Clinical investigation: prostate
Late morbidity profiles in prostate cancer patients treated to 79–84 Gy by a simple four-field coplanar beam arrangement

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Abstract

Purpose: To describe the frequency and magnitude of late GI and GU morbidity in prostate cancer patients treated to high dose levels with a simple three-dimensional conformal technique.

Methods and Materials: A total of 156 intermediate- and high-risk patients were treated between January 1, 1992 and February 28, 1999 with a simple four-field three-dimensional conformal technique to 79–84 Gy. All patients were treated with a four-field conformal technique; the prostate received 82 Gy and the seminal vesicles and periprostatic tissue 46 Gy. GI and GU toxicity was scored according to the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer Late Morbidity Grading Scale and compared using Kaplan-Meier estimates.

Results: The late Grade 2 GI complication rate was 9% and 38% at 3 years for patients treated with and without rectal blocking, respectively (p = 0.0004). No Grade 3 late GI complications developed. The rate of Grade 2 late GU complications was 5%, 8%, and 12% at 12, 24, and 36 months, respectively. The Grade 3 late GU complication rate was 2% at 36 months. These differences were not statistically significant.

Conclusion: The treatment method described is a simple four-field conformal technique that can be easily implemented in the general radiation community. A dose of 79–84 Gy can be safely delivered to the prostate, with a 9% rate of late Grade 2 GI, 12% rate of late Grade 2 GU, and 2% rate of late Grade 3 GU complications.

Introduction

Results from multiple series of patients with prostate cancer have demonstrated improvements in biochemical control when radiation doses between 76 and 82 Gy are delivered compared with conventional doses <70 Gy. This benefit is most evident for patients with intermediate- and high-risk feature 1, 2, 3, 4, 5. With standard conventional techniques, it has been evident that with the increase in dose, normal tissue toxicity increases. The Patterns of Care Studies suggest that severe complication rates double when conventional techniques are used to treat at doses >70 Gy (6). The goal of delivering higher doses to tumor while minimizing the dose to normal tissue has been the driving force behind the development of three-dimensional conformal radiotherapy (3D-CRT). Additional strategies used in conjunction with conformal techniques to better localize the target while restricting the dose to adjacent normal tissues have used daily ultrasonography, fiducial markers, and daily CT scanning for improved organ localization (7). Although these later advances are vital to the future of radiation oncology, they are not yet widely available in the general community. To improve the treatment of patients receiving their care in the 1500 facilities across the United States, it is important to develop treatment techniques that can be used in the general radiation community. It is important that such a technique meet certain requirements: (1) sufficient dose delivery, (2) demonstrated cure rates, (3) tolerable side-effect profile, (4) easy implementation with standard treatment equipment, and (5) quality assurance with standard port films. This communication presents a 3D conformal treatment technique developed in 1989–1992 that we believe fits these criteria.

Section snippets

Methods and materials

A review of our prospectively maintained prostate cancer data base revealed 156 patients treated for prostate cancer with a four-field, 3D conformal technique to 79–84 Gy between January 1, 1992 and February 28, 1999. Patients treated during this period with more complex beam arrangements such as noncoplanar techniques were excluded. All patients were believed to be at increased risk of failure because of the presence of at least one of the following presenting characteristics: T2b-T3 tumor,

GI complications

The median follow-up was 26 months for the cohort of interest and 86 months for the comparison group. The 5-year actuarial rate of Grade 2 GI complications was 9% in patients treated with lateral rectal shielding and 38% in patients treated without rectal blocking (p = 0.0004; Fig. 4). Late Grade 2 GI complications consisted primarily of rectal bleeding. Of the 132 patients treated with rectal blocking, 10 experienced late Grade 2 GI complications; 9 experienced rectal bleeding and 1 bowel

Discussion

This communication reports our observations on late GI and GU morbidity in patients with prostate cancer treated with 3D-CRT. We demonstrate that a dose that has been previously described to be associated with higher biochemical control rates can be safely delivered to the prostate with a four-field technique. A late Grade 2 GI morbidity rate of 9%, late Grade 2 GU morbidity rate of 12%, and a late Grade 3 GU morbidity rate of 2% were found. This is comparable to the morbidity rates for 3D-CRT

Conclusion

The treatment method described is a simple four-field conformal technique that can be easily implemented in the general radiation community. A dose of 79–84 Gy can be safely delivered to the prostate, with a 9% rate of late Grade 2 GI, 12% rate of late Grade 2 GU, and 2% rate of late Grade 3 GU complications.

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