Expression of PD-L1 in melanoma in-transit metastases (ITMs) may be associated with a complete response to diphencyprone (DPCP), suggests a study published in the Annals of Surgical Oncology.
The exploratory study investigated the utility of BRAF mutation status, CD8, PD-1, PD-L1 and tumour-infiltrating lymphocytes (TILs) distribution as biomarkers for response of ITMs to topical immunotherapy.
The ITM deposits of 40 patients treated at Norfolk and Norwich University Hospital between 2008 and 2016.
After 12 weeks, 10 patients (25%) had a complete response, 12 patients (30%) had a partial response and 18 patients (45%) had no response. No significant association was found between any individual biomarker and response to DPCP or overall survival.
The BRAF mutation rate was 25 per cent (10/40). All patients with a complete response had BRAF wild-type tumour.
Peritumoral CD8+ T-cells were associated with complete response (P=.041). Both CD8+ and PD-1 expressions were highly correlated (P<.0001), and the highest levels of PD-1 expression were detected at the peritumoral interface (P=.0004). Only two cases were PD-L1-positive, and both had a complete response to DPCP (P=.043).
The results suggest patients with BRAF wild-type tumour are more likely to experience a complete response to DPCP, and peritumoral TILs and PD-1 expressions may predict a better response to DPCP.
Expression of PD-L1 may be associated with a complete response to DPCP. A larger prospective study is required.
