Comparison of elective inguinal node irradiation techniques in anal cancer

To compare photon thunderbird with deep match (technique 1) with 3-field technique with electron inguinal boost (technique 2) in acute skin toxicity, toxicity-related treatment breaks and patterns of failure in elective inguinal radiation therapy (RT) for curative chemoradiation in anal cancer.

Seventeen patients treated between January 2008 and September 2010 without evidence of inguinal and distant metastasis were retrospectively reviewed. In 9 patients with technique 1, dose to inguinal and whole pelvis area was 41.4 to 45 Gy and total dose was 59.4 Gy. In 8 patients with technique 2, doses to inguinal, whole pelvis, gross tumor were 36 to 41.4 Gy, 36 to 41.4 Gy, and 45 to 54 Gy, respectively. The median follow-up period was 27.6 and 14.8 months in group technique 1 and 2, respectively.

The incidences of grade 3 radiation dermatitis were 56% (5 patients) and 50% (4 patients), dose ranges grade 3 dermatitis appeared were 41.4 to 50.4 Gy and 45 to 54 Gy in group technique 1 and 2, respectively (p = 0.819). The areas affected by grade 3 dermatitis in 2 groups were as follow: perianal and perineal areas in 40% and 25%, perianal and inguinal areas in 0% and 50%, and perianal area only in 60% and 25%, respectively (p = 0.196). No inguinal failure has been observed.

Photon thunderbird with deep match technique and 3-field technique with electron inguinal boost showed similar incidence of radiation dermatitis. However, photon thunderbird with deep match seems to increase the possibility of severe perineal dermatitis.