Inclusion Criteria:

1. Female subject with a pathologically-confirmed diagnosis of invasive ductal
carcinoma.

2. Tumor size < 2cm.

3. Negative axillary node involvement, determined by either

1. Sentinel node biopsy,

2. Axillary node dissection removing > 6 nodes

4. No evidence of metastatic disease.

5. Treated by BCS with microscopically clear resection margins (> 2mm to ink) for
invasive and non-invasive disease or no residual disease on re-excision.

Exclusion Criteria:

1. Age < 60 years.

2. Subjects who will receive adjuvant chemotherapy.

3. A known deleterious mutation in BRCA-1 and/or BRCA-2.

4. Extensive DCIS, mammographically or pathologically.

5. Tumor histology of pure lobular carcinoma (invasive or in-situ).

6. Adenoid cystic and non-epithelial malignancies (e.g. sarcoma or lymphoma).

7. Lymphovascular invasion (LVI) present.

8. Bilateral invasive malignancy of the breast (synchronous or metachronous).

9. More than one ipsilateral breast primary tumor.

10. Previous irradiation to the ipsilateral breast.

11. Presence of an ipsilateral breast implant.

12. Serious non-malignant disease that precludes radiation treatment or conscious
sedation.

13. Unable for any reason to undergo PBSI within 14 weeks of the last breast surgery.

14. Concomitant malignancies, except non-melanoma skin cancer and carcinoma in situ of
any site.

15. Significant persistent post-surgical complications.

16. Currently pregnant or lactating.

17. Psychiatric or addictive disorders which would preclude obtaining informed consent.

18. Subject not committed to at least 3 years of follow-up.

19. Low CBC levels: HB < 100 - Platelets < 100 - Neutrophil count < 1

20. Close partner not consenting

21. Inability to confidently localize/delineate the surgical cavity on CT and/or US.

22. Subject not suitable for a minimum 2-plane implant based on tumor location/breast
size.

23. Seroma exceeding 3cm

24. Seroma within the inner quadrants