Hi, your condition is of chronic itching as it comes under chronic side effect of chemotherapy. It can be due to infection developed because of chemotherapy. So, you should consult your treating radiotherapist and surgeon. You should tell them about other drug if you are taking. Some test like physical examination and complete blood count is essential. Good skin care can reduce the itching like- Maintain cool room temperature, tepid bath with mild soap and moisturizer, Frequent application of lotion, avoid perfumes, avoid direct sunlight exposure and also use sunscreen lotion. Take care, ok bye.