Clinical experience of SIB-IMRT in anal cancer and selective literature review.

Objective: To evaluate feasibility and outcome of our institutional SIB-IMRT schedule in patients with anal cancer and to selectively review the literature on different SIB-IMRT schedules.

Methods: Between 01/08-06/13 25 patients with biopsy proven squamous cell anal cancer were treated in our institution with IMRT. Radiotherapy was delivered in two series using a SIB-IMRT schedule of 45 Gy/1.8 Gy to the primary tumor and adjacent pelvic lymph nodes and 38 Gy/1.52 Gy to elective nodes followed by an IMRT boost of 7×2 Gy = 14 Gy to the primary tumor and involved nodes (cumulative prescription dose: 59 Gy).

Results: Mean follow-up was 20 months (range: 4-68). The 2-year-local control, colostomy-free survival, distant metastases-free survival and overall survival rates were 92%, 92%, 92%, and 88%, respectively. Grade 3 acute skin toxicity was observed in 6 patients (24%). No high grade gastrointestinal or urinary acute toxicity occurred. Four patients required more than one day of treatment interruption due to acute toxicity. No grade 3 or higher late sequelae were observed.

Conclusions: We present our institutional SIB-IMRT experience treating patients with anal cancer in two series using moderate single doses from 1.5-2.0 Gy. Our results, in terms of loco-regional outcome and toxicity, were comparable to other studies. The incidence of treatment interruptions was very low. Therefore this schedule appears to be safe for clinical use.