Per-oral interstitial brachytherapy catheter insertion for boost in case of recurrent tonsillar carcinoma: dosimetry and clinical outcome

Technical report: a high-dose-rate interstitial brachytherapy boost for residual sinonasal undifferentiated carcinoma

Sinonasal undifferentiated carcinoma (SNUC) is a highly aggressive and uncommon neoplasm that arises from the mucosa of the nasal cavity or paranasal sinuses. The multidisciplinary approach that includes surgery, radiation therapy (RT), and chemotherapy has been proven to improve survival rates. However, there is no established evidence for the efficacy of further (boost) irradiation following definitive RT in SNUC patients with residual primary tumor. We describe a successful case of a patient with SNUC who had an uncontrolled primary tumor following induction chemotherapy and radical concurrent chemoradiotherapy (CCRT) and underwent a high-dose-rate interstitial brachytherapy (HDR-ISBT) boost. A 75-year-old Japanese woman with unresectable locally advanced SNUC (LA-SNUC) received induction chemotherapy followed by radical CCRT. However, because the residual primary tumor was evident after planned external beam RT, she underwent an HDR-ISBT boost, and the tumor decreased significantly. A complete response (the Response Evaluation Criteria in Solid Tumors, ver. 1.1) was achieved 2 months after brachytherapy, and the patient has been disease-free for 2 years following treatment initiation. In conclusion, an HDR-ISBT boost can be a safe and effective treatment option in patients with residual and inoperable LA-SNUC in the maxillary sinus after initial RT.

Deep learning-based two-step organs at risk auto-segmentation model for brachytherapy planning in parotid gland carcinoma

Purpose

Delineation of organs at risk (OARs) represents a crucial step for both tailored delivery of radiation doses and prevention of radiation-induced toxicity in brachytherapy. Due to lack of studies on auto-segmentation methods in head and neck cancers, our study proposed a deep learning-based two-step approach for auto-segmentation of organs at risk in parotid carcinoma brachytherapy.

Material and methods

Computed tomography images of 200 patients with parotid gland carcinoma were used to train and evaluate our in-house developed two-step 3D nnU-Net-based model for OARs auto-segmentation. OARs during brachytherapy were defined as the auricula, condyle process, skin, mastoid process, external auditory canal, and mandibular ramus. Auto-segmentation results were compared to those of manual segmentation by expert oncologists. Accuracy was quantitatively evaluated in terms of dice similarity coefficient (DSC), Jaccard index, 95^th-percentile Hausdorff distance (95HD), and precision and recall. Qualitative evaluation of auto-segmentation results was also performed.

Results

The mean DSC values of each OAR were 0.88, 0.91, 0.75, 0.89, 0.74, and 0.93, respectively, indicating close resemblance of auto-segmentation results to those of manual contouring. In addition, auto-segmentation could be completed within a minute, as compared with manual segmentation, which required over 20 minutes. All generated results were deemed clinically acceptable.

Conclusions

Our proposed deep learning-based two-step OARs auto-segmentation model demonstrated high efficiency and good agreement with gold standard manual contours. Thereby, this novel approach carries the potential in expediting the treatment planning process of brachytherapy for parotid gland cancers, while allowing for more accurate radiation delivery to minimize toxicity.

Gel spacer to protect carotid artery and reconstructed jejunum in image-guided interstitial brachytherapy for recurrent hypopharyngeal cancer: a technical report

In this technical report, patient with total pharyngolaryngectomy and jejunum interposition experienced lymph node metastasis in the reconstructed mesenteric lymph nodes. Because this patient received 45 Gy of whole neck radiation therapy 24 years ago and small bowel's tolerance dose of the reconstructed jejunum was considered to be low, spacer gel injection was applied during image-guided interstitial brachytherapy to decrease doses to the reconstructed jejunum and previously irradiated carotid artery.

Hybrid Intracavitary-Interstitial brachytherapy in a case of nasal vestibule cancer penetrating the hard palate

Because of its rarity, no standard therapy exists for localized squamous cell carcinoma of the nasal vestibule. Interstitial brachytherapy (ISBT) is reported to be a preferable treatment modality of choice for early-stage localized nasal vestibule cancer. In this report, a nasal vestibule cancer with hard palate invasion (T3) was treated by definitive radiation therapy. Because it was considered to be difficult to cover the entire target volume only by ISBT, a hybrid of intracavitary (dental mold-based) and ISBT was applied to the patient following external beam radiation therapy.

Image-guided interstitial brachytherapy boost for keratinizing squamous cell carcinoma of inferior wall of the nasopharynx

High-dose-rate interstitial brachytherapy (HDR-ISBT) is relatively rarely applied for the head and neck cancer because of its anatomical complexity and difficulty of applicator placement. However, its dose distribution is more confined even better than intensity-modulated radiation therapy (IMRT) and can deliver a higher dose while sparing surrounding normal tissues. In this case report, the effectiveness of HDR-ISBT as a boost following IMRT for keratinizing squamous cell carcinoma of nasopharynx was presented. A 76-year-old female who suffered from cT3N0M0 keratinizing squamous cell carcinoma of the nasopharynx was treated with definitive concurrent chemoradiation therapy involving IMRT. However, physical examination and laryngoscope fibre finding showed evident residual tumour at 60 Gy of IMRT, then, boost HDR-ISBT was proposed. After delivering 66 Gy of IMRT, CT image-guided HDR-ISBT 4 Gy in a single fraction was performed under local anaesthesia and sedation. MRI taken 5 months after HDR-ISBT showed remarkable shrinkage of the primary tumour. After HDR-ISBT, the remaining session of IMRT was delivered from the next day until 70 Gy in 35 fractions. It was demonstrated that boost HDR-ISBT combined with IMRT for keratinizing squamous cell carcinoma of the nasopharynx was performed safely and showed favourable efficacy.

Image-guided interstitial brachytherapy boost for nasopharyngeal carcinoma: technical aspects

Nasopharyngeal cancer generally responds well to concurrent chemoradiotherapy (CCRT). However, there is a small group of patients who respond poorly to CCRT, and experience local residual tumor or local relapse. Although several attempts have been performed to such a group of patients including re-irradiation with external beam radiation therapy (EBRT) or salvage surgery, clinical results remain unsatisfactory. Intracavitary brachytherapy (ICBT) boost after CCRT with EBRT has been explored, however, its efficacy is limited to those with superficial residual tumors. For those residual tumors thickness with more than 5 mm, interstitial brachytherapy (ISBT) boost would be an appropriate modality of choice. Here, we describe technical aspects of the high-dose-rate interstitial brachytherapy (HDR-ISBT) boost for nasopharyngeal cancer (NPC) patients who responded poorly to the CCRT with EBRT.