Gynecological Cancer

PD 15 - GYN 2 - Poster Discussion

1133 - Single-Institution Experience in 3D MRI-Based Brachytherapy for Cervical Cancer for 230 Women: Can Dose Overcome Poor Response?

Wednesday, October 24
11:42 AM - 11:48 AM
Location: Room 217 A/B

Single-Institution Experience in 3D MRI-Based Brachytherapy for Cervical Cancer for 230 Women: Can Dose Overcome Poor Response?
Z. D. Horne1, P. Karukonda2, R. Kalash3, R. P. Edwards4, J. L. Kelley4, J. T. Comerci4, A. B. Olawaiye4, M. Courtney-Brooks4, M. M. Boisen4, J. L. Berger4, S. E. Taylor4, P. Sukumvanich4, and S. Beriwal5; 1Department of Radiation Oncology, UPMC Hillman Cancer Center, University of Pittsburgh School of Medicine, Pittsburgh, PA, 2Department of Radiation Oncology, UPMC Hillman Cancer Center, Pittsburgh, PA, 3Department of Radiation Oncology, Hillman Cancer Center, University of Pittsburgh School of Medicine, Pittsburgh, PA, 4Department of Gynecologic Oncology, UPMC Hillman Cancer Center, Pittsburgh, PA, 5UPMC Hillman Cancer Center, Pittsburgh, PA

Purpose/Objective(s): Brachytherapy is an essential component of the treatment of locally advanced cervical cancer; recent GEC-ESTRO guidelines recommend that the dose to 90% (D90) of the high-risk clinical target volume (HRCTV) be at least 85Gy with even higher doses for poor response to external beam radiation.

Materials/Methods: A retrospective review of brachytherapy plans delivered at a single institution were evaluated for dose parameters and local control following treatment. The HRCTV D90 was retrieved from all plans. Time to local failure was defined as time to event from completion of the last brachytherapy fraction. Significance of tumor parameters on local control was evaluated with uni- and multivariable Cox regression analysis. Correlations were determined with a linear regression model.

Results: A total of 230 women underwent high dose-rate brachytherapy for cervical cancer between 2007 and 2016 with evaluable dosimetry. Median follow up was 35.1 months. The median prescribed dose was 27.5Gy/5fx with a median HRCTV D90 of 83.7Gy (range: 74.8-93.5Gy), HRCTV volume of 31cc (range: 14.91-83.76cc), and treatment time of 7.1 weeks. Local control for the entire cohort at 3 years was 90.1%. Factors significantly correlated with higher rates of local failure were: HRCTV volume per cc increase (HR 1.047 [95%CI 1.017-1.078, p=0.002] and adenocarcinoma histology vs squamous (HR 2.773 [95%CI 1.148-6.698], p=0.023). Three-year local control for tumors < 31cc and ≥ 31cc, 3-year local control rates were not statistically different (93.5% vs 86.7%, p=0.055) but when 40cc was used as a cutoff, 3-year local control was 92.6% vs 82.2%, p=0.010. Adenocarcinomas had worse 3-year local control vs squamous cell carcinomas: 83.5% vs 91.7%, p=0.018. On multivariable analysis, HRCTV volume per cc increase (HR 1.044 [95%CI 1.014-1.075], p=0.004) and adenocarcinoma histology (HR 2.597 [95%CI 1.071-6.297], p=0.035) were both predictive of local failure. HRCTV dose at multiple thresholds (85, 90, 95Gy) did not predict for local control. There was a positive correlation between higher HRCTV volume and higher prescribed dose (R2 = 0.131, p<0.001). Adenocarcinomas were also significantly associated with higher prescribed brachytherapy dose (p=0.009). Women with HRCTV < 40cc had 3-year progression-free survival (including distant metastases) of 80.9% vs. 63.7% for ≥ 40cc (p=0.007). This translated to three-year overall survival for women with HRCTV < 40cc of 80.8% vs 61.0%% for ≥ 40cc (p=0.002).

Conclusion: Local control is excellent with MRI based planning in the entire cohort of patients. Our data suggest that a poor response to external beam radiation (larger HRCTV volume) predicted for worse local control despite a higher brachytherapy dose delivery. These poor responders are also at higher risk of overall progression and death and may require additional intervention to mitigate this risk.

Author Disclosure: Z.D. Horne: None. P. Karukonda: None. R. Kalash: None. J.L. Kelley: None. A.B. Olawaiye: None. M. Courtney-Brooks: None. P. Sukumvanich: None.

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