Paradoxical Response to Neoadjuvant Therapy in Undifferentiated Pleomorphic Sarcoma: Increased Tumor Size on MRI Associated with Favorable Pathology

Figures

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  Figure 1. Flowchart for UPS subject inclusion and exclusion.

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  Figure 2. A 77-year-old woman with marked treatment response (pR), diagnosed with UPS with FNCLCC Grade III. (A) Pre-treatment core biopsy. The H&E-stained pathology slide shows abundant viable tumor cells colored dark purple (×100 magnification). (B) Contrast-enhanced fat-saturated T1-w MRI shows a heterogeneous, enhancing mass deep-seated in the right posterior compartment of the thigh. (C) Post-radiotherapy (5000 cGy/25 fractions) resection specimen. H&E-stained pathology slide (×40 magnification) shows tumor bed with marked treatment effect and 0% viable tumor. (D) Contrast-enhanced fat-saturated T1-w MRI showed a moderate increase in size compared to baseline and large, central areas of non-enhancing tissue, likely necrotic or hemorrhagic areas. Increase in maximum tumor diameter was +43%, +26%, and +21% in X, Y, and Z directions. (E) A 65-year-old woman with mild treatment response (pNR). Pre-treatment core biopsy. H&E pathology slide (×40 magnification) shows a spindle cell and pleomorphic cell population, diagnostic of UPS (Grade II). (F) Contrast-enhanced fat-saturated T1-w MRI shows a round-shaped deep-seated mass in the right posterior thigh, with small central areas of…

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  Figure 3. Percentage change in tumor sizes across the main axes (X, Y, and Z) for both therapies and within each therapeutic subgroup, including radiotherapy and chemoradiation, for responders (pR) and non-responders (pNR). Each plot shows a p-value for the mean difference (pR-pNR) between responders and non-responders, calculated using Tukey’s HSD test.

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  Figure 4. Percentage change in tumor sizes across the main axes (X, Y, and Z) for responders and non-responders, comparing patients with and without recurrence. Each plot shows a p-value for the mean difference between patients with (Yes) and without (No) recurrence, calculated using Tukey’s HSD test.

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  Figure 5. Upper row: A 71-year-old woman diagnosed with UPS (Grade II) in her right forearm. Upper row: Pre-treatment MRI shows a superficial, oval-shaped mass characterized by irregular margins and intense contrast-enhancement. After unsuccessful nCRT (viable cells 80%), size did not change significantly, nor the contrast-enhancement. Three years after surgical excision with margins of excision negative for tumor, an irregular area of nodular contrast-enhancement within the surgical bed was described at imaging. It was then confirmed histologically to be a recurrent UPS (Grade III), and the patient underwent re-excision. Lower row: An 84-year-old woman diagnosed with UPS (Grade III) in her left anterior thigh. Pre-treatment MRI shows a deep-seated round-shaped mass characterized by intense enhancement. After successful nCRT (viable cells <1%), the lesion did not show any enhancement areas but a slight increase in size likely due to hemorrhagic and necrotic content. The surgery was successful, with margins of resection negative for malignancy. Sixteen months after resection, a local recurrence was clinically suspected. After imaging and core-needle biopsy, final diagnosis of locally…

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  Figure 6. ROC curves illustrating the performance of different tumor size change cutoffs in predicting (A,B) response to radiotherapy and (C,D) recurrence among non-responders. The optimal cutoff (solid black dot) for each ROC curve was determined by maximizing the product of sensitivity and specificity.