Dealing with Psoriatic Arthritis and Cancer

I am posting for the first time on the Forum out of desperation! My 87 year old mother has been using Skyrizi biologic injections for 18 months and it has worked well for her so far. Unfortunately she was diagnosed in January this year with endometrial cancer and underwent a hysterectomy in mid April. Because of the operation she was advised to miss her April injection by which time the psoriasis had already started to rear its ugly head (probably due to the stress of the diagnosis). We are now at the end of May and she has been advised that she needs a 5 week course of radiotherapy as the cancer has spread to her lymph nodes. Her Dermatologist at the hospital has suggested that biologics would not be compatible with radiotherapy but has not given a reason for this. Her quality of life has become so poor with psoriasis now taking over every part of her body and the pain from her arthritis becoming unbearable she is seriously considering foregoing the radiotherapy just to ensure she can return to her Skyrizi injections to improve her quality of life (no matter how long this may be). I would be very interested to hear from anyone who has had to deal with cancer treatment alongside severe psoriasis. She has tried many other treatments in the past and the dreaded Methotrexate which made her very poorly so is not an option. We have an appointment with her Dermatologist on Tuesday next week to discuss her options but I fear the injections (which we know worked in the past) will be withdrawn from the table. Thank you in anticipation of any advice/experience shared. Alderney1