[Management of locally advanced anal canal carcinoma with modulated arctherapy and concurrent chemotherapy]

Abstract

The standard treatment of locally advanced (stage II and III) squamous cell carcinoma of the anal canal consists of concurrent chemoradiotherapy (two cycles of 5-fluoro-uracil, mitomycin C, on a 28-day cycle), with a dose of 45 Gy in 1.8 Gy per fraction in the prophylactic planning target volume and additional 14 to 20 Gy in the boost planning target volume (5 days per week) with a possibility of 15 days gap period between the two sequences. While conformal irradiation may only yield suboptimal tumor coverage using complex photon/electron field junctions (especially on nodal areas), intensity modulated radiation therapy techniques (segmented static, dynamic, volumetric modulated arc therapy and helical tomotherapy) allow better tumour coverage while sparing organs at risk from intermediate/high doses (small intestine, perineum/genitalia, bladder, pelvic bone, etc.). Such dosimetric advantages result in fewer severe acute toxicities and better potential to avoid a prolonged treatment break that increases risk of local failure. These techniques also allow a reduction in late gastrointestinal and skin toxicities of grade 3 or above, as well as better functional conservation of anorectal sphincter. The technical achievements (simulation, contouring, prescription dose, treatment planning, control quality) of volumetric modulated arctherapy are discussed.

Keywords: Anal canal; Arcthérapie volumique modulée; Canal anal; Cancer; Carcinome épidermoïde; Chemoradiotherapy; Chimioradiothérapie; Dynamic intensity modulated radiation therapy; Gap; Helical tomotherapy; Intervalle libre; Local control; RCMI dynamique; Squamous cell carcinoma; Static segmented IMRT; Statique segmentée; Tomothérapie hélicoïdale; Treatment break; Volumetric modulated arc therapy.