Lower Gastrointestinal Morbidity and Management
During the weeks following the implant in a prostate cancer patient, there may be changes in bowel habits in the form of diarrhea or constipation, tenesmus, and rectal pressure 47, 57, 58. These symptoms generally respond to conservative symptomatic management. Late injury includes proctitis, rectal ulceration, fistula formation, and incontinence 59. The most common of these is proctitis, which often presents as a painless bleeding that is usually self-limited. Bleeding from proctitis presents late, about 1 to 2 years after implantation and may be exacerbated by constipation. Conservative management is recommended with stool softeners and local steroid creams or foams. Aggressive measures such as biopsies and laser treatments may precipitate ulceration and fistula formation and should be avoided whenever possible 47, 60.
The incidence of proctitis has been reported to range from 1% to 12% 47, 61. While the 12% proctitis rate reported by Wallner et. al. represents the early experience with CT-based implants, subsequent refinements of the technique indicate that proctitis rates have decreased to 2-6% 47, 62. In a review of 825 patients, Gelblum and Potters identified a 9.4% incidence of proctitis and 6.6% incidence of limited rectal bleeding at a mean time of 8 months post-implant. Four patients developed rectal ulceration with 2 of these patients having had rectal biopsies performed by a gastroenterologist 47. Synder et. al. reporting on Grade 2 proctitis following I-125 implants concluded that the incidence of proctitis was volume dependent for each dose studied 63. The 5 year actuarial risk of grade 2 proctitis was 5% if 1.3cc or less of the rectal volume received the prescription dose of 160Gy, and 17% for >1.3cc (p=0.001). Others have tried to correlate the risk of proctitis relative to the delivered dose and volume of the rectum with less success 61. While there is currently no specific recommendation on dose, intraoperative planning systems allow the operator to measure and limit the rectal dose during the case 31, 64.
The addition of external beam to permanent prostate brachytherapy may be a risk factor for increased rectal toxicity. A study by Zeitlin et. al. reporting a 2.3% fistula rate raises concern that combination therapy may be associated with more rectal injury 59. This observation was also identified by Brandeis et. al. in a study comparing quality of life indicators between implant alone and when combined with external radiation 8. In that study rectal bother was significantly higher in those patients treated with combination therapy.
Sexual function morbidity and management
Acute changes in sexual function following permanent prostate brachytherapy include pain with ejaculation and hematospermia. These symptoms generally dissipate over time and correlate to the acute prostatitis that the patient experiences. Erectile dysfunction (ED) following brachytherapy may be multifactorial, as a result of changes to the patients neurologic, vascular and/or psychologic makeup. Zelefsky et. al. have identified a potential vascular mechanism for impotence following radiation while Merrick et. al. have examined and tried to correlate the radiation dose to the penile bulb as a mechanism for impotence 65, 66. Other confounding factors include co-morbidities such as diabetes, hypertension and smoking.
There are no prospective data looking at the sexual potency following permanent prostate brachytherapy. However, retrospective data indicates a wide range of potency rates following brachytherapy, with as many as 80-85% remaining potent for men less than age 60 treated with only an implant, versus 29% remaining potent following combination therapy with external radiation, androgen deprivation and an implant (Figure 3)67. The use of sildenafil to correct for impotence showed a 62% response rate with patients having never been treated with androgen deprivation responding better 67.
In a study on 416 patients treated only with an implant, Stock et. al. identified that preservation of potency was 79% at 3 years and 59% at 6 years 68. Pre-treatment potency was the only significant predictor of later erectile dysfunction. Among treatment-related factors, hormone therapy and dose affected potency. In a multivariate analysis, pre-treatment potency and the implant dose was significant factors for impotency.