question;Medicare 'care'

Hi to all:
Are any of you covered only by Medicare with no supplement insurance? If so, have you ever felt that scans were delayed longer for you than what you read or hear about others on fuller coverage?
Why I am asking, is because my aunt who is 77 was diagnosed with bone mets last week. This is her third recurrence so you would think when she started complaining to her doctor with severe back pain that she would have immediatly sent her for a bone scan. My poor aunt complained for 3 months and then just demanded something more be done (she had bone scan a bit over a year ago, and it was okay--and a MRI a few months ago and they didn't see it then). Last week she got her bone scan and the bad news. I was telling a friend today about my aunt and my friend has several elderly relatives receiving different kinds of treatments, and she said her experience had been that doctors would delay doing scans,etc. on their medicare patients if they did not have a supplement insurance provider. I think this is deplorable if true--so that is why I am asking if anyone else has heard of or been through a similar experience. Thank you so much for any advise you can give. God bless you all.
Love and hugs from Brenda