The views expressed by me are for educational purposes only and do not establish a doctor patient relationship.
Thanks for your question.
Inflammatory breast cancer is associated with poor prognosis.
Stage 4 inflammatory breast cancer without any chemoradiation therapy carries worst prognosis.
The average survival may vary between 1 month to 18 months in stage 4 without any treatment.
Hormonal treatment opted by your sister may provide some benefit.
It is very unfortunate situation and average survival will be less than a year.
The 5 year survival is only 40% with surgery, radiation and adjuvant chemotherapy.
Hence, without any treatment, the average life span will be less than a year, barring exceptions.
and my full sympathy
I thank you for your honesty and found basically the same from my own research. I needed a confirmation and very greatly appreciate your forthright answer.