Abstract
PurposeIntensity-modulated radiotherapy (IMRT) and helical tomotherapy (HT) have been adopted for radiotherapy treatment of anal canal carcinoma (ACC) due to better conformality, dose homogeneity and normal-tissue sparing compared to 3D-CRT. To date, only one published study compares dosimetric parameters of IMRT vs HT in ACC, but there are no published data comparing toxicities. Our objectives were to compare dosimetry and toxicities between these modalities.Methods and materialsThis is a retrospective study of 35 ACC patients treated with radical chemoradiotherapy at two tertiary cancer institutions from 2008–2010. The use of IMRT vs HT was primarily based on center availability. The majority of patients received fluorouracil (5-FU) and 1–2 cycles of mitomycin C (MMC); 2 received 5-FU and cisplatin. Primary tumor and elective nodes were prescribed to ≥54Gy and ≥45Gy, respectively. Patients were grouped into two cohorts: IMRT vs HT. The primary endpoint was a dosimetric comparison between the cohorts; the secondary endpoint was comparison of toxicities.Results18 patients were treated with IMRT and 17 with HT. Most IMRT patients received 5-FU and 1 MMC cycle, while most HT patients received 2 MMC cycles (p < 0.01), based on center policy. HT achieved more homogenous coverage of the primary tumor (HT homogeneity and uniformity index 0.14 and 1.02 vs 0.29 and 1.06 for IMRT, p = 0.01 and p < 0.01). Elective nodal coverage did not differ. IMRT achieved better bladder, femoral head and peritoneal space sparing (V30 and V40, p ≤ 0.01), and lower mean skin dose (p < 0.01). HT delivered lower bone marrow (V10, p < 0.01) and external genitalia dose (V20 and V30, p < 0.01). Grade 2+ hematological and non-hematological toxicities were similar. Febrile neutropenia and unscheduled treatment breaks did not differ (both p = 0.13), nor did 3-year overall and disease-free survival (p = 0.13, p = 0.68).ConclusionsChemoradiotherapy treatment of ACC using IMRT vs HT results in differences in dose homogenity and normal-tissue sparing, but no significant differences in toxicities.
Highlights
Since the 1980s, standard management of anal canal carcinoma (ACC) has been definitive chemoradiation therapy (CRT), with salvage abdominal-perineal resection (APR) for those who fail CRT [1,2,3]
Helical tomotherapy (HT) delivery, a newer RT technique, has shown improved target conformality, dose homogeneity and normal-tissue sparing compared to intensitymodulated radiotherapy (IMRT) in other tumor sites [12,13]
All patients were treated with IMRT or HT, and chemotherapy consisting of 2 cycles of 5-FU and 1–2 cycles of mitomycin C (MMC) or cisplatin
Summary
Since the 1980s, standard management of anal canal carcinoma (ACC) has been definitive chemoradiation therapy (CRT), with salvage abdominal-perineal resection (APR) for those who fail CRT [1,2,3]. Treatment breaks in up to 40-50% of patients have been reported due to hematological, dermatological and gastrointestinal toxicities [7,8]. Efforts have been made to reduce toxicities through newer chemotherapy regimens and radiotherapy (RT) techniques [9,10,11]. Development of more conformal RT techniques has reduced normal tissue toxicity and the need for unintended treatment breaks [11]. RTOG 0529 demonstrated significantly lower hematological, gastrointestinal and dermatological toxicities with intensitymodulated radiotherapy (IMRT) compared to conventional 2D-planning in ACC treatment [12]. Helical tomotherapy (HT) delivery, a newer RT technique, has shown improved target conformality, dose homogeneity and normal-tissue sparing compared to IMRT in other tumor sites [12,13]
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