Abstract 3329
Background
Squamous cell carcinoma of the anal canal (SCCA) is a rare malignancy especially in Asia. It is widely known that SCCA is linked to prior infection with human papillomavirus (HPV) in western countries. However, it is unclear whether HPV is associated with SCCA in Japan. In addition, expression of PD-L1, potential predictive marker for anti-PD-1 antibody, and its prognostic impact on locoregional SCCA remain to be elucidated. The aim of this study is to examine expression rates and prognostic impact of p16 and PD-L1 in Japanese patients with SCCA.
Methods
34 patients with locoregional SCCA were treated by concurrent CRT at the Cancer Institute Hospital between 2007 and 2017. Among them, 28 patients whose biopsy specimens were available were enrolled. Radiation consisted of 45.0-59.4 Gy. Chemotherapy was given during radiation: 1000mg/m2 daily fluorouracil on day 1-4 and 29-32, and a single dose of mitomycin C 10mg/m2 administered on day 1 and 29. Data on relapse and death were obtained until March 2018. p16 positive was defined as p16 was stained on tumor nuclei. PD-L1 positive was also defined as PD-L1 was overexpressed on tumor membrane with more than 2+ score and the area was more than 5%.
Results
Of 28 patients, the median age was 59 (range 35-82) years. Male to female sex ratio was 1:6. 6 (21.4%) were clinically staged as I, 4 (14.3%) as II, 5 (17.9%) as IIIA, and 13 (46.4%) as IIIB. SCCA remained or recurred in 1 with cStage II, 1 with cStage IIIA and 7 with cStage IIIB. 3-year disease free survival (DFS) was 65.8% (95%CI, 44.3-80.6%), and 3-year overall survival (OS) was 79.2% (95%CI, 53.4-91.7%). Of 28 cases, 27 (96.4%) were positive for p16, and 6 (21.4%) were positive for PD-L1. In univariate analysis for DFS and OS, lymph node metastasis was significantly related to poor outcomes (DFS, p = 0.0289; OS, p < 0.0001). T factor (p < 0.0001) and tumor stage (p = 0.0035) significantly influenced OS. No significantly difference was found in terms of PD-L1 expression (DFS, p = 0.595; OS, p = 0.544).
Conclusions
High expression rate of p16 was observed in Japanese patients with locoregional SCCA. Lymph node metastasis, advanced T factor and tumor stage were negative prognostic factors for CRT, but no prognostic impact of PD-L1 was found.
Clinical trial identification
Legal entity responsible for the study
Ryo Takahashi.
Funding
Has not received any funding.
Editorial Acknowledgement
Disclosure
All authors have declared no conflicts of interest.