Table 6.

Qualitative Themes and Representative Quotations (N=7)

Theme	Experiences Supporting Theme	Reference Quotes
Theme 1: Burden and distress related to delayed diagnosis and treatment (N = 6)	ICs endured the burden of advocating for the patient through misdiagnosis and skepticism about the legitimacy of the patient’s illness.	“They… they kept asking me are you sure he doesn’t do drugs, are you sure he doesn’t do drugs? So - - no, he’s never done drugs in his life. It’s not that. […] They misdiagnosed him […] I got mad actually at the doctors here and decided to drive him to Mayo Clinic. And the guy up there, he knew his stuff, he knew right away what it was.”
	ICs experience emotional distress witnessing the patient’s deteriorating health during the period of diagnosing ECD.	“Then her condition got worse and worse all through the Fall, the blood pressure problem was worse until finally – I guess around December or so and we had get her to the hospital because of the blood pressure and it was so bad that her kidney shut down. She went on dialysis. Meanwhile, they still didn’t know what the – what was going on. I guess they thought the brain problem was separate from the blood pressure problem, but it wasn’t.”
Theme 2: Lack of reliable information about ECD and the burden of caregiver expertise (N = 5)	ICs feel obligated to become an expert about ECD in order to reassure the patient and family members, despite the lack of available reliable information.	“There’s not much information to draw on. You know? So when you have questions, you’re just really limited to how much information is out on the internet or you know how you get very much information so that’s difficult.”
		“I know that from all the reading I’ve done, and I just told him, I’m in charge, you don’t have to worry, I’ve got it all covered.”
Theme 3: Anxiety and isolation resulting from poor understanding of ECD symptomatology and prognosis (N = 7)	ICs experience tremendous anxiety as a result of not knowing the prognosis of ECD, i.e. how long the patient is expected to survive and what the future holds. They find it difficult to prepare for the future.	“So… it’s scary. It’s been terrifying, it’s not knowing like -- before he got diagnosed what was wrong with him and then once he got diagnosed… you know you hear that word and it scares you and you don’t know what the future holds and it’s… it makes me anxious like… I don’t know if he’s going to be around in ten years and… so all our plans we had for the future have are just kind of toast -- connotation like that’s what we’re going to plan to do, assuming I still have that ten years or assuming he’s still alive in five years.”
	Cognitive symptoms cause worry about neurodegenerative disease.	“He’s fixated on certain things and yeah, I don’t know [if it’s] ECD or it’s his aging process […] It’s always been there it’s just so much more now. I don’t know if anybody can say it’s this disease, I mean, right? […] I will tell you, because I think it’s of note, that his father died of complications from Alzheimer’s, a specific type of Alzheimer’s and I hope – you know that I really pray we don’t have – we have enough down the road and I hope the absentmindedness is not early symptoms of that.”
	ECD patients are often not recognizable as ill to others, and ICs receive less support and concern from friends and family who are not aware of the seriousness of the illness.	“We went to a birthday party yesterday for the family and she was a full participant. When people look at her, they can’t understand […] It doesn’t affect your appearance at all and all her… when we go to the annual meeting, that’s something that people say [about having ECD], ‘you look fine, you talk fine, what’s wrong with you?’ […] When you look at her, she looks fine. The neighbor – I saw him out on Friday. He goes, ‘was that your wife out front yesterday? ‘Cause she never goes outside hardly at all, out front’ and – I go, yeah and he goes, ‘I thought she was sick. She looks good; must be doing really good.’ I go, well, you know….”
Theme 4: Dynamic sense of Caregiver identity (N = 6)	Rather than embracing the identity of a “caregiver,” some ICs conceptualize their responsibilities as an extended function of their pre-existing relationship with the patient; especially after the initial treatment period has ended.	“I’m 71 now, so let’s say I was 64 or so when this began, and we were married for I don’t know – 30 something years by then. So it was just like part of the deal.”
		“I don’t know if I really qualify because my husband’s pretty self-sufficient…”
	Although a caregiver may have taken on an “active” role during diagnostic process, once symptoms are managed and the patient is stable, their role may have shifted from physical to emotional support.	“But it’s out and about and in terms of her daily needs, there’s not as much need for that. I’ll offer her my arm if she’s not using a cane if we’re walking somewhere but it’s not extreme in terms of the amount of caregiving.” “You know my caregiving consists of consoling, because now she says this is not the life I expected. “
Theme 5: Need for psychosocial support that is specific to the ECD caregiving experience (N = 5)	ICs found support in the community of other ECD ICs. This highlights the importance of social media as an avenue of support for rare cancer ICs	“I think certainly the ECD caregiver chat has been helpful in sharing experiences and […] there’s a couple of different ways people can offer support. One is just by kind of empathizing, hey, I’ve been there. I know what it’s like. Keep hanging in there. And the other is kind of understanding what they’re going through”
	Supportive groups and experiences attended only by ICs were critical in their allowing ICs to express their fears and vulnerabilities.	“That was extremely powerful to me to be able to go in a room where every -- with all the other caregivers and you know it’s never your -- my husband is never going to hear what I have to say. He’s never going to hear that it’s hard ‘cause I don’t let him see that. I try not to let him see that, you know what I mean?”