Association Between the Cancer Diagnosis-to-Intervention Interval and Short-Term Analgesic Response Following Interventional Pain Treatment: A Retrospective Cohort Study

Background/Objectives: Cancer-related pain remains difficult to control in a substantial proportion of patients despite contemporary pharmacological treatment, and interventional procedures may provide additional analgesic benefit. However, the relationship between the timing of these procedures and analgesic response remains insufficiently characterized. This study investigated whether the interval between cancer diagnosis and interventional pain treatment was associated with short-term analgesic response. Methods: We retrospectively analyzed 106 patients who underwent interventional procedures for cancer-related pain. Pain intensity was assessed using the Numeric Rating Scale (NRS), and opioid consumption was expressed as morphine equivalent daily dose (MEDD). Pain intensity was assessed at baseline, 1 week, and 1 month, whereas opioid consumption was assessed at baseline and 1 month. The primary outcome was a ≥50% reduction in NRS score at 1 month. Multivariable logistic regression was used to evaluate factors associated with response. Model assumptions, calibration, and internal validation were examined, and sensitivity analyses included generalized estimating equations, parsimonious and Firth-penalized models, and an analysis restricted to neurolytic procedures. Results: At 1 month, 52 patients (49.1%) achieved a ≥50% reduction in pain intensity. NRS scores decreased significantly over time (p < 0.001), while the reduction in MEDD at 1 month was statistically significant but modest (p = 0.005). Changes in NRS and MEDD were strongly correlated (ρ = 0.809, p < 0.001). A longer diagnosis-to-intervention interval was associated with lower odds of treatment response (OR = 0.913 per month; 95% CI, 0.853–0.977; p = 0.008). Metastatic disease was also associated with lower odds of response (OR = 0.067; 95% CI, 0.015–0.310; p < 0.001). These associations were directionally consistent across sensitivity analyses, and spline analysis showed no statistical evidence of a non-linear relationship between the diagnosis-to-intervention interval and response. Conclusions: A longer interval between cancer diagnosis and interventional pain treatment was associated with lower odds of short-term analgesic response. However, this interval does not represent pain duration or treatment delay and may reflect differences in disease burden and other unmeasured clinical factors. These findings should therefore be interpreted as associative rather than causal and warrant prospective investigation.