Eliminating Surgery After Systemic Therapy in Treating Patients With HER2 Positive or Triple Negative Breast Cancer

PRIMARY OBJECTIVES:

I. To determine the 6 months (mo), 1, 2, 3, and 5-year biopsy confirmed ipsilateral breast
tumor recurrence rate (IBTR, invasive, and/or in situ) among patients who do not undergo
surgery.

SECONDARY OBJECTIVES:

I. To determine the number (%) of patients where final biopsy reveals residual disease and
quantify the residual disease (residual cancer burden, RCB) determined by routine pathologic
examination of surgery specimens.

II. To assess baseline, 6 months, 1, 3, and 5 years decisional comfort of clinical trial
participation using the Decisional Regret Scale (DRS).

III. To determine patient-reported cosmetic outcome, breast pain, and functional status using
the Breast Cancer Treatment Outcomes Scale (BCTOS) at baseline, 6 months, 1, 3, and 5 years.

IV. To determine the 6 mo, 1, 2, 3, and 5-year incidence of ipsilateral breast and nodal
recommendation and performance of biopsy based on breast imaging follow-up.

V. Correlate "liquid biopsy" analyses (after neoadjuvant systemic therapy [NST], 6 months and
one year postradiotherapy or surgery) among protocol participants with pathologic complete
response (pCR), utilizing circulating tumor cells (CTCs) and circulating
tumor-deoxyribonucleic acid (DNA) (ctDNA).

VI. Among patients who decide to proceed with routine surgery, record the results of final
biopsy compared with routine pathologic examination of surgery specimens.

VII. To determine patient-reported quality of life using the Functional Assessment of Cancer
Therapy-Breast version 4 (FACT B+4) instrument at baseline, 6 months, 1, 3, and 5 years after
treatment.

OUTLINE:

Within 12 weeks of completing neoadjuvant systemic therapy, patients undergo whole breast
irradiation over 15-25 fractions on consecutive days. Patients then undergo external beam
radiation therapy (EBRT) boost over 7 fractions on consecutive days beginning the day
following completion of whole breast irradiation.

After completion of study treatment, patients are followed up every 6 months for 5 years.

Inclusion Criteria:

- Pathologically confirmed unicentric invasive breast cancer defined as radiologic
clinical stage T1 or T2 (=< 5 cm), N0 or N1 (=< 4 abnormal axillary nodes on initial
ultrasound), clinical stage M0

- HER2 positive (immunohistochemistry [IHC] 3+ and or fluorescence in situ hybridization
[FISH] amplified) or triple receptor negative (triple negative [TN], estrogen receptor
[ER]/progesterone receptor [PR] < 10% HER2 negative [IHC 1+ or 2+ FISH non-amplified])
receiving any standard routine clinical NST regimen

- Patient desires breast conserving therapy

- Age 40 years or older; this age cutoff is justified because breast cancers in women
under the age of 40 are known to have a significantly higher risk of IBTR presumably
due to underlying biologic differences

- Female sex

- If the patient has a history of a prior non-breast cancer, all treatment for this
cancer must have been completed prior to study registration and the patient must have
no evidence of disease for this prior non-breast cancer

- Patient must have an initial nodal ultrasound that does not demonstrate more than four
suspicious lymph nodes, any suspicious lymph nodes should be biopsied to determine if
nodal metastatic disease present

Exclusion Criteria:

- Radiologic evidence for a stage T3 or clinical stage T4 breast cancer

- Clinical or pathologic evidence for distant metastases

- Prior diagnosis of invasive or ductal carcinoma in situ breast cancer in the
ipsilateral breast

- Clinical evidence of progression of disease > 20% in the breast or new evidence of
nodal metastases

- Patient is known to be pregnant

- Patient is participating in a NST protocol in which surgical excision of the breast
and or lymph nodes are required