Introduction

Immune checkpoint inhibitors (CPI) have revolutionised cancer outcomes, but frequently trigger immune related adverse effects, including life-threatening colitis. Tissue resident memory (TRM) T cells are key cells involved in the pathogenesis of CPI-induced colitis (CPI-C), but the mediators they produce to facilitate disease are poorly defined.

Aims & Methods

We utilised our previously published in vivo pre-clinical model of CPI-C, which occurs when mice are given combination anti-CTLA4 and anti-PD1 and a proinflammatory microbiota mix, to define the role of the Granzyme A/B cytotoxicity pathway in disease. Disease was induced in wildtype (WT) and Granzyme A/B double knockout (GzmAB^-/-) mice. Clinical outcomes (colon and spleen mass, histology and infiltrating neutrophils) from these mice were assessed to measure the severity in disease. T cell populations were also analysed using flow cytometry.

Results

GzmAB^-/-mice showed a significant reduction in disease features compared to WT mice, with reduced colon mass, reduction in infiltrating neutrophils and fewer inflammatory monocytes. Flow cytometry analysis of the T cell compartment revealed a significant reduction in both bulk CD4 and CD8 T cells and also CD4 and CD8 tissue resident memory T cells in both the cLP and IEL in GzmAB^-/-mice treated with CPI-C in comparison to WT mice treated with CPI-C. GzmAB^-/-mice treated with CPI-C also had a reduction in IFNγ and TNFα production from both CD4 T cells and CD8 T cells. These data highlight the importance of granzymes in inducing the disease phenotype in CPI-C. In order to investigate whether CD4 T cells or CD8 T cells were more important, we depleted these cells in vivo in WT mice treated with CPI-C at both 1 and 3 weeks. Here, we found that WT mice with CD4 T cells depleted got significantly worse disease with colon masses increasing and there being increased infiltrating neutrophils. There was an increase in cytotoxic cytokines being produced by CD8 T cells when CD4 T cells were depleted. However, when CD8 T cells were depleted, there was no change in any clinical features or cytokine production from CD4 T cells.

Conclusion

Using GzmAB^-/- mice we have demonstrated that CPI-colitis is at least partially dependent on the granzyme cytotoxicity pathway. Targeting the cells that produce granzyme in the colon of patients with CPI-colitis might offer an attractive novel treatment option for patients with CPI-colitis.

References

1. Lo, J.W., Cozzetto, D., Alexander, J.L. et al. Immune checkpoint inhibitor-induced colitis is mediated by polyfunctional lymphocytes and is dependent on an IL23/IFNγ axis. Nat Commun 14, 6719 (2023). https://doi.org/10.1038/s41467-023-41798-2
2. Luoma A. M. et al. Molecular pathways of colon inflammation induced by cancer immunotherapy. Cell 182, 655-671.e22 (2020).
3. Sasson, S. C. et al. Interferon-gamma-producing CD8(+) tissue resident memory T cells are a targetable hallmark of immune checkpoint inhibitor-colitis. Gastroenterology 161, 1229–1244.e1229 (2021).
4. Gupta T, Antanaviciute A, Hyun-Jung Lee C, et al. Tracking in situ checkpoint inhibitor-bound target T cells in patients with checkpoint-induced colitis. Cancer Cell. 2024 May 13;42(5):797-814.e15. doi: 10.1016/j.ccell.2024.04.010. PMID: 38744246.

Introduction

There has been a rise in the uptake of endoscopic submucosal dissection (ESD) for superficial pharyngeal cancers, including in patients with previous history of radiotherapy, whether as salvage treatment of residual lesions or for metachronous lesions inside the irradiated field. Previous studies have demonstrated the safety and effectiveness of ESD for pharyngeal cancers¹. However, the safety and the effectiveness of pharyngeal ESD in cases with previous history of radiotherapy is not clear^2,3.

Aims & Methods

Our aim was to investigate whether radiotherapy affects outcomes after pharyngeal ESD. We conducted a retrospective cohort study of consecutive patients who underwent pharyngeal ESD between December 2016 and February 2025 at our institution. All the cases were managed together with otolaryngologists, including the daily assessment of the wound and swallowing function with the transnasal flexible laryngoscope in order to decide the timing of the re-initiation of food after ESD. The ESD itself, as well as the short and long-term outcomes were compared between the patients with or without history of radiotherapy.

Results

There were 22 cases (25 lesions) of ESD performed with previous history of radiotherapy and 32 cases (33 lesions) without prior radiotherapy. The median age was 71 (range 55-85) and 98.3% were men. Radiotherapy dose ranged from 54 to 70 Gy. There were no significant differences in the baseline characteristics between the groups of patients with or without prior radiotherapy including the age, sex, or the proportion of patients with previous history of pharyngeal ESD. En-bloc resection was achieved in all cases. ESD in the pharynx post-radiotherapy was associated with an increased percentage of cases with severe fibrosis (41% vs. 14% p<0.05), and the speed of dissection was slower (33.4mm²/min vs. 45.8mm²/min p=0.03), but there were no significant differences in the short-term outcomes between the groups of patients with or without prior radiotherapy in terms of of bleeding (0% vs. 3%), aspiration pneumonia (8% vs. 9%), the duration to the resumption of food (median 4 vs. 5 days) or hospital stay (median 9 vs. 9 days). During a median follow-up period of 906.5 days (range 22-3021 days), the 3-year overall survival rate was lower in patients with previous history of radiotherapy compared to patients without prior radiotherapy (55.1% vs. 100%, p=0.000177). Of the patients with previous history of radiotherapy, one patient died from metastatic recurrence of pharyngeal cancer, but the other five deaths were not directly associated with pharyngeal cancer (1=acute cardiac death, 1=unknown cause but unrelated to pharyngeal cancer, 1=lung cancer, 1=mantle cell lymphoma, 1=sinonasal neuroendocrine cancer) . There were no significant differences in the 3-year recurrence-free survival and the 3-year disease-related survival rates between the patients with and without prior history of radiotherapy (92.9% vs. 91.7% and 92.3% vs. 100%, respectively).

Conclusion

Previous history of radiotherapy increases the risk of severe fibrosis during ESD and is associated with slower speed of dissection, but does not compromise the safety or the swallowing function. In the long-term, ESD is an effective method for the treatment of superficial pharyngeal cancers, including in patients with previous history of radiotherapy. Furthermore, ESD is a minimally-invasive and surgery-sparing treatment option, which may be all the more important in patients with prior history of radiotherapy, given the worse prognosis from illnesses other than pharyngeal cancers in this group of patients.

References

1. Watanabe A, Taniguchi M, Kimura Y, Hosokawa M, Ito S, Tsukamoto S, Sasaki S. Synopsis of transoral endoscopic laryngopharyngeal surgery for superficial pharyngeal cancers. Head Neck. 2017 Sep;39(9):1779-1787.
2. Yoshida T, Shimizu Y, Ono S, Oridate N, Kato M, Asaka M. Successful salvage endoscopic mucosal resection for residual superficial hypopharyngeal carcinoma after chemoradiotherapy, with long-term survival. Endoscopy. 2009 Jun;41(6):568-9.
3. Satake H, Yano T, Yoda Y, Fujii S, Zenda S, Tomioka T, Shinozaki T, Miyazaki M, Kaneko K, Hayashi R. Feasibility of salvage endoscopic resection for patients with locoregional failure after definitive radiotherapy for pharyngeal cancer. Endosc Int Open. 2015 Aug;3(4):E274-80.