Phaeophyceae, commonly known as brown algae (including genera such as Laminaria, Fucus, and Undaria), has been studied for potential anticancer properties. The justification for its use in cancer support is primarily scientific, although evidence is still emerging and largely preclinical. Brown algae are rich in bioactive compounds such as fucoidan, laminarin, and phlorotannins, which have shown anticancer effects in laboratory and animal studies. Fucoidan, in particular, has demonstrated the ability to induce apoptosis (programmed cell death) in certain cancer cell lines, inhibit tumor growth, and modulate immune responses. Several in vitro studies and a limited number of animal models suggest that these compounds can affect pathways involved in cancer progression, such as angiogenesis and metastasis. However, robust human clinical trials are lacking, and the available human data are limited to small-scale studies or adjunctive settings.

Despite promising preclinical results, the current clinical evidence does not support the use of Phaeophyceae or its extracts as a standalone cancer therapy. Most scientific literature emphasizes its potential as a complementary approach rather than a replacement for conventional treatments. The overall evidence rating is therefore moderate-low (2/5), reflecting the gap between laboratory research and clinical application. Further well-designed human studies are needed to establish efficacy, optimal dosing, and safety in cancer patients.