Patients diagnosed with locally advanced, ER-positive breast cancer (defined by ER-pos. in > 10% of cancer cells) suitable for neoadjuvant anti-hormonal therapy («pre-surgical downstaging») will be considered for this protocol. Locally advanced breast cancer is in general defined as either T3-T4, and/or N2-3 primary breast cancer. However, limited systemic metastasis (not life-threatening metastasis to the lungs, liver, bone, lymphnodes, skin etc.) may be allowed. The rationale for presurgical treatment in these patients is to avoid loss of local tumor control in the long run. Loss of control concerning the primary tumor in the breast is in general experienced as very disturbing for the patients (causing local bleeding, bad smell, eksudation, social isolation etc.). Patients with primary tumors above 4 cm in diameter („large T2-tumors“) may also be recruited in accordance with the international trend to provide neoadjuvant therapies to these patients in clinical trials.
At least 24 patients (12 starting with letrozole and 12 starting with exemestane) should complete the study. Thereafter, the protocol will be closed for further inclusion, but each patient included up to that time point will be completed according to the protocol procedures.
All patients have to be postmenopausal to be able to benefit from aromatase inhibition (definition of postmenopausal status: age above 55 years or age above 50 years and at least 2 years of amenorrhea in addition to LH-, FSH-, and plasma estradiol levels in the postmenopausal range).
Patients with ER-positive and HER-2 positive breast cancer may be treated in the present protocol if they are evaluated as no candidates for standard neoadjuvant chemotherapy due to other co-morbidities (impaired heart function, high age etc.).
Triple-negative breast cancer is of course an exclusion criteria. Patients with life-threatening metastasis (advanced visceral metastasis, brain-metastasis, high liver enzymes; defined as above 3 times normal values) are also excluded from this trial as they will need treatment options with immediate effect like chemotherapy.