Abstract 870P
Background
PD-L1 and VISTA are thought to play a role in escape from the immune system, tumor progression and treatment response in tumoral tissue. It has been suggested that radiotherapy may increase the expression levels of immune biomarkers. The current study aimed to evaluate the effects of radiotherapy (RT) and chemoradiotherapy (CRT) on PD-L1 and VISTA expression in head and neck cancers.
Methods
PD-L1 and VISTA expressions were compared between the primary biopsy at the time of diagnosis and refractory tissue biopsies of patients who received definitive CRT or recurrent tissue biopsies of patients who received surgery with adjuvant RT/CRT. Expression of PD-L1 was evaluated by tumor proportion score (TPS) and VISTA expression was evaluated by Immune Cell Score.
Results
A total of 47 patients were included. PD-L1 and VISTA expression levels did not change with RT/CRT in head and neck cancers, respectively (p=0,542 and p=0,425). The PD-L1 and VISTA expression levels of first and second biopsies are shown in the table. Positive correlation was found between PD-L1 and VISTA expression (p<0,001; r=0,560). PD-L1 and VISTA expression of first biospy was found to be significantly higher in clinical lymph node-positive patients compared to node-negative patients (PD-L1 p=0,038; VISTA p=0,018). The overall survival of patients with VISTA expression >1% on the first biopsy was found to be significantly shorter than those with <1% [52,4 months (95% CI, 16,2-88,5 months) vs 110,1 months (95% CI, 23,1-145 months), respectively p= 0.048]. Table: 870P
PD-L1 and VISTA expression levels of first and second biopsies
| Localization | First Biopsy PD-L1 TPS | Second Biopsy PD-L1 TPS | P value | |||||||
| 0 | 1 | 2 | 3 | 0 | 1 | 2 | 3 | |||
| Larynx | n | 8 | 7 | 8 | 3 | 9 | 5 | 8 | 4 | 0,873 |
| % | 30,8 | 26,9 | 30,8 | 11,5 | 34,6 | 19,2 | 30,8 | 15,4 | ||
| Oral Cavity | n | 3 | 6 | 4 | 6 | 4 | 4 | 4 | 7 | 0,760 |
| % | 15,8 | 31,6 | 21,1 | 31,6 | 21,1 | 21,1 | 21,1 | 36,8 | ||
| Hypopharynx | n | 2 | 1 | 1 | 0,18 | |||||
| % | 100 | 50 | 50 | |||||||
| First Biopsy VISTA IC | Second Biopsy VISTA IC | P value | ||||||||
| 0 | 1 | 2 | 3 | 0 | 1 | 2 | 3 | |||
| Larynx | n | 11 | 6 | 2 | 7 | 11 | 4 | 2 | 9 | 0,496 |
| % | 42,3 | 23,1 | 7,7 | 26,9 | 42,3 | 11,4 | 7,7 | 34,6 | ||
| Oral Cavity | n | 4 | 1 | 6 | 8 | 4 | 2 | 5 | 8 | 1 |
| % | 21,1 | 5,3 | 31,6 | 42,1 | 21,1 | 10,5 | 26,3 | 42,1 | ||
| Hypopharynx | n | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 0,655 |
| % | 50 | 50 | 0 | 0 | 50 | 0 | 0 | 50 |
Conclusions
It was shown that PD-L1 and VISTA expression did not change with radiotherapy or chemoradiotherapy. Further studies are needed to evaluate the relationship between PD-L1 and VISTA expression with RT and CRT.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
T.C. Sağlık Bakanlığı Bilimsel Araştırma Platformu.
Disclosure
All authors have declared no conflicts of interest.