Dataset Information

Delivered dose can be a better predictor of rectal toxicity than planned dose in prostate radiotherapy.

ABSTRACT:

Background and purpose

For the first time, delivered dose to the rectum has been calculated and accumulated throughout the course of prostate radiotherapy using megavoltage computed tomography (MVCT) image guidance scans. Dosimetric parameters were linked with toxicity to test the hypothesis that delivered dose is a stronger predictor of toxicity than planned dose.

Material and methods

Dose-surface maps (DSMs) of the rectal wall were automatically generated from daily MVCT scans for 109 patients within the VoxTox research programme. Accumulated-DSMs, representing total delivered dose, and planned-DSMs, from planning CT data, were parametrised using Equivalent Uniform Dose (EUD) and 'DSM dose-width', the lateral dimension of an ellipse fitted to a discrete isodose cluster. Associations with 6 toxicity endpoints were assessed using receiver operator characteristic curve analysis.

Results

For rectal bleeding, the area under the curve (AUC) was greater for accumulated dose than planned dose for DSM dose-widths up to 70Gy. Accumulated 65Gy DSM dose-width produced the strongest spatial correlation (AUC 0.664), while accumulated EUD generated the largest AUC overall (0.682). For proctitis, accumulated EUD was the only reportable predictor (AUC 0.673). Accumulated EUD was systematically lower than planned EUD.

Conclusions

Dosimetric parameters extracted from accumulated DSMs have demonstrated stronger correlations with rectal bleeding and proctitis, than planned DSMs.

SUBMITTER: Shelley LEA

PROVIDER: S-EPMC5486775 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Publications

Delivered dose can be a better predictor of rectal toxicity than planned dose in prostate radiotherapy.

Shelley L E A LEA Scaife J E JE Romanchikova M M Harrison K K Forman J R JR Bates A M AM Noble D J DJ Jena R R Parker M A MA Sutcliffe M P F MPF Thomas S J SJ Burnet N G NG

Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology 20170428 3

<h4>Background and purpose</h4>For the first time, delivered dose to the rectum has been calculated and accumulated throughout the course of prostate radiotherapy using megavoltage computed tomography (MVCT) image guidance scans. Dosimetric parameters were linked with toxicity to test the hypothesis that delivered dose is a stronger predictor of toxicity than planned dose.<h4>Material and methods</h4>Dose-surface maps (DSMs) of the rectal wall were automatically generated from daily MVCT scans f ...[more]

PMID: 28460825

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Project description:When pooling retrospective data from different cohorts, slice thicknesses of acquired computed tomography (CT) images used for treatment planning may vary between cohorts. It is, however, not known if varying slice thickness influences derived dose-response relationships. We investigated this for rectal bleeding using dose-volume histograms (DVHs) of the rectum and rectal wall for dose distributions superimposed on images with varying CT slice thicknesses. We used dose and endpoint data from two prostate cancer cohorts treated with three-dimensional conformal radiotherapy to either 74 Gy (N = 159) or 78 Gy (N = 159) at 2 Gy per fraction. The rectum was defined as the whole organ with content, and the morbidity cut-off was Grade ?2 late rectal bleeding. Rectal walls were defined as 3 mm inner margins added to the rectum. DVHs for simulated slice thicknesses from 3 to 13 mm were compared to DVHs for the originally acquired slice thicknesses at 3 and 5 mm. Volumes, mean, and maximum doses were assessed from the DVHs, and generalized equivalent uniform dose (gEUD) values were calculated. For each organ and each of the simulated slice thicknesses, we performed predictive modeling of late rectal bleeding using the Lyman-Kutcher-Burman (LKB) model. For the most coarse slice thickness, rectal volumes increased (?18%), whereas maximum and mean doses decreased (?0.8 and ?4.2 Gy, respectively). For all a values, the gEUD for the simulated DVHs were ?1.9 Gy different than the gEUD for the original DVHs. The best-fitting LKB model parameter values with 95% CIs were consistent between all DVHs. In conclusion, we found that the investigated slice thickness variations had minimal impact on rectal dose-response estimations. From the perspective of predictive modeling, our results suggest that variations within 10 mm in slice thickness between cohorts are unlikely to be a limiting factor when pooling multi-institutional rectal dose data that include slice thickness variations within this range.

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Dataset Information

Delivered dose can be a better predictor of rectal toxicity than planned dose in prostate radiotherapy.

Background and purpose

Material and methods

Results

Conclusions

Publications

Delivered dose can be a better predictor of rectal toxicity than planned dose in prostate radiotherapy.

Similar Datasets

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