According to Wiki: '55,573 killed out of a total of 125,000 aircrew (a 44.4% death rate)'.
I believe I have heard that the Lancaster was relatively narrow and hard to get out of in an emergency compared to the B-17 and B-24.
I noticed that the same Wikpedia which listed 55,573 killed out of 125,000 also listed 9,838 as prisoners of war a ratio of 5.6 to 1 killed vs. POW. For the U.S. Eight Air Force it shows 26,000 killed out of 350,000 and 23,000 prisoners of war for a ratio of close to 1 to 1. I am curious as to whether that difference is to the ability of escaping the aircraft flown.