Abstract A80: Acral melanoma in the Hawaiian Islands: Exploring immunologic PDL-1 signature in the minority population

Abstract

Abstract Background: While acral melanoma (AM) is the least common subtype amongst the principal histologic variants of cutaneous melanoma (CM), darker-skinned individuals such as Asians, Pacific Islanders, and African Americans are more frequently affected. Asian/Pacific Islanders with AM in particular, exhibit the worst survival amongst all ethnic groups. Recent studies have profiled the importance of programmed cell death ligand 1 (PDL-1) in the therapeutic armamentarium for melanoma. However, the pathologic features and immunologic characteristics of AM evaluating PDL-1 in the minority population have not been thoroughly analyzed. Methods: IRB approval was obtained for this retrospective analysis. From 2004 to 2011, 17 Asian/Pacific Islander patients histologically confirmed to have invasive AM were evaluated at a tertiary institution. Data including age, gender, tumor location, Breslow thickness, ulceration, tumor infiltration lymphocyte (TIL) status, and mitoses per mm squared were compiled. Immunohistochemistry was performed targeting the PDL-1 (CD274) antigen on primary tumor cells in formalin-fixed paraffin-embedded archived biospecimens. PDL-1 expression was graded on a scale from 0 (absent) to 2 (high). Results: Our findings demonstrated that PDL-1 expression was low in this series (3/17; 17.6%). All AM patients had a non-brisk TIL response. A significant proportion of our entire cohort (8/17; 47.1%) exhibited thick primary lesions (>4.0 mm) with a high propensity for ulceration (8/17; 47.1%). Demographics of the Asian/Pacific Islander cohort included mean age of 63.8 years (range 40-86) and male gender (9/17; 53 %). Tumor location primarily involved the foot (11/17; 64.7%); median Breslow thickness was 3.98 mm (range 0.96-11.0), and mean mitoses per mm squared was 3.9 (range 0-10). Conclusion: Asian/Pacific Islanders with AM were found to have a low frequency of PDL-1 expression. The lack of a brisk lymphocytic host response in AM may provide insight into its mechanism of tumorigenesis. This is the first study to our knowledge that has examined the immunologic signature of TIL and PDL-1 status in a multi-ethnic population of AM patients. This is compelling data that may be applied to patient selection in future trials utilizing immunotherapy. Citation Format: Shane Y. Morita. Acral melanoma in the Hawaiian Islands: Exploring immunologic PDL-1 signature in the minority population. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr A80. doi:10.1158/1538-7755.DISP13-A80