I'm fairly new to the forum and I couldn't quite find anything that matches my dad's recent experience, so I thought I'd just ask. I apologize if this has been addressed elsewhere.
Long story short, Dad was diagnosed with State III multiple myeloma in December of last year. He's 77, about to be 78. He mostly had significant issues walking and feeling tired all the time.
He started cyclophosphamide, Velcade, and dexamethasone (CyBorD) treatment in January and had a good response, but recently "plateaued." His protein levels were hovering between 8.0 and 8.4 (down from his initial 11.2). His light chains were significantly decreased (can't remember the numbers of the top of my head), but were still elevated. He was feeling "fantastic!" and felt like going for a run. He was extremely content and looking forward to our vacation next fall (2019). We also had a second consult with a doctor at University of Texas Southwestern, and he and my dad's current oncologist have been working together.
Anyway, both doctors recommended switching to Revlimid, something I had resisted from the beginning due to its cost and the fact that CyBorD was working. We applied for and received a grant to cover his co-pays. At the end of August, he started his new treatment, VRd (Velcade, Revlimid, and dexamethasone). The plan was to take 25 mg Revlimid daily, and then get Velcade shots twice a week with 20 mg dex the day of the Velcade and the day after. He would do that for two weeks and get on week off. He was also started on aspirin 81 mg/day.
Well, the first week wasn't awful, but he started losing his taste and appetite (which made him depressed because he loves to eat and all he could taste were sweets and he was getting tired of those). The second week, he started getting very dizzy, losing his balance, and his gait changed (started "shuffling"). Then he reported that he felt like he was sunburned all over whenever he took a shower. Over the next few days, he developed a low-grade fever, low blood pressure, fatigue, horrible body aches all over, chills, and mental confusion. I thought it sounded like he had an infection, so we went and saw the PA for his oncologist and she put him on Augmentin (amoxicillin and clavulanic acid) for 10 days (this was a week ago). His symptoms did not get any better, and he was absolutely miserable.
I went over to see him on Saturday and he mentioned swelling in his feet and ankles. I checked and there was definitely mild edema, which is new for him. I called oncology and spoke to doctor on call who said go to ER to get checked for deep vein thrombosis (DVT). Test was negative. The doctor said it looked like his lungs could have had an infection and to stay on antibiotic. We went home with a recommendation for compression socks (duh?).
Sunday, I called to see how he was doing and his edema was better, but now he had a sore throat and his ears were hurting and he was still aching all over and got chills. I told him to take some Tylenol (acetaminophen / paracetamol) since he really didn't want to go to the ER again and see if that helped. It seemed to help some.
Tuesday was his scheduled appointment for when he was supposed to start back on Revlimid. The oncologist said his hemoglobin was really low and wondered if he needed a blood transfusion. We discussed the possibility of him having the flu and their office didn't have the rapid test, so she wheeled him over to the ER. At this time, he was also experiencing a little bit of coughing and occasional pains in his ribcage when he took deep breaths. Flu test came back negative in ER and his hemoglobin showed it was a little higher (this was several hours later). Ordered chest CT to rule out pulmonary embolism. Another negative result.
He said the Tylenol seems to be helping, but he is still having trouble walking and with his balance. His taste is coming back a little bit, but it's not completely back. He has sensitivity (sunburn feeling) on the top of his head and when I spoke with him today, he said his chest was really itchy and felt like he was getting a rash.
Anyway, the only thing I can conclude is that these are all side effects of the VRd. It just seems strange that they are lingering for so long. I just got a chance to look at his labs more carefully, and before he started the VRd, his eGFR was 75 and creatinine was 1.1. Most recently, his eGFR was 48 and creatinine was up to 1.5.
I am wondering how long it will take for him to get "back" to how he was feeling pre-VRd. I know the doctor is likely going to recommend "VRd lite". I am devastated at the sudden change in his condition, and I am hoping the kidney function and balance issues aren't permanent...

A few other things. Dad lives alone and is not eligible for a stem cell transplant (due to his age). He doesn't know his way around this city very well and prior to all of this was already having some issues with getting easily confused (could be early stages of dementia and/or Alzheimer's, or just his age in general).
I did not plan for this to be a novel, so if you've made to the end, thank you for at least letting me get all of this out.