Comparing outcomes and toxicities from intensity-modulated radiation therapy and three-dimensional conformal radiation therapy for anal cancer: Is one really better?

Abstract

589 Background: Intensity-modulated radiation therapy (IMRT) has largely supplanted 3-dimensional conformal radiation (3D-CRT) for definitive treatment of anal cancer due to its decreased toxicity and potentially improved outcomes. Convincing data directly demonstrating its advantages, however, remain limited. We compared outcomes, acute, and post-treatment toxicity of patients with anal cancer treated with concurrent chemotherapy and IMRT vs. 3D-CRT. Methods: We performed a single institution retrospective review of patients treated with IMRT or 3D-CRT as part of definitive Mitomycin-C/5-FU based chemoradiation for anal cancer from January 2003-December 2012. Results: 61 and 104 patients received IMRT and 3D-CRT respectively. Overall, 92.7% had squamous cell carcinoma. The mean pelvic dose before boost was 48.3Gy and 44Gy for IMRT and 3D-CRT respectively. Complete response, partial response, and disease progression rates were similar (83.6%, 8.2%, 8.2% for IMRT; 85.6%, 6.7%, 7.7% for 3D-CRT; p = ns). There was no significant difference in overall survival (p = 0.971), event free survival (p = 0.900), and local or distant recurrence rates (p = 0.118, p = 0.373). IMRT caused significantly less acute grade 1-2 incontinence (p = 0.035), grade 3-4 pain (p = 0.033) and fatigue (p = 0.030). Patients receiving IMRT had significantly fewer post-treatment toxicities (p = 0.008), outperforming 3D-CRT in 7/8 toxicities reviewed. Though total length of treatment was comparable between IMRT and 3D-CRT (43.6 and 44.5 days), the IMRT group had fewer, shorter treatment breaks (p = ns). Conclusions: This report represents the largest series directly comparing concurrent chemotherapy with IMRT vs. 3D-CRT for definitive treatment of anal cancer. IMRT significantly reduced acute and post-treatment toxicities and allowed for safe and effective pelvic dose escalation.