The Significance of Soluble Interleukin-2 Receptor in Monitoring Disease Relapse in Patients with Nasopharyngeal Cancer

Background: Soluble interleukin-2 receptor α (sIL-2Rα) is a well-known indicator of T-cell activation noted to be increasing in nasopharyngeal cancer. However, the significance of sIL-2Rα in monitoring disease relapse is unclear. This study was initiated to address this issue. Methods: Serum of 56 patients with NPC, which underwent either primary, salvage, or palliative treatments, from 1992 to 1993 at the Cancer Center, Veterans General Hospital-Taipei, were collected from our serum bank. According to their disease status at the time of study, at least two years after last treatments, the 56 patients were divided into four groups. The remission group represented those in remission at the time of study (n=24). The metastasis group represented those with distant metastasis present at the time of study (n=17). The recurrence group represented those with locoregional recurrence present at the time of study (n=11). The combined group represented those with locoregional recurrence as well as distant metastasis (n=4). The serai sIL-2Rα concentrations of the 56 NPC patients were determined with enzyme-linked immunoabsorbent assay. The combined group was excluded in our statistical analysis. We performed statistical analysis on the differences of paired serum sIL-2Rα concentrations between different periods of the diseases. The first analysis was on the differences of sIL-2Rα concentrations between diagnosis and post-radiotherapy periods for 13 out of 24 patients in the remission group and 7 out of 11 patients in the recurrence group. The second analysis was on the differences of sIL-2Rα concentration between follow-up before detection-of-relapse and after detection-of-relapse for 5 out of 17 patients in the metastasis group and six out of 11 patients in the recurrence group. Results: The first statistical analysis revealed no significant differences of sl L-2Rα concentrations for the remission group (P=0.946) and the recurrence group (P=0.156) between diagnosis and post-radiotherapy periods. The second statistical analysis revealed no significant differences of sIL-2Rα concentrations between before and after detection-of-relapse for the recurrence group, neither (P=0.438). The results for the metastasis group were different. The sIL-2Rα concentrations were shown to increase after the detection of metastasis for the 5 paired samples from the metastasis group, although the Wilcoxon signed ranks test on the differences only showed borderline significance (P=0.063). Conclusions: Our findings show that sIL-2Rα; would be of no value in monitoring the development of locoregional recurrence but might be useful in monitoring distant metastasis. Although our current limited data did not provide strong support for the role of sIL-2Rα in monitoring metastasis, it might be delineated in the future by collecting more data.