Radiation Oncology-Specific Surveillance After Palliative Radiation Treatment for Spine and Non-Spine Bone Metastases

Abstract

Palliative radiation therapy (RT) can be an effective tool for bone metastases. NCCN guidelines recommend imaging every 3 months after RT for spine metastases (SM), yet no standard surveillance guidelines exist after RT for non-spine bone metastases (NSBM). We sought to evaluate factors associated with radiation oncology-specific follow-up after palliative RT.In a large single-institution retrospective cohort analysis, we identified all patients receiving RT for bone metastases by ICD-10 codes and RT prescription from 2017-2019. Demographic, clinical, and RT data were collected. Overall survival (OS) was calculated using Kaplan-Meier analysis. Factors associated with urgent care (UC) evaluation and radiation oncology follow-up were evaluated with multivariable logistic regression among patients surviving or followed to 3 months post-RT.Overall, 3082 patients (39% NSBM, 61% SM) received RT for bone metastases. Within 3 months of RT, 49% had radiation oncology follow-up, 79% underwent imaging, and 27% were seen in the UC. For patients with NSBM, follow-up CT was most common (55%) while for SM, MRI and CT were common (both 54%). Median OS was 10.0 months for SM (95% CI 8.9-11.0) and 13.5 months for NSBM (95% CI 11.5-15.5), with 1343 (71%) SM patients and 923 (77%) NSBM patients surviving to > = 3 months post-RT. Of the 2266 3-month survivors (41% NSBM, 59% SM), 1619 (71%) had radiation oncology follow-up, with higher performance status (OR 2.1, 95% CI 1.44-3.05) and younger patients (< 65yo; OR 1.2 95% CI 1.04-1.50) more likely to have follow-up. Median time-to-visit was 59 days (IQR 38-77), with follow-up time distributions significantly different between SM and NSBM (U = 333075, P = 0.01). Of the 3-month survivors, 553 (24%) patients were seen in the UC, with older and white patients less likely to visit the UC (P < 0.05). Median OS for NSBM was longer than the OS for SM patients (22.1 v 17.5 months; HR 0.87 [95% CI 0.78-0.98]). A minority of patients (397, 18%) underwent a subsequent RT course, occurring within 3 months for 183 patients and at a median time of 95 days [IQR 61-130]. Younger age and race were associated with a subsequent RT course (P < 0.05), while performance status and gender were not associated.After RT for bone metastases, most patients had radiation oncology-specific surveillance, which was associated with younger age and improved performance status. Most patients survived to 3 months post-RT, with a substantial minority receiving a second RT course. Patients with NSBM had longer survival and different time-to-follow-up compared to SM, highlighting the need for further clarification on what the optimal follow-up should be for NSBM. Race was a predictor of UC visits, likely reflecting health disparities that require further investigation. These data support radiation oncology specific follow-up after RT, particularly among younger patients and those with higher performance status with specific attention to racial disparities.