A comparison of dosimetric and clinical parameters between different IMRT boost techniques in preoperative rectal cancer.

Abstract

Purpose: In this study we compared the clinical and dosimetric outcomes of simultaneous integrated boost intensity modulated radiation therapy (SIB-IMRT) and sequential boost (SEQ-IMRT) techniques in preoperative rectal cancer (RC).

Methods: We analyzed 67 preoperative RC patients who received RT with Helical TomoTherapy (HT) device. 27 of patients were irradiated with SEQ-IMRT and 40 were irradiated with SIB-IMRT technique. The primary tumor and involved lymph nodes were simultaneously treated using the SIB-IMRT (50.4Gy/25 fraction). SEQ-IMRT delivered 45Gy/25 fractions to primary tumor (involved lymph nodes) and 5.4Gy/3fractions to boost volume. Dosimetric parameters, acute toxicities and 5year overal survival (OS), disease-free survival (DFS) and local control (LC) between two techniques were compared.

Results: In the SIB-IMRT group planning treatment volume (PTV) homogeneity index (HI) was better than in the SEQ-IMRT group. PTV doses of Dmax for SEQ-IMRT group were higher than the SIB-IMRT group (p<0.05). The bladder doses of Dmax in the SIB-IMRT group were higher than SEQ-IMRT group (p<0.005). There were no significant differences in other dosimetric parameters between groups. Median follow up was 29.06 months (range 4.3-92.07) and 36.46 months (range 8.7-79.6) in the SIB-IMRT and SEQ-IMRT groups, respectively. No significant difference was found between the SIB-IMRT and SEQ-IMRT groups in acute toxicity (p=0,909). Five-year OS, DFS and LC were 73.15%, 66.75% and 75.55% in SIB-IMRT group and 65.19%, 55.53% and 60.22% in the SEQ-IMRT group, respectively. No statically significant differences were found between the two groups regarding 5-year OS, DFS and LC.

Conclusions: SIB-IMRT and SEQ-IMRT tecniques provided similar outcomes for dosimetric and clinical results for RC in HT treatment.