ΔBSIJ: A quantitative marker for early detection of medication-related osteonecrosis of the jaw in patients with prostate cancer receiving bone-modifying agents

Objective: Medication-related osteonecrosis of the jaw (MRONJ) is a severe complication of bone-modifying agent (BMA) therapy in patients with prostate cancer and bone metastasis. This study aimed to assess the effectiveness of the temporal changes in jaw-specific bone scan index (ΔBSIJ) as quantitative markers for early prediction of MRONJ in patients with prostate cancer receiving BMA therapy. Methods: This retrospective study included 33 patients with prostate cancer with bone metastases who underwent bone scintigraphy before and after BMA initiation. BSIJ was measured using BONENAVI software, and the difference between pre- and post-BMA BSIJ values was considered ΔBSIJ. Statistical analyses, including paired t-test, receiver operating characteristic (ROC) curve analysis, and Kaplan–Meier survival estimate, were employed to assess the predictive value of ΔBSIJ for MRONJ. Results: Of the 33 patients, 10 developed MRONJ during a median follow-up period of 29 months. ΔBSIJ was significantly higher in the MRONJ group than in the non-MRONJ group (0.05 vs. –0.04, p = 0.002). ROC analysis revealed the highest area under the curve (AUC = 0.823) for ΔBSIJ compared with the pre- and post-BMA BSIJ values. A ΔBSIJ cutoff of 0.039 predicted MRONJ with 60% sensitivity and 91% specificity. Patients with ΔBSIJ ≥ 0.039 exhibited significantly shorter MRONJ-free survival than those with ΔBSIJ < 0.039 (median: 18.4 months vs. not reached, p < 0.001). Conclusion: ΔBSIJ is a novel and clinically useful quantitative marker for the early detection of MRONJ in patients with prostate cancer receiving BMA therapy. This study highlights the potential of leveraging functional imaging and temporal changes in BSIJ to improve MRONJ management.