Dose escalated simultaneous integrated boost of gross nodal disease in gynecologic cancers: a multi-institutional retrospective analysis and review of the literature.

Purpose: Typical doses of 45-50.4 Gy used to treat regional nodes have demonstrated inadequate control of gross nodal disease (GND) in gynecologic cancer, and accelerated repopulation may limit the efficacy of a sequential boost. We reviewed outcomes of patients treated with a simultaneous integrated boost (SIB) at 2.25 Gy per fraction to positron emission tomography (PET) avid GND to evaluate toxicity and tumor control using this dose-escalated regimen.

Materials and methods: A total of 83 patients with gynecologic cancer and PET avid inguinal, pelvic, or para-aortic lymphadenopathy were treated using intensity-modulated radiation therapy (IMRT) with SIB. Primary cancers were mostly cervical (51%) and endometrial (34%), and included patients who received concurrent chemotherapy (59%) and/or brachytherapy boost (78%).

Results: Median follow-up from radiation completion was 12.6 months (range, 2.7 to 92.9 months). Median dose to elective lymphatics was 50.4 Gy (range, 45 to 50.4 Gy) at 1.8 Gy/fraction. Median SIB dose and volume were 63 Gy (range, 56.3 to 63 Gy) and 72.8 mL (range, 6.8 to 1,134 mL) at 2-2.25 Gy/fraction. Nodal control was 97.6% in the SIB area while 90.4% in the low dose area (p = 0.013). SIB radiotherapy (RT) field failure-free, non-SIB RT field failure-free, and out of RT field failure-free survival at 4 years were 98%, 86%, and 51%, respectively. Acute and late grade ≥3 genitourinary toxicity rates were 0%. Acute and late grade ≥3 gastrointestinal toxicity rates were 7.2% and 12.0%, respectively.

Conclusion: Dose escalated SIB to PET avid adenopathy results in excellent local control with acceptable toxicity.