A Prospective, Open-label, Exploratory Basket Trial to Evaluate the Efficacy and Safety of Sintilimab Combined With Pyrotinib ± Chemotherapy in Patients With Advanced Digestive System Tumors

Dosage Form: Intravenous (IV) infusion Dosage: 200 mg Frequency: Every 3 weeks (Q3W) Duration: Until disease progression, unacceptable toxicity, or up to 2 years

Dosage Form: Oral tablet Dosage: 400 mg once daily (QD) Frequency: Continuous daily dosing Duration: Until disease progression or intolerable toxicity

"1. FOLFOX:~ Oxaliplatin 85 mg/m² IV Day 1, leucovorin 400 mg/m² IV Day 1, 5-FU 400 mg/m² IV bolus + 2400 mg/m² continuous infusion over 46h (Days 2-3)~2. GEMOX:~ Gemcitabine 1000 mg/m² and oxaliplatin 100 mg/m² IV Day 1~3. GC:~ Gemcitabine 1000 mg/m² and cisplatin 25 mg/m² IV on Days 1 and 8~4. XELOX (CapeOX) Oxaliplatin 130 mg/m² IV Day 1, capecitabine 1000 mg/m² PO BID Days 1-14~5. SOX:~ Oxaliplatin 130 mg/m² IV Day 1, S-1 PO BID Days 1-14 (dose based on BSA: \<1.25 m² = 40 mg, 1.25-\<1.5 m² = 50 mg, ≥1.5 m² = 60 mg)~6. TS:~ Paclitaxel 80 mg/m² IV Days 1 and 8, S-1 as above~7. mFOLFOX6: Same as FOLFOX; used primarily in colorectal cancer~8. FOLFIRINOX:~ Leucovorin 400 mg/m², 5-FU (bolus + continuous), irinotecan 180 mg/m², oxaliplatin 85 mg/m² IV Day 1~9. AG:~Nab-paclitaxel 125 mg/m² and gemcitabine 1000 mg/m² IV on Days 1 and 8"