ASTRO 2022: Bladder Only versus Bladder Plus Pelvic Lymph Node Chemoradiation for Muscle-Invasive Bladder Cancer

(UroToday.com) The 2022 ASTRO annual meeting featured a session on bladder and kidney preservation, including a presentation by Dr. Sagar Patel discussing bladder only versus bladder plus pelvic lymph node chemoradiation for muscle-invasive bladder cancer. Approximately 25% of new bladder cancer cases in the United States are muscle invasive, and bladder-sparing chemoradiation therapy is a definitive first-line treatment option for these patients. Multiple studies have shown high bladder preservation rates and comparable disease-specific and overall survival as radical cystectomy. Importantly, for cN0 muscle invasive bladder cancer, up to 18-40% of patients may harbor micrometastasis in the pelvic lymph nodes. However, there is considerable variability in radiotherapy target volumes in the United States, and ongoing cooperative trials (SWOG/NRG 1806) support either bladder only or bladder plus pelvic nodal treatment. Whether the addition of pelvic lymph node treatment impacts outcomes is unknown. The aims of this study were to (i) assess utilization trends of bladder only versus bladder + pelvic lymph node radiation for muscle-invasive bladder cancer in the United States, and (ii) evaluate whether survival outcomes are affected by bladder only versus bladder + pelvic lymph node treatment for muscle invasive bladder cancer treated with definitive chemoradiation.

 Dr. Patel and colleagues identified 2,104 patients in the National Cancer Database with cT2-4N0M0 urothelial cell carcinoma of the bladder treated with definitive-intent chemoradiation therapy following maximal transurethral resection of bladder tumor from 2004 to 2016. Patients were included if total radiation dose was ≥40 Gy and chemotherapy was initiated within 30 days of radiation. They also excluded those who were post-cystectomy, node-positive, or metastatic; who had variant histology, history of prior malignancy, or received palliative-intent therapy. The exposure of interest was bladder only versus bladder plus pelvic lymph node radiation. Annual use from 2004 to 2016 was compared using Cochran-Armitage test for trend. Overall survival (OS), defined from the date of diagnosis, was compared using Kaplan-Meier, log-rank test, and multivariable Cox proportional hazard analysis. Final multivariable model, developed via backward selection with an alpha level of 0.10 for removal, included age, race, diagnosis year, comorbidity score, insurance provider, education level, geographic region, and T stage. Sensitivity analysis tested an interaction term for T stage.

 This study identified 578 patients treated with bladder only and 1,526 patients treated with bladder plus pelvic lymph node chemoradiation therapy. Median dose to the pelvic nodes was 45 Gy (IQR 39.6-50) and the median dose to the bladder (in both groups) was 64.8 Gy (IQR 59.4-64.8). The complete patient characteristics are as follows:

 

ASTRO 2022 Sagar A. Patel_0 

 

There was a significant increase in use of pelvic nodal treatment from 2004 to 2016 (66.9% to 76.8%, p < 0.0001 for trend):

 

ASTRO 2022 Sagar A. Patel_1 

 

With a median follow up of 6.2 years, there was no difference in survival between groups: 5-year and 10-year OS 27.4% (95% CI 23.4-31.4%) in the bladder only group versus 31.9% (95% CI 29.3-34.6%) in the bladder plus pelvic lymph node group, and 13.1% (95% CI 9.7-17.1%) in the bladder only group versus 13.2% (95% CI 10.6-16.0%) in the bladder plus pelvic lymph node group, respectively (log-rank p = 0.10):

 

ASTRO 2022 Sagar A. Patel_2 

 

On multivariable analysis, there was no significant association between pelvic nodal coverage and OS (adjusted HR 0.93, 95% CI 0.84-1.03, p = 0.09). Additionally, there was no difference in effect by T stage (T3-4 versus T2, interaction p = 0.52) or by radiotherapy type received (3D-CRT versus IMRT/protons, interaction p = 0.39).

 

Dr. Patel concluded his presentation discussing bladder only versus bladder plus pelvic lymph node chemoradiation for muscle-invasive bladder cancer with the following take home messages:

  • These hypothesis-generating results suggest that routine inclusion of pelvic nodal coverage is not needed for patients undergoing definitive chemoradiation therapy for node-negative muscle-invasive bladder cancer
  • Use of pelvic nodal treatment, however, has continued to increase in the United States
  • Prospective investigation with adverse event, quality of life, and cancer-specific endpoints is warranted (ie. SWOG/NRG 1806)

 

Presented by: Sagar A. Patel, MD, Department of Radiation Oncology, Winship Cancer Institute of Emory University, Atlanta, GA

Co-Authors: Y. Liu2, A. A. Solanki3, B. C. Baumann4, J. A. Efstathiou5, A. Jani6, B. W. Fischer-Valuck7, and T. J. Royce81Department of Radiation Oncology, Winship Cancer Institute of Emory University, Atlanta, GA, 2Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, 3Loyola University Chicago, Loyola University Medical Center and Edward Hines Jr., VA Hospital, Stritch School of Medicine, Department of Radiation Oncology, Cardinal Bernardin Cancer Center, Maywood, IL, 4Washington University School of Medicine in St. Louis, Department of Radiation Oncology, St. Louis, MO, 5Department of Radiation Oncology, Harvard School of Medicine, Boston, MA, 6Department of Radiation Oncology, Emory University, Atlanta, GA, 7Winship Cancer Institute, Department of Radiation Oncology, Emory University, Atlanta, GA, 8The University of North Carolina at Chapel Hill, Chapel Hill, NC

Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2022 American Society of Radiation Oncology (ASTRO) Annual Hybrid Meeting, San Antonio, TX, Sat, Oct 22 – Wed, Oct 26, 2022.

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