Tumour tracking for radiotherapy of lung tumours”

Tumour tracking for radiotherapy of lung tumours”

Abstract

One of the main causes of death for males in New Zealand is lung cancer. Lung cancer has a poor prognosis. The 5-year survival for lung cancer patients is as low as 10-15%. One of the treatment options is radiotherapy. One of the difficulties in treatment of lung cancers with radiotherapy is that intra-fractional movement of lung tumours necessitates considerable treatment margins around the lesion to ensure sufficient dose coverage. These margins result in the treatment volumes to be several folds larger than the actual tumour volume. Consequently, a large fraction of healthy lung tissue surrounding the tumour receives an undesired high dose, which may lead to considerable side effects. As a consequence, treatment of lung cancers with radiotherapy is often restricted to non-optimal radiation doses. This is despite the clinical evidence that higher radiation doses to the tumour result in a survival advantage.

One way of reducing the treatment margins and thereby enabling higher radiation doses to the tumour is to track and correct for tumour motion in real-time. In the past few years, I have been involved in developing the Wuerzburg Adaptive Tumour Tracking System (WATTS). The WATTS acquires two independent (non-optimal) data sets, one based on real-time megavoltage imaging and the other on an optical tracking device to record abdominal movement, to infer the tumour position in real-time. This information is processed and passed to the control system of a robotic hexapod table. The idea is to move the hexapod table continuously against the direction of the tumour motion in such a way that the moving tumour remains stationary in space.