Breast cancer is the most common malignancy for females in North America. Around 5-15% of the estimated 200,000 new cases diagnosed each year will present with locally advanced breast cancer (LABC) (The definition of what constitutes "LABC" is complex and variable. Clinically these tumours are usually considered to be those greater than 5cm in size and/or extend beyond the breast tissue into the surrounding skin or muscle. Patients with matted axillary lymph nodes (N2) or internal mammary nodes (N3) or ipsilateral supraclavicular lymph node involvement are also considered to have LABC. In view of the extensive nature of these tumours at presentation, women with LABC have a poor outcome in terms of both local and systemic recurrence. Standard treatment for these patients is usually neoadjuvant systemic (chemotherapy or less frequently endocrine therapy) followed by surgery and radiotherapy. Patients who have hormone receptor positive tumours will then receive endocrine therapy. With the use of multidisciplinary therapy, 10-year disease free survival rates of 50% for Stage IIIA and 33% for Stage IIIB disease have been reported.
The impetus for undertaking this study is that we are searching for imaging methods that could potentially serve as surrogate indicators of pathological response. One such modality that we wish to investigate as it may be ultimately useful in this patient population is diffuse optical spectrometry. This modality depends on differentiating oxygenated from deoxygenated tissue but is also sensitive to other changes in tissue characteristics. It has been used before in proof-of-principle studies differentiating benign from malignant disease but we hypothesize that it may be more useful in terms of monitoring tumour responses to treatment. This is a non-invasive imaging modality that is easy to administer and relatively inexpensive.