Tsunku? has announced through his official website and blog that he will be going on hiatus to treat laryngeal cancer.  

According to the announcement, he will undergo immediate intensive care as the cancer was found in its early stages. "Regarding post-treatment, I don't know when I will be able to use my voice. There are a lot of unknown things, so regarding when I will return to jobs where I use my voice, I will let everyone know accordingly," he commented and continued, "After an intensive period of treatment, I will return to desk work and plan to do what I have been doing as much as I can." He concluded, "I am looking forward to the day when I can deliver songs to everyone again."

Source: natalie

Thanks to Reina for the tip.