High-dose-rate brachytherapy in combination with conformal external beam radiotherapy in the treatment of prostate cancer
Introduction
Radiotherapy (RT) has an established role as a curative treatment modality in localized prostate cancer. Dose escalation with 3-dimensional conformal external beam radiotherapy (3DCRT) or intensity-modulated radiation therapy (IMRT) improves outcome with acceptable toxicity profiles [1], [2]. Results from two randomized controlled trials [3], [4] and single-institutional reports of high-dose-rate (HDR) brachytherapy in combination with 3DCRT demonstrate an alternative technique for dose escalation, with tumor control rates similar to those obtained with 3DCRT alone (Table 1). HDR brachytherapy in combination with 3DCRT allows the delivery of a highly conformal radiation treatment, and compared with 3DCRT, it has the potential advantages of delivering dose with greater accuracy and overcoming the problem of organ movement [11], [12]. Other advantages of HDR brachytherapy are the rapid dose falloff and ability to optimize dose distribution by varying source dwell times along the catheters (13). This potentially allows for greater sparing of rectum and bladder than is achievable with external beam radiation alone (11). Finally, the possibility of a low α:β ratio for prostate cancer provides a radiobiologic advantage for hypofractionated RT [14], [15].
Although results from Phase III studies demonstrate long-term efficacy of combined treatment [3], [4], there is significant heterogeneity in treatment technique, dose, fractionation, use of androgen deprivation, and patient characteristics. Other potential disadvantages of HDR brachytherapy include the invasiveness of the procedure, the specialized skills, and resources needed. The purpose of this study was to report the outcomes of men treated with HDR brachytherapy for dose escalation in combination with 3DCRT, and compare them with men treated contemporaneously with 3DCRT alone.
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Patients
We reviewed 587 consecutive patients treated for prostate cancer between July 1, 1998, and December 31, 2003. Patients provided informed consent for data collection, analysis, and aggregated reporting, and hospital ethics approval was obtained before data analysis. In all, 196 men (33.4%) received combined HDR brachytherapy and 3DCRT (the combined group) and 391 (66.6%) were treated with 3DCRT alone. All patients had biopsy-proven adenocarcinoma reported using the Gleason system but without
Patient characteristics
The median follow-up time for all 587 patients was 5.5 years (interquartile range, 4.2–7 years; 90th percentile, 8.1 years). Table 2 summarizes the patient characteristics. Patients in the combined group were significantly younger at diagnosis, presented with a higher iPSA, and were more frequently in a high-risk group: 50% in the combined group compared with 39% in the 3DCRT alone group (p < 0.001). The use of neoadjuvant ADT was also more common. Twenty-eight patients treated with HDR
Discussion
This study evaluates the use of HDR brachytherapy and 3DCRT for dose escalation, compared with 3DCRT alone, in terms of BC for localized prostate cancer. Strength of this study is the long median follow-up of 5.5 years, allowing 7-year estimates showing no difference in BC or survival between treatment groups. Patients treated with HDR brachytherapy in combination with 3DCRT presented with a higher percentage of unfavorable prognostic factors relative to the external beam group, and on
Conclusion
This retrospective, single-institutional study demonstrated that HDR brachytherapy may be used safely in achieving dose escalation combined with 3DCRT for localized prostate cancer. For the convenience of patients, treatment time was shortened with the potential for improving therapeutic ratio by hypofractionation (13). On multivariable analysis, the combined treatment was associated with a statistically significant improved BC when compared with standard external beam RT adjusting for adverse
Acknowledgments
The authors gratefully acknowledge the important contribution of Karen Scott, Data Management.
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Supported in part by the Peter Grant Hay Fund.
Presented in part at the 2008 World Congress of Brachytherapy, Boston, MA, May 4–6, 2008.