The campaign is the first created by Harrison Troughton Wunderman, which won the account last year. It provides an insight into a typical day in one of the trust's centres.
The print work shows a waiting room with several empty chairs. Beside the chairs writing explains what happened to patients who sat in them.
One says: "Today Mrs Taylor and her husband broke down when she found out her cancer had gone into remission." Another explains how: "Mrs Da Silva completed her final chemotherapy session."
The strapline on the ad reads: "Just another ordinary day in an extraordinary place."
Angela Roden, the campaign director at Royal Marsden, said: "The theme is very emotive, focusing on everyone who walks through our doors - from patients to visitors to staff. It shows what extraordinary events happen day in and day out at the Royal Marsden."
The campaign breaks on 14 February on Classic FM, followed by press ads in the South East and London, supported by outdoor, direct marketing and ads in taxis. Media was bought by Media Insight.
"The vignettes are based upon the creative teams' discussions with those who work in the hospital, and their own experiences of suffering and hope," Steve Harrison, the HTW creative director, said.
The ad was art directed by Jason King, Matt Williams and Chris Catchpole and written by Steven Timms.