Comparative Outcomes of Intensity Modulated Radiation Therapy Versus 3D Conformal Radiation Therapy for Squamous Cell Carcinoma of the Anal Canal

Abstract

Background/PurposeDefinitive chemoradiation for anal cancer using 3D conformal radiation therapy (3DCRT) technique results in excellent long-term outcomes, but at the cost of potentially severe treatment-related toxicity that may necessitate a treatment break. The emergence of intensity-modulated radiation therapy (IMRT) in the treatment of anal cancer has dramatically lowered the incidence of severe toxicity while maintaining excellent long-term outcomes. We compared our institutional experience using 3DCRT versus IMRT for anal cancer.Materials/MethodWe performed a retrospective review of all non-metastatic anal cancer patients treated at our institution using definitive chemoradiation. Patients receiving IMRT were treated with 2 Gy fractions to PET-avid gross disease (median 56 Gy) and with 1.8 Gy fractions to the regional lymphatics (36 Gy and 45 Gy for node negative and node positive patients, respectively). The 3DCRT patients received 1.8 Gy fractions to both the regional lymphatics (median 45 Gy) and gross disease (median 59.4 Gy). All patients received concurrent chemotherapy with the majority (93.3%) receiving mitomycin-C and 5-FU.ResultsWe evaluated 89 patients (37 3DCRT, 52 IMRT). Median follow up was 26.5 months (range, 3.5-133.6 months) for all patients while for the IMRT and 3DCRT patients alone it was 19 months (range, 3.5-125.5 months) and 61.9 months (range, 7.6-133.6), respectively. There was no significant difference in patient characteristics with the exception of a higher percentage of stage IIIA/B patients in the IMRT group (46.2% vs. 21.6%; p = 0.01). Three-year overall survival (OS), progression free survival (PFS), locoregional control (LRC), and colostomy free survival (CFS) were 91.1%, 82.3%, 90.8%, and 91.3% for the 3DCRT patients and 86.1%, 72.5%, 91.9%, and 93.7% for the IMRT patients (all p > 0.1). More patients in the CRT group required a treatment break (11 vs. 4 days; p = 0.006), but there was no difference in the median treatment break duration (12.2 vs. 8 days; p = 0.35). Three-year OS, PFS, LRC, and CFS did not differ based on whether a treatment break was required (all p > 0.1). Overall, acute grade ≥3 non-hematologic toxicity was 59.5% in the 3DCRT group vs. 21.2% in the IMRT group (p < 0.0001). Acute grade ≥3 skin toxicity was significantly worse in the 3DCRT group (p = 0.01).ConclusionThis study represents the largest retrospective review comparing 3DCRT versus IMRT for definitive treatment of anal cancer. Despite the IMRT group having a higher percentage of stage III patients, there was no difference in outcome with less grade ≥3 toxicity. Background/PurposeDefinitive chemoradiation for anal cancer using 3D conformal radiation therapy (3DCRT) technique results in excellent long-term outcomes, but at the cost of potentially severe treatment-related toxicity that may necessitate a treatment break. The emergence of intensity-modulated radiation therapy (IMRT) in the treatment of anal cancer has dramatically lowered the incidence of severe toxicity while maintaining excellent long-term outcomes. We compared our institutional experience using 3DCRT versus IMRT for anal cancer. Definitive chemoradiation for anal cancer using 3D conformal radiation therapy (3DCRT) technique results in excellent long-term outcomes, but at the cost of potentially severe treatment-related toxicity that may necessitate a treatment break. The emergence of intensity-modulated radiation therapy (IMRT) in the treatment of anal cancer has dramatically lowered the incidence of severe toxicity while maintaining excellent long-term outcomes. We compared our institutional experience using 3DCRT versus IMRT for anal cancer. Materials/MethodWe performed a retrospective review of all non-metastatic anal cancer patients treated at our institution using definitive chemoradiation. Patients receiving IMRT were treated with 2 Gy fractions to PET-avid gross disease (median 56 Gy) and with 1.8 Gy fractions to the regional lymphatics (36 Gy and 45 Gy for node negative and node positive patients, respectively). The 3DCRT patients received 1.8 Gy fractions to both the regional lymphatics (median 45 Gy) and gross disease (median 59.4 Gy). All patients received concurrent chemotherapy with the majority (93.3%) receiving mitomycin-C and 5-FU. We performed a retrospective review of all non-metastatic anal cancer patients treated at our institution using definitive chemoradiation. Patients receiving IMRT were treated with 2 Gy fractions to PET-avid gross disease (median 56 Gy) and with 1.8 Gy fractions to the regional lymphatics (36 Gy and 45 Gy for node negative and node positive patients, respectively). The 3DCRT patients received 1.8 Gy fractions to both the regional lymphatics (median 45 Gy) and gross disease (median 59.4 Gy). All patients received concurrent chemotherapy with the majority (93.3%) receiving mitomycin-C and 5-FU. ResultsWe evaluated 89 patients (37 3DCRT, 52 IMRT). Median follow up was 26.5 months (range, 3.5-133.6 months) for all patients while for the IMRT and 3DCRT patients alone it was 19 months (range, 3.5-125.5 months) and 61.9 months (range, 7.6-133.6), respectively. There was no significant difference in patient characteristics with the exception of a higher percentage of stage IIIA/B patients in the IMRT group (46.2% vs. 21.6%; p = 0.01). Three-year overall survival (OS), progression free survival (PFS), locoregional control (LRC), and colostomy free survival (CFS) were 91.1%, 82.3%, 90.8%, and 91.3% for the 3DCRT patients and 86.1%, 72.5%, 91.9%, and 93.7% for the IMRT patients (all p > 0.1). More patients in the CRT group required a treatment break (11 vs. 4 days; p = 0.006), but there was no difference in the median treatment break duration (12.2 vs. 8 days; p = 0.35). Three-year OS, PFS, LRC, and CFS did not differ based on whether a treatment break was required (all p > 0.1). Overall, acute grade ≥3 non-hematologic toxicity was 59.5% in the 3DCRT group vs. 21.2% in the IMRT group (p < 0.0001). Acute grade ≥3 skin toxicity was significantly worse in the 3DCRT group (p = 0.01). We evaluated 89 patients (37 3DCRT, 52 IMRT). Median follow up was 26.5 months (range, 3.5-133.6 months) for all patients while for the IMRT and 3DCRT patients alone it was 19 months (range, 3.5-125.5 months) and 61.9 months (range, 7.6-133.6), respectively. There was no significant difference in patient characteristics with the exception of a higher percentage of stage IIIA/B patients in the IMRT group (46.2% vs. 21.6%; p = 0.01). Three-year overall survival (OS), progression free survival (PFS), locoregional control (LRC), and colostomy free survival (CFS) were 91.1%, 82.3%, 90.8%, and 91.3% for the 3DCRT patients and 86.1%, 72.5%, 91.9%, and 93.7% for the IMRT patients (all p > 0.1). More patients in the CRT group required a treatment break (11 vs. 4 days; p = 0.006), but there was no difference in the median treatment break duration (12.2 vs. 8 days; p = 0.35). Three-year OS, PFS, LRC, and CFS did not differ based on whether a treatment break was required (all p > 0.1). Overall, acute grade ≥3 non-hematologic toxicity was 59.5% in the 3DCRT group vs. 21.2% in the IMRT group (p < 0.0001). Acute grade ≥3 skin toxicity was significantly worse in the 3DCRT group (p = 0.01). ConclusionThis study represents the largest retrospective review comparing 3DCRT versus IMRT for definitive treatment of anal cancer. Despite the IMRT group having a higher percentage of stage III patients, there was no difference in outcome with less grade ≥3 toxicity. This study represents the largest retrospective review comparing 3DCRT versus IMRT for definitive treatment of anal cancer. Despite the IMRT group having a higher percentage of stage III patients, there was no difference in outcome with less grade ≥3 toxicity.