ESTRO 2023 - Abstract Book

S1922

Digital Posters

ESTRO 2023

To analyze if concurrent chemoradiotherapy (CCRT) with high dose cisplatin and fluorouracil (PF) can effectively reduce the total radiation dose in cervical cancer. Materials and Methods We retrospectively analyzed cervical cancer patients who underwent PF-CCRT at our institution between 2014 and 2017 and who had CT scan at the time of intracavitary brachytherapy (ICBT). At the time of treatment, a dose was prescribed for point A. We retrospectively created high-risk clinical target volume (CTVHR) on the CT scan taken at the time of ICBT with reference to MRI which was taken just before the ICBT. Then, 90% target doses (D90) to CTVHR and D2cc of rectum and bladder were re-calculated. Doses delivered by external beam radiotherapy (EBRT) and ICBT were summed by converting to Equivalent doses in 2-Gy fractions (EQD2). α / β =10 was used for the evaluation of CTVHR and α / β =3 was used for the evaluation of bladder and rectum. Overall survival (OS), local control (LC), and disease-free survival (DFS) were plotted using the Kaplan-Meier methods. The log-rank test and cox regression models were used to evaluate differences in survival due to stage, the volume of CTVHR, and prescribed doses. Adverse events (AEs) were evaluated according to the Common Terminology Criteria for Adverse Events v 5.0 (CTCAE). Results Of 201 patients treated with high dose PF-CCRT, 47 patients had CT scan at the time of ICBT. The median age was 46 (28- 74) years and the median follow-up period for all patients was 66 (5-87) months. The numbers of patients with FIGO (2018) ≤ IIA and ≥ IIB were 12 (26%) and 35 (74%), respectively. The numbers of patients with squamous cell carcinoma (SCC), adenocarcinoma, and adeno-squamous carcinoma were 44 (94%), 1 (2%), and 2 (4%), respectively. Thirty-eight (81%) patients completed the scheduled 5 courses of PF. The median volume of CTVHR was 20 (8-63) cc and the median D90 of CTVHR and D2cc of bladder and rectum were 67 (52-115) Gy, 67 (48-135) Gy, and 64 (53-109) Gy, respectively. The 5-year OS, LC, and DFS for all patients were 84%, 98%, and 69%, respectively. The 5-year OS for the 44 patients with SCC was 83%. Univariate analysis showed no significant difference in OS for any of the factors. The 5-year OS for patients with FIGO ≤ IIA and ≥ IIB was 91% and 82% (p=0.5), D90 ≥ 67 Gy and < 67 Gy groups was 85% and 84% (p=0.7), and CTVHR volume ≥ 20cc and < 20cc groups was 80% and 93% (p=0.5). Multivariate analysis showed no independent prognostic factors affecting OS, including D90 of CTVHR. As for AEs, no treatment-related deaths were observed; rectal bleeding of Grade2 or less was seen in 12 patients (G1: 10, G2: 2) (26%), but no G3 or greater. Bladder bleeding was also present in only 6 patients (G1: 5, G3: 1) (13%). Conclusion In our study, CCRT for patients with locally advanced cervical cancer showed good outcomes even with relatively low doses to CTVHR. The administration of high dose PF may have contributed to this result.

PO-2137 A packing technique for enhanced rectum sparing during HDR brachytherapy in cancer cervix.

S. Vats 1 , S. Thakur 1 , M. Gupta 1 , L. Chandrakant 1 , V. Fotedar 1 , P. Thakur 1 , D. Tuli 1

1 IGMC Shimla, Radiotherapy and Oncology, Shimla, India

Purpose or Objective The capacity of the vagina varies from patient to patient at the time of intracavitary brachytherapy (ICB). At one end of the spectrum, there are patients with roomy vagina, and at the other end, there is a subset of patients with narrow vagina and shallower fornices. Patients in this subset are ideal for tandem-ring (TR) applicators (Figure1). But in practice, their use is not restricted to the ideal subset of patients. During conventional ICB procedure using TR applicators, after assembling a rectal retractor blade (RR), the remaining space in the posterior fornices becomes inaccessible. This modified technique enables us to overcome this limitation and makes customised vaginal gauze packing (VP) possible for a range of spaces, posterior and superior to RR, in different patients. This helps to supplement the displacement achieved with RR alone especially in patients with roomy vagina. We compare the standard International Commission on Radiation Units and Measurements-38 (ICRU-38) rectal and bladder point doses with the modified technique of combining radio-opaque VP and a RR versus the conventional technique of using RR alone during HDR-ICB with TR applicators.

Materials and Methods