Developing strategies to inflame tumors is critical for increasing response to immunotherapy. Here, we report that low-dose radiotherapy (LDRT) of murine tumors promotes T-cell infiltration and enables responsiveness to combinatorial immunotherapy in an IFN-dependent manner. Treatment efficacy relied upon mobilizing both adaptive and innate immunity and depended on both cytotoxic CD4+ and CD8+ T cells. LDRT elicited predominantly CD4+ cells with features of exhausted effector cytotoxic cells, with a subset expressing NKG2D and exhibiting proliferative capacity, as well as a unique subset of activated dendritic cells expressing the NKG2D ligand RAE1. We translated these findings to a phase I clinical trial administering LDRT, low-dose cyclophosphamide, and immune checkpoint blockade to patients with immune-desert tumors. In responsive patients, the combinatorial treatment triggered T-cell infiltration, predominantly of CD4+ cells with Th1 signatures. Our data support the rational combination of LDRT with immunotherapy for effectively treating low T cell–infiltrated tumors. Significance: Low-dose radiation reprogrammed the tumor microenvironment of tumors with scarce immune infiltration and together with immunotherapy induced simultaneous mobilization of innate and adaptive immunity, predominantly CD4+ effector T cells, to achieve tumor control dependent on NKG2D. The combination induced important responses in patients with metastatic immune-cold tumors. This article is highlighted in the In This Issue feature, p. 1

Preclinical data have shown that proton pump inhibitors (PPI) can modulate the microbiome, and single-arm studies suggested that antibiotics (ATB) may decrease the efficacy of immune checkpoint inhibitors (ICI), but randomized controlled trial data are lacking. This pooled analysis evaluated the effect of ATB and PPI on outcome in patients randomized between ICI and chemotherapy. This retrospective analysis used pooled data from the phase II POPLAR (NCT01903993) and phase III OAK (NCT02008227) trials, which included 1512 patients with previously treated non-small-cell lung cancer (NSCLC) randomly assigned to receive atezolizumab (n = 757) or docetaxel (n = 755). The main objective of this analysis was to assess the impact of ATB and PPI use on overall survival (OS) and progression-free survival (PFS). A total of 169 (22.3%) patients in the atezolizumab group and 202 (26.8%) in the docetaxel group received ATB, and 234 (30.9%) and 260 (34.4%), respectively, received PPI. Multivariate analysis in all patients revealed that ATB were associated with shorter OS [hazard ratio (HR) 1.20, 95% confidence interval (CI) 1.04-1.39], as was PPI (HR 1.26, 95% CI 1.10-1.44). Within the atezolizumab population, OS was significantly shorter in patients who received ATB (8.5 versus 14.1 months, HR 1.32, 95% CI 1.06-1.63, P = 0.01) or PPI (9.6 versus 14.5 months, HR 1.45, 95% CI 1.20-1.75, P = 0.0001). PPI use was associated with shorter PFS in the atezolizumab population (1.9 versus 2.8 months, HR 1.30, 95% CI 1.10-1.53, P = 0.001). There was no association between ATB and PPI use and PFS or OS within the docetaxel population. In this unplanned analysis from two randomized trials, data suggest that ATB or PPI use in patients with metastatic NSCLC is associated with poor outcome and may influence the efficacy of ICI.

Current efforts combining immunotherapy and radiation have focused on high-dose radiation delivered to few tumor lesions, aiming to generate diffuse abscopal effects; however, these effects are uncommon in patients. Three recent studies in mouse tumor models and human cancer patients show that low-dose radiation (LDRT) delivered to all tumor lesions effectively mobilizes innate and adaptive immunity and synergizes with immunotherapy. These new findings suggest LDRT's potential as an immune amplifier capable of reprogramming the tumor microenvironment, instigating inflammation, and sensitizing 'cold' tumors to immune checkpoint blockade responsiveness.

FLASH radiation therapy (RT) is a promising new paradigm in radiation oncology. However, a major question that remains is the robustness and reproducibility of the FLASH effect when different irradiators are used on animals or patients with different genetic backgrounds, diets, and microbiomes, all of which can influence the effects of radiation on normal tissues. To address questions of rigor and reproducibility across different centers, we analyzed independent data sets from The University of Texas MD Anderson Cancer Center and from Lausanne University (CHUV). Both centers investigated acute effects after total abdominal irradiation to C57BL/6 animals delivered by the FLASH Mobetron system. The two centers used similar beam parameters but otherwise conducted the studies independently. The FLASH-enabled animal survival and intestinal crypt regeneration after irradiation were comparable between the two centers. These findings, together with previously published data using a converted linear accelerator, show that a robust and reproducible FLASH effect can be induced as long as the same set of irradiation parameters are used.

To compare the prognostic value of different anatomical and functional metabolic parameters determined using [18F]FDG-PET/CT with other clinical and pathological prognostic parameters in cervical cancer (CC). Thirty-eight patients treated with standard curative doses of chemo-radiotherapy (CRT) underwent pre- and post-therapy [18F]FDG-PET/CT. [18F]FDG-PET/CT parameters including mean tumor standardized uptake values (SUV), metabolic tumor volume (MTV) and tumor glycolytic volume (TGV) were measured before the start of CRT. The post-treatment tumor metabolic response was evaluated. These parameters were compared to other clinical prognostic factors. Survival curves were estimated by using the Kaplan-Meier method. Cox regression analysis was performed to determine the independent contribution of each prognostic factor. After 37 months of median follow-up (range, 12–106), overall survival (OS) was 71 % [95 % confidence interval (CI), 54–88], disease-free survival (DFS) 61 % [95 % CI, 44–78] and loco-regional control (LRC) 76 % [95 % CI, 62–90]. In univariate analyses the [18F]FDG-PET/CT parameters unfavorably influencing OS, DFS and LRC were pre-treatment TGV-cutoff ≥562 (37 vs. 76 %, p = 0.01; 33 vs. 70 %, p = 0.002; and 55 vs. 83 %, p = 0.005, respectively), mean pre-treatment tumor SUV cutoff ≥5 (57 vs. 86 %, p = 0.03; 36 vs. 88 %, p = 0.004; 65 vs. 88 %, p = 0.04, respectively) and a partial tumor metabolic response after treatment (9 vs. 29 %, p = 0.0008; 0 vs. 83 %, p < 0.0001; 22 vs. 96 %, p < 0.0001, respectively). After multivariate analyses a partial tumor metabolic response after treatment remained as an independent prognostic factor unfavorably influencing DFS and LRC (RR 1:7.7, p < 0.0001, and RR 1:22.6, p = 0.0003, respectively) while the pre-treatment TGV-cutoff ≥562 negatively influenced OS and DFS (RR 1:2, p = 0.03, and RR 1:2.75, p = 0.05). Parameters capturing the pre-treatment glycolytic volume and metabolic activity of [18F]FDG–positive disease provide important prognostic information in patients with CC treated with CRT. The post-therapy [18F]FDG-PET/CT uptake (partial tumor metabolic response) is predictive of disease outcome.