A COMPARISON OF CONVENTIONAL AND CONFORMAL RADIOTHERAPY OF THE ESOPHAGUS - WORK-IN-PROGRESS

A retrospective treatment planning study was carried out in five patie nts to assess the effectiveness of conformal radiotherapy of the oesop hagus. A two-phase conventional treatment plan was created for each pa tient, with a prescribed dose of 55 Gy. This plan was compared with a single-phase conformal plan consisting of the same held arrangement as the second phase of the conventional treatment, but with conformal bl ocks shaped to the beam's eye view of the planning target volume. A fu rther comparison was made between the conventional plan and a two-phas e plan using the same beam angles and weights as the conventional plan , but with conformal field shapes. The effectiveness of each treatment plan was assessed using dose-volume histograms and normal tissue comp lication probabilities for the lungs. On average, the single-phase con formal technique increased the mean lung dose from 22.5% (+/-6.2 SD) o f the prescribed dose to 29.5% (+/- 5.2 SD) compared with the conventi onal technique (p = 0.0001). This indicates that this technique did no t offer any benefit in terms of reducing the risk of pneumonitis. Howe ver, the two-phase conformal technique reduced the mean lung dose from 22.5% (+/- 6.2 SD) of the prescribed dose to 19.8% (+/-4.6 SD) (p = 0 .03), showing that this technique should reduce the risk of pneumoniti s. Further work is underway to study more patients and to investigate tumour control probability and dose escalation.