High-Dose IMRT Postop Does Not Affect Erectile Function

CHICAGO—Nerve-sparing prostatectomy has become increasingly common as younger men diagnosed with prostate cancer seek to preserve erectile function. Although postoperative radiotherapy has improved control of prostate cancer, few studies have examined its effect on erectile function.

Researchers from Baylor College of Medicine, Houston, evaluated intensity-modulated radiation therapy (IMRT) after nerve-sparing prostatectomy. Even with high radiation doses (nearly 70 Gy) delivered to the prostatic bed and surrounding nerves, the technique did not negatively affect potency, reported Michael Bastasch, MD, radiation oncology resident in the Department of Radiology, at the 87th Annual Meeting of the Radiological Society of North America (RSNA abstracts 37 and 38).

The first study evaluated erectile function, defined as an erection sufficient for vaginal penetration, in 51 men between the ages of 46 and 77 who had aggressive prostate cancer. Eighty percent of the men in the study had tumors with Gleason scores between 7 and 10, and all had stage T2 or T3 lesions. Approximately half of the men underwent bilateral and half unilateral nerve-sparing prostatectomy.

The men then received IMRT at a mean dose of 69.6 Gy (range, 64 to 72.3 Gy). Their erectile function was assessed by questionnaire before and after radiotherapy, and the men were followed for a median of 27.2 months (range, 15.9 to 38.7 months). Of the 51 men who underwent nerve-sparing prostatectomy, 18 remained potent afterward, and all 18 remained potent after IMRT, regardless of the radiation dose.

"Dosimetric parameters broken down on the basis of potency status reflected the fact that we did not take potency status into account at the time of treatment planning and prescription," Dr. Bastasch said. The group’s initial conclusion, therefore, was that the dose of radiotherapy did not have an adverse effect on the patient’s potency status postoperatively. The results need to be confirmed by longer follow-up and studies involving larger cohorts, Dr. Bastasch noted.

Searching for Causes

The second study further explored why some men became impotent after nerve-sparing prostatectomy and some did not by analyzing factors associated with the patient (age, medical and psychiatric comorbidities, medication history, body mass index, vital signs, and previous surgical history); the type of surgical procedure; the use of hormonal ablation; and the nature of the tumor.

The analysis showed that men with a Gleason score greater than 7 were more likely to be impotent postoperatively than those with a lower Gleason score. Only one man with a Gleason score greater than 7 remained potent; all the others were impotent, Dr. Bastasch said.

Men who had unilateral nerve-sparing prostatectomy fared worse than those having bilateral nerve-sparing surgery: 72% of men were potent after bilateral surgery vs 28% after unilateral surgery (P = .025). "Our research is consistent with findings that if you spare two nerves vs one nerve, you’ll have higher rates of potency preservation," Dr. Bastasch said.

Hypertension, defined by the World Health Organization as blood pressure readings greater than 140/90 mm Hg on two separate occasions, also was a highly significant predictor of postoperative im-potence: 85% of the impotent men were hypertensive, while 61% of the potent men were normotensive (P < .001). The study suggests that preoperative control of hypertension may help preserve erectile function after nerve-sparing surgery, the researchers concluded.