Assessing the Accuracy of Tumor Biopsies After Chemotherapy to Determine if Patients Can Avoid Breast Surgery

Inclusion Criteria:

• The patient must have signed and dated an Institutional Review Board (IRB)-approvedconsent form that conforms to federal and institutional guidelines

• The patient must have an Eastern Cooperative Oncology Group (ECOG) performancestatus of 0 or 1

• Patients must have had ER analysis performed on the primary breast tumor collectedprior to neoadjuvant therapy according to current American Society of ClinicalOncology (ASCO)/College of American Pathologists (CAP) guideline recommendations forhormone receptor testing; if negative for ER, assessment of progesterone receptor (PgR) must also be performed according to current ASCO/CAP Guideline Recommendationsfor hormone receptor testing. Patients who have a primary tumor that is hormonereceptor-positive or hormone receptor-negative are eligible.

• Patients must have had HER2 testing performed on the primary breast tumor collectedprior to neoadjuvant chemotherapy according to the current ASCO/CAP guidelinerecommendations for human epidermal growth factor receptor 2 testing in breastcancer; patients who have a primary tumor that is HER2-positive, HER2-equivocal, orHER2-negative are eligible

• Patients must have had a biopsy marker placed within the tumor bed with imagingconfirmation (preferably mammogram but ultrasound or magnetic resonance imaging [MRI] is acceptable) of marker placement prior to neoadjuvant chemotherapy

• Patients with operable focal or multifocal (T1-T3, stage II or III invasive ductalcarcinoma [all receptor phenotypes]), and who have completed neoadjuvantchemotherapy with a clinical complete response (by clinical examination)

• Patients with synchronous bilateral breast cancer are eligible if at least one ofthe synchronous breast cancers has a cCR, and the side with a cCR meets criteria. (Patients with previous contralateral invasive breast cancer treated withanti-cancer therapy are eligible.)

• Patients must have achieved a complete or near complete radiologic tumor response onbreast imaging with mammogram, ultrasound, and MRI during or after completion ofappropriate neoadjuvant chemotherapy defined as:

• Mammogram with malignant appearing calcification or mass ≤ 1 cm; or

• Ultrasound with a hypoechoic area ≤ 2 cm; or

• Breast MRI not demonstrating a residual mass with rapid rise and washout typeIII kinetics.

• At the time of consent, the patient's intent must be to undergo breast conservingtherapy.

• Patient must be able to undergo stereotactic-vacuum-assisted breast biopsy with clipplacement after completion of neoadjuvant chemotherapy. (The patient must beenrolled on the study before performing the post-neoadjuvantstereotactic-vacuum-assisted breast biopsy.)

• Patient must have completed neoadjuvant chemotherapy.

• Patients with HER2-positive tumors must have received neoadjuvant anti-HER2 therapy (either with all or with a portion of the neoadjuvant chemotherapy regimen), unlessmedically contraindicated.

• Patients treated with PD-1 or PD-L1 inhibitors, CDK 4/6 inhibitors, or otherimmune-based therapy are eligible.

Exclusion Criteria:

• T4 tumors including inflammatory breast cancer

• Patients with distant metastatic disease

• Lumpectomy performed prior to study entry

• Patients with any history of prior radiation therapy in the affected breast

• Patients with a prior history of ipsilateral invasive breast cancer; (patients withprevious ipsilateral/contralateral DCIS or previous contralateral invasive breastcancer treated with anti-cancer therapy are eligible)

• Patients with invasive lobular carcinoma

• Patients who have multicentric disease

• Patients treated with neoadjuvant hormonal therapy only are not eligible

• Patients who are medically unfit to undergo surgical resection

• Patients without breast biopsy marker documented by imaging at tumor bed site priorto initiation of neoadjuvant therapy

• Patients with one or more of the following imaging criteria from any of the 3imaging modalities after completion of NCT demonstrating incomplete radiologicresponse are not eligible:

• Mammogram with malignant appearing calcifications or mass > 1 cm; or

• Ultrasound with a hypoechoic area > 2 cm; or

• Breast MRI demonstrating a residual mass with rapid rise and washout type IIIkinetics.

• Psychiatric or addictive disorders or other conditions that, in the opinion of theinvestigator, would preclude the patient from meeting the study requirements orinterfere with interpretation of study results

• Pregnancy or lactation at the time of study registration; (Note: Pregnancy testingaccording to institutional standards for women of childbearing potential must beperformed within 2 weeks prior to study registration.)