Clinical Outcomes of Sidewall/Parametrial Simultaneous Integrated Boost for Patients with Cervical Cancer

Abstract

In the treatment of cervical cancer, simultaneous integrated boost (SIB) is a common technique to deliver increased dose to gross disease in the para-aortic and pelvic nodal basins. However, SIB to the pelvic sidewall/parametria is not well characterized in the literature. We hypothesized that sidewall simultaneous integrated boost (SIB) in the treatment of cervical cancer is associated with acceptable levels of toxicity. From 1/2009-12/2018, patients who received concurrent chemoradiation with external beam radiation therapy, utilizing a sidewall SIB technique, followed by low dose rate or high dose rate brachytherapy treatment were retrospectively identified. Sidewall SIB was defined as treatment at 2.1-2.4Gy/fraction to the parametria-usually performed for those with disease width >4cm at time of treatment start. Acute and late toxicity grading was defined by the Common Terminology Criteria for Adverse Events Version 5.0. Overall survival (OS), local control, progression-free survival (PFS), and toxicity were analyzed utilizing the Kaplan Meier method. Potential associations between cumulative D2cc for bladder and rectum and time to toxicity were investigated using Cox regression. Fifty-six patients with IB2-IVB cervical cancer treated with sidewall SIB were identified, with a median follow up of 7.0 years (95% CI: 6.3, 8.3). Patients had a median age of 43 years (range: 26-68); 2 (3.6%) had FIGO stage I, 7 (12.5%) stage II, 46 (82.1%) stage III, and 1 (1.8%) stage IV disease. A majority had squamous cell histology (83.9%). Nearly all patients (96.4%) received concurrent cisplatin chemotherapy. Rates of acute grade ≥3 gastrointestinal (GI), genitourinary (GU), vaginal, and hematologic toxicity were 1.8%, 1.8%, 0%, and 15.9% respectively. Rates of late grade ≥3 GI, GU, and vaginal toxicity were 11.3%, 18.5%, and 11.1% respectively. OS and local control rates at five years were 0.61 (95% CI: 0.46, 0.73) and 0.95 (95% CI: 0.84, 0.98), respectively. Median PFS was 7.8 years (95% CI: 2.4, Not reached). Cumulative D2cc bladder was not significantly associated with time to Grade 2 or greater (HR 1.04, p = 0.33) or Grade 3 or greater (HR 1.02; p = 0.64) GU toxicity. Cumulative D2cc rectum was not significantly associated with time to Grade 2 or greater (HR 1.06, p = 0.06) or Grade 3 or greater (HR 1.08; p = 0.09) GI toxicity. Sidewall SIB is a feasible technique for dose escalation in the treatment of cervical cancer with rates of acute and late toxicity consistent with other reports.