Abstract
BACKGROUND: The gemcitabine plus S-1 (GS) regimen is a first-line chemotherapy for unresectable locally advanced or metastatic pancreatic cancer (PC), a disease associated with high mortality. However, severe adverse events associated with the standard GS (gemcitabine plus daily S-1) regimen adversely affect treatment adherence and clinical outcomes. Recent studies suggest that modified GS regimens may improve tolerability without compromising efficacy in select populations. Here, we report a case demonstrating that an adjusted GS (gemcitabine plus alternate-day S-1) regimen could represent a viable alternative first-line chemotherapy for patients with standard GS protocol intolerance. CASE DESCRIPTION: In January 2020, a 61-year-old female with upper abdominal pain was diagnosed with unresectable locally advanced pancreatic ductal adenocarcinoma (PDAC) confirmed by biopsy (T3N0M1). She received one cycle of standard GS chemotherapy but developed severe toxicity (grade 3 neutropenia and stomatitis). Given the intolerance, the patient was transferred into an adjusted GS regimen (gemcitabine 1,000 mg/m(2) on days 1, 8; S-1 80 mg/m(2) on alternate days) in March 2020. The patient tolerated this adjusted GS regimen well, achieving partial remission with reduced carbohydrate antigen 19-9 (CA19-9; from >1,000 to 85.3 U/mL) and decreased tumor size (59 mm × 20 mm to 25 mm × 18 mm) within 14 months. She completed 12 cycles of adjusted GS regimen, followed by S-1 monotherapy. At 58-month follow-up, she remained alive with controlled disease (stable tumor size) and preserved quality of life. CONCLUSIONS: This case highlights the potential of an adjusted GS regimen to achieve prolonged disease control and manageable toxicity in patients with standard GS intolerance. This modified approach may serve as a potential alternative to the standard GS regimen for select patients who experience intolerance to conventional therapy. A future multicenter randomized controlled study will investigate the efficacy and safety of this adjusted GS treatment strategy.