A treatment planning study comparing helical tomotherapy with intensity-modulated radiotherapy for the treatment of anal cancer☆

Abstract 

Purpose

A planning study to compare helical tomotherapy (HT) and intensity-modulated radiotherapy (IMRT) for the treatment of anal canal cancer.

Materials and methods

Sixteen (8 males and 8 females) patients with anal cancer previously treated radically were identified. HT and IMRT plans were generated and dosimetric comparisons of the plans were performed. The planning goals were to deliver 54Gy to the tumor (PTV_54Gy) and 48Gy to the nodes at risk (PTV_Node) in 30 fractions.

Results

PTVs: HT plans were more homogeneous for both men and women. Male patients: HT vs. IMRT: D_max: 55.87±0.58 vs. 59.17±3.24 (p=0.036); D_min: 52.91±0.36 vs. 44.09±6.84 (p=0.012); female patients: HT vs. IMRT: D_max: 56.14±0.71 vs. 59.47±0.81 (p=0.012); D_min: 52.36±0.87 vs. 50.97±1.42 (p=0.028). OARs: In general, HT plans delivered a lower dose to the peritoneal cavity, external genitalia and the bladder and IMRT plans resulted in greater sparing of the pelvic bones (iliac crest/femur) for both men and women. Iliac crest/femur: the difference was significant only for the mean V10Gy of iliac crest in women (p⩽0.012). External genitalia: HT plans achieved better sparing in women compared to men (p⩽0.046). For men, the mean doses were 18.96±3.17 and 15.72±3.21 for the HT and IMRT plan, respectively (p⩽0.017). Skin: both techniques achieved comparable sparing of the non-target skin (p=NS).

Conclusions

HT and IMRT techniques achieved comparable target dose coverage and organ sparing, whereas HT plans were more homogeneous for both men and women.

Keywords: Anal cancer, IMRT, Tomotherapy