To report cancer control rates and adverse events (AEs) of curative-intent, extended-field chemoradiation therapy administered to patients with squamous cell carcinoma (SCC) of the anal canal presenting with distant metastasis limited to the para-aortic (PA) lymph nodes.

This was a retrospective review of patients with SCC of the anal canal metastatic to the PA lymph nodes at initial diagnosis who were treated with curative-intent, extended-field chemoradiation therapy between September 2002 and February 2016 at two tertiary care centers. Outcomes assessed included treatment-related AEs (Common Terminology Criteria for Adverse Events, version 4.0), disease control (cumulative incidence estimates), and survival (Kaplan-Meier estimates).

Thirty patients were included. Involved and elective PA nodes were treated to median doses of 51 Gy (range 45-57.6) and 45 Gy (range 30.6-50.4) in 29 fractions (range 17-32). All patients received one of these concomitant regimens: 6 weekly cycles of cisplatin with 5-fluoruracil/capecitabine (5-FU) (n = 22), 2 cycles of mitomycin-C with 5-FU (n = 7), or daily capecitabine (n = 1). After a median follow-up period of 3.1 years, 18 patients (60%) remained alive and 17 patients were without evidence of anal cancer after definite and salvage treatments. Overall and disease-free survival at 3 years was 67% (95% CI 49%-89%) and 42% (95% CI 25%-69%). Fifteen (50%) patients experienced a recurrence at a median of 0.9 year (range 0.5-3.5 years). The predominant site of recurrence was distant metastases, with a 3-year cumulative incidence of 50% (95% CI 20%-68%). There was no acute grade 5 AE. Grade 3 to 4 gastrointestinal, dermatologic, and hematologic AEs occurred in 30%, 27%, and 20% of patients respectively.

Extended-field chemoradiation therapy is a potentially curative treatment option for patients presenting with SCC of the anal canal with metastases limited to the PA lymph nodes.