Abstract 876P
Background
Microsatellite instability (MSI) has been reported in skin melanoma and is thought to be a progression dependent phenomenon seen predominantly on metastases. However, a paucity of data is available about frequency, predictive and prognostic value of MSI in melanoma, in particular using the pentaplex panel of markers approved for colon cancer. Primary aim of this study was to provide a descriptive analysis of the presence of MSI in distant melanoma metastases, regardless of BRAF status and type of first-line treatment.
Methods
The study retrospectively reviewed a consecutive series of patients with stage IV melanoma who were treated from January 2011 to December 2018 at the Academic Hospital of Udine, Italy. Archival tumor tissue of the metastases was available for all patients and the sample temporally closest to the first-line treatment start was selected to evaluate MSI status with a pentaplex panel of mononucleotides markers (NR-27, NR-21, NR-24, BAT-25, and BAT-26). The study protocol was approved by the Ethical Committee of the Italian Friuli-Venezia Giulia Region (protocol n. 0025936) and written informed consent for analysis on archival tissue was obtained for all the alive patients.
Results
Overall, we included 90 patients: 63.3% males and 36.7% females. Median age at the first-line treatment start for stage IV melanoma was 68 years (range 30-87). In detail, 18.9%, 15.6%, 41.1% and 24.4% presented with stage M1a, M1b, M1c and M1d, respectively, of which 18 had de novo metastatic disease. A BRAF V600 mutation was present in 44.4% of cases and in 28.9% of patients LDH value was above the upper normal limit. The metastases sample was most frequently obtained from skin and subcutaneous tissue (30.0%), followed by lymph nodes (28.9%), lung (17.8%), liver (6.7%), central nervous system (5.6%) and other sites (11.0%). Microsatellite stability (MSS) was detected in 81 of 82 (98.8%) evaluable metastatic tissue samples.
Conclusions
A low frequency of MSI (1.2%) in distant melanoma metastases was found in our retrospective observational study. In order to evaluate the possible predictive and prognostic role of MSI in metastatic melanoma, further research is needed.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.