Abstract
BackgroundTo investigate whether the incorporation of 18FDG-PET into the automatic treatment planning process may be able to decrease the dose to active bone marrow (BM) for locally advanced anal cancer patients undergoing concurrent chemo-radiation (CHT-RT).MethodsTen patients with locally advanced anal cancer were selected. Bone marrow within the pelvis was outlined as the whole outer contour of pelvic bones or employing 18FDG-PET to identify active BM within osseous structures. Four treatment planning solutions were employed with different automatic optimization approaches toward bone marrow. Plan A used iliac crests for optimization as per RTOG 05–29 trial; plan B accounted for all pelvic BM as outlined by the outer surface of external osseous structures; plan C took into account both active and inactive BM as defined using 18FDG-PET; plan D accounted only for the active BM subregions outlined with 18FDG-PET. Dose received by active bone marrow within the pelvic (ACTPBM) and in different subregions such as lumbar-sacral (ACTLSBM), iliac (ACTIBM) and lower pelvis (ACTLPBM) bone marrow was analyzed.ResultsA significant difference was found for ACTPBM in terms of Dmean (p = 0.014) V20 (p = 0.015), V25 (p = 0.030), V30 (p = 0.020), V35 (p = 0.010) between Plan A and other plans. With respect to specific subsites, a significant difference was found for ACTLSBM in terms of V30 (p = 0.020)), V35 (p = 0.010), V40 (p = 0.050) between Plan A and other solutions. No significant difference was found with respect to the investigated parameters between Plan B,C and D. No significant dosimetric differences were found for ACTLSPBM and ACTIBM and inactive BM subregions within the pelvis between any plan solution.ConclusionsAccounting for pelvic BM as a whole compared to iliac crests is able to decrease the dose to active bone marrow during the planning process of anal cancer patients treated with intensity-modulated radiotherapy. The same degree of reduction may be achieved optimizing on bone marrow either defined using the outer bone contour or through 18FDG-PET imaging. The subset of patients with a benefit in terms of dose reduction to active BM through the inclusion of 18FDG-PET in the planning process needs further investigation.
Highlights
To investigate whether the incorporation of 18FDG-PET into the automatic treatment planning process may be able to decrease the dose to active bone marrow (BM) for locally advanced anal cancer patients undergoing concurrent chemo-radiation (CHT-RT)
The identification of hematopoietically active bone marrow using either magnetic resonance (MR), single-photonemission positron tomography (SPECT), 18F–fluorodeoxyglucose-labeled positron-emission tomography (18FDG-PET) or 3′-deoxy-3′-18F-fluorothymidine-labeled positron-emission tomography (18FLT-PET), gives the potential opportunity to selectively avoid the portion of BM responsible for blood cells generation [15,16,17,18]
In cases where the analysis of variance (ANOVA) resulted as statistically significant we evaluated the probability that the means of two populations were equal using Fisher-Hayter pairwise comparisons
Summary
To investigate whether the incorporation of 18FDG-PET into the automatic treatment planning process may be able to decrease the dose to active bone marrow (BM) for locally advanced anal cancer patients undergoing concurrent chemo-radiation (CHT-RT). Intensity-modulated radiotherapy (IMRT) provides robust conformality and modulation, abrupt dose fall-off and reliable consistency and may reduce the dose to organs at risk such as bladder, bowel, perineal skin, genitalia and bone marrow, potentially lowering toxicity [5]. Even with this approach, acute toxicity is not negligible, as seen in the RTOG 05–29 trial [6]. Aim of the present planning comparison study is to test the hypothesis that the use of 18FDG-
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