Q: Is it possible to recover lost iPhone photos without any backup?

If you have no back up, those photos no longer exist. There is no where to recover them from.

I've had good results with iPhone Data Recovery - able to recover about 94% of files from undamaged disks with trashed files.

It's $49 but much less than you'd pay for a data recovery service...

But maybe this will be a good lesson to you to ALWAYS maintain one or more backup schemes.

Good luck,

Roger

Also, iOS 8 moves deleted photos to the Recently Deleted album, which are retained for a period before removing them permanently. That offers a secondary resource for users that disable iCloud syncing for their iPhone. Really, both are good options.