Temporal Structures in Positron Spectra and Charge-Sign Effects in Galactic Cosmic Rays

We present the precision measurements of 11 years of daily cosmic positron fluxes in the rigidity range from 1.00 to 41.9 GV based on 3.4×10^{6} positrons collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The positron fluxes show distinctly different time variations from the electron fluxes at short and long timescales. A hysteresis between the electron fluxes and the positron fluxes is observed with a significance greater than 5σ at rigidities below 8.5 GV. On the contrary, the positron fluxes and the proton fluxes show similar time variation. Remarkably, we found that positron fluxes are modulated more than proton fluxes with a significance greater than 5σ for rigidities below 7 GV. These continuous daily positron fluxes, together with AMS daily electron, proton, and helium fluxes over an 11-year solar cycle, provide unique input to the understanding of both the charge-sign and mass dependencies of cosmic rays in the heliosphere.

[Efficacy and safety analysis of an improved overlength biliary stent in the treatment of biliary stricture]

Objective: To evaluate the efficacy and safety of an improved overlength biliary stent in the treatment of bile duct stricture. Methods: Prospective randomized controlled study. Patients with bile duct stricture in Peking University International Hospital from February 2016 to June 2021 were randomly divided into the conventional plastic biliary stents (CPBS) group and the improved overlength biliary stents (IOBS) group by envelope random method. CPBS or IOBS were placed after endoscopic retrograde cholangiopancreatography (ERCP) breast catheterization was successfully conducted and the stenosis length was determined by angiography. The incidence of postoperative complications, median patency time of postoperative stent and reoperation rate within 6 months were compared between the two groups, Kaplan-Meier method was used to draw the survival curve, and log-rank test was conducted to evaluate the safety and efficacy of IOBS in the treatment of bile duct stricture. Results: A total of 90 patients were included. There were 45 patients in IOBS group, including 28 males and 17 females, aged (67.2±11.7) years. There were 45 patients in CPBS group, including 26 males and 19 females, aged (64.6±14.4) years. The patients in the both groups were balanced and comparable. There were no significant differences in success rate of operation, operation time, hospitalization time, operation cost and prospective complication rate between the two groups (all P>0.05). There were no significant differences in the changes of liver function index before and 72 hours after operation between the two groups (both P>0.05). The median patency time of stents in IOBS group was longer than that in CPBS group [M(Q1, Q3), 201(155,246) vs 109(55,167) d, P=0.002].The IOBS group had lower reoperation rate than the CPBS group within 6 months [46.2% (18/39) vs 78.9%(30/38), P=0.003]. Conclusion: IOBS has good safety in the treatment of bile duct stricture and the clinical efficacy is superior to CPBS.

Efficacy of Postoperative Radiotherapy for Patients with New N2 Descriptors of Subclassification in Completely Resected Non-Small Cell Lung Cancer: A Real-World Study

PURPOSE/OBJECTIVE(S)

Patients with N2 non-small cell lung cancer (NSCLC) were heterogeneous groups and required further stratification. The International Society for the Study of Lung Cancer (IASLC) added new descriptors of three sub-stages for stage N2 NSCLC: N2 at a single station without N1 involvement (N2a1), N2 at a single station with N1 involvement (N2a2), and N2 at multiple stations (N2b). This study aimed to investigate the efficacy of postoperative radiotherapy (PORT) for patients with these N2 descriptors.

MATERIALS/METHODS

Patients with histologically confirmed NSCLC after complete resection and divided into PORT group and non-PORT group. The primary endpoint was DFS. The second endpoints were overall survival (OS) and locoregional recurrence-free survival (LRFS). Propensity-score matching (PSM) of baseline characteristics between the PORT and non-PORT groups was used for validation.

RESULTS

Totally 1832 patients were enrolled, including 308 N2a1 patients, 682 N2a2 patients, and 842 N2b patients. The median follow-up time was 50.1 months. The survival outcomes of the PORT and non-PORT groups before PSM were shown in Table 1. For patients with N2a1, PORT could not improve the DFS (median DFS of the PORT group and the non-PORT group: not reached vs. 46.8 months, P = 0.41), OS (P = 0.85), or LRFS (P = 0.32), which were consistent with the multivariate analysis and data after the PSM. For patients with N2a2, PORT significantly improved the DFS (median DFS 29.7 vs. 22.2 months, P = 0.02), OS (P = 0.03), and LRFS (P = 0.01). The multivariate analysis and data after the PSM confirmed the benefits in DFS and LRFS, but no benefit was observed in OS (multivariate analysis: HR 0.79, P = 0.18; median OS after PSM: 103.7 vs. 63.1 months, P = 0.34). For patients with N2b, PORT could not improve the DFS (median DFS 20.6 vs. 21.2 months, P = 0.39) but significantly improved the OS (P<0.001) and LRFS (P<0.001). However, the multivariate analysis showed that PORT significantly improved DFS (HR 0.81, P = 0.03), consistent with the data after the PSM (median DFS 20.6 and 17.6 months, P = 0.04).

CONCLUSION

PORT significantly improved the DFS and LRFS in patients with N2a2 and significantly improved the DFS, LRFS, and OS in patients with N2b. Patients with N2a1 could not benefit from PORT.

Combined Modeling of CT Radiomics and Clinical Parameters for Risk of Cachexia in Extensive-Stage Small Cell Lung Cancer Patients Treated with First-Line Immunotherapy

PURPOSE/OBJECTIVE(S)

Cachexia occurs in about 60% of patients with extensive-stage small cell lung cancer (ES-SCLC), which may contribute to resistance to immunotherapy. This study integrating CT radiomics and clinical parameters aimed to identify patients at risk of developing cachexia that may be associated with prognosis in extensive-stage small cell lung cancer patients treated with first-line immunotherapy.

MATERIALS/METHODS

This study retrospectively included 200 ES-SCLC patients treated with first-line immunotherapy. All patients were randomly divided into training cohort and validation cohort according to a ratio of 7:3. The clinical characteristics and CT images before treatment were collected. Univariable and multivariable logistic regression analyses were conducted to evaluate the predictive role clinical characteristics. 3D slicer was used to retrieve radiomics features from CT images at the level of the third lumbar vertebra (L3). The radiomics signature was conducted by using the least absolute shrinkage and selection operator (LASSO). The receiver operating characteristic (ROC) curve analysis and Delong test were performed to determine and compare the predictive performance of radiomics, clinical and combined models.

RESULTS

All patients were divided into training (n = 140) and validation (n = 60) cohorts. Survival analysis indicated the inferior PFS (7.3 vs 8.7 months, p = 0.0053) and OS (7.9 vs 9.3 months, p = 0.00099) for patients with cachexia. The multivariate analysis indicated that pretherapeutic lactate dehydrogenase (LDH) and post-treatment advanced lung cancer inflammation index (pretreatment BMI×serum albumin/NL) were independent risk factors for cachexia. A total of 883 radiomics features were obtained from each patient's CT scan, and four CT features were selected to build radiomics signature. The radiomics signature achieved area under curves (AUCs) of 0.706 (95% CI 0.624-0.780) in the training cohort, and 0.610 (95% CI 0.475-0.733) in the validation cohort. The combined model achieved AUCs of 0.769 and 0.674 in the training and validation cohorts, respectively, which performed better than clinical model or radiomics model only. Kaplan-Meier survival analysis showed that for the training cohort, the PFS (p = 0.0012) and OS (p = 0.0007) were significantly longer among patients with low RS compared to patients with high RS. For the validation cohort, similar results could also be observed in training cohort for PFS (p = 0.029) and OS (p = 0.091) estimation, respectively.

CONCLUSION

The combined model based on CT and clinical parameters improved the performance for predicting cachexia in ES-SCLC patients receiving first-line immunotherapy. It provided a novel strategy for clinicians to identify ES-SCLC patients who may suffer from the cachexia and early interventions would improve prognosis of response to immunotherapy.

PD-1 Inhibitors and Chemotherapy Combined with or without Radiotherapy for Patients with Oligometastatic Esophageal Cancer

PURPOSE/OBJECTIVE(S)

Oligometastatic esophageal cancer (OMEC) is an intermediate state between local advanced and widespread metastatic disease, which is associated with better prognosis compared to poly-metastatic esophageal cancer (EC). The previous studies demonstrated the survival benefit from local radiotherapy for OMEC patients. But the data of PD-1 inhibitors combined with radiotherapy for OMEC is still scarce. The purpose of the present study was to determine the efficacy and safety of PD-1 inhibitors plus radiotherapy in OMEC.

MATERIALS/METHODS

OMEC was defined as "up to five measurable metastatic lesions and up to three organs involved". Patients with OMEC receiving PD-1 inhibitors plus chemotherapy in a single center were retrospectively analyzed in this study. They were dichotomized according to whether or not they had received radiotherapy. The efficacy and safety of immunochemotherapy combined with radiotherapy (RT group) and immunochemotherapy alone (NRT group) were investigated.

RESULTS

A total of 226 patients were included; 108 patients received PD-1 inhibitors plus chemotherapy and radiotherapy, while other 118 patients were treated with immunochemotherapy alone. Baseline characteristics were well balanced between the groups. The overall response rate (ORR) was 58.3% in the RT group and 41.5% in the NRT group (P = 0.012), respectively. The median PFS was 13.5 months (95% CI, 10.0-17.1) for the RT group and 8.8 months (95% CI, 9.2-12.0) for the NRT group (P = 0.000). The addition of radiotherapy was the major prognostic factor for PFS (hazard ratio, 0.56; 95% CI, 0.406-0.761; P = 0.000) by univariate Cox regression analysis. Patients were well-tolerated, and the overall incidence of adverse events was similar between the RT group and NRT group. In addition, the incidence of treatment-related pneumonitis did not differ between the two groups. Grade 3-5 pneumonitis was observed in 3.7% and 5.1% of patients in the RT and NRT groups, respectively.

CONCLUSION

The additional of radiotherapy to PD-1 inhibitors and chemotherapy improved PFS of patients with OMEC and showed acceptable toxicity. Further prospective studies investigating the combination of immunochemotherapy and radiotherapy are warranted.

Outcome Supervised Deep Learning Model on Pathological Whole Slide Images for Survival Prediction of Immunotherapy in Non-Small Cell Lung Cancer Patients: A Multicenter Study

PURPOSE/OBJECTIVE(S)

Although PD-(L)1 inhibitors were marked by durable efficacy in non-small cell lung cancer patients (NSCLC), about 60% of patients still suffer from recurrence and metastasis after PD-(L)1 inhibitors treatment. And there were no robust biomarkers of the response of PD-(L)1 inhibitors. Whole slide images (WSIs) of H&E-stained specimens have been found to characterize the tumor microenvironment, and might be the potential prognostic predictors of NSCLC patients. To accurately predict the response to PD-(L)1 inhibitors, we presented the deep learning model based on WSI of H&E-stained specimens of NSCLC patients.

MATERIALS/METHODS

Two independent cohorts of NSCLC patients receiving PD-(L)1 inhibitors from two hospitals were enrolled for model training and testing respectively. The WSI images of H&E-stained histological specimens were obtained from these patients, and patched into 1024×1024 pixels. The labels of patched images were determined due to their progression free survival (PFS) with the interval of 4 months. The patch-level model was firstly trained based on Vit to identify the predictive patches in training cohort, and patch-level probability distribution was performed. Then we trained patient-level survival model-based Vit-RNN framework, and tested it in external validation cohort.

RESULTS

A total of 291 WSI images of H&E-stained histological specimens from 198 NSCLC patients in primary cohort and 62 WSI images from 30 NSCLC patients in testing cohort were included for model training and external validation. All patients were divided into 4 groups due to their PFS after PD-(L)1 inhibitors. There were 246,318 patches from 291 images in primary cohort after image pre-processing, and all images were randomly divided into train cohort and validation cohort with the proportion of 7:3. The patch-level Vit model with the highest accuracy was saved and the predictive patches were selected after 50 epochs training. All patches were ranked by the probability of correct prediction, and the first 50 top-ranked patches from each WSI image are sequentially passed to the patient-level Vit-RNN model. The Vit-RNN survival achieved an accuracy of 88.6% in the validation cohort, and an accuracy of 81% in the testing cohort. The multivariate cox analysis also indicated the Vit-RNN survival model remained a statistically independent predictor of survival from PD-(L)1 inhibitors (P = 0.0085).

CONCLUSION

The outcome supervised Vit-RNN survival model based on pathological WSIs could be used to predict the efficacy the PD-(L)1 inhibitors in NSCLC patients, laying the foundation for the deployment of computational pathomics in clinical practice of immunotherapy.

A Phase 0 Study Assessing the Intracranial Activity of a Metabolic Radiosensitizer in Patients with Glioblastoma

PURPOSE/OBJECTIVE(S)

Efforts to overcome treatment resistance in glioblastoma (GBM) have been unsuccessful due to tumor heterogeneity and poor intracranial drug penetration. Targeting altered metabolism is a promising approach to improve GBM therapy despite this heterogeneity. Mycophenolate mofetil (MMF) is an inhibitor of purine synthesis that sensitizes GBM to radiation and temozolomide (TMZ) in vitro and in vivo, but its ability to cross the blood brain barrier and inhibit GBM metabolism in patients is unknown. NCT04477200 is a phase 0/1 dose escalation study of MMF combined with radiation and temozolomide in GBM. Here we report the phase 0 results of this study assessing the intracranial activity of MMF.

MATERIALS/METHODS

Purine (GTP and IMP) and mycophenolic acid (MPA, the active metabolite of MMF) concentrations were determined using mass spectrometry in flash-frozen tumor (enhancing and non-enhancing) and normal cortex obtained from 8 patients with recurrent GBM who received MMF (500, 1000, 1500 and 2000 mg BID, N = 2 patients each dose level) for 1 week prior to re-resection and 5 control patients who did not receive MMF prior to re-resection. Plasma MPA concentration was similarly quantified to calculate the enhancing tumor, non-enhancing tumor and normal cortex to plasma MPA ratios.

RESULTS

Patients who received MMF had a mean MPA concentration of 2.2 ± 0.7 µM in the enhancing tumor samples, 1.2 ± 0.5 µM in the non-enhancing tumor samples and 1.3 ± 0.5 µM in normal cortex. MPA concentration was negligible in control patients. This corresponded to tissue/plasma MPA ratios of 0.31, 0.17 and 0.10 for enhancing tumor, non-enhancing tumor and normal cortex, respectively. The GTP/IMP ratio was decreased by 75% in enhancing tumor in MMF-treated patients compared to untreated controls (p = 0.009), indicating effective target engagement and inhibition of purine synthesis. The GTP/IMP ratio was also decreased in cortex and non-enhancing tumor, though a paucity of control samples prevented statistical analysis.

CONCLUSION

Twice daily MMF treatment yields intracranial drug concentrations above 1 µM and lowers the GTP/IMP ratio in GBMs, consistent with target engagement. As we have previously observed radiosensitization in vitro with MPA concentrations of 1 µM, these data suggest that MMF may achieve adequate CNS penetration for therapeutic benefit. The Phase 1 component of this study to determine the dose limiting toxicity and maximally tolerated dose of MMF when combined with reirradiation in recurrent GBM and radiation and TMZ in newly diagnosed GBM is ongoing.

The Impact of a High Radiation Dose to the Immune Cells on Tumor Control and Survival in Patients with Non-Small Cell Lung Cancer Undergoing Postoperative Radiotherapy

PURPOSE/OBJECTIVE(S)

Previous studies showed that the estimated dose of radiation to immune cells (EDRIC) was correlated with the overall survival (OS) of patients who received definitive thoracic radiotherapy. However, planning target volume (PTV) may be a confounding factor. The PTV is relatively uniform for patients undergoing postoperative radiotherapy (PORT). We further assessed the prognostic value of EDRIC on survival in patients with non-small cell lung cancer (NSCLC) undergoing PORT.

MATERIALS/METHODS

Patients with NSCLC who received PORT between 2004 and 2019 were analyzed. EDRIC was calculated as a function of the number of radiation fractions and mean doses to the lung, heart, and remaining body based on a model developed by Jin et al. The correlation between EDRIC and OS, PFS, local progression-free survival (LPFS), and distant metastasis-free survival (DMFS) were analyzed using univariable and multivariable Cox models. Kaplan-Meier method was used to show the survival difference between patients with high and low EDRIC.

RESULTS

A total of 345 patients were eligible. The mean EDRIC was 7.6 Gy. Multivariate analysis showed that EDRIC was associated with OS (HR 1.14, P = 0.002), PFS (HR 1.08, P = 0.016), LRFS (HR 1.111, P = 0.008), and DMFS (HR 1.10, P = 0.018). Patients were divided into low and high EDRIC groups according to median EDRIC. The 3-year OS was 82.7% and 72.2% (p = 0.03). The 3-year PFS was 40.3% and 17.8% (p < 0.01). The 3-year LRFS was 71.39% and 59.18% (p = 0.05). The 3-year DMFS was 74.4% and 63.4% (p = 0.06).

CONCLUSION

EDRIC was an independent prognostic factor for survival. Higher doses of radiation to the immune system were associated with tumor progression and death after the PORT of NSCLC. The organ at risk for the immune system should be considered during radiotherapy planning.

A photo-controlled, all-solid, and frequency-tunable ultra-wideband pulse generator

With the continuous exploration of the bioelectric effect, nanosecond and picosecond pulsed electric fields used in cancer therapy and drug introduction have attracted great attention. In this paper, an ultrashort pulsed electric field generator is proposed, which connects two photoconductive semiconductor switches in parallel to generate unipolar and bipolar pulses. We described the experimental scheme of the generator and the simulation of the radio frequency combiner. A 532 nm laser with pulse widths of 1 ns and 500 ps is used to trigger the photoconductive semiconductor switches. The experimental results show that the scheme can achieve adjustments of 357 and 720 MHz for the center frequency and the 3 dB bandwidth, respectively. The results confirm that this proposed scheme can be used for unipolar/bipolar frequency-adjustable ultra-wideband pulse generation.

Safety and Efficacy Analysis of Patients with Extensive-Stage Small Cell Lung Cancer (ES-SCLC) Treated with SHR-1316 Plus Chemotherapy and Sequential Chest Radiotherapy as First-Line Therapy from a Phase II Trial

PURPOSE/OBJECTIVE(S)

CAPSTONE-1, a phase 3 trial, showed that SHR-1316 (PD-L1 antibody) combined with standard first-line chemotherapy could prolong overall survival (OS) in patients (pts) with ES-SCLC. The CREST trial reported consolidative thoracic radiotherapy (TRT) of 30 Gy in 10 fractions provided a 10% 2-year OS benefit and more intensive TRT should be investigated in ES-SCLC. In the era of immunotherapy, the role of TRT also needs further exploration. Therefore, we designed this clinical trial to investigate the efficacy and safety of SHR-1316 plus first-line chemotherapy followed by TRT combined with SHR-1316.

MATERIALS/METHODS

Key inclusion criteria were pts aged 18-75 years, with previously untreated histologically or cytologically confirmed ES-SCLC, and an ECOG performance status of 0-1. Eligible pts would receive 4∼6 cycles of SHR-1316 (20mg/kg, D1, q3w) combined with EP/EC (etoposide, 100mg/m2, D1-5, q3w and cisplatin, 75mg/m², D1-3, q3w or carboplatin, AUC = 5, D1, q3w), followed by SHR-1316 combined with TRT (≥3 Gy*10 f or ≥2 Gy*25 f, involved-field irradiation), and then the maintenance therapy with SHR-1316 until disease progression or intolerable adverse events (AEs). The main endpoints included ORR, PFS and safety.

RESULTS

From October 2020 to January 2023, 33 pts received SHR-1316 and sequential consolidative TRT. Among them, 19 pts received high-dose TRT (>3 Gy*10 f or ≥2 Gy*25 f) and 14 pts received low-dose TRT (≤3 Gy*10 f or<2 Gy*25 f). The median age was 62 (range: 38-73). Most pts were male (28, 84.8%), former smokers (22, 66.7%) with an ECOG performance status 1 (32, 97%). Ten (30.3%) pts were diagnosed with brain metastasis and 10 (30.3%) pts had liver metastasis at baseline. At the data cutoff date, 9 pts remained on treatment, the average number of treatment cycles was 9.2. 33 pts had at least one 1 post-treatment tumor assessment. The confirmed ORR and DCR were 90.9% (30/33) and 100% (33/33) in all pts, were 89.5% (17/19) and 100% (19/19) in high-dose TRT group, and were 92.9% (13/14) and 100% (14/14) in low-dose TRT group. The median PFS was 10.2(CI: 5.8∼14.7) months in all pts, was 7 (CI: 3.8∼10.2) months in high-dose TRT group and 10.4 (CI: 8.4∼12.3) months in low-dose TRT group. AEs occurred in 27 (81.8%) pts and grade 3 or 4 AEs occurred in 20 (60.6%) pts. The most common grade 3 or 4 AEs included neutropenia (15, 45.5%), leukopenia (8, 24.2%), lymphocytopenia (5, 15.2%), pneumonia (3, 9.1%), anemia (3, 9.1%) and thrombocytopenia (2, 6.1%).

CONCLUSION

SHR-1316 plus chemotherapy and sequential TRT as first-line therapy for ES-SCLC showed promising efficacy and acceptable safety. There is no significant difference between high-dose and low-dose TRT groups in terms of safety and efficacy according to current data.

Role and Modality of Combining Radiotherapy with Immunotherapy in Stage III-IV Unresectable Small Cell Lung Cancer

PURPOSE/OBJECTIVE(S)

The combination of radiotherapy and immunotherapy was rarely reported in the management of small cell lung cancer (SCLC). We retrospectively assessed the role and modality of this combination in Stage III-IV unresectable SCLC.

MATERIALS/METHODS

Patients with stage III and IV SCLC were enrolled according to AJCC 8th edition. Both efficacy and safety of immunotherapy combined with radiotherapy were evaluated. Thereinto, patients received first-line chemo-immunotherapy and sequential thoracic consolidation radiotherapy (TCRT) were further evaluated. Survival and descriptive analyses were performed.

RESULTS

Between January 1, 2019 and December 31, 2021, 51 patients were included in our analysis. Median follow-up was 28.0 months (95% CI 22.8-33.2). Patients received radiotherapy in treatment course had a prolonged 2-year overall survival (OS). And in the first-line immunotherapy cohort of 27 patients, the addition of TCRT significantly improved 2y-OS (72.22% vs. 13.89%, p = 0.0048), 2y-locoregional recurrence free survival (LRRFS) (90.00% vs 48.00%, p = 0.011), and 2y-distance progression free survival (DPFS) (66.67% vs. 16.67%, p = 0.039). Subgroup analyses showed that TCRT rendered superior outcomes regardless of brain metastases. Dose-escalation (45 Gy/15f) and earlier radiotherapy seemed to improve the benefit. Of 70.37% (19/27) patients experienced disease progression in the TCRT evaluation cohort, 63.16% (12/19) patients failed in brain. A tendency toward better OS and superior brain metastases free survival (BMFS) were observed after receiving prophylactic cranial irradiation (PCI). Finally, the most common grade 2 or higher toxic effects were pneumonitis in all patients (11.76% of immune-related vs. 7.84% of radiation related).

CONCLUSION

Earlier addition of TCRT to immunotherapy could significantly improve survival and extracranial control for stage IIIA-IVB unresectable SCLC patients, with no increased risk of adverse events. In the era of immunotherapy, PCI may still be a recommended strategy. Further investigation is warranted.

Investigating Incidence of Nausea and Vomiting in Patients Receiving Concurrent Chemoradiotherapy: A Real-World Cohort Study

PURPOSE/OBJECTIVE(S)

Vomiting and nausea (VN) caused by anticancer agents and/or radiation therapy (RT) can significantly affect a patient's quality of life, leading to poor compliance with further anticancer agents and/or RT. Few studies pay attention to synergistic effect of RT and concurrent highly emetogenic chemotherapy for inducing vomiting and nausea. The aim of this real-world study is to investigate the incidence of VN in patients receiving concurrent chemoradiotherapy (CCRT).

MATERIALS/METHODS

From June 2022 to December 2022, patients receiving concurrent chemoradiotherapy in our center were consecutively enrolled in this study. Patients received moderate and low emetic agents were excluded. The antiemesis regimens were NK1 receptor antagonist plus 5-HT3 antagonist and dexamethasone (NHD) with or without olanzapine, which were recommended by guideline of National Comprehensive Cancer Network. Acute and delayed VN were analyzed in the following stratification factors: tumor site and antiemesis regimen. Acute VN usually occurred after administration of anticancer agents and commonly resolves within the first 24 hours. Delayed VN develops in patients more than 24 hours after anticancer agent administration. The grade of VN was evaluated according to Common Terminology Criteria for Adverse Events Criteria.

RESULTS

A total of 312 patients were enrolled for analysis. During the CCRT period, the incidence rate of acute VN in all patients was 28.2%, the delayed VN occurred in 139 of 312 patients (44.6%). The incidence rate of acute nausea in head and neck, thorax and abdomen were 33.8%, 28.9% and 25.2%, respectively. The incidence rate of acute vomiting in head and neck, thorax and abdomen were 7.0%, 3.9% and 5.2%, respectively. The incidence rate of delayed nausea in head and neck, thorax and abdomen were 51.1%, 35.5% and 45.9%, respectively. The incidence rate of delayed vomiting in head and neck, thorax and abdomen were 14.0%, 5.3% and 9.6%, respectively. There were not significant differences between NHD regimen and NHD plus olanzapine in VN (acute nausea, 25.5% vs. 30.3%, P = 0.356; acute vomiting, 4.4% vs. 6.8%, P = 0.352; delayed nausea, 40.1% vs. 48%, P = 0.166; delayed vomiting, 8.0% vs. 10.8%, P = 0.4). Multivariate logistic regression analysis showed age <50 years (P = 0.030. HR, 95% CI: 1.893, 1.062-3.374) and history of vomiting = 0.017, HR, 95% CI: 2.249, 1.154-4.384) were risk factor for acute nausea; female (P = 0.026, HR, 95% CI: 4.254, 1.192-15.186) and sleeping time <7 hours (p = 0.049, HR, 95% CI: 3.373, 1.003-11.344) were risk factors for acute vomiting; pregnancy (P = 0.011, HR, 95% CI: 2.424, 1.228-4.783) was risk factor for delayed nausea; pregnancy = 0.013, HR, 95% CI: 3.060, 1.269-7.380) and history of vomiting = 0.020, HR, 95% CI: 2.845, 1.182-6.844) were risk factors for delayed vomiting in patients receiving CCRT.

CONCLUSION

CCRT still contributed high incidence of delayed nausea in patients receiving standard antiemesis regimen.

30 Gy vs. 45 Gy Consolidative Thoracic Radiation (cTRT) for Extensive Stage Small Cell Lung Cancer (ES-SCLC): A Multicenter, Randomized, Phase 3 Trial

PURPOSE/OBJECTIVE(S)

Consolidative thoracic radiotherapy (cTRT) showed potential benefit to extensive stage small cell lung cancer (ES-SCLC). However, the optimum dose of cTRT is unknown. The purpose of this randomized trial was to compare the effect of 45 Gy in 15 fractions with 30 Gy in 10 fractions cTRT in ES-SCLC.

MATERIALS/METHODS

This phase III, randomized trial was conducted in 12 public hospitals in China. Eligible patients with pathologically confirmed ES-SCLC who responded to 4-6 cycles of etoposide plus cisplatin (EP) or carboplatin (EC) chemotherapy were randomized 1:1 to receive either 30 Gy in 10 fractions or 45 Gy in 15 fractions cTRT. The primary outcome was 2-year overall survival (OS). Secondary outcomes included 2-year progression-free survival (PFS), 2-year local control (LC) and radiation treatment related toxicity. The primary objective was to detect an OS improvement in 45 Gy cTRT group at 2 years from 13% to 26% assuming a two-sided a = 0.05 and power of 85%, with a planned sample size of 186 patients. This trial was registered with Clinical Trials.gov, number NCT02675088.

RESULTS

Between January 15, 2016, and September 20, 2022, 90 patients were randomly assigned either 30 Gy in 10 fractions (n = 50) or 45 Gy in 15 fractions (n = 40) cTRT group. Recruitment to the trial closed early due to slow accrual since first-line chemoimmunotherapy has become the new standard of care for ES-SCLC. The median age of patients was 58 years, 87.8% were male, 76.7% had a smoking history, 95.6% received IMRT, and 58.9% received prophylactic cranial irradiation. At a median follow-up of 39.9 months (IQR 27.2-59.2), there was no significant difference in the 2-year OS between the 45 Gy group and the 30 Gy group, at 43.4% (95% CI 29.3%-64.3%) and 40.0% (95% CI 27.9%-59.1%), respectively (log-rank p = 0.62; HR 1.13 [95% CI 0.69-1.84]). The 2-year PFS was 12.1% (95% CI 4.3%-33.8%) in the 45 Gy group and 9.0% (95% CI 3.2%-25.2%) in the 30 Gy group (log-rank p = 0.25, HR 0.76(95% CI [0.478-1.22]). There were also no significant differences in locoregional recurrence free survival (log-rank p = 0.75; HR 0.888 [95% CI 0.423-1.863]) and distant metastasis free survival (log-rank p = 0.95; HR 1.015 [95% CI 0.624-1.651]) between two groups. No grade 5 toxicity was observed in both groups. Patients treated with higher cTRT dose presented with increased incidence of grade 3+ radiation pneumonitis (10% vs 2%) and hematological toxicity (20% vs 12.5%).

CONCLUSION

This randomized trial did not find a higher probability of survival improvement in patients with ES-SCLC receiving cTRT of 45 Gy in 15 fractions compared with 30 Gy in 10 fractions. In contrast, there was an increase in toxicity, especially radiation pneumonitis. Additional randomized studies investigating the role of cTRT in ES-SCLC after a response to chemoimmunotherapy are warranted.

Thoracic Radiotherapy Improves the Outcomes of Extensive Stage Small-Cell Lung Cancer Patients Receiving First-Line Immunotherapy: A Multicenter Retrospective Analysis

PURPOSE/OBJECTIVE(S)

Platinum-etoposide chemotherapy combined with immune checkpoint inhibitors has been recommended as the first line standard treatment for extensive-stage small-cell lung cancer (ES-SCLC). However, the role of thoracic radiotherapy (TRT) was still unknown for these patients. The aim of this study was to evaluate the efficacy and safety of TRT for ES-SCLC patients receiving first-line immunotherapy and chemotherapy MATERIALS/METHODS: ES-SCLC patients who received 4 to 6 cycles of chemotherapy and immunotherapy as first-line therapy from two hospitals were included in analysis between July 2018 and January 2023. All patients were divided into two groups based on whether receiving TRT or not during the first-line setting. The primary endpoints were overall survival (OS) and progression-free survival (PFS), and the secondary endpoint was toxic effects. The Kaplan-Meier method was used to estimate overall survival and progression-free survival. All adverse events were graded by the senior doctors according to the Common Terminology Criteria for Adverse Events version 5.0.

RESULTS

A total of 253 patients from two hospitals were enrolled in analysis. The median age was 62 years and most patients were men (83%), and 36% patients were staged T4 and 52% N3. The most common sites of metastasis were brain (32%), liver (32%) and bone (30%). There were 107 patients (42%) receiving TRT and 146 (58%) without TRT. Baseline characteristics were well balanced between the two groups. The median follow-up time was 16.7 months. Statistically significant benefit was observed for patients receiving TRT compared to patients without TRT (median PFS, 10.4 vs 7.3 months, P< 0.001; median OS, 22.2 vs 13.7 months, P = 0.009). In terms of safety, no significant increase of any grade adverse event (AE) (P = 0.115) and grade 3 or 4 AE (P = 0.631) were observed for patients receiving TRT. The most common grade 3 or 4 AE were neutrophil count decreased, white blood cell count decreased, and nausea in the two groups. In the TRT group, the most common grade 1 or 2 AE related to TRT were esophagitis (40%) and pneumonitis (25%). Grade 3 or 4 esophagitis and pneumonitis were 4% and 8%, respectively. Only one patient developed grade 4 toxic effect of pneumonitis leading to radiotherapy withdrawal. No grade 5 adverse event occurred.

CONCLUSION

Addition of TRT showed significant survival benefits and well tolerability in ES-SCLC patients receiving platinum-etoposide chemotherapy and immune checkpoint inhibitors, which could be a feasible first-line treatment strategy for ES-SCLC patients.

Respiratory Motion Compensation Using Xsight Diaphragm Tracking for Liver Tumor in CK Synchrony Treatment: A Feasibility Study

PURPOSE/OBJECTIVE(S)

This study investigates the feasibility of using Xsight Diaphragm Tracking (XDT) for liver tumors located near or in the diaphragm during CyberKnife Synchrony Treatment.

MATERIALS/METHODS

Eight patients (46 fractions) with liver tumors located near or in the diaphragm were reviewed retrospectively. Prior to motion data analysis, baselines were flattened to remove the portions with significant changes and improve accuracy. To reduce the uncertainty about sudden irregular breathing, respiratory data were calculated as a rolling average. The overall tracking accuracy based on the patient-specific respiratory curve was evaluated using E2E testing with CIRS (18023-A) dynamic phantom.

RESULTS

Three main trajectories were observed in this work: Linearity (1/8), Linear radial type (6/8) and Hysteresis (1/1). The mean amplitude was 8.56±4.54 mm, 2.77±2.83 mm, and 4.23±3.92 mm for S-I, L-R, and A-P components. The linear trajectory patient had a more concentrated amplitude distribution. The baseline shifts were 5.88 mm (S-I), 2.53 mm (L-R), and 3.48 mm (A-P). Except for patient 2, all standard deviations of the center phase shift were less than 1 mm. The values of XDT correlation and prediction errors were 1.38±0.65 mm vs. 0.65±0.16 mm (S-I), 1.28±0.48 mm vs. 0.34±0.10 mm (L-R), and 0.96±0.32 mm vs. 0.22±0.072 mm (A-P), respectively. The strong positive correlations were amplitude vs. prediction error, SD of center phase vs. prediction error, and SD of center phase vs. amplitude. The median patient curve-based targeting accuracy was less than 1mm. Additionally, the mean target coverage for all patients with a 3 mm margin was 98.03±1.54%.

CONCLUSION

This study proved that the diaphragm could be used as a tracking surrogate for liver tumors located in or near the diaphragm instead of placing golden fiducial markers. A reduction in motion amplitude and respiration training were necessary during liver SABR treatment, along with respiration control and evaluation.

Effect of Segmental Abutting Esophagus-Sparing Technique to Reduce Severe Esophagitis in Limited-Stage Small-Cell Lung Cancer Patients Treated with Concurrent Hypofractionated Thoracic Radiation and Chemotherapy

PURPOSE/OBJECTIVE(S)

To evaluate the effect of segmental abutting esophagus-sparing (SAES) radiotherapy to reduce severe (G3+) acute esophagitis from 20% to 5% in patients with limited-stage small cell lung cancer (LS-SCLC) treated with concurrent chemoradiotherapy.

MATERIALS/METHODS

Patients with a clinical target volume (CTV) ≤1 cm close to the esophagus were enrolled in the experimental arm (45 Gy in 3 Gy daily fractions in 3 weeks) of an ongoing phase III randomized clinical trial (NCT02675088), which enrolled patients with histologically confirmed SCLC and clinically staged as LS or I-IIIB (AJCC 7th). This trial was designed to determine whether HYPO TRT (45 Gy in 3 Gy QD, experimental arm) has the same efficacy as CF TRT (60 Gy in 2 Gy QD, controlled arm) in patients with LS-SCLC. The whole esophagus was divided into the involved esophagus and abutting esophagus (AE) to receive different dose limitations according to the distance from the edge of the CTV. The primary endpoint was grade ≥ 3 acute esophagitis.

RESULTS

From 1 May 2021 to 30 April 2022, 30 patients were enrolled and completed four cycles of planned chemotherapy and radiotherapy. Our patient population was predominantly male (66.7% men vs. 33.3% women), with a median age of 62 years. A majority of patients presented with Stage N2-3 (90.0%) and T2-4 (76.7%), in which 4 patients had ultracentral-located primary tumors. With the SAES technique, all dosimetric parameters were significantly reduced for the whole esophagus and AE. The maximal and mean dose of the esophagus (47.4±1.9 Gy and 13.5 ± 5.8 Gy, respectively) and AE (42.9±2.3 Gy and 8.6 ± 3.6 Gy, respectively) in the SAES plan were significantly lower than those (esophagus 48.0±1.9 Gy and 14.7± 6.1 Gy, AE 45.1±2.4 Gy and 9.8± 4.2 Gy, respectively) in the non-SAES plan. After the follow-up of more than 7 months (range, 7.0-18.1 months) for all patients, only one patient (3.3%, 95% CI 0.1%-17.2%) experienced grade 3 acute esophagitis and no grade 4-5 acute esophagitis happened (Table 3). For late toxicities, one patient suffered sustained grade 1 late esophagitis and all others had no symptoms of esophagitis. The rate of radiation pneumonitis was very low, with one grade 3 event and no grade 4-5 event. Twelve (40.0%) patients had G3+ hematologic toxic events, including 2 patients with febrile neutropenia. The 1-year OS, LRFS, DMFS and PFS was 96.4%, 88.7%, 78.4% and 64.3%, respectively. No patient developed local recurrence in the abutting esophagus-sparing region.

CONCLUSION

SAES radiotherapy has significant dosimetric advantages compared with standard radiotherapy, which are successfully translated into clinical benefits for patients with LS-SCLC treated with 45 Gy in 3 Gy daily fractions. This may facilitate dose escalation for TRT in LS-SCLC patients.

The expression of annexin-A1 in esophageal squamous cell carcinoma and its association with the biological behavior of the primary human esophageal squamous carcinoma cell line

This study aimed to observe the differential expression of Annexin-A1 in esophageal squamous cell carcinoma (ESCC) and explored the effect of small interfering ribonucleic acid (RNAi)-Annexin-A1 on the biological behavior of CE81T-0 cells. An immunohistochemical approach was used to detect the expression of Annexin-A1 in 86 pairs of ESCC samples. Quantitative reverse transcription polymerase chain reaction was used to detect the expression of Annexin-A1 in CE81T-0 and CE81T-4 cells, and the expression of Annexin-A1 in CE81T-0 cells was knocked out by RNAi. A methyl-thiazolyl-tetrazolium assay was used to observe the effect of Annexin-A1 on cell proliferation, and flow cytometry was conducted to analyze its effect on cell cycles and apoptosis. A scratch assay and a Transwell chamber were used to detect changes in cell migration and invasion. From the results, compared with the Annexin-A1 expression rate of 59.3% in para-carcinoma tissues, the expression of Annexin-A1 in cancer was reduced to only 32.6% in ESCC cells. Annexin-A1 was strongly expressed in highly differentiated ESCC cells without lymphatic metastasis and highly expressed in the CE81T-0 cell group with low metastasis. Annexin-A1 gene silencing promoted cell proliferation and inhibited apoptosis, blocked cells in the S-phase, and increased cell migration, leading to an increase in the number of invaded cells. Above all, Annexin-A1 could reflect the differentiation degree and lymph node metastasis of ESCC cells to some extent and was involved in the invasion, metastasis, proliferation, and other biological behaviors of ESCC cells, indicating an experimental basis for Annexin-A1 as a molecular marker in the early diagnosis of ESCC and the prediction of cell metastasis, invasion, and differentiation degree.

PD-L1 Inhibitors Combined with Thoracic Radiotherapy in First-Line Treatment of Extensive Stage Small Cell Lung Cancer: A Propensity Score-Matched, Real-World Study

PURPOSE/OBJECTIVE(S)

The CREST study showed that the addition of thoracic radiotherapy (TRT) could improve the survival of extensive stage small cell lung cancer (ES-SCLC), but whether TRT can bring survival benefit in the era of immunotherapy is controversial. This study aims to explore the efficacy and safety of adding TRT to the combination of PD-L1 inhibitors and chemotherapy.

MATERIALS/METHODS

Thepatients who received PD-L1 inhibitors combined with platinum-based chemotherapy as the first-line treatment of ES-SCLC from January 2019 to December 2021 were retrospectively collected. According to whether they received TRT, they were divided into two groups, and the follow-up analysis was performed. Propensity score matching (PSM) in with a 1:1 ratio was performed to balance the baseline characteristics of the two cohorts. The endpoints were progression-free survival (PFS) and OS.

RESULTS

A total of 211 patients with ES-SCLC were enrolled, of whom 70 (33.2%) patients received standard therapy plus TRT as first-line treatment, and 141 (66.8%) patients in the control group received PD-L1 inhibitors plus chemotherapy. After PSM, a total of 65 pairs of patients were enrolled in the analysis. There were no significant differences in baseline characteristics between the two groups of patients who received TRT and those who did not. In all patients, the median PFS (mPFS) in the TRT group and the non-TRT groupwere 9.5 months and 7.2 months, respectively, with HR = 0.60 (95% CI 0.41-0.87, p = 0.007). The median OS (mOS) in the TRT group was also significantly longer than that in the non-TRT group (24.1 months vs. 18.5 months, HR = 0.53, 95% CI 0.32-0.85, p = 0.009). Multivariable analysis showed that baseline liver metastasis and bone metastasis were independent prognostic factors for OS. In terms of safety, immunotherapy combined with thoracic radiotherapy increased the incidence of treatment-related pneumonia (p<0.001), most of which were grade 1-2.

CONCLUSION

This real-world study shows that adding TRT to durvalumab or atezolizumab plus chemotherapy significantly improves survival in ES-SCLC. It leads to more treatment-related pneumonia, but most of them can be relieved after symptomatic treatment. This treatment model deserves to be explored in prospective clinical trials.

Residual ctDNA Detection Predicts Benefit From Definitive Chemoradiotherapy and Immune Checkpoint Inhibitors in Locally Advanced NSCLC

PURPOSE/OBJECTIVE(S)

Therapeutic efficacy differs across unresectable locally advanced non-small cell lung cancer (LA-NSCLC) patients receiving definitive chemoradiotherapy (CRT), and the dynamic change in circulating tumor DNA (ctDNA) is closely associated with clinical outcomes. However, evidence for the predictive effect of ctDNA in LA-NSCLC patients with CRT and immunotherapy, the current standard of care, remains limited. It is unclear whether residual ctDNA after definitive CRT can guide clinical decisions on further use of immune checkpoint inhibitors (ICIs) consolidation.

MATERIALS/METHODS

We prospectively included 73 patients with unresectable stage II-III NSCLC. All patients received definitive concurrent or sequential CRT, with the prescribed dose of 60 Gy and ≥2 cycles of platinum-based chemotherapy. Thirty-seven (50.7%) patients further underwent ICIs therapy (18 durvalumab, 9 pembrolizumab, 10 others). Peripheral blood samples were collected from all patients before any treatment (baseline), 1 month after CRT (post-CRT), and at the time of progression. All plasma specimens were analyzed with next-generation sequencing panel of 474 cancer-related genes. Plasma samples with ≥1 variant detected were defined as detectable ctDNA. The primary endpoint was progression-free survival (PFS).

RESULTS

After the median follow-up of 25.4 months, median overall survival (OS) was not reached (NR), and median PFS was 16.7 months (95% CI, 12.4-26.6) for all patients. Compared with baseline, ctDNA abundance significantly decreased after definitive CRT (P<0.001) but relatively increased at progression (P = 0.051). Patients treated with CRT plus ICIs exhibited significantly longer OS (median, NR vs 22.1 months [95% CI, 16.7-NR]; P = 0.002) and PFS (median, 24.8 months [95% CI, 16.1-NR] vs 11.4 months [95% CI, 6.5-NR]; P = 0.016) than those with CRT alone. Post-CRT residual ctDNA was associated with significantly poorer OS (median, 18.3 months [95% CI, 14.8-NR] vs NR; P = 0.002) and PFS (median, 6.5 months [95% CI, 5.6-NR] vs 24.8 months [95% CI, 18.8-NR]; P<0.001), whereas baseline ctDNA predicted neither OS (P = 0.310) nor PFS (P = 0.570). For patients with post-CRT detectable ctDNA, further ICIs therapy brought significant benefit in both OS (median, NR vs 14.8 months [95% CI, 12.0-NR]; P = 0.012) and PFS (median, 16.1 months [95% CI, 5.8-NR] vs 6.2 months [95% CI, 4.2-NR]; P = 0.043). However, in patients with post-CRT ctDNA clearance, there was no significant difference in OS (P = 0.080) or PFS (P = 0.151) between patient with and without ICIs, which suggested less clinical benefit.

CONCLUSION

Post-CRT residual ctDNA predicted worse survival in LA-NSCLC, but indicated more benefit from further ICIs therapy and thereby could facilitate personalization of consolidation immunotherapy. Further prospected studies with large sample size are warranted to validated these findings.

Distribution Pattern of Metastatic Lymph Nodes in 870 Cases of Nasopharyngeal Carcinoma: A Clue for Individualized Elective Prophylactic Neck Irradiation

PURPOSE/OBJECTIVE(S)

We aimed to explore a potential individualized elective prophylactic neck irradiation (iEPNI) to optimize the current strategy by investigating the distribution of metastatic lymph nodes (LNs) in nasopharyngeal carcinoma (NPC).

MATERIALS/METHODS

Magnetic resonance imaging (MRI) and clinical data of 870 non-distant metastatic NPC patients admitted to the Hunan Cancer Hospital between January 2019 and December 2019 were reviewed. All patients were staged using the 8th TNM staging system, and the LNs location was assigned based on the 2013 guidelines. According to the distribution patterns of the LNs in NPC, the intra-regional lymphatic drainage levels were categorized into the following three stations: Station 1st of level VIIa and II; Station 2nd of level III and Va; and Station 3rd of level IV, Vb, and Vc. Other levels were defined as extra-regional areas.

RESULTS

The incidence of LNs metastasis was 822/870 (94.5%), including 198 cases of unilateral metastasis and 624 cases of bilateral metastasis. Among the 870 patients, the most frequently involved intra-regional lymphatic drainage was level IIb (87.1%), followed by level VIIa (80.0%), IIa (61.8%), Va (30.6%), IV (21.4%), Vb (8.9%), and Vc (1.1%). In the extra-regional areas, the detailed LNs distribution was: level Ia (0.2%), level Ib (7.7%), level VI (0.1%), level VIIb (5.6%), level VIII (5.5%), level IX (0.3%), and level X (0.2%). The rates of LNs metastasis in Station 1st, Station 2nd, and Station 3rd were 820/870 (94.3%), 532/870 (61.1%), and 199/870 (22.9%), respectively. Only 4 patients were considered to be skipping metastasis among the three stations (4/870, 0.5%). Additionally, in 203 patients with unilateral Station 1st LNs metastasis, there were 86 (42.4%) and 37 (18.2%) patients with ipsilateral Station 2nd and Station 3rd metastasis, respectively, and 3 (1.5%) and 1 (0.5%) patients with contralateral Station 2nd and Station 3rd LNs metastasis, respectively.

CONCLUSION

LNs spread from Station 1st to Station 3rd successively with rare skipping metastasis. A potential iEPNI strategy of prophylactical neck irradiation to the ipsilateral latter node-negative station might be feasible, which is detailed as follows: irradiation to Station 1st in patients with no LNs metastasis, irradiation to Station 2nd in patients with only Station 1st metastasis, and irradiation to Station 3rd in patients with Station 2nd metastasis but without Station 3rd metastasis. Further prospective investigations are expected to validate the strategy.

Mass spectrometry-based metabolic profiling for identification of biomarkers related to footpad dermatitis in ducks

1. A new assessment method for duck footpad dermatitis (FPD) evaluation was developed, combining visual and histological characters using the images and sections of 400 ducks' feet at 340 d of age. All ducks were graded as G0 (healthy), G1 (mild), G2 (moderate) and G3 (severe) according to the degree of FPD.2. To reveal the potential biomarkers in serum related to duck FPD, non-targeted metabolomics and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were used to explore differential metabolites in each group.3. There were 57, 91 and 210 annotated differential metabolites in groups G1, G2 and G3 compared with G0, which meant that the severity of FPD increased in line with the number of metabolites. Four metabolites, L-phenylalanine, L-arginine, L-leucine and L-lysine, were considered potential biomarkers related to FPD.4. KEGG enrichment analysis showed that the FPD was mainly involved in glycolysis, the tricarboxylic acid (TCA) cycle, the pentose phosphate pathway and amino acid metabolism. These are related to production metabolism and can affect the physiological activities of ducks, which might explain the decrease in production performance.

Doxorubicin Enhances the Abscopal Effect Depending on Tumor Cell Mitochondrial DNA and cGAS/STING

PURPOSE/OBJECTIVE(S)

Localized radiotherapy (RT) can cause a T cell-mediated abscopal effect on non-irradiated tumor lesions, especially in combination with immune checkpoint blockade (ICB). However, this effect is still clinically rare and improvements are highly desirable. We investigated whether triple combination with a low dose of clinically approved liposomal doxorubicin (Doxil) could augment abscopal responses compared with RT+ICB, Doxil+ICB, or RT+Doxil.

MATERIALS/METHODS

We used Doxil in combination with RT and αPD1 in two tumor models (B16-CD133 melanoma and MC38 colon carcinoma) with mice bearing two tumors, only one of which was irradiated.

RESULTS

Triple therapy with RT, αPD1, and single low-dose Doxil strongly enhanced the RT-induced abscopal effect compared to all double and single treatments in both tumor models (p < 0.05, n = 5-10 mice/group). Complete cures of non-irradiated tumors were mainly observed in triple-treated mice. Triple therapy induced more cross-presenting dendritic cells (DCs) and tumor-specific CD8 T cells than RT/αPD1 and Doxil/αPD1 (p < 0.05, n = 5 mice/group), particularly in non-irradiated tumors. CD8 T cell depletion or implanting STING-deficient tumor cells abolished the abscopal effect. By using inhibitors and knockout cells, we show that doxorubicin/Doxil-induced IFNβ1 markedly depended on the cGAS/STING pathway (p < 0.05) which drives antitumor CD8 T cell responses through cross-presenting DCs. In mitochondrial DNA (mtDNA)-depleted tumor cells, doxorubicin/Doxil induced less IFNβ1 (p < 0.05), the related T cell-recruiting chemokine CXCL10 (p < 0.0001), and ATP (p < 0.0001); coincubation with mtDNA-depleted tumor cells strongly reduced IFNβ1 (p < 0.01) secretion by DCs. Implantation of mtDNA-depleted tumor cells, particularly at the non-irradiated site, substantially diminished the Doxil-enhanced abscopal effect and tumor infiltration by tumor-specific CD8 T cells (p < 0.05).

CONCLUSION

Single low-dose Doxil can substantially enhance the RT-induced abscopal effect, with a strong increase in cross-presenting DCs and CD8 tumor-specific T cells particularly in abscopal tumors compared with RT/αPD1 and Doxil/αPD1. The mtDNA/cGAS/STING/IFN-I axis is important for the immunogenic doxorubicin effects. Our findings may be helpful for the planning of clinical radiochemoimmunotherapy trials in (oligo)metastatic patients.