Hello and thanks for your enquiry,

It is completely understandable to feel worried about switching from pembrolizumab (Keytruda) to chemotherapy tablets, and having to stop pembrolizumab early due to side effects is quite common, and your oncology (hospital cancer team) team will have worked out the best plan for you moving forward.

Pembrolizumab does not attack cancer cells directly; instead, it retrains your immune system’s T-cells to recognise and destroy them. Clinical studies show that once the immune system is "switched on" by immunotherapy, that anti cancer response can persist in the body for a very long time, even after the drug is stopped.

People that develop immune related side effects, like your underactive thyroid (hypothyroidism) and adrenal insufficiency is noted in clinical studies with a highly active immune response against the cancer. It means the pembrolizumab successfully woke up your immune system.

Chemotherapy tablets work through a different path than pembrolizumab by directly stopping cancer cells from dividing and growing. The chemotherapy drugs are given to catch any remaining cancer cells, whilst stopping the immune driven inflammation that affected your endocrine glands. Developing an underactive thyroid and becoming steroid dependent due to adrenal gland changes, are known side effects of pembrolizumab, which can sometimes be permanent. This does mean that your body now requires medication for the hormones thyroxine and cortisol. Fortunately, at least, these conditions are manageable with daily medication.

I hope this helps,

Best wishes,

Vanda

Thank you so much for your reply .. I now understand how it works and as you say the immunotherapy at least definitely woke up my immune system … even only having 4 infusions. 
All so confusing tbh. 
My other question is that after 10 weeks since my mastectomy, my shoulder, collar bone and arm although have normal movement often cause pain .. a little like funny bone pain which I’m assuming is a nerve maybe ? I have it a little pain on the other shoulder too. I have been doing all the exercises I was given but everything worries me at the moment. I have tried so many times calling my breast nurse but no one ever returns my call. 
Thank you 

Hello and thank you for getting back in touch.

It sounds as though you have been through a great deal recently, and, understandably, you are feeling worried. Coping with a cancer diagnosis, surgery, and knowing that there is still more treatment ahead can feel overwhelming. Many people tell us that the uncertainty can be one of the hardest parts, so your feelings are a very normal response to a very difficult situation.

It's also understandable that the pain is making you anxious. After breast surgery, it is not unusual to have ongoing pain, discomfort, or unusual sensations while the body is healing. If nerves have been affected during surgery, this can sometimes cause pain that lasts for weeks or even months afterwards. Although healing can be slow, these symptoms often improve gradually over time.

That said, if the pain is getting worse rather than better, if you develop any new symptoms, or if you are concerned at any point, it's important to let your hospital team know so they can assess you and make sure you are recovering as expected. Breast Cancer Now has some helpful information about ongoing pain after breast surgery, which you may find reassuring to read.

I appreciate it must be frustrating not being able to get hold of your breast care nurse, especially when you are feeling worried. Do keep trying. If you do not hear back, you could contact your GP, or get in touch with your breast surgeon's secretary, who may be able to arrange for someone from the team to speak with you.

I hope this is helpful and you can get support with this soon.

Take care

Jemma