This is an interesting case of anorectal signet ring carcinoma with first presentation of an early stage disease, showing the aggressive disease and the undetectable behavior of this type of histology which can mislead diagnosis. Brain/CNS metastasis from colorectal cancer (CRC) is rare occurring in 3% of cases, and leptomeningeal carcinomatosis (LMC) is extremely rare in CRC (<0.02%). Symptoms and signs of LMC are pleomorphic and may be localized to three compartments: cerebral hemispheres, cranial nerves, and spinal cords and roots. Treatment of metastatic rectal cancer has been improving over the last few years with a lot of changes toward longer survival and improvement in quality of life and to change the disease into a chronic condition. However, in our case, the overall survival from the onset of LMC was 3 weeks only. Revising the evidence in the treatment of signet ring histology of rectal cancer, there is no specific treatment recommendation that is for this histology and for such very aggressive behavior which could be considered as a separate entity to the classic adenocarcinoma histology.
used in the calculation: needle-tip positions identified directly from the ultrasound images (data1), needle-tip positions calculated from the residual needle length (data2), and using the average of the two plus a random uncertainty between 0-5 mm (data3). Treatment plans were generated based on data2 and then recalculated for other two data sets. Results: The average tip position difference between data1 and data2 for all needles from the 40 cases was 3.6 mm while maximum values can be over 10 mm because of imaging artifacts. The average prostate V100% for the original plans was 97.3%, urethra V125% was 0.31 cc, rectum V75% was 0.24 cc and bladder V75% was 0.13 cc. The prostate V100% dropped to 96.8% after recalculated using data1, the number further dropped to 95.4% using data3. Average urethra, rectum and bladder dose kept almost unchanged. New plans were generated to cover a prostate expansion of 2 mm along needle direction as the planning target. The average prostate V100% was 97.6%, urethra V125% was 0.34 cc, rectum V75% was 0.29 cc and bladder V75% was 0.22 cc. The prostate V100% was 97.3% and 97.1% by using data 1 and data3 in this approach. Conclusion: The needle-tip position errors for TRUS-based high-dose-rate prostate brachytherapy can have a considerable dose impact on prostate dose coverage. A small margin along the needle direction can significantly reduce the dose coverage uncertainty while still maintain low dose level to critical structures.
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