DISEASE CHARACTERISTICS:

• Pathologically confirmed adenocarcinoma of the pancreas

  • Locally advanced disease
  • Maximum dimension of the tumor ≤ 8 cm
• Radiographically assessable disease

• All malignant disease must be encompassable within a single irradiation field

  • Prior radiotherapy field must not overlap with the 20% isodose line of the current radiotherapy field
• Patients with biliary* or gastroduodenal obstruction are eligible provided drainage or surgical bypass was performed prior to initiation of study treatment NOTE: *Patients with biliary obstruction must undergo biliary decompression either through endoscopic placement of a biliary stent or percutaneous transhepatic drainage.
• No distant metastases

PATIENT CHARACTERISTICS:

• Karnofsky performance status 60-100%
• ANC ≥ 1,500/μL
• Platelet count ≥ 100,000/μL
• Serum creatinine ≤ 2 mg/dL
• Total bilirubin ≤ 2.0 mg/dL (in the absence of biliary obstruction) OR < 4.0 mg/dL (in the presence of biliary obstruction)
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• Able to take oral medications
• Able to undergo staging laparoscopy and marker implantation (e.g., gold clip, surgical clip, a common bile duct stent adjacent to the tumor that may be used as an internal marker, or prior staging laparoscopy without marker implantation and the markers can be implanted prior to beginning radiotherapy)
• No history of allergy to chemotherapy agents or to antiemetics appropriate for administration in conjunction with study-directed chemotherapy
• No concurrent uncontrolled illness (e.g., ongoing or active infection requiring IV antibiotics; symptomatic congestive heart failure; unstable angina pectoris; or serious, uncontrolled cardiac arrhythmia) that might jeopardize the ability of the patient to receive the chemotherapy program outlined in this study with reasonable safety
• No other malignancy within the past 5 years, except adequately treated basal cell or squamous cell skin cancer or noninvasive carcinoma
• No active duodenal ulcer or bleeding
• No history of gastrointestinal fistula, perforation, or other significant bowel problem (i.e., severe nausea, vomiting, inflammatory bowel disease, or significant bowel resection)
• No HIV infection
• No hepatic insufficiency

PRIOR CONCURRENT THERAPY:

• No prior multiple abdominal surgeries unless the patient has a common bile duct stent adjacent to the tumor that may be used as an internal marker
• No prior chemotherapy for pancreatic cancer
• No prior radiotherapy to the abdomen
• More than 5 years since prior chemotherapy or radiotherapy for other malignancies
• More than 1 month since prior and no other concurrent investigational agents

• No concurrent drugs that are contraindicated with nelfinavir, including any of the following:

  • Amiodarone
  • Quinidine
  • Rifampin
  • Dihydroergotamine
  • Ergonovine
  • Ergotamine
  • Methylergonovine
  • Hypericum perforatum (St. John's wort)
  • Lovastatin
  • Simvastatin
  • Pimozide
  • Midazolam
  • Triazolam
• No other concurrent anticancer agents