Discussion
In the present study, there was a high incidence of metastatic disease at presentation (50.70%). Pakos et al 30, in an international OS compilation, where OS Brazilian Group was included, showed 13% of the patients with metastatic disease, the same could be seen in the OS Children Oncology Group (COG) (27%) and Cooperative Ewing Sarcoma Study (CESS) group (30%) 30–34. Patients arrived at INCA with advanced disease and this characteristic probably influenced in their pain status in all follow-up moments.
At registration, pain was related as the most frequent symptom (61.27%). Even if pain scales were not used, the majority of patients self-assessed pain as moderate to severe and three children had excruciating pain. At that moment, the most frequent drugs used for pain control were mild analgesics (paracetamol or dipyrone) and treatment was changed in 42.25% of patients. This data contrasts with the WHO recommendation, that suggested the use of strong opioids at that level of pain, specially morphine. This undertreatment could be attributed to the fear of using opioids 16,35–38.
By contrast, end-of-life patients used strong opioids and morphine was the most frequently used, followed by anticonvulsant and antidepressant drugs, as well as other drugs and procedures, as a multimodal therapy. This has been used in agreement with international references.27,28,35,39
Along the follow-up period, more patients had their pain classified. Also, pain complaint decreased, and no excruciating pain was observed at last evaluation. At registration, 34.21% had no pain and at last evaluation 73.77% of all patients had no pain. These results suggest the effectiveness of the management of pain control associated during follow-up.
However, we observed association between pain at last evaluation and the presence of disease progression. Those patients presented 3.5 times more pain compared to the others. Comparing with previous international cooperative pediatric bone cancer groups studies, the influence of this variable followed the same direction, being associated to pain20–23,31–34,40–42.
At last evaluation we observed no difference in pain complaint between end-of-life patients and the others. This suggests that pain management was effective. Also, it was observed opioid use associated to pain complaint at last evaluation, this is a reverse cause-effect association, as those who have more pain use more opioids. However,19.64% of end-of-life patients and 18.60% of those undergoing treatment or in disease control still presented moderate and severe pain, at last evaluation. We suggest that this might have occurred because of family misconception for the use of pain control drugs. Similar results were seen by Snaman et al., who revealed difficulty in pain control, with the principal obstacle being lack of information and misconceptions of opioid use. 5,29,27,43.