Chavez will travel to Brazil for summit - ambassador

* Venezuelan leader in Cuba for medical treatment

* Presence or not at summit would indicate his health

CARACAS, Dec 3 (Reuters) - Venezuela's President Hugo Chavez will travel to Brazil for a regional summit at the end of this week despite cancer-related medical treatment in Cuba, Brazil's ambassador said on Monday.

If confirmed, the 58-year-old Chavez's presence at the Mercosur trade bloc meeting would indicate his latest health scare is not as bad as some are speculating.

Venezuelan officials would not immediately confirm the ambassador's statement. Chavez was in Cuba on Monday and it was unknown if he would return home first if he should decide to go on to Brazil.

Having won re-election in October for a new six-year term, Chavez has made scant appearances since then and not been seen in public since Nov. 15.

Last week, he left for Cuba, saying in a letter he was to receive "hyperbaric oxygenation" - a treatment used to alleviate bone decay caused by radiation therapy. The president has undergone three cancer operations in Cuba since mid-2011.

So while officials are playing his latest treatment down as a secondary follow-up to successful removal of two cancerous tumors he has had in the pelvic area, media is awash with rumors that his condition could be much graver.

"His presence is confirmed, that's what I understand," Brazil's ambassador in Venezuela, Jose Antonio Marcondes de Carvalho, told Reuters when asked if Chavez would be at the Mercosur meeting.

Chavez's unusual silence and invisibility has extended to his normally humming Twitter account where he has posted no new messages since Nov. 1.

Venezuela's widely traded bonds have been rallying on the renewed speculation over the socialist leader's health, reflecting Wall Street's appetite for a more business-friendly government in Caracas.