RATIONALE: Shark cartilage extract may help shrink or slow the growth of colorectal cancer or breast cancer cells.

PURPOSE: Randomized phase III trial to determine the effectiveness of shark cartilage in treating patients who have advanced colorectal cancer or advanced breast cancer.

OBJECTIVES:

• Determine whether the addition of powdered shark cartilage (BeneFin™) to standard therapy improves overall survival in patients with advanced colorectal or breast cancer.
• Determine whether this therapy has any impact on toxicity in these patients.
• Determine whether this therapy improves the quality of life in these patients.

OUTLINE: This is a randomized, double-blind, placebo-controlled, multicenter study. Patients are stratified according to disease type (breast vs colorectal female vs colorectal male), age (49 and under vs 50-69 vs 70 and over), ECOG performance status (0-1 vs 2), baseline quality of life (UNISCALE rating less than 50% vs 50-75% vs more than 75%), and concurrent chemotherapy (yes vs no). Patients are randomized to 1 of 2 treatment arms.

DISEASE CHARACTERISTICS:

• Breast or colorectal primary tumor sites

  • Considered incurable

• Breast cancer patients must have disease progression after at least 2 different chemotherapy regimens (may include chemotherapy given as an adjuvant treatment)

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Sex:

• Male or female

Performance status:

• ECOG 0-2

Life expectancy:

• More than 3 months

Hepatic:

• Bilirubin no greater than 3 times upper limit of normal (ULN)

Renal:

• Calcium less than 1.2 times ULN

Other:

• Not pregnant or nursing
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Chemotherapy:

• Concurrent chemotherapy allowed
• No concurrent participation in a cytotoxic chemotherapy clinical trial

Other:

• At least 60 days since prior shark cartilage