The Colossus Rises By Peter Lerangis

Jack McKinley s an ordinary boy with an extraordinary problem. In six months Jack's going to die.
Then Jack wakes up on a mysterious island, where a secret organisation promises to save his life - but with one condition. Jack must retrieve seven magical objects that, only when combined together, can keep him alive.
These objects have been missing for a thousand years, hidden in the ruins of the Seven Wonders of the Ancient World. With no one else to turn to, Jack and his three friends have no choice but to undertake the quest.
First stop: The Colussus of Rhodes, where they realise that there's way more at stake than just their lives...