Surgery during Herceptin treatment

I am in London, UK. I had neo-adjuvant chemotherapy and currently await recovery fromm mastectomy 8 weeks ago before undergoing radiotherapy. I am about to start a one-year course of Herceptin treatment in 4 days' time. I am EXTREMELY large-breasted and therefore need reduction surgery to my remaining breast as, whether or not I am eventually suited for reconstruction, life is very difficult with one huge unbalanced breast. Accordingly, although I am not anxious for further butchery, I hope I do not have to wait unnecessarily long for reduction.

Does anyone know whether surgery is contra-indicated during Herceptin treatment?