Elsevier

Radiotherapy and Oncology

Volume 80, Issue 3, September 2006, Pages 355-362
Radiotherapy and Oncology

Prostate radiotherapy
Evaluating the relationship between erectile dysfunction and dose received by the penile bulb: Using data from a randomised controlled trial of conformal radiotherapy in prostate cancer (MRC RT01, ISRCTN47772397)

https://doi.org/10.1016/j.radonc.2006.07.037Get rights and content

Absrtact

Aim

To evaluate the relationship between erectile function and the radiation dose to the penile bulb and other proximal penile structures in men receiving conformal radiotherapy (CFRT) for prostate cancer (PCa).

Methods

The Medical Research Council (MRC) RT01 trial randomised 843 men who had localised PCa to receive either 64 or 74 Gy after 3–6 months neoadjuvant hormonal treatment. Fifty-one men were selected who were potent prior to hormonal treatment, having completed both pre-hormone and 2-year post-CFRT Quality of Life assessments, and on whom dose volume data were available for analysis. The men were divided into three groups according to 2-year follow-up: potent, reduced potency, and impotent. The bulb of the penis together with the crura, were outlined on restored treatment plans. Dose–volume histograms were generated and compared between the three groups. An ordered logistic regression model was used to calculate the odds ratio of a range of dose–volume parameters to the penile bulb and effect on erectile dysfunction. The dose to the penile bulb was correlated to the dose received by the crura.

Results

Of the 51 patients, 12 remained potent, 22 had reduced potency, and 17 were impotent at 2 years. No differences were seen in mean dose to the penile bulb by allocated treatment (t test = 1.61, p = 0.11). The mean doses to the penile bulb received by the potent, reduced potency, and impotent groups were 45.5 Gy (SD 17.1), 48 Gy (SD 16.1), and 59.2 Gy (SD 13.8), respectively. There was a strong correlation between the mean dose received by the penile bulb and dose to the crura (r = 0.82, p < 0.0001). 83.3% of impotent patients received a D90 ⩾50 Gy to the penile bulb compared with 29.4% of patients who maintained potency at 2 years (p = 0.006).

Conclusion

There is evidence from this study to suggest a dose volume effect on the penile bulb and erectile dysfunction. A D90 ⩾50 Gy is associated with a significant risk of erectile dysfunction and this should form a basis for selecting dose constraints in future dose escalation studies.

Section snippets

Trial and trial treatment

The MRC RT01 trial was a phase III open-treatment multi-centre randomised controlled trial of CFRT dose with an initial cohort study of neo-adjuvant androgen deprivation prior to randomisation. The RT01 trial was coordinated from the MRC Clinical Trials Unit (CTU), London, UK. The trial followed the principles of the Declaration of Helsinki. Ethical approval was attained by each centre and all men gave informed consent prior to registration. Prior to participation each centre had to ensure that

Results

From 843 patients randomised to RT01, 51 (6%) patients met the criteria for this sub-study (Fig. 1). Table 2 summarises the patient baseline demographic, clinical and treatment related parameters between the three groups. The median age for the whole cohort was 66 yr. Although clinical stage was fairly well balanced between the groups, those that became impotent were, perhaps, a little older (Potent 65 yr, Intermediate 66 yr and Impotent 70 yr). However there was no statistical difference observed

Discussion

This study demonstrates evidence of a dose–volume effect for radiation dose to the penile bulb (PB) and the presence at 2-years of erectile dysfunction (ED) in those receiving CFRT for localised PCa. The study focused on a tightly defined group of 51 men who were all potent before neo-adjuvant hormones were initiated and whose testosterone values had recovered by the 2-year assessment.

There are two principle reasons for such a low yield of patients from the cohort. Firstly 284 of the 843

Conclusions

Our study confirms that a dose–volume relationship exists between the PB and ED. It is possible to escalate the dose to the prostate without irradiating the PB to high dose. A D90  50 Gy is associated with a significant risk of ED, whilst the threshold for preservation of potency lies between 40 and 50 Gy. We advocate that the PB should be incorporated into CFRT plans for PCa as an avoidance structure and recommend excluding it from the high dose area.

We hope to incorporate the findings from this

Acknowledgments

This work was undertaken in The Royal Marsden NHS Foundation Trust who received a proportion of its funding from the NHS Executive; the views expressed in this publication are those by the authors and not necessarily those of the NHS Executive. This work was supported by the Institute of Cancer Research, the Bob Champion Cancer Trust and Cancer Research UK Section of Radiotherapy [CUK] grant number C46/A2131.

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