* Photos show smiling Chavez at airport
* Doubts persist over his condition as vote looms
By Andrew Cawthorne
CARACAS, May 11 (Reuters) - Venezuelan President Hugo Chavez headed home on Friday after a series of cancer radiation treatments in Cuba to a nation fretting over his health five months before a presidential election.
Photos issued by the Venezuelan government showed Chavez smiling as he bade farewell to Cuban President Raul Castro at the airport before boarding the flight back on Friday evening.
But the images, showing Chavez from the waist up dressed in loose-fitting sports clothes, gave few clues to the real state of health of a man only seen once in public in the last month.
"I'm on the plane, on the runway of 'Jose Marti' airport. Heading for the Venezuelan fatherland. With more optimism than ever! We will live and we will conquer!" Chavez said in a message on Twitter.
The official line is that Chavez has been out of the public limelight due to the effects of radiation treatment, but is on the road to recovery and will soon begin his re-election campaign ahead of the Oct. 7 vote.
But there are fears, stoked by leaks from pro-opposition journalists citing sources in Chavez's medical team, that his condition may have turned grave.
The implications of that are enormous for the South American OPEC member nation that Chavez has dominated for the last 13 years without grooming a successor.
Rumors are flying of a nascent succession struggle among his closest allies. Opposition presidential candidate Henrique Capriles is struggling to win public attention amid the national obsession over Chavez's condition.
Critics say the nation is in paralysis.
"He is a president who never delegates anything. Even the most mundane, daily decision in a ministry, people don't dare take decisions if they think they don't have the president's blessing," Capriles ally Maria Corina Machado told Reuters.
"This is a country that is practically paralyzed."
Chavez's condition remains a state secret, with few details divulged beyond the fact he has had three operations in a year to remove two malignant tumors in his pelvic region.
The Venezuelan president declared himself "completely cured" at the end of 2011, only to acknowledge a recurrence of cancer early this year. That has fed skepticism and speculation among Venezuelans over Chavez's future.
The wider region is also watching the saga closely.
Communist-run Cuba depends on subsidized Venezuelan oil to keep its ailing economy afloat, while the United States has long viewed Chavez as its principal foe in the region. (Additional reporting Deisy Buitrago; Editing by Stacey Joyce)