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Purpose: When squamous cell carcinoma of the buccal mucosa (BSCC) extends surrounding anatomical sites such as gingiva, retromolar triangle, or hard palate, it might be challenging to ensure adequate tumor coverage by sole interstitial brachytherapy due to the complexity of catheter implantation. By combining interstitial catheters with an enoral placed, individually assembled “oral spacer plus embedded catheters” device (hybrid of intracavitary-interstitial brachytherapy), it should be easier to deliver the necessary tumoricidal dose to irregular-shaped tumor volumes (clinical target volume – CTV) with improved conformity. The purpose of this analysis was to compare the dose distribution created by the hybrid of intracavitary-interstitial brachytherapy (HBT) with the dose distribution of an interstitial catheter only-approach, based on the interstitial catheters used for HBT (ISBT-only) by evaluating respective treatment plans (HBT plan vs. ISBT-only plan) for the treatment of early stage BSCC.
Material and methods: A retrospective analysis was performed for patients with localized BSCC treated between April 2013 and October 2017. All patients received sole HBT without additional external beam radiation therapy or planned neck dissection. Dosimetric parameters taken into account for comparison between actual HBT and virtual ISBT-only were CTV D90, CTV V100, CTV V150, CTV V200, mandible D2cc, and mucosal surface D2cc.
Results: Dosimetrically, HBT showed a trend toward better CTV D90 compared to ISBT-only. In addition, HBT demonstrated statistically better CTV V100 coverage compared to ISBT-only. There was no statistically significant difference with respect to CTV V150, CTV V200, and mucosal surface D2cc, while a trend was seen in better mandible D0.1cc between HBT and ISBT-only.
Conclusions: The HBT approach appears to enable improved dose coverage of irregular-shaped enoral tumor volumes compared to ISBT-only for patients with early stage BSCC.
Purpose: The purpose of this study was to report our initial experience of hyaluronic acid gel injection (HGI) in the vesicovaginal septum (VVS) for bladder dose reduction in brachytherapy (BT) for uterine cervical carcinoma.
Material and methods: Between September 2016 and May 2018, 15 uterine cervical cancer patients received HGI in the VVS as a part of their definitive radiotherapy (RT) treatment consisting of external beam radiation therapy (EBRT) with additional BT. Of those, 9 patients received BT both with and without HGI, and remaining 6 patients were excluded because these 6 patients received HGI in the VVS for all BT fractions. All 9 patients received HGI in the rectovaginal septum. For these patients, the dosimetric parameters bladder D2cc, HR-CTV D90, and rectum D2cc were selected, and two groups were generated (BT with vs. without HGI in the VVS) for dosimetric comparison.
Results: The median cumulative EQD2 for HR-CTV, rectum D2cc, and bladder D2cc for the 9 patients were 73.3, 52.8, and 67.1, respectively. While no statistical difference could be detected for rectal dose reduction, bladder dose was significantly less in the group with HGI in the VVS compared to that without (449 cGy [range, 416-566, 1SD = 66.1] vs. 569 cGy [range, 449-647, 1SD = 59.5], p = 0.033), with no compromising of target coverage. Although it did not reach statistically significance, there was a trend toward better HR-CTV D90 in the group with HGI compared to that without HGI in the VVS (713 cGy vs. 706 cGy, p = 0.085). No severe bleeding, hematuria, bladder wall injury, or urethral injury requiring hospitalization was experienced in association with HGI in the VVS.
Conclusions: HGI in the VVS can be performed safely and can effectively reduce the bladder dose in BT for uterine cervical cancer patients.
Purpose: Dosimetric treatment planning evaluations concerning patient-adapted moulds for iridium-192 highdose-rate brachytherapy are presented in this report.
Material and methods: Six patients with perinasal skin tumors were treated with individual moulds made of biocompatible epithetic materials with embedded plastic applicators. Treatment plans were optimized with regard to clinical requirements, and dose was calculated using standard water-based TG-43 formalism. In addition, retrospective material-dependent collapsed cone calculations according to TG-186 protocol were evaluated to quantify the limitations of TG-43 protocol for this superficial brachytherapy technique.
Results: The dose-volume parameters D90, V100, and V150 of the planning target volumes (PTVs) for TG-43 dose calculations yielded 92.2% to 102.5%, 75.1% to 93.1%, and 7.4% to 41.7% of the prescribed dose, respectively. The maximum overall dose to the ipsilateral eyeball as the most affected organ at risk (OAR) varied between 8.9 and 36.4 Gy. TG-186 calculations with Hounsfield unit-based density allocation resulted in down by –6.4%, –16.7%, and –30.0% lower average D90, V100, and V150 of the PTVs, with respect to the TG-43 data. The corresponding calculated OAR doses were also lower. The model-based TG-186 dose calculations have considered reduced backscattering due to environmental air as well as the dose-to-medium influenced by the mould materials and tissue composition. The median PTV dose was robust within 0.5% for simulated variations of mould material densities in the range of 1.0 g/cm³ to 1.26 g/cm³ up to 7 mm total mould thickness.
Conclusions: HDR contact BT with individual moulds is a safe modality for routine treatment of perinasal skin tumors. The technique provides good target coverage and OARs’ protection, while being robust against small variances in mould material density. Model-based dose calculations (TG-186) should complement TG-43 dose calculations for verification purpose and quality improvement.
In combination with radiotherapy, immunotherapy is becoming an increasingly used strategy in treating advanced, recurrent, or metastatic cancer. The evident impact of radiotherapy on local and systemic immune response is an indication of the synergistic effect of these two modalities. There is a strong rationale to combine radiotherapy and immunotherapy to enhance response rates and overcome resistances. Therefore, the combination of radio- and immunotherapy holds a variety of opportunities as well as challenges in treating primary cancer and is progressively tested in curative settings. Brachytherapy is also known as internal radiation therapy and only offers a local therapy option at first glance: due to tumor-specific antigens, released by a high local radiation dose, a systemic immune response could be plausible and eminent. Accordingly, brachytherapy could be an underestimated partner with immuno-therapeutic approaches in both curative and palliative settings, to generate local and systemic response. In this review, we summarized the potential benefit of a potential combination of brachytherapy and immuno-therapeutic approaches vs. the background of limited data.