Patients will be treated with cryoablation using the Endocare SlimLine Cyroprobe under real time ultrasound guidance and local anesthesia. The cryoablation consists of a 10 minute freeze phase followed by a 10 minute passive thaw, and ends with a second 10 minute freeze cycle. The freeze-thaw-freeze times may be adjusted at the physician's discretion depending on tumor size.

Lumpectomy will be performed under general anesthesia as per standard operative procedures at Washington University and Siteman Cancer Center.

If there is evidence of residual or recurrent tumor on follow-up imaging evaluation (6 month MRI (if can tolerate) and yearly MRI/mammography), patients in the cryoablation safety lead-in and who were randomized to receive cryoablation only will be crossed over to receive a rescue lumpectomy followed by adjuvant treatment based on standard of care.

Patients will be treated with cryoablation (Day 1) using the Endocare SlimLine Cyroprobe followed by adjuvant treatment.

The Endocare(TM) SlimLine (TM) Cryoprobe is a single use, disposable device designed for use with Endocare Cryocare Surgical Systems. Endocare cryoprobes are designed to deliver cold temperatures for cryoablation using high-pressure argon gas circulated through the cryoprobe, followed by active thawing using helium gas.

The Cryocare CS Surgical System is intended for use in open, minimally invasive, or endoscopic surgical procedures in the areas of general surgery, urology, gynecology, oncology, neurology, dermatology, ENT, proctology, pulmonary surgery, and thoracic surgery. The system is designed to freeze/ablate tissue by the application of extreme cold temperatures.

Excessive adverse events will be graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) v5.0. They are defined as toxicities occurring within 30 days after the cryoablation procedure and are at least possibly related to the cryoablation. These include death, life-threatening adverse events, inpatient hospitalization or prolongation of existing hospitalization, a persistent or significant disability/incapacity, or complications related to cryoablation which interfere with adjuvant therapy such that the adjuvant therapy cannot be performed at all or delayed for a period longer than 6 months or which result in unplanned mastectomy.

IBTR defined from date of procedure to date of ipsilateral breast cancer recurrence, with the occurrence of ipsilateral breast tumor recurrence as the event and patients will be censored at the last follow-up.

Excessive adverse events will be graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) v5.0. They are defined as toxicities occurring within 30 days after the cryoablation procedure and are at least possibly related to the cryoablation. These include death, life-threatening adverse events, inpatient hospitalization or prolongation of existing hospitalization, a persistent or significant disability/incapacity, or complications related to cryoablation which interfere with adjuvant therapy such that the adjuvant therapy cannot be performed at all or delayed for a period longer than 6 months or which result in unplanned mastectomy.