Role of Ethnicity and Tumour Factors in Pain Perception and Radiation Analgesia among Breast Cancer Patients with Metastatic Bone Pain

Abstract

Background: Palliative external beam radiotherapy (PRT) had been reported as an indispensable tool for an effective pain relief in cancer patients with metastatic bone pain. Although many scholars reported a link between pain perception and ethnic background of an individual, but its role in cancer patients with interplay of other tumour factors needs to be evaluated to ascertain the actual impact it may have on pain perception and responses to radiation analgesia. Methods: We retrospectively reviewed patient’s data of breast cancer with metastatic bone pain between 2015 and 2018. Patient’s demographic factors like age, sex, ethnic group, tumour histology, RBS grade and sites of metastasis were extracted and grouped accordingly. Other Radiotherapy doses used for palliation of pain were extracted. Visual analogue pain assessment scale (0-10) was used by doctors (majority from Hausa-Fulani ethnic origin) to asses’ pain at presentation and four weeks post-irradiation. SPSS version 23 was used for data analyses; univeriate and multivariate analyses were conducted to test for any significant associations between predictive factors and dependent variables. Results were presented in pie-charts, bar-charts and tables. Results: A total of 161 patients reviewed during the study period, 159 (99%) were females and 2(1%) were males with mean age of 45.2 years, the age groups of 20-29 yrs presented with highest pain score. Among the three major ethnic groups, Yoruba constituted 31.7% with mean pain score of 7.5 ±1.4, followed by Igbo (26.1%) with mean pain score of 7.1 ±1.4. The commonest histology were invasive ductal (IDC) and invasive lobular (ILC) carcinoma with each having 7 as the highest mean pain score. Patients with grade 2 and 3 were the commonest and presented with mean pain score of 6.9±1.4 and 6.7±1.6 respectively. Patients with spinal cord compression (5.6%) presented with highest mean pain score of 7.3±1.3, followed by metastasis to long bones with pain score of 7.0±1.5. Pain alone was the highest presenting symptom (92.5%) from bone metastasis and Conventional X-ray was the common imaging modality used in confirmation of metastatic sites (68.3%). Common palliative radiation doses used were 11-20Gy in 4-6# (60%). Overall mean pain score at presentation was 6.8 ± 1.5 and 0.6 ± 0.7 four weeks after irradiation. In univariate analysis (binary comporason) only ethnicity was highly significant (p-0.001) in pain perception pre-radiotherapy and the significance exist after controlling other influential factors using multivariate analysis (p< 0.001). In post-irradiation using univariate analysis, ethnicity and metastatic sites shows significant association with pain relief, after multivariate analysis when influential factors were controlled, it appeared only metastatic sites with p-value of 0.008. Conclusion: Ethnicity of three major tribes in Nigeria played a role in pain perception from bone metastasis at presentation, with Yoruba higher pain perception compared to Hausa-Fulani and Igbo. But ethnicity appeared insignificant in response to radiation analgesia. Similarly, tumour factors appeared in significant in pain perception and response to radiation analgesia. However, metastatic sites influence response to radiation analgesia, with good pain relief in patients with metastasis to ribs and long bones.