Technical hints for high dose rate interstitial tongue brachytherapy

A 3D-printed patient-specific applicator guide for use in high-dose-rate interstitial brachytherapy for tongue cancer: a phantom study

A patient-specific applicator guide system (PSAG) for tongue-cancer high-dose-rate (HDR) interstitial brachytherapy (ISBT) was developed by utilizing a 3D printing technique. An effectiveness of the 3D-printed PSAG (3D-PSAG) was evaluated for HDR ISBT. Six patients with tongue cancer were retrospectively selected for this study. For each patient, a total of three virtual clinical target volumes (CTV) requiring the insertion of four catheters (CTV4), six catheters (CTV6), and eight catheters (CTV8) were defined. For each CTV, treatment plans were generated to deliver 45 Gy in nine fractions. The 3D-PSAG was fabricated using a 3D-printer and the patient's CT-images. The resulting 3D-PSAG took the form of a shell conforming to the patient's contours with tubes for catheter insertion. For each CTV, catheters were inserted into the phantom with and without the 3D-PSAG. After that, CT-images of the phantom with the inserted catheters were acquired. Differences between the planned positions and those of the actually inserted catheters were evaluated from the CT-images. Given the actual catheter insertion positions, the dose distributions were reconstructed and analyzed. The maximum positional errors with and without the 3D-PSAG were 0.2 mm and 4.5 mm, respectively. For CTV6, the D _90% values of the original plan, the reconstructed plan with the 3D-PSAG, and the reconstructed plan without the 3D-PSAG, were 48.8  ±  1.7 Gy, 49.0  ±  2.9 Gy, and 45.6  ±  3.3 Gy, respectively. The D _1cc values for the mandible were 51.3  ±  9.2 Gy, 61.6  ±  8.3 Gy, and 81.1  ±  16.7 Gy, respectively. The dose homogeneities in the CTVs into which the catheters had been inserted with the 3D-PSAG were always superior to those into which the catheters had been inserted without the 3D-PSAG. The present phantom study demonstrated the feasibility of more accurate interstitial tongue brachytherapy while simplifying the treatment process by utilizing the 3D-PSAG.

Adjuvant high-dose-rate brachytherapy in the management of oral cavity cancers: 5 years of experience in Iran

Purpose

Brachytherapy is a cost-effective method for the management of oral cavity cancers in low to middle income countries. We aimed to evaluate the clinical outcomes of high-dose-rate interstitial brachytherapy (HDR-IBT) in patients with oral cavity cancer.

Material and methods

From 2009 to 2013, 78 patients (49 combined external beam radiotherapy [EBRT] plus IBT and 29 IBT monotherapy) with oral cavity cancers had been treated in our center. Slightly more than half the patients were male, and the median age was 54 years. The treatment was planned based on the Paris system. The main outcomes were disease-free and overall survival.

Results

The median follow-up duration was 36.5 months (range, 1.17-54.23). The actuarial four-year overall and disease-free survival rates were 83% and 65%, respectively. The local and locoregional control was achieved among 89.74% and 87.17% of patients, respectively. None of the factors including tumor size, node status, gender, and radiation modality (IBT alone vs. IBT + EBRT) had a significant statistical correlation to the local control rate. All the patients tolerated the planned treatment in the IBT alone group. Late complications included a case of trismus and three cases of catheter insertion site fibrosis.

Conclusions

HDR-IBT as a monotherapy or in combination with EBRT is an appropriate option for the management of oral cavity squamous cell carcinomas, and supports the improvement in treatment outcomes and toxicity profiles in adjuvant settings.

High-dose-rate interstitial brachytherapy in early stage oral tongue cancer - 15 year experience from a tertiary care institute

Purpose

To determine outcomes of interstitial high-dose-rate brachytherapy (HDR-BT) in patients with early stage oral tongue cancer.

Material and methods

Ninety-two patients with stage I and II oral tongue cancer were treated with HDR-BT between 1999 and 2014: brachytherapy alone = 62 (67.4%), and combination of external beam radiotherapy (EBRT) and brachytherapy = 30 (32.6%). Median follow-up was 53.5 months. Patterns of failure, overall survival (OS), disease-free survival (DFS), local control rates (LCR), and nodal control rates (NCR) were determined.

Results

5-year OS, DFS, LCR, and NCR were 73.2%, 58.2%, 64.2%, and 83.8%, respectively. In total, 43 patients (46.7%) failed treatment: isolated local failures = 28 (30.4%), isolated nodal failures = 8 (8.7%), both local and regional failures = 7 (7.6%). While in T1 stage, 5 year LCR were significantly higher in brachytherapy alone group compared to combined EBRT and brachytherapy group (81.7% vs. 62.5%, p = 0.04), the isolated nodal failure rates were not significantly different among the two groups. For T2 stage, NCR were higher in combined EBRT and brachytherapy group compared to brachytherapy alone (92.9% vs. 74.3%). Acute mucositis (grade ≥ 2) was seen more in brachytherapy alone group compared to the combined modality group (87% vs. 66%), and this correlated significantly with the higher biological equivalent dose (BED) in the brachytherapy alone group.

Conclusions

Our study recommends treating patients with brachytherapy alone in T1 stage, and demonstrates the need for addressing nodal region either by neck dissection or nodal irradiation in T2 stage patients. Also, the study highlights the need for dose escalation (from the doses used in the study) in both T1 and T2 stage tumors when using interstitial brachytherapy either as sole modality or as a boost.

Shielding effect of a customized intraoral mold including lead material in high-dose-rate 192-Ir brachytherapy for oral cavity cancer

A high-dose-rate (HDR) 192-Ir brachytherapy using a customized intraoral mold is effective for superficial oral cavity cancer, and the surrounding normal tissue is kept away from the radioactive source with gauze pads and/or mouth piece for reducing the dose on the normal tissues. In the Tokushima university hospital, the mold has a lead shield which utilizes the space prepared with sufficient border-molding by a specific dental technique using modeling compound. In HDR 192-Ir brachytherapy using a lead shielded customized intraoral mold, there are no reports measuring the absorbed dose. The purpose of the present study is to measure the absorbed dose and discuss the optimum thickness of lead in HDR 192-Ir brachytherapy using a customized intraoral mold with lead shield using a 1 cm thickness mimic mold. The thickness of lead in the mold could be changed by varying the arrangement of 0.1 cm thickness sheet of the acrylic resin plate and lead. The measured doses at the lateral surface of the mold with thermo-luminescence dosimeter were reduced to 1.12, 0.79, 0.57, 0.41, 0.31, 0.24 and 0.19 Gy and the ratios to the prescription dose were reduced to 56, 40, 29, 21, 16, 12 and 10 percent as lead thickness increased from 0 to 0.6 cm in 0.1 cm increments, respectively. A 0.3 cm thickness lead was considered to be required for a 1 cm thickness mold, and it was necessary to thicken the lead as much as possible with the constraint of limited space in the oral cavity, especially at the fornix vestibule.

Two-piece customized mold technique for high-dose-rate brachytherapy on cancers of the buccal mucosa and lip

OBJECTIVE

High-dose-rate (HDR) brachytherapy using a customized mold is a minimally invasive treatment for oral cancer; however, it is difficult to use this technique for buccal and lip cancers involving the commissura labiorum, owing to its anatomic form. The purpose of this study was to introduce an improved customized mold consisting of 2 pieces to allow the fixation of molds to these sites.

STUDY DESIGN

Five patients with buccal carcinoma and 1 patient with lip carcinoma were treated with this technique after external beam radiotherapy. One patient with neck metastasis underwent both neck dissection and partial tumor resection before HDR brachytherapy.

RESULTS

At the end of the follow-up period, 5 patients had no tumor recurrence, and 1 patient had suffered local recurrence.

CONCLUSIONS

Our technique is a viable therapeutic option for patients with buccal and lip carcinomas for whom the therapeutic modalities are limited by age, performance status, and other factors.

Use of megavoltage computed tomography with image registration for high-dose rate treatment planning of an oral tongue cancer using a custom oral mold applicator with embedded lead shielding

PURPOSE

A patient with a lateral oral tongue cancer was treated with high-dose rate brachytherapy using an oral applicator with embedded lead shielding making conventional simulation, using either kilovoltage computed tomography or radiographs, impossible because of scatter artifact.

METHODS AND MATERIALS

Treatment simulation was accomplished using megavoltage computed tomography (MVCT) simulation on a helical tomotherapy unit. Because of difficulty in visualization of the catheters on the patient MVCT images, Velocity AI image registration software (Velocity Medical Solutions, Atlanta, GA) was used to register an MVCT of the applicator itself with the patient MVCT simulation. The treatment plan was manually optimized to prescribe 4Gy/fraction to the gross tumor volume.

RESULTS

The patient tolerated the treatment well, with no evidence of disease 6 months after treatment. Thermoluminescent dosimeter measurements showed that the shielding reduced the dose by up to 90%, depending on the location of the thermoluminescent dosimeter. While the patient was treated using dose distributions calculated in a homogeneous medium (Task Group-43), an approximation of the true dose distributions was retrospectively calculated using Acuros (Varian Medical Systems Inc., Palo Alto, CA), which accounts for heterogeneities in the patient.

DISCUSSION

Use of the MVCT with image registration allowed treatment planning in the presence of lead shielding. Dose-volume histograms showed that recalculation of the dose using heterogeneity correction did not affect the dose to the gross tumor volume, but that the dose to normal structures (maxilla and mandible) was reduced by the lead shielding.

CONCLUSION

The use of MVCT and image registration allows for optimized planning in the presence of shielding, which would not be possible with conventional kilovoltage computed tomography.

A comparison of brachytherapy and surgery for the treatment of stage I–II squamous cell carcinoma of the tongue

The treatment method for early stage tongue cancer is still controversial in Japan. The aim of this study is to compare the prognosis for patients with early tongue cancer treated with brachytherapy and surgery. A retrospective study was conducted to compare the efficacy of low-dose-rate brachytherapy (LDR), high-dose-rate brachytherapy (HDR), and surgery for early tongue cancer. A total of 180 patients with stage I-II tongue cancer were divided into three treatment groups: LDR (78), HDR (26), and surgery (71). Local recurrence was seen in thirteen patients (17%) of the LDR, nine (35%) of the HDR, and four (6%) of the surgery group. After salvage therapy, final local cure was obtained for 71 patients (91%) of the LDR, 22 (85%) of the HDR, and 71 (100%) of the surgery group. Neck failure was recorded for eight patients in the LDR, six in the HDR, and three in the surgery group. The respective 5-year overall survival rates for the LDR, HDR and surgery groups were 84.0%, 72.9%, 95.4% for stage I, and 72.2%, 51.5%, 93.8% for stage II. These findings show that surgery is the optimal treatment method for patients with stage I-II tongue cancer.

High dose rate brachytherapy: its clinical applications and treatment guidelines

Brachytherapy has the advantage of delivering a high dose to the tumor while sparing the surrounding normal tissues. With proper case selection and delivery technique, high-dose-rate (HDR) brachytherapy has great promise, because it eliminates radiation exposure, allows short treatment times, and can be performed on an outpatient basis. Additionally, use of a single-stepping source, allows optimization of dose distribution by varying the dwell time at each dwell position. However, when HDR brachytherapy is used, the treatments must be executed carefully, because the short treatment times do not allow any time for correction of errors, and mistakes can result in harm to patients. Hence, it is very important that all personnel involved in HDR brachytherapy be well trained and be constantly alert. It is expected that the use of HDR brachytherapy will greatly expand over the next decade and that refinements will occur primarily in the integration of imaging (computed tomography, magnetic resonance imaging, intraoperative ultrasonography) and optimization of dose distribution. It is anticipated that better tumor localization and normal tissue definition will help to optimize dose distribution to the tumor and reduce normal tissue exposure. The development of well-controlled randomized trials addressing issues of efficacy, toxicity, quality of life, and costs-versus-benefits will ultimately define the role of HDR brachytherapy in the therapeutic armamentarium.

Modeling volume effects of experimental brachytherapy in the rat rectum: uncovering the limitations of a radiobiologic concept

PURPOSE

To analyze the significance of volume effects in experimental brachytherapy, based on modeling normal tissue complication probability.

METHODS AND MATERIALS

Experimental brachytherapy in the rat rectum was based on an eight-step 2.5-mm step size source configuration for 192Ir, afterloaded into an unshielded polystyrene applicator. Volume effects were studied using a half-circumferential lead-shielded applicator and a shorter (two-step) source configuration. The main end point was rectal stenosis.

RESULTS

Rectal stenosis was always caused by a radiation ulcer. With the shielded configuration, single-dose ED50 (50% incidence of rectal stenosis) increased from 23 Gy to 36.5 Gy. Single-dose ED50 for the short configuration was 77.9 Gy. The data showed a reasonable fit to a three-parameter version of the biophysical model described by Jackson et al. (1995). This model assumes that organs consist of a large number of radiobiologically independent subunits and that radiation causes a complication if the fraction of the organ damaged is greater than its functional reserve. The fraction of the organ damaged is calculated summing over fractions of the organ damaged at each dose level. The calculated mean functional reserve (nu50) of the rat rectum, assuming a cumulative functional reserve distribution in the group of experimental rats, was 0.53.

CONCLUSIONS

The volume effect observed within small brachytherapy volumes agreed well with clinical experience of large tolerance doses in contact X-ray therapy. However, the nu50 value was comparable to the high functional reserve value reported for liver. Experimental volume effects probably reflect repair processes originating in the areas adjacent to small radiation fields of brachytherapy more than the radiobiologic characteristics of the cells in the irradiated volume.

High dose rate brachytherapy for early stage oral tongue cancer

BACKGROUND

High dose rate (HDR) interstitial brachytherapy of the oral tongue is a new treatment modality. Our study evaluates the outcomes of patients with early stage oral tongue cancer as treated by HDR interstitial implant.

METHODS

We reviewed the records of 19 patients who were seen between 1994 and 2000 with carcinoma of the oral tongue and whose primary tumors were treated solely with interstitial implant using HDR remote afterloading technique. Ten patients had T1 N0 disease, and the remaining 9 had T2 N0 disease. Elective neck treatment was withheld for 12 patients. The remaining seven patients had ipsilateral elective neck dissection. The male-female ratio was 1:0.9, and the median age was 60 years (range, 32-81 years). The median follow-up time was 43 months (range, 6-78 months). The afterloading catheters were positioned by the submandibular approach with the assistance of a template set. Fifteen patients had single planar implants, and the remaining four had double planar implants. The median number of catheters inserted was 5 (range, 4-9). The median dose given was 55 Gy in 10 fractions over 6 days. The minimal interfraction interval was 7 hours for the first 7 patients and was extended to 8 hours for the other 12. Mandibular shields were inserted before treatment.

RESULTS

The mucositis lasted for 6 to 20 weeks (median, 9 weeks). One patient had local failure, and the 4-year local failure-free survival rate was 94.7%. Three of the 12 patients without elective neck treatment had ipsilateral regional failure develop. They were salvaged by neck node dissection and regionally remained in control. One patient with multiple nodal metastases and extracapsular spread had biopsy-proven liver metastases and died 6 months after implant. One of the seven patients who were treated with elective neck dissection had multiple nodal metastases and extracapsular spread. She was treated with postoperative radiotherapy to the neck. She died 30 months after implant with evidence of regional and distant failure. One patient treated with double planar implant had grade II necrosis of the soft tissue and bone develop. The necrosis resolved with conservative treatment. Another four patients had small area of soft tissue deficit of the tongue attributed to aggressive debulking or biopsy before brachytherapy.

CONCLUSIONS

Our experience in treating early stage tongue cancer with HDR remote afterloading technique is encouraging, because it gives a local control rate of 94.7% at 4 years with acceptable morbidity. Further studies are eagerly awaited to delineate the optimum schedule for this new treatment modality.

The American Brachytherapy Society recommendations for high-dose-rate brachytherapy for head-and-neck carcinoma

PURPOSE

To develop recommendations for use of high-dose-rate (HDR) brachytherapy in patients with head-and-neck cancer.

METHODS

A panel consisting of members of the American Brachytherapy Society (ABS) performed a literature review, added information based upon their clinical experience, and formulated recommendations for head-and-neck HDR brachytherapy.

RESULTS

The ABS recommends the use of brachytherapy as a component of the treatment of head-and-neck tumors. However, the ABS recognizes that some radiation oncologists are reluctant to employ brachytherapy in the head-and-neck region because of the complexity of the postoperative management and concerns about radiation safety. In this regard, HDR eliminates unwanted radiation exposure and thereby permits unrestricted delivery of clinical care to these brachytherapy patients. The ABS made specific recommendations for previously untreated and recurrent head-and-neck cancer patients on patient selection criteria, implant techniques, target volume definition, and HDR treatment parameters (such as time, dose, and fractionation schedules). Suggestions were provided for treatment with HDR alone and in combination with external beam radiation therapy. It should be recognized that only limited experiences exist with HDR brachytherapy in patients with head-and-neck cancers. Therefore, some of these suggested doses have not been extensively tested in clinical practice. Hence, these guidelines will be updated as significant new outcome data are available. Any clinician following these guidelines is expected to use clinical judgment to determine an individual patient's treatment.

CONCLUSIONS

Little has been published in the clinical literature on HDR brachytherapy in head-and-neck cancer. Based upon the available information and the clinical experience of the panel members, general and site-specific recommendations were offered. Areas for further investigations were identified.

High-dose rate interstitial brachytherapy for stage I-II tongue cancer

OBJECTIVE

This retrospective clinical study evaluated the usefulness of high-dose rate (HDR) brachytherapy for stage I-II tongue cancer in comparison with traditional low-dose rate (LDR) brachytherapy.

MATERIALS AND METHODS

Twenty-five patients with stage I-II tongue cancer underwent HDR between 1995 and 1999. The status of local control and late neck metastasis, survival rate, and frequency of osteonecrosis in these patients were examined in comparison with a historical control made up of 71 patients who underwent LDR between 1980 and 1995.

RESULTS

The local control rate and survival rate were lower in the HDR group than in the LDR group. There were no apparent differences in the frequency of late neck metastasis between the two groups. Osteonecrosis occurred earlier and more frequently in the HDR group.

CONCLUSION

We would caution the use of HDR brachytherapy until further studies are done in many institutions.