The true efficacy of EUS-guided ethanol lavage (EEL) of pancreatic cystic neoplasms is unclear. This study aimed to assess long-term outcomes and adverse events of EEL by using a standardized protocol.

Single-center, prospective, pilot study in which participants with suspected mucinous cyst neoplasms or branch duct intraductal papillary mucinous neoplasms ≥1 cm in maximum diameter underwent EEL with 80% ethanol. Follow-up cross-sectional imaging was obtained to assess for changes in cyst volume.

Twenty-three patients underwent EEL (57% male, mean age 70 years). Mean duration of follow-up was 40 months (range 9-82 months). Mean calculated final concentration of ethanol achieved in treated cysts was 50% (range 0%-79%). Complete resolution of pancreatic cystic neoplasms occurred in 2 participants (9%). When stratified into those participants who achieved ≥80% versus <80% reduction in cyst volume, no statistically significant differences were seen with regard to patient demographics, cyst characteristics, or final concentration of ethanol achieved in the treated cyst. Greater decreases in cyst volume were seen in presumed nonmucinous cysts compared with presumed mucinous cysts (P = .006). Two early adverse events occurred. Five participants died during the study follow-up period (4 from nonpancreatic causes), including 1 participant who was diagnosed with pancreatic adenocarcinoma thought to have arisen from the treated branch duct intraductal papillary mucinous neoplasm 41 months after undergoing EEL.

As performed in this study, EEL therapy does not appear to be a promising method for prevention of malignancy in pancreatic cysts. Endoscopic methods that effectively and completely ablate pancreatic cystic neoplasms are needed. (Clinical trial registration number: NCT02158039.)