Clinical Investigation
RTOG GU Radiation Oncology Specialists Reach Consensus on Pelvic Lymph Node Volumes for High-Risk Prostate Cancer

https://doi.org/10.1016/j.ijrobp.2008.08.002Get rights and content

Purpose

Radiation therapy to the pelvic lymph nodes in high-risk prostate cancer is required on several Radiation Therapy Oncology Group (RTOG) clinical trials. Based on a prior lymph node contouring project, we have shown significant disagreement in the definition of pelvic lymph node volumes among genitourinary radiation oncology specialists involved in developing and executing current RTOG trials.

Materials and Methods

A consensus meeting was held on October 3, 2007, to reach agreement on pelvic lymph node volumes. Data were presented to address the lymph node drainage of the prostate. Extensive discussion ensued to develop clinical target volume (CTV) pelvic lymph node consensus.

Results

Consensus was obtained resulting in computed tomography image-based pelvic lymph node CTVs. Based on this consensus, the pelvic lymph node volumes to be irradiated include: distal common iliac, presacral lymph nodes (S1-S3), external iliac lymph nodes, internal iliac lymph nodes, and obturator lymph nodes. Lymph node CTVs include the vessels (artery and vein) and a 7-mm radial margin being careful to “carve out” bowel, bladder, bone, and muscle. Volumes begin at the L5/S1 interspace and end at the superior aspect of the pubic bone. Consensus on dose–volume histogram constraints for OARs was also attained.

Conclusions

Consensus on pelvic lymph node CTVs for radiation therapy to address high-risk prostate cancer was attained and is available as web-based computed tomography images as well as a descriptive format through the RTOG. This will allow for uniformity in evaluating the benefit and risk of such treatment.

Introduction

Pelvic lymph node (LN) radiation was a required part of the treatment for high-risk/locally advanced prostate cancer patients treated on all the prospective randomized trials used to establish the role of hormone therapy and radiation for this patient population 1, 2, 3, 4. In addition, published data suggest that treating these volumes may improve outcomes for prostate cancer patients if the risk of lymph node involvement is significant (5). Furthermore, there are two open Radiation Therapy Oncology Group (RTOG) trials for high-risk prostate cancer patients who require pelvic lymph node radiation therapy 6, 7.

The challenge is that there are significant differences of opinion regarding appropriate pelvic LN volumes to be treated in this cohort of patients. A 2007 survey of RTOG genitourinary (GU) cancer experts indicated that significant variability existed among a group of radiation oncologists experienced in the treatment of prostate cancer and design of prostate cancer clinical trials (8). Given the widely adopted use of intensity-modulated radiation therapy to treat the pelvic lymph nodes and spare organs at risk (OAR) it is imperative that a consensus be obtained to establish the appropriate nodal volumes for these patients so that the relative safety and merit of such treatment can be established. The purpose of this study was to establish such a consensus.

Section snippets

Materials and Methods

Given the established variability in LN treatment volumes by the RTOG GU Radiation Oncologists, a consensus meeting was held on October 3, 2007, sponsored by the RTOG. All physicians/institutions involved in the original contouring project were invited to attend (8). Data were presented (C.L.) to address the lymph node drainage of the prostate using prostatic lymphography, extended lymph node dissection, the sentinel lymph node concept, anatomy texts, pelvic magnetic resonance imaging imaging,

Results

Data presented regarding prostatic lymphography 9, 10 reveal prostatic lymph node drainage to the internal iliac, external iliac, presacral and common iliac nodes, with the main drainage to the internal iliac and presacral lymph nodes (9).

Extended lymph node dissection data, which generally involved resection of the external and internal iliac and obturator lymph nodes as well as the common and presacral lymph nodes, showed evidence of nodal drainage in multiple nodal sites 11, 12, 13, 14, 15.

Conclusions

Adenocarcinoma of the prostate is the second most common cause of cancer death in US males with more than 27,000 deaths estimated for 2007 (23). Many of these patients will have presented with locally advanced/high-risk disease where regional pelvic lymph node involvement is a reality. The role of radiation therapy in the cure of these patients is evolving, but certainly many can be controlled if not cured with the use of radiation and hormonal manipulation 3, 4, 12. These cures are the result

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Supported by grants from the National Cancer Institute, CA21661, CA32115, and CA37422.

Conflict of interest: none

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