Adapting a trial design based on feasibility of recruitment where several treatment groups are possible and the outcome is long-term: pre-empt flexible-entry internal pilot study

Middleton L, Daniels J, Tryposkiadis K, Gennard L, Leighton L, Bhattacharya S
Trials · 2015 · PMC4658679
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A flexible-entry internal pilot study randomized 74 women with endometriosis to assess recruitment feasibility for long-acting reversible contraceptives, determining that a two-arm trial comparing preferred LARC versus COCP was feasible.

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This paper describes the design and execution of a flexible-entry internal pilot study aimed at evaluating the feasibility of recruiting participants into a four-arm trial comparing long-acting reversible contraceptives against other treatments for endometriosis. Conducted over one year, the pilot randomized 74 women to two, three, or four treatment groups to assess patient preferences and recruitment viability before fixing the final trial structure. The results indicated that while most patients had strong preferences for either LARCs or non-LARCs, a two-arm design stratified by preference was deemed feasible, whereas four-way and three-way designs were ruled out due to low acceptance rates. This paper is centrally about endometriosis — specifically the methodological adaptation of a clinical trial design to address patient preferences regarding post-operative contraceptive treatments for preventing lesion recurrence.

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Methods

During the pilot, patients could be randomised to two, three or four treatment options provided one was a LARC and one was a non-LARC. An assessment of feasibility based on recruitment to these options and a substantive trial design was considered by an independent oversight committee. This design was fixed to ensure adequate power at the end of the study.

Results

The study ran for one year from April 2014 and 74 women were randomised. Only 5 (7%) women were happy to be randomised to all groups, with 60 (81%) having a LARC preference and 53 (72%) a non-LARC preference. Four-way and three-way designs were ruled out with a two-way (preferred LARC v COCP), stratified by LARC preference, considered feasible.

Background

Endometriosis occurs when the endometrium grows in abnormal locations outside of the womb, resulting in pain and reduced quality of life. See-and-treat surgery removes endometriotic lesions but the risk of recurrence is high. A HTA commissioning call asked to evaluate the long-term (three years) effectiveness of post-operative long-acting reversible contraceptives (LARCs) in preventing recurrence. A survey of gynaecologists indicated there was no consensus about which LARC (LNG-IUS or DMPA) or comparator (COCP or no treatment) should be evaluated. We designed a ‘flexible-entry’ internal pilot to assess whether a four-arm trial was feasible in light of possible strong patient preferences.

Conclusions

Where multiple treatment options are available a flexible approach to randomisation in a pilot phase can be used to assess feasibility and adapt a trial design.

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