Abstract
BackgroundTo evaluate clinical outcomes of simultaneous integrated boost (SIB) - intensity modulated radiotherapy (RT) in patients with non metastatic anal cancer compared to those of a set of patients treated with 3-dimensional conformal RT and sequential boost (SeqB).MethodsA retrospective cohort of 190 anal cancer patients treated at 3 academic centers with concurrent chemo-RT employing either SIB or SeqB was analysed. The SIB-group consisted of 87 patients, treated with 2 cycles of Mitomycin (MMC) and 5-Fluorouracil (5FU) using SIB-IMRT delivering 42-45Gy/28–30 fractions to the elective pelvic lymph nodes and 50.4-54Gy/28-30fractions to the primary tumor and involved nodes, based on pre-treatment staging. The SeqB group comprised 103 patients, treated with MMC associated to either 5FU or Capecitabine concurrent to RT with 36 Gy/20 fractions to a single volume including gross tumor, clinical nodes and elective nodal volumes and a SeqB to primary tumor and involved nodes of 23.4 Gy/13 fractions. We compared colostomy-free survival (CFS), overall survival (OS) and the cumulative incidence of colostomy for each radiation modality. Cox proportional-hazards model addressed factors influencing OS and CFS.ResultsMedian follow up was 34 (range 9–102) and 31 months (range 2–101) in the SIB and SeqB groups. The 1- and 2-year cumulative incidences of colostomy were 8.2% (95%CI:3.6–15.2) and 15.0% (95%CI:8.1–23.9) in the SIB group and 13.9% (95%CI: 7.8–21.8) and 18.1% (95%CI:10.8–27.0) in the SeqB group. Two-year CFS and OS were 78.1% (95%CI:67.0–85.8) and 87.5% (95%CI:77.3–93.3) in the SIB group and 73.5% (95%CI:62.6–81.7) and 85.4% (95%CI:75.5–91.6) in the SeqB, respectively. A Cox proportional hazards regression model highlighted an adjusted hazard ratio (AdjHR) of 1.18 (95%CI: 0.67–2.09;p = 0.560), although AdjHR for the first 24 months was 0.95 (95%CI: 0.49–1.84;p = 0.877) for the SIB approach.ConclusionsSIB-based RT provides similar clinical outcomes compared to SeqB-based in the treatment of patients affected with non metastatic anal cancer.
Highlights
To evaluate clinical outcomes of simultaneous integrated boost (SIB) - intensity modulated radiotherapy (RT) in patients with non metastatic anal cancer compared to those of a set of patients treated with 3dimensional conformal RT and sequential boost (SeqB)
We focused on the first 2 years because, for 17 out of 103 patients in the SeqB group, we could not retrieve an updated follow up, which could potentially affect the colostomyfree survival (CFS) rates as death from any cause is considered as an event
The present study is the first to report on comparative outcomes of anal cancer patients treated with Concurrent chemo-radiation (RT-CHT) employing a SIB strategy compared to a SeqB approach
Summary
To evaluate clinical outcomes of simultaneous integrated boost (SIB) - intensity modulated radiotherapy (RT) in patients with non metastatic anal cancer compared to those of a set of patients treated with 3dimensional conformal RT and sequential boost (SeqB). In the simultaneous integrated boost (SIB) strategy, a differential dose per fraction is delivered to selected sub-regions during the same treatment session, heading to different total nominal doses given to target volumes in the same number of fractions [1]. To evaluate the potential impact of different treatment strategies on clinical outcomes, we compared data of 2 cohorts of anal cancer patients treated either with SeqB or SIB approaches, in terms of CFS as primary endpoint, after adjusting for known prognostic factors, and in terms of OS and cumulative incidence of colostomy as secondary endpoints
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