Genitourinary Cancer

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TU_15_3464 - Lymph Node-Directed Simultaneous Integrated Boost in Patients with Clinically Lymph Node-Positive Cervical Cancer Treated with Definitive Chemoradiation: Clinical Outcomes and Toxicity

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Lymph Node-Directed Simultaneous Integrated Boost in Patients with Clinically Lymph Node-Positive Cervical Cancer Treated with Definitive Chemoradiation: Clinical Outcomes and Toxicity
K. R. Jethwa1, S. Jang1, K. Gonuguntla1, J. D. Evans1, M. S. Block2, A. Kumar3, C. L. Langstraat3, T. J. Whitaker1, C. N. Day4, C. L. Deufel1, M. G. Haddock1, and I. A. Petersen1; 1Department of Radiation Oncology, Mayo Clinic, Rochester, MN, 2Division of Medical Oncology, Mayo Clinic, Rochester, MN, 3Department of Obstetrics and Gynecology, Division of Gynecologic Surgery, Rochester, MN, 4Department of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN

Purpose/Objective(s): Gross involvement of regional lymph nodes in patients with cervical cancer negatively affects prognosis. We report clinical outcomes of patients with cervical cancer treated with intensity modulated radiation therapy (IMRT) with dose-escalated simultaneous integrated boost (SIB) to involved lymph nodes (LNs).

Materials/Methods: Between 2005 and 2017, 59 patients with clinically LN-positive cervical cancer were treated with definitive concurrent cisplatin, IMRT, and LN-directed SIB, followed by intracavitary brachytherapy boost to achieve an EQD2 of 85-90 Gy. The elective clinical target volume (CTVelect) included the cervix, uterus, and pelvic LNs, with the addition of para-aortic (PA) LNs for patients with involved PA LNs. The dose-escalated SIB target volume (CTVsib) included clinically positive LNs + 5-10 mm cropped from gastrointestinal (GI) or genitourinary (GU) organs. Small bowel (SB) dose constraints, V52Gy[cc]<0.03cc and V45Gy[cc]<195cc, were prioritized over target coverage. Acute and late adverse effects (AEs) were recorded per common toxicity criteria for adverse effects. Kaplan-Meier method was used to estimate overall survival (OS), progression free survival (PFS), and in-field locoregional control (LRC).

Results: Median age was 49 years (IQR 37-56). Squamous histology was most common (81%). FIGO stage was I (31%), II (39%), III (29%), and IVa (2%), with positive LNs present in the pelvis (56%) or pelvis and PA (44%). Median number of positive LN was 3 (IQR 2-6), with a median of 3 (IQR 2-4) pelvic, and for those with PA LN+, a median of 2 (IQR 1-4) PA. Most common CTVelect dose was 45 Gy (EQD2: 44.3 Gy, 89%) and CTVsib dose was 56.25 Gy (EQD2: 57.4 Gy, 66%) delivered in 25 fractions. Median treatment duration, including brachytherapy, was 45 days (IQR 42-50). Median follow-up was 30 months. Estimated 2 year LRC, PFS, and OS were 91% (95% CI 82-100), 63% (95% CI 49-78), and 79% (95% CI 67-92), respectively. PA nodal involvement was associated with worse 2 year PFS (HR 2.51; 95% CI 1.05-5.99; p=0.04). Risk of disease progression was most pronounced for ≥4 positive LNs (HR 2.79; 95% CI 1.16-6.71; p=0.02). Twenty (34%) patients had disease recurrence. Five (8%) patients had in-field locoregional recurrence, including cervix (1), cervix and elective PA LN (1), and boosted pelvic (1) or PA LN (2). Two (3%) patients had out-of-field isolated PA LN recurrence. Thirteen (22%) patients had distant metastasis. Acute GI/GU grade 3 or higher AE rate was 5%. Late GI/GU complications included fistula (4), and ureteral stenosis requiring stenting (7). No patients developed late small bowel obstruction.

Conclusion: LN-directed SIB as part of definitive chemoradiation for clinically LN-positive cervical cancer is well tolerated and is associated with excellent oncologic outcomes.

Author Disclosure: K.R. Jethwa: None. S. Jang: None. K. Gonuguntla: None. J.D. Evans: None. A. Kumar: None. C.L. Langstraat: None. M.G. Haddock: Board Member; ISIORT. I.A. Petersen: Co-chair Radiation Oncology Committee; NRG Oncology.

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TU_15_3464 - Lymph Node-Directed Simultaneous Integrated Boost in Patients with Clinically Lymph Node-Positive Cervical Cancer Treated with Definitive Chemoradiation: Clinical Outcomes and Toxicity



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