Chavez has neither been seen nor heard from, except for "proof-of-life" photos released in mid-February, since submitting to a fourth round of surgery in Cuba on Dec. 11 for an unspecified cancer in the pelvic area.

NPR: Venezuela: Chavez Hit By New, Severe Infection

As well as surgery, another option for doctors is radiotherapy , which will be precisely targeted on the pelvic area.

BBC: Prostate cancer