Dose-Reduced Docetaxel With Cyclophosphamide for the Treatment of Vulnerable Older Women With Stage I-III HER2 Negative Breast Cancer, the DOROTHY Trial

Inclusion Criteria:

• Ability to provided informed consent or a legally authorized representative is ableto consent on behalf of the patient

• Willing to answer questionnaires as part of their participation

• Age: >= 65 years by the time of study registration

• Histologically or cytologically confirmed breast cancer(s) that is human epidermalgrowth factor receptor 2 negative (HER2-negative) per the most recent 2018 AmericanSociety of Clinical Oncology College of American Pathologists (ASCO CAP) guidelinesrelapsed/ refractory disease

• Estrogen receptor and progesterone receptor immunohistochemistry (IHC) status mustbe known; any estrogen receptor (ER)/progesterone receptor (PR) status is eligible

• Non-metastatic, invasive breast cancer (scans are not required to documentnon-metastatic disease- any staging work-up is up to the treating providers'discretion)

• Recommended to have either standard dose neoadjuvant docetaxel, cyclophosphamide (TC) chemotherapy or adjuvant TC chemotherapy per their treating provider.Participant may be on immunotherapy concurrently with the protocol regimen at thediscretion of the treating physician

• Any surgery, nodal assessment, radiation, hormonal therapy is left up to thetreating provider but should not occur concurrently with study therapy

• Any patient who received pre-operative hormonal therapy and who is then recommendedfor neo/adjuvant chemotherapy is eligible, though hormonal therapy should be heldduring study treatment administration

• For patients with bilateral or multifocal/multicentric breast cancers, the followingcriteria must be met to enroll: (1) both cancer are HER2 negative, AND (2) theprovider feels the patient will benefit from TC for at least one of the cancers

• Patients who do not speak or read English are eligible as long as adequateinterpreter services are available or the surveys are available in the preferredlanguage (i.e. the Geriatric Assessment [GA] and Patient Reported Outcomes [PRO]surveys are available in many languages)

Exclusion Criteria:

• Participants who have already received any chemotherapy for their current breastcancer

• Patients with recurrent and/or metastatic disease will be excluded. Prior diagnosesof breast cancers (including ductal carcinoma in situ [DCIS]) are allowed, providedthat the treating provider feels that the current cancer most likely represents anew primary breast cancer and not recurrent disease

• History of allergic reactions attributed to compounds of similar chemical orbiologic composition to cyclophosphamide and/or docetaxel

• Past treatment with the regimen TC for prior breast cancer