MLR mean prediction error (0.52) was within a factor of 3, while the remaining models had mean errors (~0.3) of approximately a factor of 2. Efforts to correlate training set SCI values with any of the prospective set quality measurements were unsuccessful (data not shown).
The maximum SALI value for the training, test, and prospective data sets were approximately 200, 200 and 75, respectively, even though the prospective set had a slightly greater spread of Tanimoto values (Figure 4) Thus, the SALI summary values (SCI, S 0), S(1)) represent the SALI landscape covered by that data set only.
The predictive power of this approach may be improved by comparing the performance of the test and prospective sets with those of the training sets.
Working on a prospective data set of 14 subjects (sound recording length 840 min), proposed method achieved sensitivity, specificity, and Cohen's Kappa of 93%, 98%, and 0.65, respectively.
An independent data set (the prospective data set of GSE4115, 18 smokers with lung cancer and 17 smokers without lung cancer) was then used to evaluate the diagnostic performance of the proposed network-based biomarker.
Using the same data (the prospective data set of GSE4115), conventional bronchoscopy was shown to be 44% sensitive to cancer detection [ 3], which is only half of the proposed network-based biomarker.
An important strength of this study is the prospective setting with regular monitoring of the patients including radiographic examinations and scoring in a systematic fashion.
More results would require a prospective setting; as with many studies of prognostic or predictive markers the major weakness of this study is the use of retrospective, non-randomized material as well as the low number of the patients.
Nevertheless, the results with our treatment approach seem to be superior to palliative chemotherapy or chemoradiation alone and should be further tested in a prospective setting specifically addressing isolated local recurrences of pancreatic cancer.
