Efficacy and Safety of Epidermal Radionuclide Therapy with ¹⁸⁸ Re Resin in Patients with Nonmelanoma Skin Cancers: Long-Term Data from a Single Center

Nonmelanoma skin cancer (NMSC) occurs in photoexposed areas and is frequent in the elderly population. Surgical excision remains the treatment of choice whenever feasible. However, alternative approaches are clinically important for patients who are unsuitable for surgery. This study evaluated the efficacy and safety of ¹⁸⁸Re epidermal radionuclide therapy (¹⁸⁸Re-ERT) for local disease control in NMSCs deemed inoperable. <b>Methods:</b> In total, 124 consecutive patients (79 men, 45 women; mean age, 81 y [range, 49-94 y]) with histologic confirmation of NMSC were treated with ¹⁸⁸Re-ERT, with 181 lesions treated. Efficacy was evaluated 6 mo after ¹⁸⁸Re-ERT with videodermoscopy and biopsy. Follow-up was performed at 12, 18, 24, and 36 mo. Relapses were confirmed histologically. Safety was assessed on the basis of CTCAE version 5.0. <b>Results:</b> Lesion characteristics included surface area (mean, 6.0 cm²; range, 1-34 cm²), thickness (mean, 1.2 mm; range, 0.2-3.0 mm), volume (mean, 0.85 cm³; range, 0.05-7.7 cm³). Locations include the H area (102 lesions), scalp (39 lesions), extremities (24 lesions), and thorax (16 lesions). Histology confirmed 104 basal cell carcinoma; 71 squamous cell carcinoma, and 6 basosquamous carcinoma. Mean administered dose to the lesion was 51 Gy, the mean dose to the deepest point of cancer invasion was 25 Gy, and the mean treatment duration was 90 min. No patient reported pain during or after the treatment. Overall, 165 of 181 lesions (91.1%) were relapse-free at 36 mo. Relapses occurred in 16 patients as follows: 6 at 6 mo, 3 at 12 mo, 2 at 18 mo, 3 at 24 mo, and 2 at 36 mo. Lesions less than 8 cm² demonstrated a relapse rate of 1.4% at 6 mo. Larger lesion area volumes were significantly associated with relapse. Early adverse skin reactions classified according to CTCAE version as G1 (minimal skin changes, faint erythema, or dry desquamation) or G2 (moderate erythema, patchy moist desquamation, and edema) were observed in 165 of 181 lesions (91.1%) and resolved within a mean time of 32 d; G3 skin reactions (severe skin changes without pain) were present in 16 lesions, lasting up to 8-12 wk. <b>Conclusion:</b> ¹⁸⁸Re-ERT showed high efficacy with a relapse-free rate of 91.1% at 36 mo. Larger lesions were associated with an increased risk of relapse. Adverse events were generally mild, resolving within 32 d. These results support ¹⁸⁸Re-ERT as a safe and effective alternative for patients with inoperable NMSC.