In the present study, the three prognostic tools were validated and compared simultaneously for predicting the survival of patients with advanced cancer in mainland China, especially for patients who received home-based palliative care services. Our results indicate that the ChPS is more suitable for advanced cancer patients in the HPC setting than the PPI and PS-PPI.
The ChPS was initially developed for predicting the survival of advanced cancer patients in the HPC setting in China.[10] Group B (total scores 28.1–124.0) in ChPS exhibited a significantly shorter survival time than group A (total scores 0.0–28.0) in the present study, which is consistent with the results of Zhou et al.[10] The overall accuracy for predicting the survival of less than 90 days with a ChPS score of 28 was 68.3%, which is similar to the outcome from the original article that the overall accuracy of the testing set was 65.4%.[10] In the present study, the AUROC of the ChPS was significantly higher than that of the PPI and PS-PPI for 7-, 14, 21-, 42-, 90-, 120-, 150- and 180-day survival, and the sensitivity and PPV of the ChPS for predicting 90-day survival were 86.1% and 71.5%, respectively. However, the ChPS had low specificity and NPV in the present study. Low NPV indicated that there were some patients with ChPS scores (0.0–28.0) who lived less than 90 days. In practice, false-positive predictions are more critical than false-negative predictions because the predicted survival time being longer than the actual survival time may induce the problem in communication between clinicians and patients or their family for decision making.[37, 38] Based on this view, the ChPS could be utilized as a screening tool for prognostication because of its high sensitivity and PPV, which is a prerequisite for a useful screening tool. Besides, the classification of primary cancer was included in some scoring systems in previous studies.[39–41] Patients with different types of cancer may have individual survival time because primary cancer is considered a significant factor related to survival time. In addition, previous studies reported that the specific site of metastasis was associated with survival time.[42–44] Yin et al. [42] reported that liver metastasis was regarded as an independent predictor related to poor prognosis for patients with cervical cancer. Another study reported that metastatic renal cell carcinoma patients with isolated liver metastases seemed to have worse outcomes.[43] However, the primary site of the tumor and the specific site of metastasis were not considered in the ChPS. Further studies are needed to confirm that the accuracy of the ChPS could be improved by including factors relative to the primary site of the tumor and the particular site of metastasis.
In a retrospective study, Hamano et al.[27] suggested that the PPI might not be suitable as a screening tool for poor prognosis patients with relatively good performance status in the home care setting considering its low sensitivity, but might be suitable for predicting survival longer than 21 days because of its high specificity. A further prospective study supported this finding.[29] A similar outcome was presented in our study that the sensitivity for 21-day and 42-day survival of the PPI was lower than that of the original article when the cutoff score was set at 6.0 and 4.0, respectively, and the PPI had a high specificity with the same cutoff scores. The discrepancy of the sensitivity may be attributed to differences between the patients. The low sensitivity in the HPC setting could be interpreted by the lowest prevalence for PPI > 6 (11.1%), which indicated that patients with advanced cancer in the HPC setting may be in a better general condition and have fewer complications.[10, 45] Characteristics related to the survival of patients were different for various studies.[29, 46] The median survival time of the patients in the present study was 52 days, whereas Morita et al. [24] reported 27 days, and Maltoni et al. [30] reported 22 days in the hospice setting. In addition, the prevalence of severely reduced oral intake, edema, dyspnea at rest, and delirium was lower than those in the original article. Some scholars hold the view that a one-shot PPI assessment might not be accurate enough as a prognostic tool because patients’ clinical features changed dynamically during the end-of-life trajectory.[47–49] Arai et al. [49] reported a retrospective cohort study that reassessment of the PPI was necessary because of the change in the PPI as an important and independent factor associated with the survival of advanced cancer patients. Another previous study reported by Kao et al. [48] showed that the combination of initial PPI and score change was more accurate to predict the actual prognosis. Further studies are needed to modify the PPI for advanced cancer patients in the HPC setting.
In the previous study,[31] the PS-PPI was as accurate as the PPI to predict the survival of advanced cancer patients, which paralleled our findings that the AUROCs of the PPI and PS-PPI were not significantly different from each other. Survival time among the three risk groups of the PS-PPI was significantly different from each other. However, survival time between group B (4.1-6.0) and group C (6.1–15.0) in PPI was not significantly different from each other, which is not in accordance with previous findings.[30, 50] One possible reason is that patients with PPS scores (30–50) accounted for 74.2% in the present study, which indicated that the performance status of patients might be overestimated by the physicians.[10] Another reason is that patients with moderate performance status could not be distinguished precisely by the KPS. The difference between the PPI and PS-PPI is that ECOG PS is used to take the place of PPS for performance status assessment. Performance status has been found to be strongly correlated with survival time in previous studies.[10, 51–54] The European Association for Palliative Care has recommended the performance status as significant prognostic factors.[1] Myers et al.[55] reported that the ECOG scale, PPS, and KPS have a highly significant linear correlation. Another study reported by Chow et al. [56] suggested that there was a notable correlation of performance status scores among the ECOG scale, PPS, and KPS, and with no one tool statistically superior to others. In the present study, the KPS-to-ECOG and KPS-to-PPS conversion were based on the formula reported by Ma et al.[34] Thus, further studies are needed to compare the PPI and PS-PPI for advanced cancer patients in the HPC setting.
This study has some limitations. First, our study was carried out retrospectively and included only economically disadvantaged patients from a single institution, which may not be representative of patients with advanced cancer in the HPC setting in mainland China and worldwide. Second, ECOG PS scores and PPS scores were both transferred from KPS scores, which may affect the accuracy of the PPI and PS-PPI. Third, clinical characteristics of patients might be recorded in mistake without standardized specific assessment tools in a retrospective study. Notwithstanding these limitations, a large number of advanced cancer patients in the HPC setting were included in the present study. Meanwhile, the three prognostic tools we selected do not require blood tests and complicated calculations.