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Abstract
Objectives To compare tumor volumes & doses to organs at risk in computed tomography (CT)-derived & positron emission tomography/computed tomography (PET/CT) fusion-derived radiotherapy plans, with detection of geographic miss. Also, to evaluate the impact of using PET/CT as a diagnostic tool on the treatment decision. Design Prospective self-controlled dosimetric study of radiotherapy treatment planning for cancer esophagus patients presenting to National Cancer Institute, from December 2015 to December 2016. Methods 20 patients were enrolled in the study. Each patient had PET/CT done. Delineation of tumor target volumes was done on CT images then on PET/CT fused images. Organs at risk were also delineated. Radiotherapy treatment plans were designed for CT-derived & for PET/CT fusion-derived contouring plans. Target volumes in cubic centimeter along with doses to organs at risk were obtained. Geographic miss was detected.The results of PET/CT altered the treatment decision, from curative to palliative, in 25% of the patients, after detection of distant metastases that were missed on CT. There was a highly statistically significant reduction in the tumor volumes based on PET/CT in comparison to CT (p value <0.001). Moreover, PET/CT could detect areas of tumor involvement that were missed on CT 2geographic miss3 in 70% of the patients. In addition, the radiation doses to the heart and lungs were significantly reduced in PET/CT-derived treatment plans compared to CT-derived plans (p value <0.001). The doses to the spinal cord had a marginal significant reduction in PET/CT-derived treatment plans compared to CT-derived plans (p value = 0.08)