3D-printed needle guides for cervical cancer brachytherapy: Optimized dosimetry and improved local control outcomes.

Objective: We previously designed three-dimensionally-printed needle guides (3D-NG) for cervical cancer brachytherapy, which improved procedure efficiency and tumor coverage while achieving similar organs at risk (OAR) sparing compared to non-3D-printed techniques (non-3D). The subject of this study was whether 3D-NG can help improve local control and other brachytherapy outcomes.

Methods: This single institution cohort study includes 130 patients who underwent definitive external-beam radiotherapy and high-dose-rate intracavitary +/- interstitial brachytherapy from February 2017 to July 2023. 3D-NG were implemented for all cases after December 2019 (N = 77). Non-3D included applicator-only/no-needles (N = 28) or freehand-placed needles (N = 25).

Results: Median follow-up was 24 months. 3D-NG, versus non-3D, achieved higher mean D90 (+5.2 Gy, p < 0.001), D98 (+4.3 Gy, p < 0.001), and V100average (+5.9%, p < 0.001)-with greater improvement for larger tumors (high-risk[HR]-CTV>30 cubic-centimeters[cc]) (Pinteraction<0.10 for all). Maximum D2cc for all OAR were comparable between 3D-NG and non-3D (p > 0.05). 2-year LF was lower with 3D-NG compared to non-3D (8.2% vs. 22.0%; aHR 0.31, p = 0.036)-and compared to freehand-needles alone (8.2% vs. 20.6%, p < 0.001 [log-rank])-particularly among cases with higher cumulative HR-CTV dose (D90 >85 Gy; pinteraction = 0.013) and lower HR-CTV volume (≤30 cc; pinteraction = 0.048). 2-year LF was also lower with concurrent cisplatin (aHR 0.20, p = 0.001) and ≥40% decrease in tumor diameter after EBRT (aHR 0.16, p = 0.010); but higher among minority race (aHR 4.21, p = 0.06).

Conclusions: 3D-NG for cervix brachytherapy were associated with improved 2-year LF compared to non-3D/freehand-needles, with higher achievement of EMBRACE II goals for D90 and D98, with similar OAR doses. This study highlights the potential for 3D-NG to simplify needle insertion while simultaneously improving needle position, dosimetry, and disease control outcomes.