The agencies, both owned by Blue Rubicon, will be running a campaign using digital insight from Blue Rubicon and the public affairs and healthcare knowledge of Open Road.
The account will be led by Blue Rubicon’s Mark Pack and Lucy Kenyon-Jones along with Open Road’s Alexa Knight.
Layla Theiner, Cancer Research UK’s head of public affairs and campaigning, said: "The public-facing element of our campaign is essential to capture the imagination of our many supporters who we hope will help us engage politicians ahead of the next Parliament.
"Raising understanding of cancer among policymakers is an important part of our commitment to beat cancer sooner," she added.
Blue Rubicon is on Cancer Research UK’s social media roster and was asked to present a proposal, which the two agencies presented together.
Blue Rubicon associate director Mark Pack said: "The best digital campaigns are rooted in insight. Our approach combines digital and political research and understanding to spark creative ideas."
Cancer Research UK's work with PLMR will not be affected.
Yesterday the PRCA wrote to the Electoral Commission seeking clarity on the impact that the Lobbying Act would have on charity campaigners and PRs.
The move follows fears raised that the act would limit the ability of non-profit organisations to campaign in the run up to the election.