Research based predominantly on females undergoing chemotherapy, has indicated patients’ pre-treatment response expectancies of treatment side-effects often predicts their subsequent toxicity experience; therefore, screening for high expectancies may identify those requiring additional support. This study investigated the predictive strength of expectancies above and beyond known and unique influences, in a novel, homogenous cohort and treatment modality; men with prostate cancer undergoing a similar dose of radiotherapy.
A longitudinal, within-participant design requiring 30 patients, accrued 35 men with prostate cancer, naïve to external beam radiation therapy (EBRT), who completed baseline measures 4-weeks before commencing 7.5 weeks of weekday treatment. These included study-specific assessments of toxicity expectancies (visual analogue scales; VAS, 0-100), baseline symptoms, demographics, standardised measures of emotional state (Depression Anxiety and Stress Scale 21; DASS21), and coping style (Mental Adjustment to Cancer; MAC Scale). Two-weeks into EBRT, current toxicity experience was assessed alongside future expectancies, relevant to toxicity experience measured again at the 7-week point.
Controlling emotional state, coping style, and demographic/health variables, a series of multiple linear regressions found pre-treatment expectancies uniquely predicted six toxicity experiences (p<0.05) 2-weeks into treatment, contributing 12-39% of explained variance (β=0.39-0.67), despite toxicities not medically expected until approximately 5 weeks into EBRT. Expectancies assessed 2-weeks into treatment uniquely predicted seven toxicities (p<0.05) experienced 7-weeks into EBRT, explaining 23-60% of the variance (β=0.49-0.94). Sexual side-effect expectancies revealed the strongest associations with their experience (β=0.46-0.94; p<0.01), particularly by 7-weeks.
Side-effect expectancies predict patient experience of multiple toxicities throughout EBRT. Controlling multiple influences, expectancies of sexual side-effects have the strongest effect on experience across radiotherapy for men. Although medically expected in EBRT, findings suggest psychosomatic influence given early associations in treatment for six side-effects. Sexual and other prominent toxicities require a substantial focus on psychological intervention in practice and further replication.