CARACAS (Reuters) - Venezuelan President Hugo Chavez will travel to Cuba on Tuesday for medical treatment, following a nearly two-week absence from the public eye, months after undergoing cancer surgery on the Communist-run island.
Chavez, 58, staged what appeared to be a remarkable comeback from an undisclosed type of cancer diagnosed in June 2011. In October, he won re-election following a campaign that was much more subdued than his previous bids.
In a letter to Congress, Chavez said he would receive a form of therapy known as hyperbaric oxygenation, which is often used for the prevention and treatment of bone decay caused by radiation therapy, according to the American Cancer Society.
Chavez has not appeared in public in 12 days. The absence is unusual for a leader who routinely chats for hours on live broadcasts and suggests his health has weakened since the campaign.
"Six months after I completed the last radiation therapy treatment, it has been recommended that I begin a special treatment consisting of various sessions of hyperbaric oxygenation," Chavez wrote in the letter, which was read by congressional leader Diosdado Cabello.
"Together with physical therapy, (this) will consolidate the process of strengthening my health."
The letter did not mention cancer.
Hyperbaric oxygenation therapy, also known as HBOT, involves breathing pure oxygen while in a pressurized chamber.
Chavez's centralization of power and enormous control over the country's oil revenue have made him the center of the OPEC nation that provides about 10 percent of U.S. crude imports.
If his health took a turn for the worse, his unwieldy coalition of military leaders and leftist social activists could fall apart. Investors hoping for a more market-friendly government tend to buy Venezuela's highly traded bonds on reports his health is worsening.
The country's benchmark Global 27 bond extended gains in the wake of the announcement.
Chavez's refusal to disclose his actual condition has made his health the subject of constant speculation, particularly among opposition sympathizers who quietly hope he will take a turn for the worse. He defeated opposition challenger Henrique Capriles by 10 percentage points last month.
In late 2011, Chavez declared himself completely cured of cancer, but, within months, had to return to Cuba to remove another tumor.
Doctors say a couple of years must pass without a recurrence before a patient is said to be cured.
Many Venezuelan doctors suspect Chavez used steroids and other treatments to look and feel fitter during the election campaign. That can cause other health problems.
Chavez spent several months traveling back and forth to Cuba to receive treatment. The typically hermetic atmosphere there, and his friendship with former leader Fidel Castro, helped prevent details of his condition from leaking to the press.
Venezuela's constitution says that if an incumbent leaves office in the first four years of a six-year term, a new election must be held. (Additional reporting by Eyanir Chinea, Marianna Parraga and Mario Naranajo; Editing by Daniel Wallis and Stacey Joyce)