1. The primary objective is to compare rates of persistence (continuation) of any endocrine therapy (ET) between patients assigned to standard of care follow-up (control arm) versus standard of care plus a bi-directional text messaging intervention (intervention arm)

2. The secondary objectives are:

   (i) To assess time to permanent discontinuation of ET (switching from an aromatase inhibitor to another ET is permitted). The investigators will also account for treatment breaks.

   (ii) To assess QOL at baseline, and at 6 and 12 months after initiation of ET (FACT-ES1, Brief Pain Inventory2, Overall Treatment Burden3,4, individual symptom LASA scales4) and compare between arms (iii) To assess adherence self-efficacy (SEAMS5 tool, Voils Extent of Non-Adherence Scale6), financial burden (COST tool7,8), beliefs about medications (modified BMQ tool9,10), and perceived ability to communicate with one's physician (PEPPI11 tool) and compare between arms (iv) To compare the time to endocrine therapy discontinuation in both the intervention and control arms (v) To characterize factors (including clinicopathologic features, socioeconomic status, and comorbidities) associated with non-adherence in both the intervention arm and the control arm, which may enable us to identify women who are at particularly high risk of non-adherence.

   (vi) To assess adherence to medication as reported through the BETA-Text intervention (vii) To collect the time to onset and trend of severity of side effects in women assigned to the text messaging intervention.

Inclusion Criteria:

1. Patients with histologically confirmed stage I-III, estrogen and/or progesterone receptor positive, as defined by ASCO-CAP guidelines, invasive breast cancer for whom adjuvant hormonal therapy is indicated following standard NCCN practice guidelines.42

2. Patients must initiate an aromatase inhibitor (AI), with the choice of AI (letrozole, anastrozole, or exemestane) left to the discretion of the treating provider (have just started or plan to start within 4 weeks)

3. Patients with synchronous bilateral breast cancers are eligible if both tumors are hormone receptor positive.

4. Patient must be able to provide informed consent and agree to:

   1. Complete questionnaires according to the pre-specified study design
   2. Own or have access to a personal cell phone, agree to send and receive text messages (including any costs), and share their personal cell phone number to receive text messages.
   3. Be able to read/speak English
   4. To allow research staff to contact their pharmacies to determine prescription refill dates.

Exclusion Criteria:

1. Patients with history of prior stage I-III breast cancer in the same or contralateral breast are not eligible (because exposure to prior endocrine therapy may confound results)
2. Patients with metastatic breast cancer.
3. Patients with ductal carcinoma in situ (DCIS) or other pre-malignant lesions of the breast receiving endocrine therapy as chemoprevention.
4. Prior treatment with an aromatase inhibitor, regardless of indication.
5. Prior tamoxifen for the current cancer (prior tamoxifen for DCIS or a different cancer is permitted).