ESTRO 2023 - Abstract Book

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ESTRO 2023

Conclusion Dose escalation using SIB-IMRT for clinically positive EM-PLN and E-PLN has the potential to reduce the need for LND & associated toxicity with better QoL.

PO-1396 Long-term outcomes for locally advanced anal cancer after radical chemoradiotherapy

F. Kazmi 1 , G. Shanmugasundaram 1 , E. Benn 1 , R. Fenn 1 , G. Kapur 1 , A. Ho 1 , D. Biswas 1

1 Norfolk and Norwich University Hospital, Oncology, Norwich, United Kingdom

Purpose or Objective We present real world-UK data of 10 year outcomes in locally advanced anal cancer patients who underwent radical intent chemoradiotherapy in our National Health Service trust. Materials and Methods A retrospective review was performed to assess treatment outcomes for patients with non-metastatic, histologically confirmed anal cancer from 2009 to 2022 who underwent radical chemoradiotherapy (CRT). Patients’ cancer was restaged based on AJCC-8th classification. Treatment outcome measures included 5-year (yrs) and 10-year disease free survival (DFS), anal cancer specific survival (CFS), overall survival (OS) and treatment related toxicities. An exploratory analysis was carried out to assess high risk features to predict recurrence. Kaplan-Meier curves were used to estimate survival rates. Results We identified 116 patients with locally advanced anal cancer who underwent CRT in the intention to treat (ITT) cohort. Median age was 66.7yo (IQR: 56 – 74) and ratio male/female was 24.1%/75.9%. From the ITT cohort, 100 patients received mitomycin and 5-fluorouracil based concomitant chemotherapy with radical radiotherapy and 16 patients received radical radiotherapy alone. Median radiotherapy dose prescribed was 50.4Gy (Range: 41.4 – 54Gy) in 28 (23 – 30) fractions. Median follow-up was 5.1yrs (IQR: 1.7 – 6.6). The 5 and 10-year OS was 73.4% and 59.5%. The 5 and 10-year CFS was 78.1% and 75.1%. The 5 and 10-year DFS was 71.9% and 65.9%. Overall, 32/166 (27.6%) patients had disease relapses. Of these, 11/32 (34.3%) had only local pelvic recurrence, 10/32 (31.2%) had only distant disease relapse and 11/32 (34.3%) had both local and distant relapse. On univariate analysis, high risk feature such as T3/T4 and/or node positive disease was trending towards significance in predicting for increased risk of recurrence (For T3/T4; HR = 2.04, 95% CI = 0.99 – 4.23, p = 0.052. Nodes positive; HR = 1.82, 95% CI = 0.90 – 3.67, p = 0.094). The 3 and 6-month post treatment response imaging also strongly predicted for cancer relapse. 78/116 (66.7%) patients had complete response (CR) and 27/116 (23.1%) had partial response (PR) on 3-month post treatment imaging. Interestingly, 13/27 (48.1%) PR converted to CR on 6-month imaging; however, 7/27 (25.9%) patients underwent salvage abdomino-perineal excision of rectum (APER) for persistent residual disease on 6-month imaging. The most common grade 3- 4 acute toxicities were gastrointestinal 21/116 (18.1%), skin 11/116 (9.4%)and pain 11/116 (9.4%). Late toxicities were not well reported. Conclusion Our findings are consistent with survival outcomes when compared to ACTII trial data and we provide additional longitudinal analysis with a 10 year follow-up. Almost half the patients who did not have CR on 3-month post treatment imaging had CR