Im assuming you do have secondary BC? The reason being is that obviously our in-hospital treatments continue whereas for primary BC it generally is a much shorter time scale depending on things such as whether you have Herceptin and/or pertuzamab etc. Having said that we are all covered by the disability discrimination act as far as I know which means our places of work have to make reasonable adjustment. You may need to check this out and how this affects you through Macmillan or citizens advice or a union rep as suggested. If you do have SBC this will be an ongoing situation so you might also be able to claim ESA if your hours are reduced or you can't work due to continuing treatment. I think this is also the case if you are having chemotherapy and/or radiotherapy as part of Primary BC treatment by the way but don't know the facts for PBC as I'm way past that stage!
ps good luck with the meeting and hope some allowances will be made for you