Abbas Khan, an orthopaedic surgeon from south London, was taken into custody soon after entering Syria on a humanitarian mission in 2012.
The British government believes Khan was "effectively murdered" by elements of the Syrian regime after being held in detention for over an year.
Khan's family insists he was starved and tortured during his detention by the Syrian authorities before they declared he committed suicide by hanging himself in his cell.
A fund-raising dinner, organised by Gobal Aid Project charity in partnership with Khan's family, will take place in east London next week.
"The family are so distraught but they want to keep his memory going. It's definitely the right thing to do, to make sure he was not forgotten," said David Nott, a British consultant surgeon who worked with Khan in Syria.