How do patients interpret and respond to a single-item global indicator of cancer treatment tolerability?

BACKGROUND: There is increasing interest in patient-reported measures of cancer treatment tolerability. A global measure of bother, the FACT GP5 item ("I am bothered by side effects of treatment") is potentially useful for regulatory, research, and clinical use. To understand this item's appropriateness for capturing treatment tolerability, we conducted cognitive interviews on this item with 3 samples of cancer patients. METHODS: Patients with ovarian cancer (Study 1: N = 21; on treatment), lymphoma (Study 2: N = 14; on treatment), and colorectal or lung cancer (Study 3: N = 16; treatment naïve) were interviewed about GP5's understandability and relevance to their treatment side effects. What patients think about when answering GP5 was also assessed. In all studies, the interview included both structured and open-ended questions. Qualitative data were coded to extract themes and responses to structured questions were tallied. RESULTS: Most patients on treatment (Studies 1 and 2) reported that the GP5 item wording is appropriate (88%) and its meaning is clear (97%). They were very confident or confident in their response (97%) and stated that GP5 was relevant to their cancer experience (97%). When answering GP5, patients considered their treatment and specific side effects. A large proportion (40%) of the treatment-naïve (Study 3) patients reported that GP5 was not relevant to their cancer treatment, and the largest proportion responded to GP5 thinking of negative side effect expectancies. CONCLUSION: This study provides assurance that GP5 is a useful indicator of treatment tolerability, and is meaningful to people with cancer, especially once they have started treatment.