Simultaneous integrated boost in locally advanced cervical cancer patients ineligible for brachytherapy: Dosimetric comparison of VMAT versus helical tomotherapy.

OBJECTIVE

This retrospective, exploratory study evaluated the dosimetric comparison and feasibility of simultaneous integrated boost (SIB) delivered with volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) in patients with locally advanced cervical cancer ineligible for brachytherapy (BRT).

METHODS

This exploratory study involved dosimetric treatment planning based on data from 10 patients diagnosed with locally advanced cervical cancer. SIB plans delivering 77.5 Gy to the primary tumor and 45 Gy to elective regions in 25 fractions were generated using VMAT and HT techniques. SIB plans were created using the VMAT technique in the Monaco 5.51 treatment planning system (TPS) (Elekta, Stockholm, Sweden) and the HT technique in the Precision 3.3.1 TPS (Accuray, Madison, Wisconsin, USA). Planning target volume (PTV) coverage, organ-at-risk (OAR) doses, and dose-volume metrics of SIB plans were compared between the VMAT and HT techniques using appropriate statistical tests.

RESULTS

The median PTV77.5 volume was 83.4 cc (range: 14.9-218.2 cc). For PTV77.5, HT yielded a higher mean dose (79.52 Gy vs. 77.54 Gy, p = 0.001) and a superior conformity index (0.81 vs. 0.71, p < 0.001). Bladder dose metrics were significantly lower with HT, including V53.28 Gy (5.66% vs. 10.31%; p = 0.006) and D2cc (66.47 Gy vs. 70.60 Gy; p < 0.05), while bowel V36.89 Gy volume was also reduced (94.03 cc vs. 115.13 cc; p = 0.038). No statistically significant differences were observed in rectal, sigmoid, or femoral head dose parameters. Beam-on time was significantly longer for HT than for VMAT (11.0 min vs. 3.4 min, p = 0.005).

CONCLUSIONS

BRT remains the standard of care for cervical cancer. For patients ineligible for BRT, SIB is dosimetrically feasible; in this exploratory planning study, HT-SIB provided better target coverage and OAR sparing than VMAT-SIB. Prospective multicenter validation is necessary before wider clinical adoption.