Sparing of the penile bulb and proximal penile structures with intensity-modulated radiation therapy for prostate cancer

Abstract

Quality of life is an important consideration in the treatment of early prostate cancer. Laboratory and clinical data suggest that higher radiation doses delivered to the bulb of penis and proximal penile structures correlates with higher rates of post-radiation impotence. The goal of this investigation was to determine if intensity-modulated radiation therapy (IMRT) spares dose to the penile bulb while maintaining coverage of the prostate. 10 consecutive patients with clinically organ confined prostate cancer were planned with 3D conformal radiation therapy (3D-CRT) or IMRT to give a dose of 74 Gy without specifically constraining the plans to spare the penile bulb. All 10 patients were ultimately treated with IMRT. Dose-volume histograms were evaluated and the doses to prostate, rectum, bladder and penile bulb were compared. IMRT reduced the mean penile bulb doses compared with 3D-CRT (33.2 Gy vs 48.9 Gy, p<0.001), the percentage of penile bulb receiving over 40 Gy (37.7% vs 67.2%, p<0.001) and the dose received by >95% of penile bulb (5.3 Gy vs 11.7 Gy, p=0.003). Maximum penile bulb doses were higher with IMRT (81.2 Gy vs 73.1 Gy, p<0.001) although the volume of this high dose region was small. Both methods resulted in similar coverage of the prostate. The volume of rectum receiving 70 Gy was significantly reduced with IMRT (18.4% vs 21.9%, p=0.003) but the volumes of bladder receiving 70 Gy were similar (p=0.3). IMRT may potentially reduce long term sexual morbidity by reducing the dose to the majority of the penile bulb.

An analysis of erectile function after intensity modulated radiation therapy for localized prostate carcinoma

“…Dosimetric studies of IMRT in the treatment of prostate cancer have shown the ability to reduce radiation dose specifically to proximal penile structures such as the penile bulb. 18,[42][43][44] Radiation dose to the penile bulb has been the subject of several studies concerning radiation-induced ED. 9,10,[30][31][32] Although the results of these reports are often conflicting, there is at least some evidence to suggest that by minimizing radiation dose to the proximal penile structures, the risk of radiation-induced ED may be significantly decreased.…”

Radiation therapy for prostate cancer and erectile (dys)function: The role of imaging

“…The mean dose to the proximal penile tissues was significantly reduced in IMRT plans with an average of 40%. Kao and colleagues [36] confirmed these results in a trial of ten patients treated by IMRT for PC, reporting a mean dose to the penile bulb of 49 Gy with 3D-CRT compared to 33 Gy with IMRT. Similar results were reported for rectum, while the prostate was adequately covered.…”

Erectile Dysfunction After Radiotherapy for Prostate Cancer

“…[21][22][23][24] Kao et al compared the dose to the penile bulb using IMRT versus 3D-CRT and found that it was possible to significantly reduce the dose without compromising the dose to the prostate (Table 5). 22 To precisely target the prostate with tighter margins, we currently have 4 fiducial markers implanted in the prostate prior to obtaining planning computed tomography and magnetic resonance imaging. Either 100 mL or 200 mL of saline is instilled in the rectum and the prostate is realigned daily by obtaining pretreatment radiographs and precisely realigning the fiducial markers.…”