Introduction Metastasis to the bone is a
Metastasis to the bone is a common complication of breast, lung, prostate, gastrointestinal, haematological, melanoma, and other tumours [1–3]. In many patients with primary breast, prostate and lung primary tumours, bone metastases (BoM) are signs associated with the presence of disseminated disease . These metastases to the bone will usually result in patients experiencing pain which is often palliated using single fraction radiotherapy (SFRT) or multiple fraction radiotherapy (MFRT) depending on the factors such as cancer type and presence of complication within the bone [5–8]. Although the distribution of BoM have been observed in many skeletal locations, BoM that are distal to the elbow and knee joints are considered rare and therefore are infrequently reported .
Depending on the primary tumour histopathology, the frequency of skeletal bone metastases ranges from 10% to close to 90% and bone lesions are found more commonly within the axial skeletal versus the CB-5083 . Although any skeletal bone may be involved with metastatic disease, the vertebral body is most commonly associated with metastatic disease; long bone involvement or metastases distal to the elbow and knee are rare [11–13]. This study sought to assess the incidence of distal bone metastases treated with radiotherapy in a provincial programme.
Material and methods Multivariable linear regression analysis was used to determine associations between primary tumour type and incidence of distal bone metastases. P values were two-sided, and values less than.05 were considered statistically significant. We used the SPSS statistical software package, version 19.0 (Chicago, IL), for data entry and statistical analysis. This study was approved by the combined BCCA and UBC Research Ethics Board.
Results From 2007 to 2011, 8008 patients in BC were treated with 16, 277 palliative radiotherapy courses; 425 (3%) of the courses prescribed were used to treat bones located within or distal to the elbow or knee. Male patients were treated more often than female patients (52%) and SFRT was prescribed 49% of the time (Table 1). Breast and lung malignancies were observed most commonly (23%), followed by prostate (19%), other (15%), lymphoma (11%), gastrointestinal (8%) and melanoma (1%) (Table 1). We demonstrated that Melanoma malignancies resulted in the highest frequency (5%) of distal BoM; followed by haematological (3%), lung (2%) prostate (2%), other (2%), gastrointestinal (1%), and breast (1%). Distal BoM where more commonly identified in the lower extremity (87%, p<0.001). Distal BoM were treated with SFRT significantly more often than non-distal BoM (p<0.001) (Fig. 1). Table 2 presents the multi-variable analysis performed to determine the associations between distal BoM and patient characteristics, which demonstrated that patients with melanoma have a significant higher odds of having distal bone metastases (p=0.004). The regression analysis also showed significant correlation between having distal bone metastases treated at Abbotsford Centre (odds ratio 2.37, 95% confidence interval 1.54–3.64, p<0.0001) (Table 2).
Discussion This population-based study demonstrates that patients with melanoma have the highest proportion of distal BoM. This differs from previous reports, which only present that prostate, breast, and lung cancer have the highest absolute number of distal BoM, likely because these are the most common cancers with any type of BoM [9,14–17]. Here we showed that SFRT was used to treat distal BoM more often than non-distal BoM (66% versus 49%, respectively), likely because distal BoM are located in regions that do not contain organs at risk such as the spinal cord .
Conflict of interest notification
Acknowledgement of funding Supported in part by research funding to Dr. Olson from the Northern Medical Program of the University of British Columbia and the University of Northern British Columbia.