Background
RECIST (Response Evaluation Criteria in Solid Tumors) is the accepted method for determining tumor progression. However, RECIST may not accurately estimate disease burden because the axial plane often does not produce the actual longest diameter. Volumetric measurements may be an alternative to better determine tumor size. Our aim was to compare volumetric measurements with RECIST in pancreatic ductal adenocarcinomas (PDA) and hepatocellular carcinomas (HCC).
Methods
RECIST and volumetric measurements were determined in 9 patients with metastatic PDA and 17 patients with HCC who subsequently underwent liver transplantation. Gross pathological measurements after hepatectomy were also analyzed for volumes.
Results
3-D diameter in volumetric analysis was 38% and 36% higher than RECIST diameter in PDA and HCC, respectively (p < 0.01). However, RECIST yielded 78% and 23% larger estimated tumor volumes than volumetric analysis in PDA and HCC respectively (p < 0.01). Gross pathological volume in HCC demonstrated a linear correlation with both volumetric analysis (r = 0.95, p < 0.01) and RECIST (r = 0.96, p < 0.01) but RECIST significantly overestimated gross pathological volume by an average of 28% (p < 0.01) while volumetric analysis was similar to gross pathological volume (p = 0.56). In categorizing treatment response in PDA, RECIST and volumetric analysis were in “moderate agreement” (κ = 0.49).
Conclusions
RECIST may significantly overestimate tumor burden compared to volumetric measurements in both PDA and HCC. Volumetric analysis may be the preferred method to detect tumor progression.
Intensity modulated proton therapy (IMPT) is a promising radiation therapy (RT) modality for cervical cancer treatment, especially for its potential role in reducing hematologic toxicity. IMPT dose distribution is known to be sensitive to patient anatomical changes during the treatment course. This study quantifies the effect of the anatomical change on IMPT's target coverage for cervical cancer treatment. Materials/Methods: In this IRB-approved study, 3-beam IMPT plans were generated on the planning computed tomography (CT) image for 6 enrolled patients. Three or 4 weekly CT images were obtained for each patient using the same imaging protocol in subsequent weeks after the simulation day, for a total of 21 weekly CT images. CTs of the same patient were rigidly registered to the planning CT by matching bony anatomy. The geometric cervical and nodal target volumes were the same in subsequent CTs as in the planning CT, while major organs-at-risk including bowel, bladder, and rectum were re-contoured on each weekly CT. Patient body weights at the time of each weekly CT scan were also recorded. Dose from the IMPT plan was recomputed on these weekly CTs. Dose received by at least 95% of the cervical and nodal internal target volumes (Cervical D ITV95% and Nodal D ITV95% , respectively) were compared to their planned values. Univariate analysis was performed to discover the correlation between D ITV95% to the relative changes of various anatomical factors, as well as the correlation between the anatomical factors. Results: Body weight increase was found to be significantly correlated to the decrease of both Cervical D ITV95% (Spearman rank correlation coefficient SCCZ-0.653, PZ.001) and Nodal D ITV95% (SCCZ-0.713, P<.001). Bowel volume increase was found to be significantly correlated to the decrease of Nodal D ITV95% only (SCCZ-0.502, PZ.020), but not Cervical D ITV95% (SCC Z -0.260, PZ.256). The correlations between bladder or rectum changes and target coverage were not statistically significant. Yet, there was also a significant correlation between bowel volume and body weight (SCCZ0.576, PZ.006). By deducting the bowel and bladder volume change, body weight increase was still found to be significantly correlated to the decrease of both Cervical D ITV95% (SCCZ0.613, PZ.003) and Nodal D ITV95% (SCCZ-0.646, PZ.002).
Conclusion:The decrease of target coverage in IMPT for cervical cancer was found to be significantly correlated to mainly the increase of body weight, although intercorrelations between the changes of bladder, rectum, bowel, and body weight also existed. Multivariate analysis is needed to further uncover the major anatomical factor that impacts IMPT target coverage so that patient surveillance or intervention may be applied to maintain IMPT's superior dose distribution.
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