Impact of neoadjuvant androgen ablation and other factors on late toxicity following external beam prostate radiation

Rectal toxicity profile after transperineal interstitial permanent prostate brachytherapy: Use of a comprehensive toxicity scoring system and identification of rectal dosimetric toxicity predictors

PURPOSE

To better understand rectal toxicity after prostate brachytherapy, we employed the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE version 3.0), a comprehensive system with distinct and separately reported gastrointestinal adverse event items (unlike Radiation Therapy Oncology Group morbidity scoring), to evaluate item-specific postimplant rectal toxicities.

METHODS AND MATERIALS

We analyzed 135 patients treated with brachytherapy +/- hormonal therapy, using CTCAE v3.0 to score acute/late rectal toxicities (median follow-up, 41 months). Dosimetric parameters were evaluated for ability to predict toxicities.

RESULTS

Use of CTCAE yielded a novel rectal toxicity profile consisting of diarrhea, incontinence, urgency, proctitis, pain, spasms, and hemorrhage event rates. No item had a < 5% Grade 1-2 acute toxicity rate (except spasms). Rectal dosimetry predicted late toxicities: for diarrhea, 5% Grade 1 toxicity rate for %V25 (percent of rectal volume receiving 25% of prescribed prostate dose) < or = 25% vs. 60% for %V25 > 25% (p < 0.001); for maximum toxicity, 10% Grade 1 toxicity rate for %V10 < or = 40% vs. 44% for %V10 > 40% (p = 0.007).

CONCLUSIONS

A comprehensive understanding of item-specific postimplant rectal toxicities was obtained using CTCAE. Rectal %V25 > 25% and %V10 > 40% predicted worse late diarrhea and maximum toxicity, respectively.

Influence of hormonal therapy on late rectal function after permanent prostate brachytherapy with or without supplemental external beam radiotherapy

PURPOSE

Recent clinical studies have reported a relationship between the use of hormonal therapy and degradation in rectal function after external beam radiotherapy. Using a patient-administered quality-of-life instrument, we evaluated the effect of hormonal therapy on late rectal function after permanent prostate brachytherapy with or without supplemental external beam radiotherapy.

METHODS AND MATERIALS

A total of 189 patients were mailed the Rectal Function Assessment Score (R-FAS), which consists of nine questions (score range 0-27, with higher scores indicative of poorer bowel function). Of the 189 surveys sent out, 187 (98.4%) were returned. Of the 187 patients, 149 (79.7%) were hormone naive, and 38 (20.3%) had received hormonal manipulation (median duration 4 months, range 3-36). The median follow-up for the entire group was 66.3 months. The effect of hormonal therapy on bowel function was evaluated by comparing the R-FAS scores across time, by each of the individual nine questions, and by means of a summary question evaluating the patient's perception of overall bowel function. The two groups were also evaluated in terms of clinical, treatment, and dosimetric parameters, including follow-up, age, Gleason score, clinical stage, pretreatment prostate-specific antigen level, number of pretreatment bowel movements/d, prostate volume, and rectal dosimetry.

RESULTS

The two groups were well matched in all clinical, treatment, and dosimetric parameters, except the patients receiving hormonal therapy had a statistically shorter follow-up (63.9 vs. 69.4 months, p <0.001) and higher pretreatment prostate-specific antigen level (12.0 vs. 9.8 ng/mL, p = 0.024). The R-FAS scores for the hormone-naive and hormonally manipulated patients were comparable (3.76 vs. 4.55, p = 0.083). In terms of the nine individual R-FAS questions, no statistically significant difference was reported for any question when stratified by hormonal status, including rectal bleeding (p = 0.735). Only 12% and 13% of hormone-naive and hormonally manipulated patients, respectively, reported bowel function to be worse after implantation. With time, a trend for improvement in the R-FAS was noted in both cohorts.

CONCLUSION

After permanent prostate brachytherapy, no statistically significant difference in bowel habits was discerned when stratified by hormonal status. In addition, only 12% of brachytherapy patients reported deterioration in bowel function after implantation.