2863 - A Prospective Study Comparing Acute Toxicities in FIGO Stage IIIC1r Carcinoma Cervix Patients Receiving Semi-Extended Field Radiotherapy vs. Previously Treated Patients of Whole Pelvis Radiotherapy

Purpose/Objective(s): Carcinoma cervix follows a systematic pattern of lymphatic spread, progressing from one nodal group to the next. Prophylactic treatment of lower para-aortic lymph nodes (PALN) in the presence of gross pelvic lymphadenopathy, alongside whole pelvis radiation (WPRT), may enhance local control. This study aims to compare acute toxicities between semi-extended field radiotherapy (SEFRT), incorporating prophylactic lower PALN irradiation, and WPRT in FIGO stage IIIC1r carcinoma cervix.

Materials/Methods: A total of 64 patients were analyzed. The prospective SEFRT arm included 32 patients treated between January 2019 and November 2020, while the control WPRT arm included 32 patients treated between 2014 and 2018. All patients were staged as FIGO IIIC1r (2018 staging) and received definitive radiotherapy.

• SEFRT Arm: 50.4 Gy/28 fractions (1.8 Gy/fraction) to the whole pelvis, with a simultaneous integrated boost (SIB) of 54–56 Gy (1.9–2 Gy/fraction) to gross pelvic nodes and 45 Gy (1.8 Gy/fraction) to lower PALN.
• WPRT Arm: 50.4 Gy/28 fractions (1.8 Gy/fraction) to the whole pelvis.

All patients received concurrent weekly Cisplatin (40 mg/m²) followed by brachytherapy to achieve a biologically effective dose (BED) of =80 Gy. Acute toxicities were assessed weekly using CTCAE 5.0. Comparative analysis was conducted using Chi-square or Fisher’s exact test, with a p-value <0.05 considered statistically significant. Statistical analysis was performed using statistical software.

Results: Of the total, 29 patients in the SEFRT arm and 30 in the WPRT arm were available for evaluation. Baseline characteristics were well-matched. No statistically significant differences were observed in weight loss, skin reactions, fatigue, or urinary symptoms. While gastrointestinal and hematologic toxicities were slightly more frequent in the SEFRT group, the difference was not statistically significant.

Conclusion: SEFRT with SIB to gross pelvic nodes is a safe and feasible approach for FIGO stage IIIC1r carcinoma cervix, in combination with weekly Cisplatin and brachytherapy. To mitigate toxicities, precise contouring of additional structures such as bone marrow, strict adherence to dose constraints, and rigorous weekly monitoring are essential to maintain overall treatment time and optimize outcomes. Further investigation into late toxicities in this patient cohort is ongoing.

Abstract 2863 - Table 1