Prostate movement and deformation in fractionated prostate radiotherapy

By:

Sarwar, A

Contributor(s):

Publication details: 2018Uniform titles:

Clinical Oncology

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Summary: Aims: Despite image-guided radiotherapy for prostate cancer, there remain uncertainties regarding dose delivered to intended planning target volumes [1]. To reduce intra-fraction variability, daily bowel and bladder preparation are now incorporated in most protocols [2]. However, the impact of these on prostate movements (PM) and deformation (PD) is yet not completely understood to aid anisotropic margins [3]. Our aim is to assess the impact of differential rectal filling on PM and PD. Methods: Our hypothesis is that prostate deformation is independent of prostate movement and should be incorporated in daily set-up correction. This study will assess the correlation of rectal volume to prostate volume, movement and deformation in 10 consecutive patients treated with 60 Gy/20 fractions. Here we present the data on prostate movement on the initial 4 patients. We intend to measure prostate deformation using distance in each orthogonal direction from the centre of mass of the prostate to prostate margins to acquire deformation vector fields for deformation volume histograms. We will then compare PM and PD. Results: The mean rectal volume was 42.94 ml +/- 11.98 ml. The mean prostate volume (PV) was 37.64 ml +/- 18.63 ml. The mean translational errors were: vertically e3.2 +/- 0.41 mm, longitudinally e0.4 +/- 0.24 mm and laterally 0.3 +/- 0.25 mm. Rectal volume correlated with the PV r2= 0.80 (P < 0.001, 95% CI 0.611 to 0.761). Majority of the movement in the 3 co-ordinates was superiorly (75%), anteriorly (44%) and to the right (50%).There appears to be limited correlation of prostate volume with translational movements, vertically: r2 = 0.27 (P < 0.01, 95% CI e0.009 to e0.004), longitudinally (r2 = 0.03, P = 0.89, 95% CI e0.002 to 0.000) and laterally r2 = 0.00 (P = 0.83, 95% CI e0.001 to 0.001). Conclusion: Our preliminary results demonstrate that prostate volume is influenced by rectal volume. However, the correlation between PM and PV is limited. We are currently analysing the relationship between PD, PM and PV to budget for prostate deformation for fractionated radiotherapy. [Conference abstract]

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Aims: Despite image-guided radiotherapy for prostate cancer, there remain uncertainties regarding dose delivered to intended planning target volumes [1]. To reduce intra-fraction variability, daily bowel and bladder preparation are now incorporated in most protocols [2]. However, the impact of these on prostate movements (PM) and deformation (PD) is yet not completely understood to aid anisotropic margins [3]. Our aim is to assess the impact of differential rectal filling on PM and PD. Methods: Our hypothesis is that prostate deformation is independent of prostate movement and should be incorporated in daily set-up correction. This study will assess the correlation of rectal volume to prostate volume, movement and deformation in 10 consecutive patients treated with 60 Gy/20 fractions. Here we present the data on prostate movement on the initial 4 patients. We intend to measure prostate deformation using distance in each orthogonal direction from the centre of mass of the prostate to prostate margins to acquire deformation vector fields for deformation volume histograms. We will then compare PM and PD. Results: The mean rectal volume was 42.94 ml +/- 11.98 ml. The mean prostate volume (PV) was 37.64 ml +/- 18.63 ml. The mean translational errors were: vertically e3.2 +/- 0.41 mm, longitudinally e0.4 +/- 0.24 mm and laterally 0.3 +/- 0.25 mm. Rectal volume correlated with the PV r2= 0.80 (P &lt; 0.001, 95% CI 0.611 to 0.761). Majority of the movement in the 3 co-ordinates was superiorly (75%), anteriorly (44%) and to the right (50%).There appears to be limited correlation of prostate volume with translational movements, vertically: r2 = 0.27 (P &lt; 0.01, 95% CI e0.009 to e0.004), longitudinally (r2 = 0.03, P = 0.89, 95% CI e0.002 to 0.000) and laterally r2 = 0.00 (P = 0.83, 95% CI e0.001 to 0.001). Conclusion: Our preliminary results demonstrate that prostate volume is influenced by rectal volume. However, the correlation between PM and PV is limited. We are currently analysing the relationship between PD, PM and PV to budget for prostate deformation for fractionated radiotherapy.&nbsp;[Conference abstract]

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