Abstracts Archive

UK & Ireland Prostate Brachytherapy Conference 2011

Abstract number 3

Justification of pre-treatment correction of catheter movement in single fraction high dose-rate treatment of prostate cancer.

David Inchley, Mount Vernon Cancer Centre
Gerry Lowe, Mount Vernon Cancer Centre
Clare Anderson, Mount Vernon Cancer Centre
Aled Parry, Mount Vernon Cancer Centre
David Polley, Mount Vernon Cancer Centre
Peter Hoskin, Mount Vernon Cancer Centre

Aim/Introduction: Fractionated HDR prostate brachytherapy relies upon catheter positioning to achieve adequate tumour coverage whilst minimising dose to surrounding tissues. In multi-fraction treatments, peri-prostatic oedema may cause caudal displacement of the catheters relative to the prostate during the time between planning imaging and the subsequent fractions of treatment. A correction can be performed by moving the source positions within the needle (or physical advancement of the catheters).
We have extended this procedure to cover single fraction HDR prostate treatments.

Materials and Methods: To date 70 patients have been treated using a single fraction of HDR brachytherapy following EBRT to the prostate.
These patients were imaged for a planning scan as soon as possible after implantation. Before treatment, the CT imaging was repeated, and catheter movement correction applied. Treatment commenced as soon as possible after this CT.

Results: The mean time between planning and pre-treatment CT scans was 4 hours 12 minutes.
Movements were less than 3mm in 716 (51%) catheters. However, 213 (15%) catheters showed motion of greater than 5mm in the short time between planning and pre-treatment scans. Furthermore, in some cases (14%) catheter motion was in the opposite direction to that commonly seen after 24 hours, with 6% of these having moved more than 3mm.

Conclusion: There is already a literature justifying the need to perform catheter position correction between subsequent HDR fractions in multiple fraction treatments spanning a time greater than about 24 hours. Few groups, however, have looked at the first few hours after implantation.

This study has shown a different pattern of movements from that previously reported. There is clearly a need to perform correction for catheter displacement even if the treatment is delivered within a few hours of the planning scan, and this correction can be in either direction. Neglect of this has the potential to increase critical structure dose and decrease prostate coverage significantly.