Is there any impact of PET/CT on radiotherapy planning in rectalcancer patients undergoing preoperative IMRT?

Abstract

Background/aim: To investigate the effect of positron emission tomography-computed tomography (PET/CT)-based contouring on dosimetric parameters in rectal cancer patients undergoing preoperative intensity-modulated radiation therapy (IMRT). Materials and methods:Preoperative radiation therapy plans with conformal radiotherapy (CRT) or IMRT were created and examined according to the CT-and PET/CT-based contouring of 20 rectal cancer patients, retrospectively. Results:The target volumes delineated with PET/CT were significantly larger than the volumes created by CT (P = 0.043). Dose delivered to 98% of the planning target volume was high in IMRT planning contouring with CT and PET/CT compared with CRT planning, but the difference was not statistically significant (P = 0.056). Percent volumes receiving 105% of dose and 110% of dose were low in IMRT planning when compared with CRT (P < 0.0001 and P = 0.044, respectively). The volumes receiving 45 Gy for the small intestine, femur heads, and bladder and the maximum dose received by the bladder were significantly lower in IMRT. Conclusion:We showed that the target volumes created with PET/CT are significantly larger than the target volumes created with CT and that IMRT provides lower radiation exposure to the tumor-free tissues compared to the CRT planning. The dosimetric results primarily favor IMRT planning in rectal cancer patients and consequently present the significant alteration in target volumes.

Impact of Duration of Neoadjuvant Radiation on Rectal Cancer Survival: A Real World Multi-center Retrospective Cohort Study

“…[26][27][28] Moreover, some encouraging dosimetric results have highlighted the potential role of positron emission tomography/CT-based planning approaches in neoadjuvant radiotherapy for rectal cancer. 29 The clinical impact of such approaches is yet to be shown prospectively. 30 Several limitations should be considered when interpreting the results of this study.…”

FDG-PET/CT and MR imaging for target volume delineation in rectal cancer radiotherapy treatment planning: a systematic review

“…The only study where PET/CT delineated larger volumes, 51•74 cm 3 , than CT, 46•26 cm 3 (p = 0•043), measured the clinical target volume (CTV) which encompasses both GTV and an additional margin to cover for microscopic tumour spread. 40 Comparisons of different PET/CT volume delineation methods demonstrated that auto-delineated (contoured) volumes were significantly smaller than subjective interpretation performed using visual inspection or manual delineation. 35 Whereas, gradient-based (GR) auto-contouring method defined smaller TVs than signal-to-background ratio (SBR) auto-contouring method.…”

“…Only one 33 out of the eight studies selected for the review mentioned the study design used. [34][35][36][37][38][39][40] Two of the included studies were conducted using prospective design. The included studies involved 261 patients with LARC.…”

“…The quality assessment with regards to risk of bias within individual studies were judged 'low risk of bias' in three studies and 'at risk of bias' in five studies as three studies were judged unclear in one domain. 35,38,39 One study 33 was judged high risk in one domain, while Kilic et al 40 was judged unclear in three domains. In terms of applicability, all included studies had an overall judgement of 'low concern' (see Figure 2).…”

PET imaging in adaptive radiotherapy of gastrointestinal tumors

“…Nevertheless, Anderson et al 73 showed that the mean [ 18 F]FDG-PETbased GTV was smaller than the CT-based GTV, resulting in a change in PTV in 17% of 23 patients. The real strength however of using [ 18 F]FDG-PET to optimise target volume definition lies in the co-registration of [ 18 F]FDG-PET with other imaging techniques such as CT or MRI, to delineate a more accurate biological target volume, as was demonstrated by several groups 70,[74][75][76][77][78][79][80] . The use of co-registered [ 18 F]FDG-PET/CT indeed showed a higher uniformity between observers' definition of the GTV in a study of 6 patients 74 .…”