Chris Ashton, Kyle Eastmond, Matt Kvesic, Matt Mullan, Semesa Rokoduguni and Marland Yarde are the others who will not return to training at Pennyhill Park on Sunday.
It is a big blow for Dickson, who had travelled with England for their two-week training camp in Denver.
He has missed out due to Stuart Lancaster’s preference for Saracens man Richard Wigglesworth, Leicester’s Ben Youngs and Harlequins No.9 Danny Care.
Those players will now be part of preparations for England’s first warm-up match, against France at Twickenham on August 15.
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Dickson, like Stephen Myler, who was released by England last month, will now return to training at Saints ahead of the start of the Aviva Premiership season on October 16.
“We had a great two-week camp in Denver where the entire squad worked extremely hard and were exceptional in the way they went about the training,” said England boss Lancaster.
“That has continued this week and competition for places has been very intense.
“It has been difficult to narrow down the squad as everyone has contributed and given their all.
“But what I have said to those guys who are not coming back in on Sunday is that the door is not closed by any means.
“They are only an injury away and there is a lot of international rugby to be played this season, culminating in a three-Test tour to Australia.”
“Overall we are in good shape.”
There are still six Saints players in the England squad for the World Cup, which begins on September 18.
Kieran Brookes, Alex Corbisiero, Courtney Lawes, Tom Wood, Calum Clark and Luther Burrell are all still bidding for a place in the final 31-man group.
England’s 39-man training squad: Dave Attwood (Bath Rugby), Brad Barritt (Saracens), Kieran Brookes (Saints), Mike Brown (Harlequins), Luther Burrell (Saints), Sam Burgess (Bath Rugby), Danny Care (Harlequins), Danny Cipriani (Sale Sharks), Calum Clark (Saints), Dan Cole (Leicester Tigers), Alex Corbisiero (Saints), Luke Cowan-Dickie (Exeter Chiefs), Nick Easter (Harlequins), Owen Farrell (Saracens), George Ford (Bath Rugby), Alex Goode (Saracens), Jamie George (Saracens), James Haskell (Wasps), Jonathan Joseph (Bath Rugby), Courtney Lawes (Saints), Joe Launchbury (Wasps), George Kruis (Saracens), Joe Marler (Harlequins), Jonny May (Gloucester Rugby), Ben Morgan (Gloucester Rugby), Jack Nowell (Exeter Chiefs), Geoff Parling (Exeter Chiefs), Chris Robshaw (Harlequins), Henry Slade (Exeter Chiefs), Billy Twelvetrees (Gloucester Rugby), Mako Vunipola (Saracens), Billy Vunipola (Saracens), Anthony Watson (Bath Rugby), Rob Webber (Bath Rugby), Richard Wigglesworth (Saracens), David Wilson (Bath Rugby), Tom Wood (Saints), Ben Youngs (Leicester Tigers), Tom Youngs (Leicester Tigers)