The minimal clinically important difference for decisional conflict, impact of event, body image scale and the Short Form-36 among women with breast cancer

Improved overall survival and heightened awareness combined with increasing attention for prophylactic mastectomies1 are shifting the focus of breast cancer care providers and patients to long term effects of the treatment on health related patient satisfaction and quality of life. Patient reported outcome measurements (PROMs) focus on the patient’s perspective and are becoming increasingly important in the evaluation of our treatments. Interpreting changes in scores might however be challenging as a significant difference does not equal a clinically relevant difference.

The minimal clinically important difference (MCID) is the smallest change in treatment outcome score that a patient, a care provider, or both would perceive as important. Treatments showing a statistically significant difference in scores that are lower than the MCID may not be actually clinically relevant. Therefore, establishing the MCID for outcome measures is essential to determine treatment effectiveness and therefore in sample size calculation in trial design.

At present, there is no standard as to how to assess the MCID. Different methods exist to determine the MCID: (1) based on the data’s distribution, (2) by a Delphi (expert-based) approach7 or (3) through an anchor-question. Generally, the anchor-based approach is accepted as the preferred method as it takes into account both statistical distribution and patient perspectives.

The MCID probably varies by diagnosis, treatment and in time. At present, the MCID for commonly used PROMs in breast cancer (DCS, IES, BIS and SF-36) is unknown.

In this study we aim to determine the MCID for DCS in women with breast cancer 2-4 weeks after visiting our outpatient breast cancer center using an anchor question and the MDIC 4-6 weeks postoperative and 6 months postoperative for IES, BIS and SF-36. Secondarily, we will assess flooring and ceiling effects and factors associated with low scores for DCS, IES, BIS and SF-36 among this population. We hypothesize that there are no factors associated with achieving an MCID for DCS, IES, BIS and SF-36.

We hypothesize that there are no factors associated with achieving an MCID for DCS, IES, BIS and SF-36.

- 2 - 4 weeks after surgical decision.
- 4 - 6 weeks after surgical decision.
- 6 months after surgical decision.

Consenting subjects are invited to fill out a panel of standardized questionnaires, including the DCS, IES, BIS, SF-36, PROMIS Short Form Anxiety and Depression, PCS, GSE (self-efficacy), and a study specific questionnaire.