Testing Low Dose Tamoxifen for Invasive Breast Cancer, LoTam Trial

Paused · Phase 3

Conditions studied: Anatomic Stage 0 Breast Cancer AJCC v8, Anatomic Stage 1 Breast Cancer AJCC v8, Anatomic Stage IIA Breast Cancer AJCC v8, Estrogen Receptor-Positive Breast Carcinoma, HER2-Negative Breast Carcinoma, Breast Ductal Carcinoma In Situ, Breast Lobular Carcinoma In Situ

In brief

This phase III trial compares the effect of low dose tamoxifen to usual hormonal therapy, including aromatase inhibitors, in treating post-menopausal women with hormone positive, HER2 negative early stage breast cancer. Tamoxifen is in a class of medications known as antiestrogens. It blocks the activity of estrogen (a female hormone) in the breast. This may stop the growth of some breast tumors that need estrogen to grow. Aromatase inhibitors, such as anastrozole, letrozole, and exemestane, prevent the formation of estradiol, a female hormone, by interfering with an aromatase enzyme. Aromatase inhibitors are used as a type of hormone therapy to treat postmenopausal women with hormone-dependent breast cancer. Giving low dose tamoxifen may be more effective compared to usual hormone therapy in treating post-menopausal women with hormone-positive, HER2 negative early stage breast cancer.

Key facts

Study ID: NCT06671912
Run by: Alliance for Clinical Trials in Oncology
People needed: 1556
Starts: 2025-02-19
Expected to finish: 2031-11-30
Last updated by the study team: 2026-08-05

Who can join

Age: 18 and older. Sex: any. Healthy volunteers: not accepted.

You may qualify if…

Unilateral invasive adenocarcinoma of the breast that is histologically confirmed
Invasive breast cancer is estrogen receptor positive in ≥ 10% of cells
HER2 negative by current American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines
The patient must have a multigene assay with a low-risk score, including any of the following (if more than one genomic assay was obtained, both are required to be low-risk):
Oncotype DX recurrence score ≤ 25
Mamma Print low risk
Prosigna risk of recurrence ≤ 40 Patients with pathologic tumor size ≤ 0.5cm who meet all other eligibility criteria are eligible for enrollment without multigene assay testing. The total number of enrolled patients with tumor size ≤ 0.5cm without genomic testing will be limited
Tumor size must be ≤ 3 cm by pathologic evaluation. Multifocal tumors are permitted if the largest focus of disease is ≤ 3 cm
Adequate surgical removal of all clinically evident disease in the breast with either breast conserving surgery or mastectomy. Negative margins on final pathology are required. Additional excisions may be performed to obtain clear margins before registration
No clinical (cN1, cN2, cN3) or pathologic (pN1mi, pN1, pN2, or pN3) evidence of lymph node involvement on either needle biopsy or surgical lymph node assessment. Patients with pN0(i+) or pN0 (mol+) are eligible
Surgical axillary staging (sentinel lymph node biopsy ± axillary lymph node dissection) is completed according to physician discretion
For patients age <70, clinicians may selectively choose to forego surgical axillary staging if an Ipsilateral axillary ultrasound or preop MRI shows no lymph node involvement with no evidence of lymphadenopathy or suspicious thickening is required in this scenario
For patients age ≥ 70 without surgical axillary staging, axillary ultrasound is not required in this scenario but may be obtained at the discretion of the treating investigator
No tumors that are considered pT4
No definitive clinical or radiologic evidence of metastatic disease
No palpable or radiographically suspicious axillary, supraclavicular, infraclavicular, or internal mammary lymph nodes, unless there is histologic confirmation that these lymph nodes are negative for tumor
No suspicious microcalcifications, densities, or palpable abnormalities in the ipsilateral or contralateral breast, unless biopsied and found to be benign
An interval of no more than 20 weeks between the date of surgery and the date of registration
Must have had a bilateral mammogram or MRI within 9 months prior to registration
Must be intending to take endocrine therapy for 5 years duration
No prior treatment with endocrine therapy or chemotherapy for the currently diagnosed breast cancer prior to registration. (Short course endocrine therapy of ≤ 6 weeks duration is acceptable after core biopsy and before surgery, if genomic testing is assessed on the biopsy core and meets eligibility requirements for a low-risk score.)
No use of oral hormone replacement therapy or transdermal estrogen replacement therapy (patch) within 7 days prior to registration
Age ≥ 18 years and female
Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2
Postmenopausal status confirmed as one of the following:

Where it is running

Arizona Center for Cancer Care - Gilbert — Gilbert, Arizona, United States
CTCA at Western Regional Medical Center — Goodyear, Arizona, United States
Arizona Center for Cancer Care-Peoria — Peoria, Arizona, United States
Arizona Center for Cancer Care - Biltmore — Phoenix, Arizona, United States
Arizona Center for Cancer Care - Phoenix — Phoenix, Arizona, United States
Mayo Clinic Hospital in Arizona — Phoenix, Arizona, United States
Arizona Center for Cancer Care - Osborn — Scottsdale, Arizona, United States
Arizona Center for Cancer Care - Scottsdale — Scottsdale, Arizona, United States
Arizona Center for Cancer Care-Surprise — Surprise, Arizona, United States
Arizona Center for Cancer Care — Tempe, Arizona, United States
Mercy Hospital Fort Smith — Fort Smith, Arkansas, United States
NEA Baptist Memorial Hospital and Fowler Family Cancer Center - Jonesboro — Jonesboro, Arkansas, United States
UCSF Cancer Center - Berkeley — Berkeley, California, United States
Tower Cancer Research Foundation — Beverly Hills, California, United States
Keck Medicine of USC Buena Park — Buena Park, California, United States
UCSF Cancer Center Burlingame — Burlingame, California, United States
Marshall Cancer Center — Cameron Park, California, United States
Mercy Cancer Center - Carmichael — Carmichael, California, United States
Mercy San Juan Medical Center — Carmichael, California, United States
Enloe Medical Center — Chico, California, United States
City of Hope Corona — Corona, California, United States
City of Hope Comprehensive Cancer Center — Duarte, California, United States
Kaiser Permanente Dublin — Dublin, California, United States
Mercy Cancer Center - Elk Grove — Elk Grove, California, United States
Katmai Oncology Group — Anchorage, Alaska, United States

Full record on ClinicalTrials.gov

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