Pathological complete response with immunotherapy and brachytherapy to 15 metastatic liver lesions in a single patient.Materials & methods
 High dose rate interstitial brachytherapy (HDR-IBT) treatment plan for 15 metastatic liver lesions in a patient with pancreatic cancer was retrieved and analyzed for liver dose parameters and diaphragm dose.  Serial 18F-FDG PET-CT scans were reviewed for disease response assessment and left liver lobe volume.  Serial laboratory records were analyzed for liver parameters.


 Left liver lobe volume increased from 241 cm3 pre-HDR-IBT to estimated 600 cm3 after seven sessions of HDR-IBT.  Metabolic complete response (CR) and subsequently pathological CR was confirmed in the right hepatotectomy specimen for all the 15 PET-CT avid lesions treated with HDR-IBT.  Maximum diaphragm dose in a single fraction was 82 Gy.  The liver parameters were stable and patient did not develop radiation induced liver disease.


 Discussion
 This first ever reported combined treatment of immunotherapy (IT) and HDR-IBT had likely rendered this patient disease free both at local the liver and systemically.  Metabolic CR by PET-CT can be seen as early as 46 days after HDR-IBT.  Diaphragm can tolerate very high doses of radiation and repeated treatment.


 Conclusion
 PET-CT can be used for response assessment of HDR-IBT liver.  Synergistic effect of IT with HDR-IBT and it's role as bridging for liver resection has clinical potential and should be further studied in prospective trials.
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