Females breast cancer is still the most frequent type of cancer in Europe with 21 per 100,000 women .The EORTC QLQ-BR23 was one of the first modules developed to be used in conjunction with the core questionnaire EORTC QLQ-C30 and was published in 1996. Since the beginning of the work on the EORTC QLQ-BR23 some 20 years ago, much knowledge has been gathered about the epidemiology of breast cancer, and major advances have been made with regard to diagnostic and therapeutic options. Therefore, the EORTC QLG decided to update the BC23. A phase 1 to 3 module development project has been completed. This resulted in a 45 item module, retaining 23 of the original items and adding 22 new items, particularly tapping into the side effects of new systemic and local therapies.

The aim of the Phase 4 study is to test the scale structure, reliability, responsiveness to change, and validity of the EORTC QLQ-BC45 in conjunction with the EORTC QLQ- C30 in patients diagnosed with breast cancer. Participants will be enrolled in three groups according to their disease stage (1. localized disease or locally advanced disease, 2. metastatic disease, 3. follow up). Various combinations of therapies are permissible, resulting in a total of 17 subgroups.

Inclusion Criteria:

• histologically confirmed diagnosis of breast cancer
• no previous primary or recurrent tumour
• ability to understand the language of the questionnaire
• mental fitness to complete a questionnaire
• 18 years of age or above
• written informed consent.

Exclusion Criteria:

• no histologically confirmed diagnosis of breast cancer
• previous primary or recurrent tumour
• not mentally fit to complete a questionnaire
• not able to understand the language of the questionnaire
• younger than 18
• refusal of informed consent

The study sample will be composed of a series of consecutive cancer patients who meet the study eligibility criteria in each participating centre