Standard radiation therapy for patients undergoing primary chemosensitized radiation for carcinomas of the cervix usually consists of external beam radiation followed by an intracavitary brachytherapy boost. On occasion, the brachytherapy boost cannot be performed due to unfavorable anatomy or because of coexisting medical conditions. We examined the safety and efficacy of using CyberKnife stereotactic body radiotherapy (SBRT) as a boost to the cervix after external beam radiation in those patients unable to have brachytherapy to give a more effective dose to the cervix than with conventional external beam radiation alone. Six consecutive patients with anatomic or medical conditions precluding a tandem and ovoid boost were treated with combined external beam radiation and CyberKnife boost to the cervix. Five patients received 45 Gy to the pelvis with serial intensity-modulated radiation therapy boost to the uterus and cervix to a dose of 61.2 Gy. These five patients received an SBRT boost to the cervix to a dose of 20 Gy in five fractions of 4 Gy each. One patient was treated to the pelvis to a dose of 45 Gy with an external beam boost to the uterus and cervix to a dose of 50.4 Gy. This patient received an SBRT boost to the cervix to a dose of 19.5 Gy in three fractions of 6.5 Gy. Five percent volumes of the bladder and rectum were kept to ≤75 Gy in all patients (i.e., V75 Gy ≤ 5%). All of the patients remain locally controlled with no evidence of disease following treatment. Grade 1 diarrhea occurred in 4/6 patients during the conventional external beam radiation. There has been no grade 3 or 4 rectal or bladder toxicity. There were no toxicities observed following SBRT boost. At a median follow-up of 14 months, CyberKnife radiosurgical boost is well tolerated and efficacious in providing a boost to patients with cervix cancer who are unable to undergo brachytherapy boost. Further follow-up is required to see if these results remain durable.

PURPOSE To present the clinical commissioning of a novel 103Pd directional brachytherapy device (CivaSheet™) for intraoperative radiation therapy. METHODS AND MATERIALS Clinical commissioning for the CivaSheet™ consisted of establishing: (i) source strength calibration capabilities, (ii) experimental verification of TG-43 dosimetry parameters, (iii) treatment planning system validation, and (iv) departmental practice for dose specification and source ordering. Experimental verification was performed in water with radiochromic film calibrated with a 37kVp x-ray beam. Percentage difference ([measurements – calculation] / calculation) and distance to agreement (difference between film-to-source distance and distance that minimized the percentage difference) were calculated. Nomogram values (in U/100 Gy) for all configuration (up to 20 × 20 sheets) were calculated for seed ordering. Clinical commissioning was used on patients enrolled in an ongoing IRB-approved protocol. Results A source calibration procedure was established and the treatment planning system was commissioned within standard clinical uncertainties. Percentage dose differences (distances to agreement) between measured and calculated doses were 8.6% (−0.12mm), 0.6% (−0.01mm), −6.4% (0.22mm), and −15.8% (0.72mm) at depths of 2.3mm, 5.1mm, 8.0mm, and 11.1mm respectively. All differences were within the experimental uncertainties. Nomogram values depended on sheet size and spatial extent. A value of 2.4U/100 Gy per CivaDot™ was found to satisfy most cases, ranging from 2.3 to 3.3U/100 Gy. Nomogram results depended on elongation of the treatment area with a higher variation observed for smaller treatment areas. Post-implantation dose evaluation was feasible. CONCLUSIONS Commissioning and clinical deployment of CivaSheet™ was feasible using BrachyVision™ for post-operative dose evaluation. Experimental verification confirmed that the available TG-43 dosimetry parameters are accurate for clinical use.

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