Evolution of radiotherapy techniques in breast conservation treatment

Abstract

Radiation therapy (RT) is an important component of breast cancer treatment that reduces local recurrence and improves survival after breast conservation. Breast conservation rates have increased significantly since the late 1980s and techniques have improved with greater awareness of the impact of radiation on the heart. An overview of randomized controlled trials of breast conservation using standard whole breast irradiation, whole breast hypofractionation, accelerated partial breast irradiation (APBI) and intraoperative radiation are reviewed. Selection criteria for breast conservation and the utility of adding a boost dose to the primary tumor site are reviewed. Modern dose constraints are documented and 10 different radiation techniques from the 1980s through to modern volumetric modulated arc therapy (VMAT) are compared for a patient where the breast and internal mammary nodes are treated. A radiation boost reduces the risk of a recurrence for most, but not all patients. Short courses of RT over 3-4 weeks are generally as effective as longer courses. Short-term follow-up of trials of APBI show promise for selected good prognosis subgroups. The role of intraoperative radiation remains controversial. In the last 30 years, there have been significant advances in radiation techniques. Modern radiotherapy equipment and techniques will reduce complications and improve survival rates.

Keywords: Breast neoplasms; mastectomy, segmental; neoplasm recurrence, local; radiotherapy, survival.

Figure 1

Breast conservation in the 1920s using radium needles (with permission, British Journal of Surgery).

Figure 2

Historical two dimensional planning techniques. (A) Medial tangent simulation film (heart border marked in yellow); (B) 2D radiation plan (heart not contoured); (C) coronary angiogram showing constriction of left anterior descending coronary artery (arrows) eight years after radiation to the left breast.

Figure 3

Imaging methods to determine the location of a primary tumour bed. (A) Mediolateral oblique view; arrow showing post core biopsy clip; (B) craniocaudal view (arrow showing tumor); (C) breast ultrasound showing tumor (yellow arrow); skin (blue arrow) and base of breast (red arrow); (D) pre-operative low dose CT scan as part of lymphoscintigram showing tumor (arrowed).

Figure 4

Pre-operative PET-CT scan of a patient with a tumor (arrowed) close to the chest wall.

Figure 5

Red = breast planning tumor volume (PTV); green =boost gross-tumor volume (GTV) showing titanium clips; aqua = boost clinical tumor volume (CTV = GTV + 10 mm); yellow = boost PTV (CTV + 7 mm).

Figure 6

Fused image showing heart covered by radiation beam (normal breathing, blue arrow) and missed after deep inspiration (red arrow). Primary tumor site marked at surgery by titanium clips (yellow arrow).

Figure 7

Axial and sagittal views of VMAT plan with deep inspiration breath hold (A,B), deep tangents (C,D) and conformal field-in-field plan with photon boost (E,F) (see Table 5, plan 10, 2 and 7 respectively). VMAT, volumetric modulated arc therapy.

Figure 8

Elekta Synergy^®: a modern linear accelerator used in external beam radiotherapy treatment.