The impact of tumor size and histology on local control when utilizing high-dose-rate interstitial brachytherapy for gynecologic malignancies.

OBJECTIVE: To report long-term results of an outpatient template-based high-dose-rate interstitial brachytherapy (HDR ISBT) program for the treatment of gynecologic malignancies. METHODS: Patients treated between 2006 and 2020 at an academic hospital with outpatient template based HDR ISBT without spinal or general anesthesia were reviewed. Patients who had previously received HDR ISBT were excluded. Baseline patient, tumor, and treatment characteristics, such as tumor size, histology, and/or total EQD2 including prior external beam radiation therapy (EBRT) were recorded. Local control and overall survival were estimated using the Kaplan-Meier method, and factors associated with local control and overall survival were evaluated using Cox regression analyses. RESULTS: 150 patients received HDR ISBT for a gynecologic tumor and the median follow-up time was 2.98 years (0.89-4.82). Of those, 74/150 (49%) were treated definitively, 69/150 (46%) were treated for tumor recurrence/persistence, and 7/150 (5%) were treated for durable palliation. Median tumor size was 3.00 cm (1.50-4.00). 124/150 (83%) patients received EBRT prior to HDR ISBT. Median HDR ISBT dose was 18 Gy delivered in eight fractions. Local control was 71% (64%-79%), 58% (50%-68%), and 57% (48%-67%) at one, three, and five years, respectively. On multivariate analysis, non-endometrial adenocarcinoma histology (HR = 2.423, 95% CI = 1.011-5.808, p = 0.047) and tumor size ≥ 3 cm (HR = 2.903, 95% CI 1.053-3.441, p = 0.033) were associated with lower local control. CONCLUSIONS: The majority of patients who received outpatient-based twice daily HDR ISBT had long-term local control. Larger tumor size and non-endometrial adenocarcinoma histology were detrimental to local control.

Internal dose escalation associated with increased local control for melanoma brain metastases treated with stereotactic radiosurgery.

OBJECTIVE: The internal high-dose volume varies widely for a given prescribed dose during stereotactic radiosurgery (SRS) to treat brain metastases (BMs). This may be altered during treatment planning, and the authors have previously shown that this improves local control (LC) for non-small cell lung cancer BMs without increasing toxicity. Here, they seek to identify potentially actionable dosimetric predictors of LC after SRS for melanoma BM. METHODS: The records of patients with unresected melanoma BM treated with single-fraction Gamma Knife RS between 2006 and 2017 were reviewed. LC was assessed on a per-lesion basis, defined as stability or a decrease in lesion size. Outcome-oriented approaches were utilized to determine optimal dichotomization for dosimetric variables relative to LC. Univariable and multivariable Cox regression analysis was implemented to evaluate the impact of collected parameters on LC. RESULTS: Two hundred eighty-seven melanoma BMs in 79 patients were identified. The median age was 56 years (range 31-86 years). The median follow-up was 7.6 months (range 0.5-81.6 months), and the median survival was 9.3 months (range 1.3-81.6 months). Lesions were optimally stratified by volume receiving at least 30 Gy (V30) greater than or equal to versus less than 25%. V30 was ≥ and < 25% in 147 and 140 lesions, respectively. For all patients, 1-year LC was 83% versus 66% for V30 ≥ and < 25%, respectively (p = 0.001). Stratifying by volume, lesions 2 cm or less (n = 215) had 1-year LC of 82% versus 70% (p = 0.013) for V30 ≥ and < 25%, respectively. Lesions > 2 to 3 cm (n = 32) had 1-year LC of 100% versus 43% (p = 0.214) for V30 ≥ and < 25%, respectively. V30 was still predictive of LC even after controlling for the use of immunotherapy and targeted therapy. Radionecrosis occurred in 2.8% of lesions and was not significantly associated with V30. CONCLUSIONS: For a given prescription dose, an increased internal high-dose volume, as indicated by measures such as V30 ≥ 25%, is associated with improved LC but not increased toxicity in single-fraction SRS for melanoma BM. Internal dose escalation is an independent predictor of improved LC even in patients receiving immunotherapy and/or targeted therapy. This represents a dosimetric parameter that is actionable at the time of treatment planning and warrants further evaluation.

Distant intracranial failure in melanoma brain metastases treated with stereotactic radiosurgery in the era of immunotherapy and targeted agents.

PURPOSE: Stereotactic radiosurgery (SRS) in combination with immunotherapy (IMT) or targeted therapy is increasingly being used in the setting of melanoma brain metastases (MBMs). The synergistic properties of combination therapy are not well understood. We compared the distant intracranial failure rates of intact MBMs treated with SRS, SRS + IMT, and SRS + targeted therapy. METHODS AND MATERIALS: Combination therapy was defined as delivery of SRS within 3 months of IMT (anti-CTLA-4 /anti-PD-1 therapy) or targeted therapy (BRAF/MEK inhibitors). The primary endpoint was distant intracranial failure after SRS, which was defined as any new MBM identified on brain magnetic resonance imaging. Outcomes were evaluated using the Kaplan Meier method and Cox proportional hazards. RESULTS: A total of 72 patients with melanoma with 233 MBMs were treated between April 2006 and April 2016. The number of MBMs within each treatment group was as follows: SRS: 121; SRS + IMT: 48; and SRS + targeted therapy: 64. The median follow-up was 8.9 months. One-year distant intracranial control rates for SRS, SRS + IMT, and SRS + targeted therapy were 11.5%, 60%, and 10%, respectively (P < .001). On multivariate analysis, after adjusting for steroid use and number of MBMs, SRS + IMT remained associated with a significant reduction in distant intracranial failure compared with SRS (hazard ratio [HR], 0.48; 95% confidence interval [CI], 0.29-0.80; P = .003) and compared with SRS + targeted therapy (HR, 0.41; 95% CI, 0.25-0.68; P = .001).One-year local control for SRS, SRS + IMT, and SRS + targeted therapy was 66%, 85%, and 72%, respectively (P = .044). On multivariate analysis, after adjusting for dose, SRS + IMT remained associated with a significant reduction in local failure compared with SRS alone (HR, 0.37; 95% CI, 0.14-0.95; P = .04). CONCLUSIONS: SRS with immunotherapy is associated with decreased distant and local intracranial failure compared with SRS alone. Prospective studies are warranted to validate this result.