DISEASE CHARACTERISTICS: Histologically confirmed unresectable, advanced and/or metastatic disease: Colorectal cancer Measurable or evaluable disease Epidemiologically proven fibroblast activation protein positive Failed or refused conventional treatment, and unlikely to derive significant benefit from conventional treatments No active CNS metastases No new or progressive lesions on CT scan, more than 3 months since treatment (i.e., surgery or radiotherapy) for brain metastases, and/or not receiving mitomycin Hormone receptor status: Not specified

PATIENT CHARACTERISTICS: Age: 18 and over Menopausal status: Not specified Performance status: Karnofsky 70-100% Life expectancy: At least 4 months Hematopoietic: Absolute granulocyte count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: ALT/AST no greater than 3 times upper limit of normal Bilirubin less than 2 mg/dL Renal: Creatinine no greater than 2.0 mg/dL Other: Not pregnant or nursing Fertile patients must use effective contraception No other serious illness No active infections requiring antibiotics No bleeding disorders No other diseases that may potentially interfere with obtaining accurate study results

PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior immunotherapy No prior murine, chimeric or humanized antibody and/or antibody fragment Chemotherapy: See Disease Characteristics At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas and mitomycin) Endocrine therapy: No concurrent systemic corticosteroids (except for acute management of allergic-type events) No concurrent immunosuppressive agents Radiotherapy: See Disease Characteristics Surgery: See Disease Characteristics Recovered from surgery Other: At least 4 weeks since other prior investigational agents