2811 - Improving Outcomes in Locally Advanced Cervical Cancer: A Prospective Study of Parametrial Boost with Conformal Radiation Therapy

Purpose/Objective(s): Locally advanced cervical cancer (LACC) continue to possess a significant challenge, particularly in resource-limited settings where advanced brachytherapy techniques are often unavailable. This study aimed to evaluate the clinical outcomes and toxicity profile on adding a simultaneous integrated boost (SIB) to the parametrium using conformal radiotherapy (CRT) in patients with FIGO stage IIB and IIIB cervical cancer.

Materials/Methods: Sixty-five (65) patients with histologically proven cervical cancer and FIGO stage IIB & IIIB disease were enrolled in this prospective, single-institutional study. Patients were further divided into two groups- the study group received CRT with SIB to the parametrium (45 & 54 Gy in 25 fractions), while the control group received standard CRT (50 Gy in 25 fractions). Both groups underwent concurrent weekly chemotherapy followed by image guided brachytherapy. Primary endpoints included locoregional control and toxicity profiles, while secondary endpoints were progression-free survival (PFS) and overall survival (OS). Univariate and multivariate data analysis was performed to evaluate association of parametrial boost with toxicities and PFS.

Results: After a median follow-up period of 26 months, the study group demonstrated a 72.7% complete response rate, compared to 65.6% in the control group (p=0.03). Acute toxicity was comparable between the groups, with grade 1-2 skin & mucosal toxicity being the commonest (63.6% in study group vs. 59.4% in controls). Gastrointestinal toxicity occurred in 36.4% of the study group and 43.8% of controls, with only a few cases progressing to grade 3. Hematologic toxicity was observed in 42.4% of the study group and 31.3% of controls, but no severe complications were reported. Late toxicities, including radiation proctitis and vaginal stenosis, were minimal and manageable. Dosimetric analysis showed adequate target coverage in the study group, with a mean parametrial dose of 51.78±1.17 Gy and V95 >98%. Organs at risk (OARs) were well-protected, with bladder V50 <36% and rectum V50 <34%, demonstrating the safety of the parametrial boost. The 2-year PFS was significantly higher in the study group (81.8% vs. 71.9%, p=0.04), with fewer parametrial recurrences (6.1% vs. 15.6%, p=0.03). This suggests that the parametrial boost effectively targets high-risk areas, reducing the likelihood of disease returning in the pelvis.

Conclusion: The addition of a parametrial boost using CRT significantly improved locoregional control and PFS in LACC patients, without increasing severe toxicities. This approach is particularly beneficial in settings where advanced brachytherapy techniques are unavailable. Our findings support the use of SIB as a safe and effective strategy to enhance outcomes in LACC, offering a practical solution for resource-constrained centers. Further studies with longer follow-up are needed to confirm these results and evaluate long-term toxicity.