Background: It is estimated that for 50 per cent of healthcare the effectiveness is investigated insufficiently. There is an urgent call from politicians and society to reduce increasing healthcare costs but there is limited budget for evaluation research. Therefore it is essential to prioritise knowledge gaps. The Dutch Society for Radiation Oncology (NVRO), one of the Dutch medical specialty societies, has recently developed a knowledge agenda.

Objectives: The goal is to improve the quality and efficiency of care in radiation therapy. Patient perspectives are an important factor.

Methods:Examination of knowledge gaps was done in three ways:
1) Dutch guidelines addressing oncology/radiotherapy issues were scrutinised for recommendations with a low level of evidence;
2. members of the NVRO were asked to deliver knowledge gaps via an online survey; and,
3. remaining stakeholders such as care insurers, general practitioners, the Dutch Inspection of Healthcare and patient association(s) were asked to examine and deliver knowledge gaps.

Next, a plenary meeting with radiation oncologists, stakeholders and patient association(s) was organised to prioritise the knowledge gaps per tumour type according to health gain, societal impact, urgency and ability to research. Finally, an overall top 10 was generated which will form the research programme of the NVRO in the upcoming years.

Results: An example of three knowledge gaps from the top 10 in the agenda are:
1) What is the additional value of radiotherapy in treating oligometastases with quality of life and lifespan as outcome measures?
2) What is the role of imaging techniques (such as PET or MRI) in preparing (dose and targeting), planning and executing a radiation treatment?
3) What is the effectivity of stereotactic radiation therapy in treating liver metastases of colorectal tumours?

Conclusions: Developing a knowledge agenda appears to be very useful to get insight into what evidence is missing in daily clinical care per specialty. Studying these knowledge gaps improves the level of evidence in daily practice and thereby quality and efficiency of healthcare.