Clinical Implication of Simultaneous Intensity-modulated Radiotherapy Boost to Tumor Bed for Cervical Cancer with Full-thickness Stromal Invasion

OBJECTIVE: The objective of this study was to retrospectively explore the clinical implications of simultaneous intensity-modulated radiotherapy (IMRT) boost to the tumor bed in cervical cancer with full-thickness stromal invasion (FTSI). PATIENTS AND METHODS: Patients diagnosed with the International Federation of Gynecology and Obstetrics (FIGO) 2009 stage IB and IIA cervical cancer with confirmed FTSI were included. Patients received pelvic IMRT from a dose of 50.4 Gy in 28 fractions with (or without) a simultaneous integrated boost (SIB) to 58.8 Gy in 28 fractions for the tumor bed. The progression-free survival (PFS), overall survival (OS), and pelvic-PFS (p-PFS) were analyzed using the Kaplan–Meier method, and independent prognostic factors were explored by Cox regression analyses. RESULTS: Patients without a tumor bed boost had a poor prognosis. The 5-year OS was 81.3% versus 58.3% and the 5-year PFS rates were 75.0% versus 57.6% (boost vs non-boost). The FIGO stage, pathology, adjuvant chemotherapy, and tumor bed boost were independent factors affecting both the 5-year OS and PFS. Subgroup analysis showed that the SIB group had a higher 5-year OS, PFS, and p-PFS for different stages, lymph node status, and risk groups than the non-SIB group. Recurrence occurred in 268 of 910 (29.5%) patients without SIB and 49 of 293 (16.7%) with SIB. Among patients with recurrence, 113 of 282 (40.1%) in the non-boost group compared with 14 of 51 (23.0%) patients in the boost group had a pelvic recurrence. Tumor bed boost resulted in an increase in the mean radiation dose to the intestine, rectum, and bladder, although there were no differences in the rates of acute and late toxicities between the 2 groups. CONCLUSION: Tumor bed boost by external beam radiotherapy (EBRT) is an effective and safe method for patients with FTSI and risk factors. Compared with the standard prophylactic radiation, tumor bed boost by EBRT was not associated with increased acute and late toxicities.