Dose-response of anal cancerThe dose–response of the anal sphincter region – An analysis of data from the MRC RT01 trial
Section snippets
Patient cohort
The study was performed with data from the MRC RT01 multicentre randomised controlled trial (ISRCTN 47772397). In this trial 843 prostate cancer patients were treated with 3D conformal radiotherapy, 421 with a prescribed standard dose of 64 Gy, 422 with an escalated dose of 74 Gy. Further details about the implementation of the trial can be found in Sydes et al. [15]; results were published in Dearnaley et al. [16]. Only 388 patients were eligible for dosimetric analysis, as the planning data
DSM-analysis
Statistically significant correlations were found between subjective sphincter control and the dose to the anal wall. Lateral extent as well as DSH were significantly correlated with outcome with the strongest correlation for the lateral extent at 53 Gy exceeding 56% (). Correlations between dose and outcome are illustrated in Fig. 3(a) and (b).
When analysing the mean dose to the anal surface, the strongest correlation was found for a mean dose of 45.1 Gy (). The association
Discussion
While in a previous study [19] no statistically significant correlations between the dose to the anorectal wall and subjective sphincter control could be found, this outcome was significantly correlated with the dose to the anal sphincter region. The strongest correlations were found for the lateral extent of the dose to the anal surface at 53 Gy. However, significant correlations were also found for various dose-levels of the DSH as well as the mean dose. The optimal cutpoints for the mean dose
Conclusion
Subjective sphincter control was significantly correlated with the dose to the anal sphincter region. Spatial aspects such as the lateral extent of the dose distribution were most strongly correlated with outcome, but volumetric measures such as DSH and mean dose were important for outcome, too. Consequently, three different strategies to limit the incidence of unsatisfactory subjective sphincter control could be used. First, it is desirable to limit the lateral extent of the anal surface
Acknowledgement
We acknowledge NHS funding to the NIHR Biomedical Research Centre.
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