Table 1

Quotes from interviews supporting identified recruitment challenges

Quote	Organisational challenges of conducting mesothelioma research
1	‘I actually came across some patients who had been referred too late and that’s because they’ve been, in absolutely good faith from our point of view, mismanaged in small peripheral district hospitals. I know there has been a lot of effort put into getting them onboard… When you get a patient that’s been moved back and forward from district general hospital for about six months, at that point he’s either progressed too much or simply deteriorated too much not to be able to have any treatment at all. That is a failure, not just of the trial’ (Surg06 at interview)

Quote

Organisational challenges of conducting mesothelioma research

‘I actually came across some patients who had been referred too late and that’s because they’ve been, in absolutely good faith from our point of view, mismanaged in small peripheral district hospitals. I know there has been a lot of effort put into getting them onboard… When you get a patient that’s been moved back and forward from district general hospital for about six months, at that point he’s either progressed too much or simply deteriorated too much not to be able to have any treatment at all. That is a failure, not just of the trial’ (Surg06 at interview)

	Equipoise-related issues
	Referral hesitancy
2	‘One thing I’ve been slightly disappointed about is the lack of referrals from my neighbouring Trusts, because I had expected more….I think there is some reluctance from the oncologists in some of the neighbouring Trusts about the MARS 2 study… I think that potentially they don’t believe in surgery….I guess probably because of a lack of evidence of any good from it and there is some evidence of harm’ (Onc04 at interview)
3	‘The other patients are coming from local hospitals and have been discussing the mesothelioma with some other chest physicians. Most of the time, they are already coming with the idea of not wanting anything done. That is a really difficult conversation in the clinic, because clearly the patient already has his own idea of, ‘The other doctor told me that I’m going to die. I want to just live the rest of my life in the best way possible. I don’t really want to discuss too much with you’’ (Surg04 at interview)
	Discomforts around eligibility criteria
4	‘I do get patients I see who are eligible and I look at them and think, ‘No, you’re not going to get through this easily.’ …Sometimes you do suggest to patients, ‘Although on paper you’re okay, I don’t think you’re fit. You meet the criteria for eligibility, but I just don’t think you’re strong enough’’ (Surg01 at interview)
5	‘Sending patients [with sarcomatoid cell type] to [surgical site] away from their families for something that I can’t guarantee will do them any good when I know their prognosis is rubbish whatever we do to them, doesn’t seem very sensible to me’ (Onc04 at interview)
	Imbalanced description of treatment options
6	PATIENT: And I was thinking about it and I talked it over with the lads, and I thought, you know, I think I'd just rather go for the chemotherapy ONCOLOGIST 25: Yeah. I don't think that’s the wrong thing for you, to be honest…. I would be more than happy to offer you chemotherapy treatment. I think adding surgery into the mix, particularly when it’s quite a bit further away, is probably an additional complication. It’s maybe not quite the right thing for you. And it sounds like you've come to that conclusion yourself. And I think that’s the right thing. ONCOLOGIST 25 to researcher after: ‘My patter was rather deliberately weighted a bit on the negative side [in describing surgery] as I really didn’t think this trial was the right thing for this patient. So rightly or wrongly the pitch does go along those lines as in practice the surgeons tend to take them on’
7	WIFE: [Surgeon] didn't think it was fair to put him in the trial because he would only get a 50% chance of that operation, and he thought he had a 75%, probably 85% or whatever, better chance of survival or prolonging his life with that operation. So it was [surgeon] that decided not to put him in the trial…. PATIENT: His words were, ‘Mr ‘Baldwin’, I just put a few years on your life

	Discomfort approaching patients
8	‘There’s a lot going on, they're newly diagnosed patients, we've hit them with a massive amount of information, a massive amount of life-changing information… So if they're feeling a bit like they've got information overload already, then pushing them down that route, you don't want to make them more distressed. Sometimes it’s not right for everyone…. I have had one or two patients where we've got a little way into the process and I've got a feel that they're- and I will say to them, ‘This is not compulsory. If you feel that it’s all a bit much for you and it’s a bit overwhelming then maybe the trial’s not for you, and that’s fine. You just need to let me know that you don't want to take it any further’. That has happened with one patient and he said, ‘Do you know what? You're right. I really don't want to think about it right now’. And that’s fine…. What I do then is just pop them back into the standard of care system’ (RN/P/C13 at interview)

Discomfort approaching patients

‘There’s a lot going on, they're newly diagnosed patients, we've hit them with a massive amount of information, a massive amount of life-changing information… So if they're feeling a bit like they've got information overload already, then pushing them down that route, you don't want to make them more distressed. Sometimes it’s not right for everyone…. I have had one or two patients where we've got a little way into the process and I've got a feel that they're- and I will say to them, ‘This is not compulsory. If you feel that it’s all a bit much for you and it’s a bit overwhelming then maybe the trial’s not for you, and that’s fine. You just need to let me know that you don't want to take it any further’. That has happened with one patient and he said, ‘Do you know what? You're right. I really don't want to think about it right now’. And that’s fine…. What I do then is just pop them back into the standard of care system’ (RN/P/C13 at interview)