CyberKnife Boost for Patients with Cervical Cancer Unable to Undergo Brachytherapy

Abstract

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.

Tumor Boost Using External Beam Radiation in Cervical Cancer Patients Unable to Receive Intracavitary Brachytherapy

“…Except for 1 study reporting a 5-year local tumor control rate of 21.9%, 13 most of the studies showed that approximately 60% to 100% of patients achieved local tumor control after curative whole pelvic radiotherapy and EBRT-B. 3,8,9,12,15 Likewise, we noted in our study that the 5-year local tumor control rate was 70.0%, and the rate of late grade 3 or higher toxicity was 2.6% after curative radiotherapy using FIGURE 1. A, Comparison of EQD2 10 total between patients treated with 3D-CRT versus IMRT.…”

External beam techniques to boost cervical cancer when brachytherapy is not an option—theories and applications

“…On the other hand, SBRT was the technique of choice in all the four recent studies that delivered 16-30 Gy in 2-6 Gy per fraction to the cervical target volume not amenable for BT. The preliminary results of three studies were promising (LC rates ranging from 78-100% and negligible late toxicity) although the median follow up duration was relatively short (6-36 months) (16,69,71). The study by Kubicek et al was the exception with a paradoxically high late rectal toxicity (25% grade 3 or higher) in spite of using MR imaging to define the CTV, 0.5 cm CTV to PTV expansion, Cyberknife (CK) (Accuray Incorporated, Sunnyvale, CA, USA) to track cervical implanted gold fiducial for increased SBRT precision.…”

Patient's specific integration of OAR doses (D2 cc) from EBRT and 3D image‐guided brachytherapy for cervical cancer

“…For patients unable to undergo BT, stereotactic‐body radiotherapy (SBRT) techniques have been explored with different fractionation schemes such as 20 Gy in five fractions (23 Gy 10 in EQD2),37, 38 14 Gy in two fractions (20 Gy 10 in EQD2),38, 39 25 Gy in five fractions (31 Gy 10 in EQD2),40 5 Gy in three fractions (31 Gy 10 in EQD2),41 or 6 Gy in five fractions (40 Gy 10 in EQD2) 42. 3D conformal radiotherapy (3D‐CRT) or IMRT techniques38, 39, 41, 43 along with CyberKnife (Accuracy Inc., Sunnyvale, CA, USA)37, 40, 42 have also been tested. However, the majority of clinical SBRT results37, 38, 40, 42 are still in the early stage with only small number of patients (<20 patients) and short‐term follow‐up (<26 months).…”

“…3D conformal radiotherapy (3D‐CRT) or IMRT techniques38, 39, 41, 43 along with CyberKnife (Accuracy Inc., Sunnyvale, CA, USA)37, 40, 42 have also been tested. However, the majority of clinical SBRT results37, 38, 40, 42 are still in the early stage with only small number of patients (<20 patients) and short‐term follow‐up (<26 months).…”