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Optimal cut points for quality of life questionnaire-core 30 (QLQ-C30) scales: utility for clinical trials and updates of prognostic systems in advanced hepatocellular carcinoma.

BACKGROUND
Health-related quality of life (QoL) has been validated as a prognostic factor for cancer patients; however, to be used in routine practice, QoL scores must be dichotomized. Cutoff points are usually based on arbitrary percentile values. We aimed to identify optimal cutoff points for six QoL scales and to quantify their added utility in the performance of four prognostic classifications in patients with hepatocellular carcinoma (HCC).


METHODS
We reanalyzed data of 271 patients with advanced HCC recruited between July 2002 and October 2003 from 79 institutions in France in the CHOC trial, designed to assess the efficacy of long-acting octreotide. QoL was assessed with the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (QLQ-C30). The scores ranged from 0 to 100. Identification of optimal cutoff points was based on the method of Faraggi and Simon [Stat Med 1996;15:2203-2213]. Improvement in the performance of prognostic classifications was studied with Harrell's C-index, the net reclassification improvement (NRI), and integrated discrimination improvement (IDI).


RESULTS
We found that optimal cutoff points were 50 for global health, 58.33 for physical functioning, 66.67 for role functioning, 66.67 for fatigue, 0 for dyspnea, and 33.33 for diarrhea. The addition of QoL and clinical factors improved the performance of all four prognostic classifications, with improvement in the range of 0.02-0.09 for the C-index, 0.24-0.78 for 3-month NRI, and 0.02-0.10 for IDI.


CONCLUSION
These cutoff values for QoL scales can be useful to identify HCC patients with very poor prognosis and thus improve design of clinical trials and treatment adjustment for these patients.