SOMA-trial: surgery or medication for women with an endometrioma? Study protocol for a randomised controlled trial and cohort study

E van Barneveld*, V B Veth, J M Sampat, A M F Schreurs, M van Wely, J E Bosmans, B de Bie, F W Jansen, E R Klinkert, A W Nap, B W J Mol, M Y Bongers, V Mijatovic, J W M Maas

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


STUDY QUESTIONS: The objective of this study is to evaluate the effectiveness and cost-effectiveness of surgical treatment of women suffering from pain due to an ovarian endometrioma when compared to treatment with medication (analgesia and/or hormones). The primary outcome is defined as successful pain reduction (-30% reduction of pain) measured by the numeric rating scale (NRS) after 6 months. Secondary outcomes include successful pain reduction after 12 and 18 months, quality of life, affective symptoms, cost-effectiveness, recurrence rate, need of adjuvant medication after surgery, ovarian reserve, adjuvant surgery and budget impact.

WHAT IS KNOWN ALREADY: Evidence suggests that both medication and surgical treatment of an ovarian endometrioma are effective in reducing pain and improving quality of life. However, there are no randomised studies that compare surgery to treatment with medication.

STUDY DESIGN SIZE DURATION: This study will be performed in a research network of university and teaching hospitals in the Netherlands. A multicentre randomised controlled trial and parallel prospective cohort study in patients with an ovarian endometrioma, with the exclusion of patients with deep endometriosis, will be conducted. After obtaining informed consent, eligible patients will be randomly allocated to either treatment arm (medication or surgery) by using web-based block randomisation stratified per centre. A successful pain reduction is set at a 30% decrease on the NRS at 6 months after randomisation. Based on a power of 80% and an alpha of 5% and using a continuity correction, a sample size of 69 patients in each treatment arm is needed. Accounting for a drop-out rate of 25% (i.e. loss to follow up), we need to include 92 patients in each treatment arm, i.e. 184 in total. Simultaneously, a cohort study will be performed for eligible patients who are not willing to be randomised because of a distinct preference for one of the two treatment arms. We intend to include 100 women in each treatment arm to enable standardization by inverse probability weighting, which means 200 patients in total. The expected inclusion period is 24 months with a follow-up of 18 months.

PARTICIPANTS/MATERIALS SETTING METHODS: Premenopausal women (age ≥ 18 years) with pain (dysmenorrhoea, pelvic pain or dyspareunia) and an ovarian endometrioma (cyst diameter ≥ 3 cm) who visit the outpatient clinic will make up the study population. Patients with signs of deep endometriosis will be excluded. The primary outcome is successful pain reduction, which is defined as a 30% decrease of pain on the NRS at 6 months after randomisation. Secondary outcomes include successful pain reduction after 12 and 18 months, quality of life and affective symptoms, cost-effectiveness (from a healthcare and societal perspective), number of participants needing additional surgery, need of adjuvant medication after surgery, ovarian reserve and recurrence rate of endometriomas. Measurements will be performed at baseline, 6 weeks and 6, 12 and 18 months after randomisation.

STUDY FUNDING/COMPETING INTERESTS: This study is funded by ZonMw, a Dutch organization for Health Research and Development, project number 80-85200-98-91041. The Department of Reproductive Medicine of the Amsterdam UMC location VUmc has received several research and educational grants from Guerbet, Merck KGaA and Ferring not related to the submitted work. B.W.J. Mol is supported by a NHMRC Practitioner Fellowship (GNT1082548) and reports consultancy for ObsEva, Merck KGaA and Guerbet. V. Mijatovic reports grants from Guerbet, grants from Merck and grants from Ferring outside the submitted work. All authors declare that they have no competing interests concerning this publication.

TRIAL REGISTRATION NUMBER: Dutch Trial Register (NTR 7447,


DATE OF FIRST PATIENT’S ENROLMENT: First inclusion in randomised controlled trial October 4, 2019. First inclusion in cohort May 22, 2019.

Original languageEnglish
Article numberhoz046
Number of pages9
JournalHuman reproduction open
Issue number1
Publication statusPublished - 2020


  • endometrioma
  • pain
  • quality of life
  • cost-effectiveness
  • affective symptoms
  • recurrence
  • ovarian reserve
  • surgery
  • medication
  • randomised controlled trial

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