The results of animal studies have demonstrated that the consumption of omega-3 fatty acids can slow the growth of cancer xenografts, increase the efficacy of chemotherapy and reduce the side effects of the chemotherapy or of the cancer.

Molecular mechanisms postulated to contribute to the multiple benefits of omega-3 fatty acids include:
1) suppressing the expression of cyclooxygenase-2 in tumors, thus decreasing proliferation of cancer cells and reducing angiogenesis in the tumor;
2) decreasing the expression of AP-1 and ras, two oncogenes implicated in tumor promotion;
3) inducing differentiation of cancer cells;
4) suppressing nuclear factor-B activation and bcl-2 expression, thus allowing apoptosis of cancer cells; and
5) reducing cancer-induced cachexia.

It seems reasonable to assume that after appropriate cancer therapy, consumption of omega-3 fatty acids might slow or stop the growth of metastatic cancer cells, increase longevity of cancer patients and improve their quality of life.

PMID 12421878

See following website for full manuscript.