A prophylactic agent for spontaneous cancer may contain a plant fermentation product as a mixture of (a) to (g), fermentation products of: (a) barley, black soybean, red rice, black rice, adzuki bean, adlay, Japanese barnyard millet, foxtail millet, and/or proso millet; (b) mandarin orange, grape, apple, Vitis coignetiae berry, peach, persimmon, papaya, Japanese pear, watermelon, Japanese apricot, fig, Chinese quince fruit, kabocha squash, kumquat, Yuzu, loquat fruit, apricot, jujube, chestnut, matatabi fruit, and/or Japanese plum; (c) purple sweet potato, Jerusalem artichoke, carrot, onion, sweet potato, taro, Japanese wild yarn, daikon, red turnip, great burdock, lotus root, yacon, lily bulb, arrowhead, ginger, garlic, and/or turmeric; (d) cabbage, perilla, Moms leaf, fish mint, Japanese mugwort, Sasa veitchii, and/or dandelion; (e) kelp, wakame, and/or mozuku; (f) black sesame, walnut, and/or ginkgo nut; and (g) maitake and/or shiitake. A SAM evaluation system and/or SAMP mouse may evaluate such cancers and/or substances thereon.