Dynamic Responses of Circulating T Cells After Stereotactic Body Radiation Therapy for Bone Metastasis in Patients With Breast Cancer

Efficacy and toxicity of stereotactic radiotherapy combined with third-generation EGFR-TKIs and immunotherapy in patients with brain metastases from non-small cell lung cancer

OBJECTIVE

Stereotactic radiotherapy (SRT) is fast gaining attention as a preferred treatment alternative for patients with brain metastases (BM) from non-small cell lung cancer (NSCLC). In this study, we examined the efficacy and safety of combining SRT with immunotherapy (IT) and targeted therapy (TT), either separately or concurrently with the aim to formulate an optimal therapeutic regimen for patients with NSCLC BM.

METHODS

The combination therapy were comprised of IT and TT agents. For the SRT-combined TT agents group, TT was limited to third-generation EGFR-TKIs. The administration of these drugs within 30 days before or after SRT was defined as combination therapy. The primary endpoint was 1-year progression-free survival (PFS), which was evaluated by a blinded independent review committee and categorized into local recurrence at the radiation site and the emergence of new distant intracranial metastases. Secondary endpoints included confirmed intracranial objective response rate (IORR) and intracranial disease control rate in the overall population. Post-treatment grading was performed according to CTCAE, and the levels of radiation necrosis were differentiated.

RESULTS

The 266 patients with NSCLC BM were categorized into the following four groups based on their treatment methods: SRT alone, SRT combined with IT, SRT combined with third-generation EGFR-TKIs, and SRT combined with both IT and TT. For the local radiation range, the 1‑year PFS of these four groups were 77.89% (P = 0.239), 88.75% (P = 0.266), 88.01% (P = 0.210), and 91.97% (P = 0.057), respectively. For new intracranial metastases outside of the radiotherapy site, the corresponding values were 63.96% (P = 0.039), 74.17% (P = 0.258), 88.70% (P = 0.024), and 87.81% (P = 0.015), respectively. By the end of the study period, the IORR increased from 32% with SRT alone to 46% in the IT group, 58% in the TT group, and 61% in the SRT combined with both the IT and TT groups. However, the group that received SRT in combination with IT and TT exhibited a higher occurrence rate of grade 3 adverse events, and a statistically significant difference was observed in grade 3 radiation necrosis.

CONCLUSION

For NSCLC BM, IT, TT, or both together with SRT increased the distant intracranial tumor control. Nonetheless, combining SRT with both IT and TT increased the occurrence rate of acute adverse events. Thus, while SRT provided good local control independently, the incidence of symptomatic RN was low.

TIGIT blockade increases efficacy of PD-1 blockade combined with radiation therapy in triple-negative breast cancer model

BACKGROUND AND PURPOSE

T-cell immunoreceptor with Ig and ITIM domains (TIGIT) suppresses functions of CD8+ T cells, and radiation therapy (RT) induces stimulation of regulatory T cells (Tregs), thereby limiting antitumor efficacy. This study aims to investigate the role of TIGIT in the immunosuppressive tumor environment and evaluate the potential of TIGIT blockade (αTIGIT) to enhance antitumor immune responses.

METHODS

We analyzed public transcriptomic data to identify the expression patterns of TIGIT on T cells in breast cancer and its prognostic impact. In addition, a murine TNBC model was utilized to evaluate the effects of αPD-1, local RT, and αTIGIT. T cells in tumors, tumor-draining lymph nodes (TdLNs), and the spleen were analyzed to assess the antitumor immune responses upon the treatments.

RESULTS

The analysis revealed that TIGIT is predominantly expressed on T cells within breast cancer, and the expression of TIGIT was associated with poor outcomes in TNBC patients. In the murine model, the combination of αPD-1 and RT increased TIGIT+CD226+CD8+ TILs, which are crucial for the efficacy of αTIGIT. Adding αTIGIT to αPD-1 and RT (αPD-1/RT) resulted in a synergistic antitumor effect, which was accompanied by increased infiltration of CD8+ TILs in both irradiated and nonirradiated tumors by the triple combination therapy compared to αPD-1/RT. The triple combination therapy also resulted in a less exhausted phenotype among CD8+ TILs and increased the proliferation of splenic CD8+ T cells. Moreover, αTIGIT significantly reduced Tregs in tumors, TdLNs, and the spleen when combined with αPD-1/RT.

CONCLUSION

αTIGIT exhibits synergistic effects when added to αPD-1/RT by increasing the infiltration and activation of CD8+ TILs while reducing Tregs. The study suggests that αTIGIT could be an effective strategy to enhance the antitumor efficacy of αPD-1 and RT in TNBC.

Modulation of CD8+ T Cell Responses by Radiotherapy-Current Evidence and Rationale for Combination with Immune Checkpoint Inhibitors

Radiotherapy for cancer has been known to affect the responses of immune cells, especially those of CD8+ T cells that play a pivotal role in anti-tumor immunity. Clinical success of immune checkpoint inhibitors led to an increasing interest in the ability of radiation to modulate CD8+ T cell responses. Recent studies that carefully analyzed CD8+ T cell responses following radiotherapy suggest the beneficial roles of radiotherapy on anti-tumor immunity. In addition, numerous clinical trials to evaluate the efficacy of combining radiotherapy with immune checkpoint inhibitors are currently undergoing. In this review, we summarize the current status of knowledge regarding the changes in CD8+ T cells following radiotherapy from various preclinical and clinical studies. Furthermore, key biological mechanisms that underlie such modulation, including both direct and indirect effects, are described. Lastly, we discuss the current evidence and essential considerations for harnessing radiotherapy as a combination partner for immune checkpoint inhibitors.