‘Measuring up’: A comparison of two response expectancy assessment formats completed by men treated with radiotherapy for prostate cancer

• Published in: Journal of psychosomatic research 2020-05, Vol.132, p.109979-109979, Article 109979
• Main Authors: Devlin, Elise J., Whitford, Hayley S., Denson, Linley A., Potter, Andrew E.
• Format: Article
• Language: English
• Subjects: Associations; Cancer therapies; Evaluation; Expectancy; Knee; Men; Nocebo; Oncology; Patients; Prostate; Prostate cancer; Radiation therapy; Radiotherapy; Rectum; Response expect; Self-report; Side effect; Systematic review; Urgency; Visual analogue scales
• ISSN: 0022-3999; 1879-1360
• DOI: 10.1016/j.jpsychores.2020.109979

Response expectancies of cancer treatment toxicities are often, but not always, associated with subsequent experiences. A recent meta-analysis indicated that response expectancies, measured using different assessment formats, reveal different effect sizes, potentially explaining mixed outcomes. Utilizing a clinical sample, we compared 5-point assessments and visual analogue scales, as measures of response expectancies for the incidence and severity of subsequent toxicities. Four weeks pre-radiotherapy, 45 men with prostate cancer rated their response expectancies of the same 18 toxicities on 5-point assessments and visual analogue scales, presented in random order. Descriptors anchored each end of visual analogue scales and every point of 5-point assessments was labelled, including an ‘unsure’ midpoint. Toxicities were subsequently assessed 2-weeks into radiotherapy on 100-point visual analogue scales. Across all toxicities, 17.5–62.8% of patients selected ‘unsure’ on 5-point assessments. No response expectancies were reported on 5-point assessments for ‘blood in stools’ or ‘rectal urgency’ yet 54.8%–64.3% of patients indicated response expectancies for these toxicities on visual analogue scales. Visual analogue scales and 5-point scales demonstrated small-to-moderate associations (r = 0.30–0.58) as measures of response expectancy incidence, but mostly large associations when visual analogue scales captured severity (r = 0.43–0.76). Response expectancies measured with visual analogue scales predicted more toxicities to a moderate degree or greater (68.8%) than 5-point assessments (37.5%). This novel investigation demonstrated an ‘unsure’ midpoint is often selected, potentially reducing the sensitivity of 5-point assessments. Based on their associations, and outcomes, these assessment formats should be considered independent in response expectancy research of cancer treatment toxicities. •An ‘unsure’ midpoint was commonly selected on SEEQ.•VAS appeared to detect response expectancies with more sensitivity than SEEQ.•VAS and SEEQ were not highly associated as measures of response expectancies.•Response expectancies measured with VAS predicted more toxicities than SEEQ.•VAS and SEEQ should not be used and discussed interchangeably.