageal cancer and is modulated by radiotherapy dosimetric parameters. The framework for machine learning presented can be applied broadly to study risk determinants of other adverse events, providing the basis for adapting treatment strategies for mitigation.

Severe lymphopenia acquired during chemoradiotherapy for esophageal cancer: Incidence and external validation of a prediction model

BACKGROUND

The incidence of grade 4 lymphopenia in patients treated with chemoradiotherapy (CRT) according to Chemoradiotherapy for Oesophageal cancer followed by Surgery Study (CROSS) regimen is unclear. The primary aim was to determine the incidence of grade 4 lymphopenia during CROSS for esophageal cancer. Secondary aims were to externally validate a prediction model for grade 4 lymphopenia and compare overall survival between patients with and without grade 4 lymphopenia.

METHODS

Patients who underwent CRT for esophageal cancer between 2014 and 2019 were eligible for inclusion. Patients with a planned radiation dose of 41.4 Gy (CROSS) or 50.4 Gy ("extended-CROSS") and concurrent carboplatin and paclitaxel were included. The primary outcome was the incidence of grade 4 lymphopenia during CRT defined according to Common Terminology Criteria for Adverse Events version 5.0 (i.e. lymphocyte count nadir < 0.2 µL). The secondary outcome measures were the prediction model's external performance (i.e. discrimination and calibration). Overall survival for patients with versus without grade 4 lymphopenia was compared using Kaplan-Meier analysis.

RESULTS

A total of 219 patients were included of whom 176 patients (80%) underwent CROSS and 43 patients (20%) extended-CROSS. The incidence of grade 4 lymphopenia was 11% in CROSS and 33% in extended-CROSS (p < 0.001). External discrimination yielded a c-statistic of 0.80 (95% confidence interval: 0.70-0.89). External calibration of the model was poor in CROSS but fair in extended-CROSS. Adjusted calibration using intercept correction (adjusted for the lower a-priori risk for grade 4 lymphopenia in CROSS) showed fair agreement between the observed and predicted risk for grade 4 lymphopenia. Median overall survival in patients with versus without grade 4 lymphopenia was 12.7 versus 42.5 months (p = 0.045).

CONCLUSION

The incidence of grade 4 lymphopenia is significantly higher in esophageal cancer patients receiving extended-CROSS compared to those receiving CROSS. The prediction model demonstrated good external performance in the setting of the CROSS-regimen and could be used to identify patients at high-risk for grade 4 lymphopenia who might be eligible for lymphopenia-mitigating strategies.

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.

The Influence of Severe Radiation-Induced Lymphopenia on Overall Survival in Solid Tumors: A Systematic Review and Meta-Analysis

PURPOSE

Emerging evidence suggests a detrimental prognostic association between radiation-induced lymphopenia (RIL) and pathologic response, progression-free survival, and overall survival (OS) in patients who undergo radiation therapy for cancer. The aim of this study was to systematically review and meta-analyze the prognostic impact of RIL on OS in patients with solid tumors.

METHODS AND MATERIALS

PubMed/MEDLINE and Embase were systematically searched. The analysis included intervention and prognostic studies that reported on the prognostic relationship between RIL and survival in patients with solid tumors. An overall pooled adjusted hazard ratio (aHR) was calculated using a random-effects model. Subgroup analyses for different patient-, tumor-, treatment-, and study-related characteristics were performed using meta-regression.

RESULTS

Pooling of 21 cohorts within 20 eligible studies demonstrated a statistically significant association between OS and grade ≥3 versus grade 0-2 RIL (n = 16; pooled aHR, 1.65; 95% confidence interval [CI], 1.43-1.90) and grade 4 RIL versus grade 0-3 (n = 5; aHR, 1.53; 95% CI, 1.24-1.90). Moderate heterogeneity among aHRs was observed, mostly attributable to overestimated aHRs in 7 studies likely subject to model-overfitting. Subgroup analysis showed significant prognostic impact of grade ≥3 RIL in 4 brain tumor (aHR, 1.63; 95% CI, 1.06-2.51), 4 lung cancer (aHR, 1.52; 95% CI, 1.01-2.29), and 3 pancreatic cancer (aHR, 1.92; 95% CI, 1.10-3.36) cohorts.

CONCLUSIONS

This meta-analysis demonstrates a significant detrimental prognostic association between grade ≥3 lymphopenia and OS in patients receiving radiation therapy for solid tumors. This finding appears consistent for tumors of the brain, thorax, and upper abdomen and provides an imperative to further elucidate the potential survival benefit of lymphopenia-mitigating strategies.

An in-silico assessment of the dosimetric benefits of MR-guided radiotherapy for esophageal cancer patients

PURPOSE

To assess the dosimetric benefits of online MR-guided radiotherapy (MRgRT) for esophageal cancer patients and to assess how these benefits could be translated into a local boosting strategy to improve future outcomes.

METHODS

Twenty-nine patients were in-silico treated with both a MRgRT regimen and a conventional image guided radiotherapy (IGRT) regimen using dose warping techniques. Here, the inter and intrafractional changes that occur over the course of treatment (as derived from 5 MRI scans that were acquired weekly during treatment) were incorporated to assess the total accumulated dose for each regimen.

RESULTS

A significant reduction in dose to the organs-at-risk (OARs) was observed for all dose-volume-histogram (DVH) parameters for the MRgRT regimen without concessions to target coverage compared to the IGRT regimen. The mean lung dose was reduced by 28%, from 7.9 to 5.7 Gy respectively and V20Gy of the lungs was reduced by 55% (6.3-2.8%). A reduction of 24% was seen in mean heart dose (14.8-11.2 Gy), while the V25Gy of the heart was decreased by 53% (14.3-6.7%) and the V40Gy of the heart was decreased by 69% (3.9-1.2%). In addition, MRgRT dose escalation regimens with a boost up to 66% of the prescription dose to the primary tumor yielded approximately the same dose levels to the OARs as from the conventional IGRT regimen.

CONCLUSION

This study revealed that MRgRT for esophageal cancer has the potential to significantly reduce the dose to heart and lungs. In addition, online high precision targeting of the primary tumor opens new perspectives for local boosting strategies to improve outcome of the local management of this disease.

Dynamic changes in practical inflammation and immunity markers in cancer patients receiving immune-enhancing nutritional supplementation during concurrent chemoradiotherapy

BACKGROUND

Immune-enhancing nutrition (IMN) strengthens the systematic inflammatory response and the immune system. Neutrophil to lymphocyte ratio (NLR) and absolute lymphocyte count (ALC) are affected during cancer therapies.

OBJECTIVE

We carried out an analysis of the dynamic changes in NLR and ALC over time in cancer patients with or without IMN supplementation.

METHODS

88 cancer patients receiving concurrent chemoradiotherapy (CCRT) were randomized into regular diet group, and regular diet and IMN group.Generalized estimation equation models were used to assess associations between patient's characteristics, IMN, and dynamic changes in NLR and ALC over time.

RESULTS

NLR and ALC at preCCRT were significantly associated with dynamic changes in NLR (adjusted β= 1.08, 95% confidence interval [CI]: 0.64-1.52) and ALC (adjusted β= 0.41, 95% CI: 0.36-0.46). The magnitudes of the NLR and ALC changes through CCRT were lower in patients receiving IMN, although the differences were not statistically significant except ALC at the end of CCRT in head and neck cancer patients (P= 0.023).

CONCLUSION

Dynamic negative changes in both markers were demonstrated throughout CCRT. There were non-significant trend in promising changes in both NLR and ALC values in the whole group in IMN supplementation.

Prognosis of severe lymphopenia after postoperative radiotherapy in non-small cell lung cancer: Results of a long-term follow up study

Purpose

To investigate the incidence and prognosis of severe radiation-induced lymphopenia (sRIL) after postoperative radiotherapy (PORT) for resected NSCLC.

Patients and methods

Between 1998 and 2017, 170 patients treated with PORT for NSCLC were retrospectively reviewed. Lymphopenia was divided into tertiles with severe lymphopenia defined as absolute lymphocyte counts (ALC) < 0.37 × 10³/ul.

Results

sRIL was observed in 32.3% of patients. Multivariable logistic regression analysis indicated sRIL was associated with planning target volume radiation fraction numbers (OR 1.09, p = 0.005) and total lung mean dose (OR 1.12, p = 0.006). With a median follow-up time of 12.2 years, the median progression-free survival and overall survival were 14.8 months and 28.4 months respectively in patients with sRIL, vs. 21.7 months (p = 0.008) and 48.3 months (p = 0.01) respectively in patients without sRIL. Multivariable analyses indicated sRIL significantly decreased OS (HR 1.95, p < 0.01). Since PORT for stage I-II NSCLC was done largely for positive margins, which may confound the contribution of severe RIL, we analyzed stage III separately and found that sRIL also significantly decreased OS (HR 1.88, p = 0.004) in multivariable analysis.

Conclusion

For this long-term outcome study, severe RIL correlated with total lung mean dose and radiation fractionation numbers, and was a strong prognostic factor for poor survival in PORT patients, particularly in patients with stage III NSCLC, highlighting the importance of an intact immune system for post-radiation immunologic disease surveillance.

The Impact of Lymphopenia and Dosimetric Parameters on Overall Survival of Esophageal Cancer Patients Treated with Definitive Radiotherapy

Purpose

The objectives of the present study are to perform a survival analysis of patients with thoracic esophageal squamous cell carcinoma (ESCC) receiving definitive radiotherapy and to identify prognostic factors from among the hematological and dosimetric factors.

Methods

Cases of thoracic ESCC treated with radical RT between 2014 and 2017 were identified. The impact of clinicopathological factors on overall survival (OS) were analyzed using the Cox proportional hazards model. Absolute lymphocyte counts (ALC) and the neutrophil-to-lymphocyte ratio (NLR = ANC/ALC) were assessed before, during, and after radiotherapy (RT). Cox regression was used to correlate clinical factors with hematologic toxicities, dosimetric parameters and overall survival. Multiple logistic regression analysis was used to identify associations between lymphopenia and dosimetric parameters. With the overall survival status and real time events, the X-tile program was utilized to determine the optimal cut-off value of pretreatment NLR, and ALC nadir.

Results

Ninety-nine ESCC patients were enrolled in the present study. They had a median OS of 23 months. The median RT dose was 55.75Gy (46–66Gy), and the mean dose (D_mean) of the thoracic vertebrae (TVB) was 27.04±9.65Gy. Based on the multivariate analysis, the V20 of TVB, the pretreatment NLR, and the ALC nadir were associated with significantly worse OS. Concurrent CRT, which entailed increasing the mean TVB dose and V20 of TVB, was linked to a higher probability of lymphopenia risk (P<0.05). This was ascertained through the multiple logistic regression analysis.

Conclusion

In ESCC patients who received definitive RT, V₂₀ of TVB, pretreatment NLR, and ALC nadir during RT were independent prognostic factors and chemotherapy regimen, mean TVB dose, and V₂₀ of TVB were associated with lymphopenia.

Lymphopenia in Esophageal Cancer: What Have We Learned?

Lymphopenia caused by disease or treatment is frequent in patients with cancer, which seriously affects the prognosis of these patients. Immune checkpoint inhibitors (ICIs) have garnered attention as one of the most promising strategies for the treatment of esophageal cancer (EC). The status of the immune system, such as, the lymphocyte count, is now considered to be an important biomarker for ICI treatments. Recognition of the significant impact of the lymphocyte count on the survival of patients with EC in the era of immunotherapy has revived interest in understanding the causes of lymphopenia and in developing strategies to predict, prevent and eliminate the adverse effect of lymphopenia. Here, we review what we have learned about lymphopenia in EC, including the prognostic and predictive value of lymphopenia in patients with EC, the predictors of lymphopenia, and the strategies to ameliorate the effect of lymphopenia in patients with EC.

Lymphopenia During Definitive Chemoradiotherapy in Esophageal Squamous Cell Carcinoma: Association with Dosimetric Parameters and Patient Outcomes

BACKGROUND

The objective of this study was to investigate the relationship between clinical characteristics, as well as dosimetric parameters, and the risk of treatment-related lymphopenia in esophageal squamous cell carcinoma (ESCC) treated with definitive chemoradiotherapy (CRT).

MATERIALS AND METHODS

Clinical characteristics and dosimetric parameters were collected from 436 patients with ESCC who received definitive CRT from 2010 through 2017. Absolute lymphocyte counts (ALCs) were obtained before, during, and 1 month after CRT. Grade 4 (G4) lymphopenia was defined as ALC <0.2 × 10⁹ /L during CRT. Logistic regression analysis was used to evaluate the effect of each factor on predicting G4 lymphopenia. The relationship between lymphopenia and overall survival (OS) was examined, and a nomogram was developed to predict OS.

RESULTS

G4 lymphopenia was observed in 103 patients (23.6%) during CRT. Multivariate analysis indicated that planning target volume (PTV), lung V₁₀ , heart V₁₀ , performance status, and pretreatment lymphopenia were significant risk factors for G4 lymphopenia. Patients with G4 lymphopenia had significantly worse survival than those without. Based on multivariate analysis, clinical TNM stage, radiotherapy modality, pretreatment ALC, and G4 lymphopenia were predictive of OS and were incorporated into the nomogram, yielding a concordance index of 0.71.

CONCLUSIONS

G4 lymphopenia during definitive CRT was associated with larger PTVs, higher lung V₁₀ and heart V₁₀ , and worse survival.

IMPLICATIONS FOR PRACTICE

The purpose of this study was to investigate the relationship between clinical characteristics, as well as dosimetric parameters, and the risk of treatment-related lymphopenia in 436 patients with esophageal squamous cell carcinoma who received definitive chemoradiotherapy. Grade 4 (G4) lymphopenia was observed in 23.6% of patients during radiotherapy. G4 lymphopenia was associated with larger planning target volumes, higher lung V₁₀ and heart V₁₀ , and worse survival. Then, a nomogram was built based on multivariate analysis, yielding excellent performance to predict overall survival. Prospective studies are needed to investigate potential approaches for mitigating severe lymphopenia, which may ultimately convert into survival benefits.

Radiotherapy-Related Lymphopenia Affects Overall Survival in Patients With Lung Cancer

INTRODUCTION

Lymphopenia after radiotherapy has an adverse effect on the patient's outcome. However, the relationship between radiotherapy dose delivery and lymphopenia is not fully understood. This work used image-based data mining to identify anatomical regions where the received dose is correlated with severe lymphopenia.

METHODS

A total of 901 patients with lung cancer were analyzed. A Cox model was used to assess prognostic factors of overall survival (OS). Two matched groups were defined-patients with lymphopenia of grade 3 or higher and patients without lymphopenia of grade 3-based on tumor volume, baseline lymphocytes, and prescribed dose. Then, data mining was used to identify regions where dose correlates significantly with lymphopenia of grade 3 or higher. For this, dose matrices were aligned using registration of the computed tomography images to one reference patient. Mean dose distributions were obtained for the two groups, and organs of significance were detected. Dosimetric parameters from the identified organs that had the highest correlation with lymphocytes at nadir were selected. Multivariable analysis was conducted for lymphopenia of grade 3 or higher on the full lung cohort, and the model was tested on 305 patients with esophageal cancer.

RESULTS

Adjusted Cox regression revealed that lymphopenia of grade 3 or higher is an independent factor of OS. The anatomical regions identified were the heart, lung, and thoracic vertebrae. Dosimetric parameters for lymphopenia included thoracic vertebrae V20, mean lung dose, and mean heart dose, which were further validated in the esophageal cancer cohort.

CONCLUSIONS

We report that severe lymphopenia during radiotherapy is a poor prognostic factor for OS in patients with lung cancer and could be mitigated by minimizing thoracic vertebrae V20, mean lung dose, and mean heart dose to limit the irradiation of stem cells and blood pool.

Harnessing data science to advance radiation oncology

Radiation oncology, a major treatment modality in the care of patients with malignant disease, is a technology‐ and computer‐intensive medical specialty. As such, it should lend itself ideally to data science methods, where computer science, statistics, and clinical knowledge are combined to advance state‐of‐the‐art care. Nevertheless, data science methods in radiation oncology research are still in their infancy and successful applications leading to improved patient care remain scarce. Here, we discuss data interoperability issues within and across organizational boundaries that hamper the introduction of big data and data science techniques in radiation oncology. At the semantic level, creating common underlying models and codification of the data, including the use of data elements with standardized definitions, an ontology, remains a work in progress. Methodological issues in data science and in the use of large population‐based health data registries are identified. We show that data science methods and big data cannot replace randomized clinical trials in comparative effectiveness research by reviewing a series of instances where the outcomes of big data analyses and randomized trials are at odds. We also discuss the modern wave of machine learning and artificial intelligence as represented by deep learning and convolutional neural networks. Finally, we identify promising research avenues and remain optimistic that the data sources in radiation oncology can be linked to yield important insights in the near future. We argue that data science will be a valuable complement to, but not a replacement of, the traditional hypothesis‐driven translational research chain and the randomized clinical trials that form the backbone of evidence‐based medicine.

Radiation-induced lymphopenia: the main aspects to consider in immunotherapy trials for endometrial and cervical cancer patients

BACKGROUND

Although the chemotherapy-induced depletion of circulating white blood cells (WBC) is well recognized, the impact of exclusive radiotherapy (RT) on the different subpopulations of WBC remains unexplored. This may be important for immunotherapy administrated in combination with radiation, especially in malignant tumors usually treated with RT or chemoradiotherapy (CRT), and characterized by a high mutational burden, such as endometrial (EC) or cervical cancer (CC). We aimed to evaluate the impact of RT and CRT on circulating WBC in uterine cancers and its correlation with survival.

MATERIAL AND METHODS

A total of 202 consecutive patients with uterine cancers treated with RT or CRT between 2009 and 2016 in a large European center and with available basal and post-treatment blood tests were retrospectively evaluated. EC and CC patients were analyzed separately. The differences between pre- and post- treatment WBC mean values were evaluated independently in patients treated with CRT and exclusive RT. Two-sided T test for paired samples and Kaplan-Meier curves were applied for analysis (p value < 0.05, SPSS v.23).

RESULTS

Among EC patients, 29 received CRT and 34 exclusive postoperative RT, while in CC cohort, 105 were treated with CRT and 34 with RT. In both cohorts, CRT affected significantly all WBC subtypes, whereas exclusive RT decreased only lymphocytes population (p = 0.000). Radiation-induced lymphopenia (RIL) had no impact on survival outcomes.

CONCLUSIONS

The selective depletion of lymphocytes after RT was significant in both EC and CC. Our results are of interest for further research on RIL and for design of immunotherapy-based clinical trials.

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."

Radiation-Induced Lymphopenia Predicts Poorer Prognosis in Patients With Breast Cancer: A Post Hoc Analysis of a Randomized Controlled Trial of Postmastectomy Hypofractionated Radiation Therapy

PURPOSE

The aim of this study was to determine whether radiation-induced lymphopenia affects the survival of patients with breast cancer.

METHODS AND MATERIALS

Post hoc analysis was conducted on data from 598 patients with breast cancer from a randomized controlled trial comparing postmastectomy hypofractionated radiation therapy (HFRT; 43.5 Gy in 15 fractions over 3 weeks) with conventional fractionated radiation therapy (CFRT; 50 Gy in 25 fractions over 5 weeks). Mean peripheral lymphocyte count (PLC) at different time points in the 2 groups was compared by the t test. Disease-free survival and overall survival were analyzed by the Kaplan-Meier method and compared between groups by the log-rank test.

RESULTS

Baseline PLC (pre-PLC) was comparable between HFRT and CFRT patients (1.60 ± 0.57 × 10⁹/L vs 1.56 ± 0.52 × 10⁹/L; P = .33). In both groups, the PLC declined steadily during the course of radiation therapy but started to recover at 1 month after radiation therapy. Incidence of lymphopenia was significantly lower in HFRT patients (45.4% vs 55.7%; P = .01). Nadir-PLC was significantly higher in HFRT patients (1.08 ± 0.37 × 10⁹/L vs 0.97 ± 0.31× 10⁹/L; P < .001), as was the nadir-PLC/pre-PLC ratio (0.72 ± 0.28 vs 0.67 ± 0.28; P = .02). Median follow-up was 57.6 months (interquartile range, 38.5-81.4). The 5-year disease-free survival was significantly lower in patients with a nadir-PLC/pre-PLC ratio <0.8 than in those with a ratio ≥0.8 (71.8% vs 82.6%; P = .01); however, overall survival was comparable between the groups (85.8% vs 90.6%; P = .24).

CONCLUSIONS

The risk of radiation-induced lymphopenia in patients with breast cancer is lower with HFRT than with CFRT. A low nadir-PLC/pre-PLC ratio may predict poor prognosis.