Abstract
BACKGROUND: Pain is a prevalent symptom in patients with advanced cancer. Recognition of prognostic factors associated with pain intensity, could help provide better assessment, leading to better pain management. AIM: identifying prognostic factors which could guide improvements on cancer pain classification. DESIGN: a prospective observational study on chronic cancer pain, exploring the association between average mean pain intensity during a 28 days study follow-up and patients' clinical and pain-related characteristics, including pain syndromes. To evaluate these associations, a mixed model was built. SETTING/PARTICIPANTS: Patients attending a Palliative Care and Pain Outpatient Clinic from May 2015 to June 2019 were screened. Patients with moderate to severe cancer pain who were already receiving or needed treatment with third step WHO ladder opioids were enrolled in the study. Data from 342 patients with at least one follow-up visit were analyzed. RESULTS: Pain intensity decreased significantly for all patients during time (p < 0.001). Age, sex, emotional distress, pain duration and neuropathic pain presence evaluated by the Douleur Neuropathique 4 Questions (DN4) questionnaire were not significantly associated to pain intensity. Breakthrough/episodic pain was associated with higher pain intensity during follow-up (p < 0.001). The diagnosis of pain syndrome was overall significantly associated with mean pain intensity during follow-up (p = 0.016). Particularly, the concurrent presence of visceral and soft (p = 0.026) or soft and nervous tissue pain (p = 0.043) were significantly related to worse outcome, whereas pain due to only soft tissue damage with better outcome (p = 0.032). CONCLUSIONS: The recognition of specific pain syndromes may help to better classify cancer pain.