Image-guided high-dose-rate brachytherapy of head and neck - a case series study

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.

Feasibility of accelerated image-guided high-dose-rate interstitial brachytherapy with inverse planning simulated annealing (IPSA-HDRBT) for post-operative treatment of pathologically node-negative squamous cell carcinomas of the oral tongue

PURPOSE

Inverse planning simulated annealing (IPSA) produces highly conformal dose distributions and quick optimizations for high-dose-rate interstitial brachytherapy (HDRBT). We report our dosimetry and overall outcomes using this approach for the accelerated post-operative treatment of pathologically node-negative squamous cell carcinomas of the oral tongue (OTSCC) with high risk of local recurrence.

METHODS

Patients with newly diagnosed pN0 OTSCC treated with partial glossectomy, neck dissection, and post-operative HDRBT alone from 2007 to 2021 were retrospectively reviewed. Patients received 30 Gy in 5 fractions over 2.5 days. Target volume and mandible dosimetry are reported. Actuarial rates of local control, regional control, disease-specific survival, and overall survival were estimated using the Kaplan-Meier method. Toxicity was categorized using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0.

RESULTS

19 consecutive patients were reviewed. Median follow-up was 3.2 years (IQR 1.4-8.2 years) with a 3-year estimated local control rate of 81%. Target volumes were generally small, as the median volume was 12.66 cc. Median V150% and V200% were 52% and 24%, respectively. D1cc and D2cc to the mandible were 17.31 Gy and 14.42 Gy, respectively.

CONCLUSIONS

IPSA-HDRBT is feasible and highly efficient for post-operative treatment of the primary tumor bed in patients with pathologically node-negative squamous cell carcinomas of the oral tongue. Further technical optimization and prospective clinical evaluation in a larger patient cohort are planned.

Successful salvage treatment of refractory recurrence of maxillary sinus carcinoma using image-guided high-dose-rate interstitial brachytherapy

This case report illustrates a treatment effect of image-guided high-dose-rate (HDR) interstitial brachytherapy for refractory recurrence of maxillary sinus carcinoma. A 61-year-old male was previously admitted to another hospital and received surgery because of left maxillary sinus squamous cell carcinoma (SCC) 6 years ago. Tumor regrowth was noted 2 years after the initial radical surgery. The patient accepted local excision again for the recurrence, followed by external beam radiotherapy. Despite salvage treatment with surgery and external irradiation, the lesion expanded as 4.8 × 4.4 × 4.0 cm³. Because the patient refused palliative resection, we recommended technique of image-guided HDR interstitial brachytherapy. The total doses of 42 Gy in 12 fractions were delivered to the whole recurrent tumor. Removal of the recurrent tumor was securely achieved by HDR interstitial brachytherapy, guided with ultrasound. The refractory tumor in the patient healed uneventfully after HDR interstitial brachytherapy without recurrence during 8 months of follow-up. This case is remarkable because the patient experienced complete remission by a safe and practicable method with image-guided HDR interstitial brachytherapy.

Dose-volume analysis of target volume and critical structures in computed tomography image-based multicatheter high-dose-rate interstitial brachytherapy for head and neck cancer

Purpose

To evaluate dose-volume relationships of target volume and critical structures in computed tomography (CT) image-based brachytherapy for head and neck cancer.

Material and methods

Thirty-seven patients with mobile tongue, floor of mouth, and base of tongue cancer treated with brachytherapy (post-operative alone and as a boost after external beam radiotherapy [EBRT], or definitive alone or as a boost after EBRT) were selected. Treatment plans were made using post-implant CT images. The fractionation schedule was 7-15 × 3-5 Gy for post-operative (with or without EBRT), 14-15 × 3 Gy for definitive alone, and 5-10 × 3 Gy for boost treatments. For the target volume, V₁₀₀, D₉₀, and dose non-uniformity ratio (DNR) were calculated. For the mandible, spinal cord and salivary glands doses to specified volumes were reported.

Results

The median values of V₁₀₀ and D₉₀ were 89.9% and 99.9%, respectively; the median values of DNR was 0.46. The median D_2cm³ of the mandible and spinal cord were 48.3% and 5.8%, respectively. The ipsilateral median D_2cm³ of parotid and submandibular glands were 6.4% and 12.5%, whereas on the contralateral side, the corresponding values were 5.3% and 7.0%, respectively.

Conclusions

Using conformal treatment planning, it was desirable to keep the dose to the mandible, spinal cord, and salivary glands at an acceptable level. The quantitative plan evaluation may help us find correlations between dosimetric parameters and clinical outcome, which may lead to improve the quality of the treatment, but it requires longer follow-up and results from other studies.