Bradley was diagnosed with neuroblastoma, which attacks the nervous system, in January 2013. After enduring radiotherapy, chemotherapy and stem cell transplants, he was thought to be beating the disease. However it returned in July this year and Mrs Lowery and her labourer husband Carl, 33, were told it was terminal.
As news of his story spread, the youngster was invited to be a mascot for his favourite football team, Sunderland, earlier this month and met his idol, striker Jermain Defoe.
The campaign of cards and presents began when an Everton fan tweeted: "Wouldn't it be nice if everyone sent him a Christmas card?"
A postal address was set up as the campaign snowballed. Yesterday Bradley - who also has a brother Kieran, 14 - received 14,000 cards, arriving from as far away as Australia, New Zealand and the US.
His parents are raising money to fund life-prolonging treatment for Bradley. Any left over will be put towards helping other ill youngsters.