DISEASE CHARACTERISTICS: Histologically or cytologically proven metastatic or recurrent colorectal or pancreatic cancer for which no curative surgery exists Failed at least 1 regimen of standard fluorouracil based chemotherapy for metastatic colorectal cancer or gemcitabine for pancreatic cancer Autologous peripheral blood stem cells (PBSC) or bone marrow available Diffuse bone marrow involvement allowed if: Autologous bone marrow or PBSC with no greater than 5% tumor involvement available Tumor site at least 2.0 cm in diameter confirmed by pretherapy indium In 111 monoclonal antibody MN-14 imaging and CT scan

PATIENT CHARACTERISTICS: Age: 18 to 80 Performance status: Karnofsky 70-100% ECOG 0-2 Life expectancy: At least 3 months Hematopoietic: WBC at least 3,000/mm3 Granulocyte count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 2 mg/dL SGOT no greater than 2.0 times upper limit of normal (ULN) Renal: Creatinine no greater than ULN Other: No severe anorexia, nausea, or vomiting No concurrent significant medical complications that would preclude compliance Not pregnant Fertile patients must use effective contraception during and for 3 months after study No allergy to 90Y-hMN-14

PRIOR CONCURRENT THERAPY: Biologic therapy: Prior murine monoclonal antibody allowed Chemotherapy: No prior irinotecan At least 4 weeks since prior chemotherapy and recovered (8 weeks since nitrosourea, mitomycin or 90Y-hMN-14) Endocrine therapy: Not specified Radiotherapy: At least 4 weeks since prior radiotherapy to index lesion and recovered No prior radiotherapy to greater than 25% of red marrow (pelvic field radiation as adjuvant therapy for rectal cancer allowed) No prior radiotherapy to maximum tolerated dose to any critical organ (e.g., lung, liver, or kidney) Surgery: At least 4 weeks since major surgery