Prospective evaluation of oxygen saturation endoscopic imaging for radiotherapy response in head and neck cancer

We developed an endoscopic imaging technology, oxygen saturation imaging (OS imaging), to assess real-time tissue oxygenation levels. However, its clinical impact remains unclear. This prospective observational study evaluated the association between pretreatment tumor oxygen saturation (StO₂) quantified by OS imaging and the outcomes of patients with head and neck squamous cell carcinoma (HNSCC) receiving radiotherapy (RT).

The primary endpoint was the association between pretreatment tumor StO₂ and complete response rate at 8 weeks after RT completion. Secondary endpoints were the impact of StO₂ on 1-year overall survival, progression-free survival, and local failure rates.

Of 50 patients with HNSCC enrolled from 2019 to 2022, 42 who underwent RT and OS imaging are analyzed. Of those, 41 received concurrent platinum-based chemotherapy. Median pretreatment StO₂ is significantly lower in tumor tissue than in normal mucosa (61% vs. 66%, respectively). Complete response rates at 8 weeks after RT are not significantly different between the hypoxia (StO₂ ≤ 61%, n = 22) and non-hypoxia (StO₂ > 61%, n = 20) groups (86% vs. 100%, respectively). After a median follow-up of 36 (range: 9-53) months, the hypoxia group has significantly worse 1-year overall survival (91% vs. 100%), progression-free survival (77% vs. 95%), and local failure (18% vs. 5%) rates than the non-hypoxia group.

Despite not meeting the primary endpoint, our findings suggest that pretreatment tumor StO₂ is correlated with 1-year outcomes after RT, and OS imaging may be useful for identifying RT-resistant hypoxic tumors in HNSCC.