Abstract
PurposeTo evaluate the technique, dosimetry, dose-volume-histograms (DVHs) and acute toxicity for CyberKnife® boost irradiation instead of intra-cervical brachytherapy in patients with cervical cancer.Methods and materialsEleven who were not suitable for brachytherapy with FIGO stage IIB-IIIB cervical cancer underwent primary chemoradiation. After fiducial implantation, T2 contrast-enhanced planning MRI and CT scans at 2-mm slice thickness were collected in the treatment position. The clinical target volume was defined as cervix + macroscopic residual tumour on MRI. Five fractions of 6 Gy each were prescribed to the target volume with a covering single dose 6 Gy. DVH parameters were evaluated for the target and organs at risk. Acute toxicity was documented once a week.ResultsDmeanPTV ranged from 33.6-40 Gy, median 36.7 Gy with a coverage of the PTV calculated to 100% of the prescribed dose ranging from 93.0-99.3% (median 97.7%). For the PTV the median CN was 0.78 (range, 0.66 to 0.87) and the median CI was 1.28 (range 1.15 to 1.52). Gastrointestinal (GI) and genitourinary (GU) toxicity was mild. There was no grade 3 or higher GI and GU toxicity. After 6 months of follow up, there were no local recurrences. For the complete treatment, a median EQD2 to 1 cc and 2 cc of the bladder wall was 98.8 Gy and 87.1 Gy, respectively. Median EQD2 to 1 cc and 2 cc of the rectal wall was 72.3 Gy and 64 Gy, respectively, correlating with a risk < 10% for Grade 2–4 late toxicity.ConclusionsCyberKnife robotic radiosurgery in patients with cervical cancer provides excellent target coverage with steep dose gradients toward normal tissues and safe DVH parameters for bladder, rectum and sigmoid. Acute toxicity was mild. Longer follow-up is needed to evaluate the oncological equality.
Highlights
Chemoradiation is the treatment of choice for patients with locally advanced and/or lymph-node positive cervical carcinoma
Boost dose delivered using conventional external beam radiotherapy (EBRT) devices have, compared to brachytherapy, compromised disease control compared with brachytherapy [4]
The whole treatment was completed within 45–57 days in all patients including EBRT, simultaneous chemotherapy and CyberKnife treatment
Summary
Chemoradiation is the treatment of choice for patients with locally advanced and/or lymph-node positive cervical carcinoma. Boost dose delivered using conventional external beam radiotherapy (EBRT) devices have, compared to brachytherapy, compromised disease control compared with brachytherapy [4]. Perhaps due to these disappointing findings, only a few groups have evaluated the feasibility and potential of highly conformal external-beam techniques for boosting small sub-volumes for patients with gynaecological carcinoma [5–10]. The introduction of several modern radiation technologies, such as image-guided radiotherapy (IGRT), stereotactic body irradiation, intensity modulated radiotherapy (IMRT), and volumetric arc therapy (VMAT) may allow the emulation of brachytherapy-like dose distributions, delivering high doses to the target without exceeding constraints to the organs at risk. Image-guided radiosurgery may be most suited to the present application—frameless, robotic targeting and tracking algorithms have allowed what was once soley an intracranial treatment to be extended to extracranial indications
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