Is there a dosimetric advantage of volumetric modulated arc therapy over intensity modulated radiotherapy in head and neck cancer?

OBJECTIVE

A planning study was performed to evaluate dosimetric differences between intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for head and neck cancer (HNC) for sequential boost (Seq-boost) and simultaneous integrated boost techniques (SIB).

METHODS

30 patients with HNC were included, 15 treated with SIB and 15 with Seq-Boost. For all patients both VMAT and IMRT plans were completed. The planning objective for PTV was 95% of dose covering minimum 95% of PTV; for spinal cord and brainstem Dmax was limited to 45 Gy and 54 Gy respectively. The parotids had a mean dose < 26 Gy limitation. The number of monitor units (MU) were scored for treatment delivery time efficiency.

RESULTS

Both techniques achieved the set objectives regarding PTV coverage and organ sparing. SIB plans presented a statistically significant better homogeneity for VMAT (p = 0.0096), while Seq-boost showed a statistically significant better conformity for VMAT (p = 0.0049). For parotids only SIB plans showed a lower Dmean value obtained with VMAT, while Seq-boost plans showed statistically insignificant differences. For SIB plans the MU was reduced by 33.4% with VMAT, whereas in Seq-boost plans the reduction was by 19.1%.

CONCLUSION

VMAT shows dosimetric superiority to IMRT in some cases, however an adequate coverage of the target volumes and a suitable OAR sparing can be achieved with both techniques. Though IMRT is still the standard in HNC radiotherapy, VMAT can be safely implemented, offering at least similar target coverage and organ sparing, with significantly reduced MU.