ABCSG 26/SOLE Details

A phase-III-trial evaluating the role of continuous letrozole vs. intermittent letrozole following 4 to 6 years of prior adjuvant endocrine therapy for postmenopausal women with hormone-receptor-positive, node-positive early-stage breast cancer


Contact ABCSG-Trial office

Phone: +43 1 408 92 30
Fax: +43 1 409 09 90


ABCSG 26 Design
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Trial objectives:

This trial will compare continuous letrozole for five years with intermittent letrozole over a five year period for postmenopausal women who are disease-free following 4-6 years of prior adjuvant endocrine therapy with SERM(s) and/or AI(s) for endocrine-responsive node-positive operable breast cancer.

Primary endpoint

  • Disease-free survival (includes second (non-breast) malignancies and deaths)

Secondary endpoints

  • Overall survival
  • Distant disease-free survival
  • Breast cancer free interval (events are reappearance of invasive breast cancer at any site including contralateral disease)
  • Sites of first DFS failure
  • Second (non-breast) malignancies
  • Deaths without prior cancer event
  • Adverse events

Criteria for patient eligibility/ineligibility:

  1. Patients must be postmenopausal using any one of the following criteria. Because letrozole is not effective in pre- or perimenopausal patients, and may stimulate ovarian function, definitive confirmation of postmenopausal status is required.

    Patients of any age who have had a bilateral oophorectomy (including radiation castration AND amenorrheic for > 3 months)

    Patients 56 years old or older. If the patient has any evidence of ovarian function, biochemical evidence of definite postmenopausal status (defined as estradiol, LH, and FSH in the postmenopausal range) is required

    Patients 55 years old or younger must have biochemical evidence of definite postmenopausal status (defined as estradiol, LH, and FSH in the postmenopausal range. Patients who have received prior LHRH analogue within the last year are eligible if they have definite evidence of postmenopausal status as defined above

  2. Patients must be accessible for follow-up
  3. At diagnosis, patients must have had operable, non-inflammatory breast cancer
  4. Patients must be clinically disease-free at randomization. (Note: It is recommended but not required that disease-free status be verified by abdominal ultrasound, chest xray, and bone scan (if symptomatic). A mammogram within one year prior to randomization is recommended.)
  5. Patients must have had steroid hormone receptor positive tumors (ER and/or PgR), determined by immunohistochemistry, after primary surgery and before commencement of prior endocrine therapy
  6. Following primary surgery, eligible patients must have had evidence of lymph node involvement either in the axillary or internal mammary nodes, but not supraclavicular nodes
  7. There must have been no evidence of recurrent disease or distant metastatic disease at any time prior to randomization
  8. Not eligible: Patients who have had bilateral breast cancer
  9. Patients must have had proper local treatment including surgery with or without radiotherapy for primary breast cancer with no known clinical residual loco-regional disease
  10. Patients must have clinically adequate hepatic function
  11. Not eligible: Patients who have had a bone fracture due to osteoporosis at any time during the 4-6 years of prior endocrine SERM/AI therapy
  12. Not Eligible: Patients who have had any previous or concomitant malignancy EXCEPT adequately treated: basal or squamous cell carcinoma of the skin, in situ carcinoma of the cervix or bladder, contra- or ipsilateral in situ breast carcinoma
  13. Not eligible: Patients who have had any other non-malignant systemic diseases (cardiovascular, renal, lung, etc.) that would prevent prolonged follow-up
  14. Not eligible: Patients with psychiatric, addictive, or any disorder which compromises compliance with protocol requirements
  15. Patients must have completed 4 to 6 years of prior adjuvant endocrine therapy with SERM(s), aromatase inhibitor(s), or a sequential combination of both. When calculating 4-6 years, neoadjuvant endocrine therapy should not be included
  16. Patients must have stopped prior endocrine SERM/AI therapy, and must be randomized within 12 months (1 year) of the last dose of prior endocrine SERM/AI therapy
  17. Patients may have received any type of prior adjuvant therapy, including but not limited to neoadjuvant chemotherapy, neoadjuvant endocrine therapy, adjuvant chemotherapy, trastuzumab, ovarian ablation, GnRH analogues, lapatinib
  18. Patients must have stopped hormone replacement therapy (HRT), bisphosphonates (except for treatment of bone loss), or any investigational agent at randomization (Note: These agents are also not permitted during trial treatment)
  19. Pathology material from the primary tumor must be available for submission for central review as part of the quality control measures for this protocol
  20. Written Informed Consent (IC) must be signed and dated by the patient and the investigator prior to randomization
  21. Written consent to pathology material submission, indicating the patient has been informed of and agrees to tissue material use, transfer and handling, must be signed and dated by the patient and the investigator prior to randomization