Using Radiation Therapy to Prime and Propagate an Anti-tumor Immune Response Against Brain Tumors

Safety and Efficacy of Radiotherapy Combined With Sintilimab in Advanced NSCLC Patients Who Progressed on First or Second Line Therapy: A Prospective, Multiple Center, and Single-Arm Study

BACKGROUND

This study explored the safety and efficacy of combining radiotherapy with sintilimab in non-small cell lung cancer (NSCLC) patients who have progressed after first or second-line therapy.

METHODS

In this multicenter, single-arm trial, patients with NSCLC who had progressed after first or second-line therapy were enrolled. Participants received hypofractionated stereotactic body radiotherapy (SBRT) (requiring a single-site biological dose of more than 30 Gy or planned to reach 30 Gy) followed by sintilimab every 3 weeks until disease progression or unacceptable toxicity occurred.

RESULTS

From March 1, 2019, to July 27, 2023, 14 patients were enrolled across two centers. The cohort included 64.3% males and 35.7% females, with a median age of 67 years (range 57-73 years). All participants completed radiation therapy and received at least one cycle of sintilimab. The overall response rate (ORR) was 21.4% (3/14) and the disease control rate (DCR) was 71.4% (10/14). The absent radiation response (ARR) was 14.3% (2/14). The median PFS was 4.17 months (95% CI: 1.15-8.69 months), with a 6-month PFS rate of 42.9%. The median OS was 16.17 months (95% CI: 11.69-20.64 months). Overall, 10 patients (71.4%) experienced at least one treatment-emergent adverse event (TEAE). Grade 3 adverse events included one case each of immune-related myocarditis, thrombocytopenia, and checkpoint inhibitor pneumonitis (CIP). Four patients (28.6%) had immune-related adverse events (irAEs) including skin rash and pruritus (2/14, grade 1), immune-related myocarditis (1/14, grade 3), and CIP (1/14, grade 3).

CONCLUSIONS

Radiotherapy combined with sintilimab for NSCLC patients who progressed after first-or second-line therapy showed promising efficacy outcomes.

Radiotherapy combined with immunotherapy: the dawn of cancer treatment

Radiotherapy (RT) is delivered for purposes of local control, but can also exert systemic effect on remote and non-irradiated tumor deposits, which is called abscopal effect. The view of RT as a simple local treatment has dramatically changed in recent years, and it is now widely accepted that RT can provoke a systemic immune response which gives a strong rationale for the combination of RT and immunotherapy (iRT). Nevertheless, several points remain to be addressed such as the interaction of RT and immune system, the identification of the best schedules for combination with immunotherapy (IO), the expansion of abscopal effect and the mechanism to amplify iRT. To answer these crucial questions, we roundly summarize underlying rationale showing the whole immune landscape in RT and clinical trials to attempt to identify the best schedules of iRT. In consideration of the rarity of abscopal effect, we propose that the occurrence of abscopal effect induced by radiation can be promoted to 100% in view of molecular and genetic level. Furthermore, the “radscopal effect” which refers to using low-dose radiation to reprogram the tumor microenvironment may amplify the occurrence of abscopal effect and overcome the resistance of iRT. Taken together, RT could be regarded as a trigger of systemic antitumor immune response, and with the help of IO can be used as a radical and systemic treatment and be added into current standard regimen of patients with metastatic cancer.

Differential molecular response in mice and human thymocytes exposed to a combined-dose radiation regime

In the quest for more effective radiation treatment options that can improve both cell killing and healthy tissue recovery, combined radiation therapies are lately in the spotlight. The molecular response to a combined radiation regime where exposure to an initial low dose (priming dose) of ionizing radiation is administered prior to a subsequent higher radiation dose (challenging dose) after a given latency period have not been thoroughly explored. In this study we report on the differential response to either a combined radiation regime or a single challenging dose both in mouse in vivo and in human ex vivo thymocytes. A differential cell cycle response including an increase in the subG1 fraction on cells exposed to the combined regime was found. Together with this, a differential protein expression profiling in several pathways including cell cycle control (ATM, TP53, p21^CDKN1A), damage response (γH2AX) and cell death pathways such as apoptosis (Cleaved Caspase-3, PARP1, PKCδ and H3T45ph) and ferroptosis (xCT/GPX4) was demonstrated. This study also shows the epigenetic regulation following a combined regime that alters the expression of chromatin modifiers such as DNMTs (DNMT1, DNMT2, DNMT3A, DNMT3B, DNMT3L) and glycosylases (MBD4 and TDG). Furthermore, a study of the underlying cellular status six hours after the priming dose alone showed evidence of retained modifications on the molecular and epigenetic pathways suggesting that the priming dose infers a “radiation awareness phenotype” to the thymocytes, a sensitization key to the differential response seen after the second hit with the challenging dose. These data suggest that combined-dose radiation regimes could be more efficient at making cells respond to radiation and it would be interesting to further investigate how can these schemes be of use to potential new radiation therapies.