Optimal Time to Assess Response After Chemoradiotherapy in Anal Squamous Cell Carcinoma
In a post hoc analysis of the UK ACT II trial reported in The Lancet Oncology, Glynne-Jones et al found that the best time to assess for complete response to chemoradiotherapy in patients with anal squamous cell carcinoma is at approximately 26 weeks from the start of treatment.
In the ACT II trial, patients with nonmetastatic disease were randomized to receive mitomycin or cisplatin with fluorouracil (5-FU) and radiotherapy; a second randomization after initial therapy was to maintenance therapy with 5-FU and cisplatin or no maintenance therapy. The current analysis assessed the rates of clinical response at 11, 18, and 26 weeks from the start of chemoradiotherapy and the relationship to survival outcomes.
Response by Assessment Time
Among 940 patients in the trial, complete clinical response was observed in 52% at 11 weeks, 71% at 18 weeks, and 78% at 26 weeks. Of 691 patients who attended all 3 assessments, complete clinical response was observed in 64%, 80%, and 85%, with 71% of patients without complete response at the first assessment achieving it by 26 weeks.
Survival Outcomes
Among all patients, 5-year overall survival was 83%, 84%, and 87% among patients with complete response at first, second, and third assessments and 72%, 59%, and 46% among those without complete response, respectively. In the subgroup of 691 patients attending all 3 assessments, 5-year overall survival was 85%, 86%, and 87% in those with clinical response and 75%, 61%, and 48% in those without complete response. Similar relationships were observed for progression-free survival among all patients and in the 691-patient subgroup.
The investigators concluded: “Many patients who do not have a complete clinical response when assessed at 11 weeks after commencing chemoradiotherapy do in fact respond by 26 weeks, and the earlier assessment could lead to some patients having unnecessary surgery. Our data suggest that the optimum time for assessment of complete clinical response after chemoradiotherapy for patients with squamous cell carcinoma of the anus is 26 weeks from starting chemoradiotherapy. We suggest that guidelines should be revised to indicate that later assessment is acceptable.”
The study was funded by Cancer Research UK.
Robert Glynne-Jones, FRCR, of Mount Vernon Centre for Cancer Treatment, Northwood, Middlesex, UK, is the corresponding author of The Lancet Oncology article.
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