Long-term effect and prognostic factors of a low-dose radiotherapy of painful plantar calcaneal spurs : A retrospective unicenter study.

PURPOSE To estimate the long-term effect of low-dose radiotherapy of painful plantar calcaneal spurs, and to verify possible prognostic factors. PATIENTS AND METHODS In this retrospective unicenter study, electronic patient files of patients with painful plantar calcaneal spurs treated with low-dose radiotherapy between July 2009 and February 2020 were reviewed. The low-dose radiotherapy consisted of a total dose of 3.0 Gy given with a fraction dose of 0.5 Gy three times a week. The pain reduction was estimated using a patient questionnaire with a visual analogue scale. Kaplan-Meier statistics and Cox regression analysis were used for the statistical analysis. RESULTS Altogether, 864 heels of 666 patients were reviewed. The probability of an insufficient pain control 10 years after low-dose radiotherapy was 45.9% (95% confidence interval 39.4-52.4%) in the subset of patients with a minimum follow-up of 3 months (582 heels of 467 patients). Patients with an unsatisfactory pain reduction 3 months after low-dose radiotherapy were offered a re-irradiation. Forty percent of the patients who received a re-irradiation developed good pain reduction. Occurrence of an initial aggravation of pain during or within 3 months after low-dose radiotherapy (p = 0.005), and treatment of bilateral painful plantar calcaneal spurs (p = 0.008) were identified as significant unfavorable prognostic factors on univariate analysis. On multivariate analysis, the initial aggravation of pain remained as independent significant prognostic factor (p = 0.01). No clear radiation toxicity was observed. CONCLUSIONS Low-dose radiotherapy is a safe and effective treatment option for patients with painful plantar calcaneal spurs. An initial aggravation of pain during or within 3 months after radiotherapy was identified as unfavorable prognostic factor for the treatment outcome. Re-irradiation of patients with an unsatisfactory pain reduction after low-dose radiotherapy is effective and should be offered to patients.