New Prognostic Index to Predict Survival in Patients with Cancer of Unknown Primary Site with Unfavourable Prognosis

Abstract 

Aims

To identify independent prognostic factors in patients with cancer of unknown primary site (CUP) who do not belong to prognostically favourable subsets, and to develop a prognostic index for predicting survival in these patients.

Materials and methods

In this prospective study, univariate and multivariate analyses of prognostic factors were conducted in a population of 145 patients with CUP in two clinical institutions. Subsets of patients with favourable prognostic features and those requiring well-defined treatment were excluded.

Results

The 1-year overall survival rate for all patients was 42% and the median overall survival was 330 days. Overall survival was significantly related to the following pre-treatment prognostic factors: poor Eastern Cooperative Oncology Group performance status (ECOG PS)≥2, presence of liver metastasis, elevated serum lactate dehydrogenase (LDH), high white blood cell count, anaemia, age≥63 years, and prolonged QTc interval in electrocardiography (ECG). In multivariate analysis, four independent adverse prognostic parameters were retained: elevated LDH (hazard ratio 2.21; 95% confidence interval 1.41–3.47; P=0.001), prolonged QTc interval (hazard ratio 2.10; 95% confidence interval 1.28–3.44; P=0.003), liver metastasis (hazard ratio 1.77; 95% confidence interval 1.11–2.81; P=0.016) and ECOG PS≥2 (hazard ratio 1.69; 95% confidence interval 1.05–2.73; P=0.03). We developed a prognostic index for overall survival based on the following subgroups: good prognosis (no or one adverse factor), intermediate prognosis (two adverse factors) and poor prognosis (three or four adverse factors). The median overall survival for the three subgroups was 420, 152 and 60 days, respectively, P<0.0001.

Conclusions

This study validated previously identified important prognostic factors for survival in patients with CUP. Prolonged QTc was additionally identified as a strong adverse prognostic factor. We developed a simple prognostic index using performance status, LDH, presence of liver metastasis and QTc interval in ECG, which allowed assignment of patients into three subgroups with divergent outcome.

Key words: Neoplasms of unknown origin, prognostic factors, prolonged QTc interval, survival analysis