Purpose: We conducted a secondary qualitative analysis of consultations between oncologists and their patients to explore how patient-reported outcome measures (PROMs) data were referred to in the process of (1) eliciting and exploring patients' concerns; (2) making decisions about supportive treatment and (3) making decisions about chemotherapy and other systemic treatments. Methods: We purposively sampled audio recordings of 18 consultations from the intervention arm and 4 from the attention control arm of a previous UK randomised controlled trial of the feedback of PROMs data to doctors (Velikova et al. in J Clin Oncol 22(4):714-724 ). We used a combination of content and conversation analysis to examine how opportunities for discussion of health-related quality of life issues are opened up or closed down within the consultation and explore why this may or may not lead to changes in patient management. Findings: Explicit reference to the PROMs data provided an opportunity for the patient to clarify and further elaborate on the side effects of chemotherapy. High scores on the PROMs data were not explored further if the patient indicated they were not a problem or were not related to the cancer or chemotherapy. Symptomatic treatment was more often offered for problems like nausea, constipation, pain and depression but much less so for fatigue. Doctors discussed fatigue by providing a cause for the fatigue (e.g. the chemotherapy), presenting this as 'something to be expected', minimising its impact or moving on to another topic. Chemotherapy regimens were not changed on the basis of the PROMs data alone, but PROMs data were sometimes used to legitimise changes. Conclusions: Explicit mention of PROMs data in the consultation may strengthen opportunities for patients to elaborate on their problems, but doctors may not always know how to do this. Our findings have informed the development of a training package to enable doctors to optimise their use of PROMs data within the consultation.