Currently, research is underway on the protective effect of vitamin D against many malignant diseases, including breast cancer. Vitamin D is formed, among other things, by ultraviolet radiation of the skin, which also leads to sunburn. However, there is currently no clear link between strikini and breast cancer risk.
The short and unambiguous answer is no. Stickinis do not have the slightest effect on breast cancer risk. Thus, perhaps you can protect the skin of the nipples from burns, but no more.
Tanning in a tanning salon always passes under the irradiation of ultraviolet lamps. Ultraviolet rays can penetrate into the deeper layers of the dermis and activate the formation of free radicals, causing premature aging of the skin on the chest and depleting the body's defenses. Sunburn without stikini, with exposed nipples, leads to irradiation of many blood vessels and nerve endings, which can provoke the development of fibrocystic breast disease or tumor processes. When you sunbathe in a swimsuit in the sun, the fabric is also protection. When you use a solarium or a nude beach (topless), protect your breasts not only with cream, but also with something denser, such as a stikini - they do not let in up to 99% of ultraviolet radiation.
Save completely from breast cancer? - no. There are too many reasons for this disease, and this is not only the sun. But it is important to avoid risk factors.