Secondary Peritoneal cancer

Hello my mum has recently been diagnosed with secondary peritoneal cancer and I just wanted to see if anyone has any experience with this as from what I've been reading it's quite rare. 

Everything I'm reading online says the survival rate is around 6 months, the oncologist hasn't mentioned anything about how long mum may live. Is it normal for a doctor not to say or will this conversation come later down the line. 

Best wishes everyone ️