Is this level of hair loss only treatable with a wig?

Since I worked at a construction site in 2005, I always had to wear a safety helmet, which made it difficult for sweat to evaporate. Then, in 2010, I developed cancer and stopped working at the construction site to undergo surgery and chemotherapy. I've been unsure whether I started losing hair even before that, but after that, my hair loss worsened, and now I'm in this state. Is a wig the only option at this point? When I go out, I usually wear a baseball cap, but I don't feel uncomfortable with others' gazes even if I don't wear it, so should I just continue like this?