A Multi-Institutional Registry for CyberKnife Stereotactic Accelerated Partial Breast Irradiation (CK-SAPBI)

Radiotherapy for breast cancer is delivered using several whole breast and partial breast
approaches. The optimal approach is unknown. The utilization of partial breast irradiation is
growing due to the convenience of fewer fractions versus fifteen- thirty treatments required
with conventional or hypofractionated whole breast radiation therapy.

Early results with partial breast techniques are promising, showing similar cancer control
and toxicity. There is a large body of mature Phase I/II and preliminary Phase III data
available exploring the replacement of WBI with an accelerated course of radiation therapy
restricted to the region around the tumor bed (accelerated Partial Breast Irradiation, aPBI)
using a variety of techniques. For appropriately selected patients treated with modern
techniques, the results are encouraging and the techniques have been shown to be safe,
tolerable, and highly reproducible with outcomes similar to WBI.

Currently, there is limited data assessing the quality of life, cosmetic and oncologic
outcomes following stereotactic partial breast irradiation in a large patient population. Our
study will be the first essential step in aggregating the outcomes of patients undergoing
this type of external beam irradiation in a large patient population.

Inclusion Criteria:

- Subjects are eligible to participate in the registry if they receive CK-SAPBI in 5
fractions within 12 weeks of surgery and sign an institution specific consent form.

Additionally, subjects will be considered standard risk and optimal for CK-SAPBI if they
meet the following criteria:

- Newly diagnosed AJCC (seventh edition) Stage 0 or I breast cancer.

- On histological examination, the tumor must be DCIS or invasive non-lobular carcinoma
of the breast

- Surgical treatment of the breast must have been wide excision, lumpectomy or partial
mastectomy

- Age 50 years or greater

- ER positive

- PR positive

- Her2 negative (IHC 0-1+; for IHC 2+, FISH must be non-amplified)

- Subjects with invasive tumors should undergo axillary sentinel lymph node evaluation
or axillary lymph node dissection.

- Negative inked surgical margins of excision or re-excision, clear of invasive tumor
and DCIS by at least 2 mm

- Negative post-excision or post-reexcision mammography if cancer presented with
malignancy-associated microcalcifications with no remaining suspicious calcifications
in the breast before radiotherapy. Alternatively, a specimen radiograph can be
obtained showing all the suspicious calcifications.

- No involved axillary lymph nodes, N0(i+) allowed

- Target lumpectomy cavity/whole breast reference volume must be <30% based on treatment
planning CT

Exclusion Criteria:

- -Patients with invasive lobular carcinoma or nonepithelial breast malignancies such as
sarcoma or lymphoma.

- Patients with tumors greater than 2 cm

- Patients with surgical margins which cannot be microscopically assessed or not cleared
by at least 2mm at pathological evaluation.

- Patients with multicentric carcinoma or with other clinically or radiographically
suspicious areas in the ipsilateral breast unless confirmed to be negative for
malignancy by biopsy. Breast MRI will be required to exclude multicentric disease and
additional suspicious areas will require biopsy to exclude malignancy.

- Patients with involved axillary nodes.

- Patients with collagen vascular diseases (active).

- Patient with known deleterious BRCA1/2 mutations or known mutations in other high
penetrance genes (TP53, STK11, PTEN, CDH1)

- Patients with prior ipsilateral breast irradiation.

- Patients with prior ipsilateral thoracic irradiation.

- Patients with Paget's disease of the nipple.

- Patients with diffuse suspicious microcalcifications.

- Patients with suspicious microcalcifications remaining on the post-excision mammogram.

- Patients receiving (neo)adjuvant systemic therapy other than hormonal therapy

- Patients with oncoplastic reconstruction and absence of surgical clips