45.06 IMRT is Superior to 3D-CRT for the Treatment of Anal Cancer

Posted on January 26, 2017

B. F. Gilmore1, Z. Sun1, M. A. Adam1, D. Spiegel2, B. Ezekian1, M. C. Turner1, U. Nag1, M. Palta2, J. Migaly1, C. Mantyh1  1Duke University Medical Center,Department Of Surgery,Durham, NC, USA 2Duke University Medical Center,Department Of Radiation Oncology,Durham, NC, USA

Introduction:
Current national guidelines recommend use of Intensity-Modulated Radiation Therapy (IMRT) over 3-Dimensional Conformal Radiation Therapy (3D-CRT) for anal squamous cell cancer given the benefits of reducing acute toxicity and minimizing treatment breaks. However, published data evaluating patient survival are limited. Our aim was to compare survival between patients treated with IMRT to 3D-CRT. 

Methods:
The 2004 – 2013 National Cancer Database Anal Cancer Participant Data Use File was queried for patients with anal squamous cell carcinoma who underwent chemotherapy and radiation therapy. Patients who received surgery or had metastatic disease were excluded. Patients were stratified by modality of radiation therapy (IMRT vs. 3D-CRT) and overall survival was compared between groups. 

Results:
Among 5,545 patients included, 4,758 (85.8%) underwent treatment with IMRT. Before adjustment, survival was similar between patients who received IMRT vs. those who received 3D-CRT (5-year overall survival 73% vs. 71%, p= 0.215). However, after adjustment for demographics, clinical, and tumor characteristics, patients receiving 3D-CRT had worse survival than those undergoing IMRT (adjusted hazard ratio 1.24, 95% CI: 1.046-1.468, p=0.013). Factors associated with use of IMRT include black race (odds ratio 1.60, p=0.011), academic hospital designation (odds ratio 1.496, p=0.007), and stage III disease (odds ratio 1.435, p=0.006).

Conclusion:
Use of IMRT is associated with superior survival compared to 3D-CRT for management of anal squamous cell carcinoma. In combination with the established data demonstrating improved acute toxicity profile and reduction in treatment related breaks associated with IMRT, these findings provide additional support for the current national guidelines.