Three-dimensional conformal radiation therapy (3D CRT) with appropriate • compensation using a fi eld-in- fi eld technique or intensity-modulated radiation therapy (IMRT) to provide homogeneous dose to the breast tissue is the standard technique for de fi nitive radiation therapy for early stage breast cancer. The highest level of evidence supports whole breast irradiation followed by a boost to the lumpectomy cavity as the long-established optimal radiation course. Accelerated partial breast irradiation (APBI), although not yet the standard of care, may be an acceptable alternative for select patients unable to receive several weeks of radiation therapy. In addition to thorough physical examination, adequate imaging studies and path-• ological examination should be obtained for diagnosis, staging, and planning. All patients should undergo mammogram at diagnosis. Imaging also often includes ultrasound and MRI of the breast. These imaging studies should be reviewed prior to radiation planning. Image-guided biopsy generally con fi rms a diagnosis of cancer. Surgery consisting of segmental excision alone for ductal carcinoma in situ (DCIS) and segmental excision and sentinel lymph node biopsy (SLNB) is recommended for early invasive disease. Pathology should be reviewed to ensure adequate margins and con fi rm an early stage breast cancer requiring radiation to the breast without inclusion of the regional lymphatics. Surgical clips should be placed at the time of surgery if possible to assist in delineation of the tumor bed and for radiographic localization prior to radiation delivery.
10 Early Breast Cancer
Shannon M. MacDonald and Brian Napolitano
S. M. MacDonald , M.D. • B. Napolitano (�) Department of Radiation Oncology , Massachusetts General Hospital, Harvard Medical School , Boston, MA , USA e-mail: [email protected]
74 S.M. MacDonald and B. Napolitano
For whole breast radiation planning, a CT with • £ 3-mm slice thickness should be performed in the supine or prone position. For APBI, a CT slice thickness of 1.5–2 mm through the lumpectomy cavity may enable improved delineation of the lumpectomy cavity. For supine positioning, the patient should be positioned on a breast board with • arms above the head. Patients with pendulous breasts and/or tumor bed in close proximity to the chest wall and critical structures (heart/lung) may bene fi t from prone positioning. For prone positioning, patient should be placed prone on a dedicated prone breast board, and care should be taken to ensure that the patient is comfortable as this is very important to facilitate reproducibility. Patients with orthopedic injuries to the back or neck may not be ideal candidates for prone positioning. Target volumes include the breast tissue and lumpectomy cavity for whole breast • irradiation and lumpectomy cavity, lumpectomy CTV, and lumpectomy PTV for APBI. Suggested target volumes are described in Table • 10.1 (Figs. 10.1 , 10.2 , 10.3 , 10.4 , 10.5 , and 10.6 ).
Table 10.1 Suggested target volumes for 3-Dimensional treatment planning for early stage breast cancer
Target volumes De fi nition and description Breast Clinical reference is required for breast tissue delineation. Breast tissue
may be wired, or borders may be placed clinically at the time of CT. Contour should include all glandular breast tissues. The cranial border should be below the head of the clavicle and at the insertion of the second rib. Caudal border is de fi ned by the loss of breast tissue. Medial border is at the edge of the sternum and should not cross midline. Lateral border is de fi ned by the midaxillary line but is dependent on ptosis of the breast tissue. Anterior border is the skin or a few millime-ters from the surface of the skin (for dose reporting), and the posterior border is the pectoralis muscles and muscles of the chest wall. The volume should not include these muscles or the ribs
Lumpectomy cavity Seroma, surgical clips, and notable differences in the glandular breast tissue should be included. Comparison to the contralateral breast may be useful, particularly when fl uid and/or surgical clips are not present. All imaging studies should be reviewed prior to planning to assist in delineating this volume. This volume should not extend outside of the breast tissue
Lumpectomy CTV a Lumpectomy cavity with a 1.0- to 1.5-cm expansion. This volume should not extend outside of the body or into the pectoralis muscles and/or muscles of the chest wall
Lumpectomy PTV a Lumpectomy CTV with a margin based on setup uncertainty and predicted patient motion (generally 0.5–1.0 cm). This volume may extend outside of the patient surface and into the pectoralis muscles and/or muscles of the chest wall. Adjustments to this volume may be necessary for dose-reporting purposes
a For APBI only; for whole breast irradiation, the lumpectomy cavity alone is the target for boost
7510 Early Breast Cancer
Fig. 10.1 Axial images in the supine position for a woman with left-sided stage I breast cancer
Fig. 10.2 Axial images in the prone position for a woman with left-sided DCIS
76 S.M. MacDonald and B. Napolitano
Fig. 10.4 Supine breast plan using tangent fi elds with a fi eld-in- fi eld technique for homogeneity and a small MLC block for cardiac shielding. Prescribed dose is 50 Gy at 2 Gy per fraction followed by an electron boost to the lumpectomy cavity to 10 Gy at 2 Gy per fraction
Fig. 10.3 Axial images for APBI. Lumpectomy cavity is based on seroma, clips placed by surgeon, and information from review of mammogram, US, and MRI. CTV is typically a 1.5-cm expansion around the lumpectomy cavity that excludes pectoralis muscle, rib, and chest wall and does not extend outside of the contoured breast tissue. Typically, the CTV does not extend to the skin (restricted to 5 mm from patient surface). PTV is formed by an expansion of approximately 5 mm (depending on institutional setup uncertainty) around the CTV
7710 Early Breast Cancer
Fig. 10.6 APBI plan using a mini-tangent photon fi elds in combination with an en face electron fi eld
Fig. 10.5 Prone breast plan using tangent fi elds with a fi eld-in- fi eld technique. Prescribed dose is 50 Gy at 2 Gy per fraction followed by a mini-tangent photon boost to the lumpectomy cavity to 10 Gy at 2 Gy per fraction
