Breast cancer is the most common cancer for women in Hong Kong, with 4988 new cases diagnosed in 2020. Among them, 1289 patients were treated in Queen Elizabeth Hospital (QEH), of which 769 patients received radiotherapy. Radiotherapy is an important treatment modality to reduce the risk of recurrence after breast conservation surgery or mastectomy for high risk cancers.
The majority of breast cancer patients undergo radiotherapy in supine position. However, there are drawbacks with this setup for patients with large pendulous breasts. They would usually experience more severe acute skin toxicities with moist desquamation especially at the axilla and infra-mammary fold, due to the increased separation distance of the target volume and the shape of the breast tissue which flops over laterally. Also, a larger lung volume would be irradiated which may be clinically unacceptable.
Studies have confirmed that treatment in prone position decreases desquamation in women with large pendulous breasts, and facilitates the avoidance of lung irradiation when compared with supine position, while delivering the same treatment coverage and clinical outcomes.
The prone set up position has been introduced in QEH in recent years. QEH is the only center equipped with prone breast board among the six oncology centers in Hospital Authority. The board platform has a modifiable aperture through which the target breast is positioned away from the thorax. The use of a wedge under the contralateral side achieves axial rotation of the patient towards the target breast. The process of radiation therapy includes set-up of the prone breast board, CT imaging, computer planning, image verification and treatment delivery.
The challenge with the prone set up is that some elderly patients may have difficulty in maintaining a stable prone position. But for most patients with large pendulous breasts, the prone set up is a valuable option offering significant advantages in reducing treatment toxicity while achieving equivalent clinical outcomes.
