Winger Jack Lazenby crossed for a try in each half and he was joined on the score sheet by Brett Turner, Josh Hart, Matty Plummer, Dan Parker and Sam Cator.
Stand-off Ian Kerman landed three goals and Hart one as the Hull outfit fought back from 14-10 down at the break to lift the cup.
Callum Windley was named man-of-the-match after the Wests hooker proved to be a constant threat throughout.
Centres Declan Tomlinson and Adam Hartley crossed for Easts first and last touchdowns whilst Jake Normington also went over to give his side some hope.
PREMIER DIVISION ROUND UP
HUNSLET WARRIORS relegation was confirmed with a 38-0 defeat at SKIRLAUGH.
The Hull-based hosts ran in seven tries to pick up their seventh win of the season and give them a chance of avoiding the drop with just one game to go.
Centre Ross Kemp crossed for a try and landed five goals for a home side which was 18-0 to the good by half-time.
EGREMONT RANGERS are just a point away from the play-off places thanks to a 24-16 win over LEIGH MINERS RANGERS.
Matthew Bewsher was on target with two conversions.
Miners – who are already assured of a top-six finish – replied with a try and two goals from Johnathan Youds and efforts from James Muir and Scott Travis.
SIDDAL turned out an eight-try display to see off WIGAN ST PATRICKS 40-28.
Scrum-half Chris Brooke completed the scoring with four goals.
St Pats – who are now just a point above the drop-zone with two games left – were in the contest throughout thanks to tries from Aaron Forshaw (2), Liam Gannon (2) and Jonathan Brown.
Scrum-half Brad Smith was on target with four goals.
WATH BROW HORNETS missed out on the chance to go top after a 30-18 reverse at THATTO HEATH CRUSADERS.
Fran King – who also kicked three goals – Greg Howland and Charlie Tomlinson supplied the Hornets points, but it was not enough to stop a Thatto side who had a two-try showing from loose-forward Luke Bradshaw.
HULL DOCKERS picked up a vital two points with a 16-8 win at bottom side WIGAN ST JUDES.
Steven Milne crossed for the only try of the first period to help the hosts into a 6-0 lead at the break, before Chris Lyth and Jon Eccles added further scores in the second forty and Andrew Kay landed the second of his two-goal haul.
St Judes were limited to second half efforts from winger Gareth Thomas and his centre partner Nathan Jones.