Protocol for the measurement of the absorbed dose rate to water for a planar 32P beta emitting brachytherapy source: A multi-institutional validation.

PURPOSE: This is a multi-institutional report on inter-observer and inter-instrument variation in the calibration of the absorbed dose rate for a planar 32P beta emitting brachytherapy source. Measurement accuracy is essential since the dose profile is steep and the source is used for the treatment of tumors that are located in close proximity to healthy nervous system structures. METHODS AND MATERIALS: An RIC-100 32P source was calibrated by three institutions using their own equipment and following their standard procedures. The first institution calibrated the source with an electron diode and EBT3 film. The second institution used an electron diode. The third institution used HD810 film. Additionally, each institution was asked to calibrate the source using an electron diode and procedure that was shared among all institutions and shipped along with the radiation source. The dose rate was reported in units of cGy*min-1 at a water equivalent depth of 1 mm. RESULTS: Close agreement was observed in the measurements from different users and equipment. The variation across all diode detectors and institutions had a standard deviation of 1.8% and maximum difference of 4.6%. The observed variation among two different diode systems used within the same institution had a mean difference of 1.6% and a maximum variation of 1.8%. The variations among film and diode systems used within the same institution had a mean difference of 2.9% and a maximum variation of 4.3% CONCLUSIONS: The absorbed dose rate measurement protocol of the planar beta-emitting 32P source permits consistent dosimetry across three institutions and five different electron diode and radiochromic film systems. The methodologies presented herein should enable measurement consistency among other clinical users, which will help ensure high quality patient treatments and outcomes analysis.

Brachytherapy as an Adjuvant for Recurrent Atypical and Malignant Meningiomas.

BACKGROUND: Recurrent atypical and malignant meningiomas have poor outcomes with surgical therapy alone. Neither adjuvant chemotherapy nor postoperative radiation therapy remedies this problem. OBJECTIVE: To evaluate our experience with the treatment of 15 patients treated with I-125 or Cs-131 brachytherapy radiation seeds as an adjuvant in these difficult cases. METHODS: Patients with high-grade recurrent meningioma who underwent resection and intraoperative placement of brachytherapy seeds at our institution from 2002 to 2014 were identified and studied by retrospective chart review. RESULTS: Fifteen patients with median age of 68.8 yr were treated with I-125 (n = 13) or Cs-131 (n = 2) brachytherapy seeds for cases of recurrent, grade II (n = 8), or grade III (n = 7) meningioma at our institution from 2002 to 2014. These lesions originated from a variety of locations including, convexity (3), falcine (3), frontal (2), occipital (1), parietal (2), 2 sphenoid wing (2), and temporal (2), based recurrent meningiomas. Patients had a median of 2 prior open surgical interventions and received local radiation therapy with a median dose of 55 Gy prior to brachytherapy. Survival at 2.5 yr was 56% for grade II and 17% for grade III lesions. Survival was significantly associated with patient age but not tumoral pathology. Forty percent of patients required reoperations for wound complications following brachytherapy. CONCLUSION: Brachytherapy with implantation of permanent radiation seeds provides a viable alternative treatment for recurrent meningioma while carrying a significant clinical risk of wound infection and need for reoperation.

Accelerated partial breast irradiation with low-dose-rate interstitial implant brachytherapy after wide local excision: 12-year outcomes from a prospective trial.

PURPOSE: To evaluate the long-term toxicity, cosmesis, and local control of accelerated partial breast irradiation with implant brachytherapy after wide local excision for Stage T1N0 breast cancer (BCa). MATERIALS AND METHODS: Between 1997 and 2001, 50 patients with Stage T1N0M0 BCa were treated in a Phase I-II protocol using low-dose-rate accelerated partial breast irradiation with implant brachytherapy after wide local excision and lymph node surgery. The total dose was escalated in three groups: 50 Gy (n = 20), 55 Gy (n = 17), and 60 Gy (n = 13). Patient- and physician-assessed breast cosmesis, patient satisfaction, toxicity, mammographic abnormalities, repeat biopsies, and disease status were prospectively evaluated at each visit. Kendall's tau (τ(ß)) and logistic regression analyses were used to correlate outcomes with dose, implant volume, patient age, and systemic therapy. RESULTS: The median follow-up period was 11.2 years (range, 4-14). The patient satisfaction rate was 67%, 67% reported good-excellent cosmesis, and 54% had moderate-severe fibrosis. Higher dose was correlated with worse cosmetic outcome (τ(ß) 0.6, p < .0001), lower patient satisfaction (τ(ß) 0.5, p < .001), and worse fibrosis (τ(ß) 0.4, p = .0024). Of the 50 patients, 35% had fat necrosis and 34% developed telangiectasias ≥1 cm(2). Grade 3-4 late skin and subcutaneous toxicities were seen in 4 patients (9%) and 6 patients (13%), respectively, and both correlated with higher dose (τ(ß) 0.3-0.5, p ≤ .01). One patient had Grade 4 skin ulceration and fat necrosis requiring surgery. Mammographic abnormalities were seen in 32% of the patients, and 30% underwent repeat biopsy, of which 73% were benign. Six patients had ipsilateral breast recurrence: five elsewhere in the breast, and one at the implant site. One patient died of metastatic BCa after recurrence. The 12-year actuarial local control, recurrence-free survival, and overall survival rate was 85% (95% confidence interval, 70-97%), 72% (95% confidence interval, 54-86%), and 87% (95% confidence interval, 73-99%), respectively. CONCLUSION: Low-dose-rate accelerated partial breast irradiation with implant brachytherapy provides acceptable local control in select early-stage BCa patients. However, treatment-related toxicity and cosmetic complications were significant with longer follow-up and at higher doses.

New life after prostate brachytherapy? Considering the fertile female partner of the brachytherapy patient.

OBJECTIVES: To examine several cases of unusual and unexpected pregnancy in the female partners of men treated with brachytherapy for cancer of the prostate. PATIENTS AND METHODS: Self-reported pregnancy of partners of patients who had had prostate brachytherapy was assessed. The dosimetry to the testicles and sperm counts were used to examine the feasibility of pregnancy in the partners. RESULTS: Three reported cases of pregnancy showed the men to have viable counts of within several or all of the parameters of the World Health Organisation criteria for normal semen analysis. CONCLUSIONS: These cases provide a cautionary tale and suggest that all men being treated with prostate brachytherapy should be counselled about the possibility of continued fertility. Documentation of this 'risk' on the consent form will allow for proper discussion of this issue in a clinical and medicolegal context. The key to addressing this problem is to propagate much better patient information. The topic should be addressed clearly in information booklets for the patients. Prostate brachytherapy may allow for pregnancy to be achieved in the fertile partners of patients, even after full radiation treatment of the patient.

Intraoperative dural irradiation by customized 192iridium and 90yttrium brachytherapy plaques.

PURPOSE: After vertebral or paravertebral tumor resection, tumor cells may remain on the dura. Because a tumoricidal dose is difficult to achieve using external beam radiotherapy without exceeding the spinal cord tolerance, we developed intraoperative applicators to deliver additional dose to the dura. METHODS AND MATERIALS: Eight patients with vertebral or paravertebral tumor underwent conformal external beam radiotherapy, tumor resection, and intraoperative radiotherapy to the dura involved by tumor. At surgery, vertebra, soft tissue, and epidural tumor were resected. A radioactive applicator plaque was placed on the dura to deliver 7.5-15 Gy, and then removed. Vertebral reconstruction and stabilization was completed. Chemotherapy was administered for large, high-grade sarcomas. RESULTS: We progressed through three plaque designs, initially (192)Ir, subsequently liquid (90)Y, and finally (90)Y foil in a semicylindrical polycarbonate plaque, in the treatment of 8 patients. The low-energy (90)Y beta-emissions provided a more attractive depth dose profile than that achievable with iridium and gave negligible staff radiation exposure. The (90)Y depth dose measured 29% at 2 mm and 9% at 4 mm from the surface of the foil plaque, with acceptable surface dose homogeneity. The average surface dose rate ranged from 18.7 to 47.6 cGy/min for the iridium plaques and 45.2 to 187.5 cGy/min for the (90)Y plaques. The treatments have been without acute or late neurologic complications. The disease of 6 of 8 patients was locally controlled at median potential follow-up of 24 months. CONCLUSIONS: The (90)Y foil applicator is technically elegant, easy to use, and superior to the earlier models. It has been incorporated into a protocol for spinal tumor treatment.

Dose-volume analysis of radiotherapy for T1N0 invasive breast cancer treated by local excision and partial breast irradiation by low-dose-rate interstitial implant.

PURPOSE: To evaluate the toxicity of partial breast irradiation (RT) using escalating doses of low-dose-rate interstitial implant as the sole adjuvant local therapy for selected T1N0 breast cancer patients treated by wide local excision. The results of a European Organization for Research and Treatment of Cancer study have demonstrated a significant local control benefit using external beam RT to 65 Gy compared with 50 Gy. Thus, the tolerance of escalating doses of partial breast RT should be determined, because this approach may become a standard treatment for patients with early-stage breast cancer. METHODS AND MATERIALS: Between 1997 and 2001, 48 patients with T1N0M0 breast cancer were enrolled into an institutional review board-approved Phase I/II protocol using low-dose-rate brachytherapy implants after wide local excision and lymph node staging surgery. Brachytherapy was started 3-4 days after surgery at a dose rate of 50 cGy/h, using (192)Ir sources evenly spaced to cover 3 cm around the resection margins. Typically, 2-3 planes were used, with a median of 14 catheters (range 10-16). The total dose was escalated in three groups: 50 Gy (n = 19), 55 Gy (n = 16), and 60 Gy (n = 13). The implant volume was calculated and used to classify patients into quartiles: 76-127 cm(3) (n = 12), 128-164 cm(3) (n = 12), 165-204 cm(3) (n = 12), and >204 cm(3) (n = 12). Cosmesis, patient satisfaction, treatment-related complications, mammographic abnormalities, rebiopsies, and disease status were recorded at each scheduled patient visit. RESULTS: The median follow-up for all patients was 23.1 months (range 2-43). Very good to excellent cosmetic results were observed in 91.8% of patients. Ninety-two percent of patients were satisfied with their cosmetic outcome and said they would choose brachytherapy again over the standard course of external beam RT. Six perioperative complications occurred: two developed bleeding at the time of catheter removal, two had abscesses, one developed a hematoma, and one had a nonhealing sinus tract requiring surgical intervention. Significant fibrosis (moderate-to-severe scarring and thickening of the skin and breast) was noted in only 4 patients; 1 had received 55 Gy and 3 had received 60 Gy. Abnormal posttreatment mammograms were seen in 19 patients. Eight patients underwent rebiopsy for abnormalities found either by mammography or on physical examination; all proved to be fat necrosis or post-RT changes. The rebiopsy rates appeared to correlate with doses >/=55 Gy (6 [75%] of 8 compared with 29 [60%]of 48 overall) and implant volumes >/=128 cm(3) (7 [87.5%] of 8 compared with 36 [75%] of 48 overall). To date, no local, regional, or distant recurrences have been observed. CONCLUSION: Low-dose-rate implants up to 60 Gy were well-tolerated overall. With an implant dose of 60 Gy, the incidence of posttreatment fibrosis (25%) appeared to be increased. Only the long-term follow-up of this and other implant studies will allow an understanding of the total radiation dose necessary for tumor control and the volume of breast that requires treatment.