• brachytherapy
• cervical cancer
• organ motion
• radiotherapy

Introduction: The endpoint of this study is to evaluate the effectiveness and accuracy of simulation procedures used to performing radiotherapy treatment for locally advanced cervical cancer treated with definitive concurrent cisplatin-based chemo-radiotherapy (CCRT). Moreover we also have evaluated the dose coverage of the target and organ at risk (bladder and rectum) during radiotherapy, correlating with the clinical outcome.
Material and methods: Between Jan. 2015 and Dec. 2019 we retrospectively analysed 30 patients with FIGO stage IB2-IVA cervical cancer who underwent CCRT. All the patients received External Beam Radiotherapy (EBRT) on the cervix and local extension of tumour, uterus, lateral parametria, proximal half of the uterosacral ligaments, upper half of the vagina or two cm below known vaginal disease and pelvic lymph nodes (obturator, external and internal iliac, subaortic presacral and common iliac nodes) up to a total dose of 45-50.4 Gy in 5-6 weeks (daily fractions of 1.8-2Gy).EBRT was delivered with Linac True Beam, 6 MeV Photons and VMAT technique. Concomitant chemotherapy (cisplatin [CDDP] 40mg/m2 weekly) was used in overall patients. Twenty-six (86.6%) women received dose-dense NACT consisted of weekly PTX (80 mg/m2) plus CBDCA (AUC 2) for 6 cycles. Twenty-three (76.6%) patients received additional (4-20Gy) EBRT sequential boost on primary tumor site and 28 (93.3%) received (6-28Gy) HDR-BT boost (daily fractions of 5-7Gy) delivered with a three-way Fletcher-Williamson applicator set (Nucletron B.V., Veenendaal, Netherlands). CTV expansion to PTV was between 5 to 10 mm.
Results: Variations in bladder volume was from -77% to +435% and in rectum volume was from -67% to +415%. The displacement ranges were large, though the mean value was within 1 cm except for the superior direction which was +4.71cm. Among the 5 directions, the most prominent
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positional change was observed in the cranio-caudal direction. We also observed only 2 (6.6%) G3 acute gastrointestinal toxicity and 2 (6.6%) G3 acute genitourinary toxicity.
In univariate analysis PTV ≤ 5 mm is associated with lower Overall Survival [OS] (p=0.044), higher Progression Disease [PD] (p=0.029) and higher gastrointestinal toxicity (p=0.088). Also high risk histology (adenocarcinoma) is also associated with higher PD [p=0.016].Multivariate analysis shows that adenocarcinoma histology had lower Progression Free Survival (PFS).
Conclusions: So It is necessary to perform an accurate check of patient's positioning and of dimensions of uterus, rectum and bladder through CBCTs. Because variations in volume of organ at risk can cause a shift of our target outside the PTV and an increase of radiation toxicity. Furthermore the contouring of a PTV ≥ 5 mm is strongly recommended; in agreement with literature our study suggest to use an isotropic expansion of about 8-10 mm at CTV1. CBCTs is an effective modality to evaluate and improve the inter-fraction setup reproducibility in radiation treatment for patients with local advanced cervical cancer with higher intrafractional organ motion.