Conventional high-dose-rate brachytherapy with concomitant complementary IMRT boost: a novel approach for improving cervical tumor dose coverage.

ABSTRACT

PURPOSE: To investigate the feasibility of combining conventional high-dose-rate (HDR) brachytherapy with a concomitant complementary intensity-modulated radiotherapy (IMRT) boost for improved target coverage in cervical cancers. METHODS AND MATERIALS Six patients with cervical cancer underwent conventional HDR (C-HDR) treatment. Computed tomography (CT) and magnetic resonance imaging (MRI) scans were acquired with a CT/MRI-compatible applicator in place. The clinical target volumes (CTVs), defined as the gross target volume with a 3-mm margin and the uterus, were delineated on the CT scans, along with the organs at risk (OARs). The IMRT plans were optimized to generate dose distributions complementing those of C-HDR to cover the CTV while maintaining low doses to the OARs (IMRT-HDR). For comparison, dwell-weight optimized HDR (O-HDR) plans were also generated to cover the CTV and spare the OARs. The three treatment techniques (C-HDR, O-HDR, and IMRT-HDR) were compared. The percentage of volume receiving 95% of the prescription dose (V(95)) was used to evaluate dose coverage to the CTV, and the minimal doses in the 2.0-cm(3) volume receiving the greatest dose were calculated to compare the doses to the OARs. RESULTS: The C-HDR technique provided very poor CTV coverage in 5 cases (V(95) <62%). Although O-HDR provided excellent gross tumor volume coverage (V(95) > or =96.9%), it resulted in unacceptably high doses to the OARs in all 6 cases and unsatisfactory coverage to the whole CTV in 3 cases. IMRT-HDR not only yielded substantially improved CTV coverage (average V(95) = 95.3%), but also kept the doses to the bladder and rectum reasonably low. CONCLUSION: Compared with C-HDR and O-HDR, concomitant IMRT boost complementary to C-HDR not only provided excellent CTV coverage, but also maintained reasonably low doses to the OARs.