How do you approach a young patient with undifferentiated pleomorphic sarcoma of the upper extremity who developed ifosfamide-induced nephrotoxicity after two cycles of adjuvant AIM chemotherapy?

In the adjuvant setting, I would suggest to stop further therapy and observe the patient. There is no clear survival benefit with the use of adjuvant therapy. However, I do say this with the knowledge that Sarculator-based analysis of EORTC-STBSG 62931 has demonstrated an OS benefit in patients receiving AIM-75. (Pasquali et al., PMID 30690293). Having said that, I would not recommend risking nephrotoxicity with Ifosfamide any further. Single-agent doxorubicin or doxorubicin-dacarbazine is not recommended as an adjuvant therapy. 

At this point, one has to be cognizant of keeping the organ function intact to prevent further deterioration and allow the patient to participate in clinical trials, should the need arise. I also send patients to nephrology to optimize medical management for ifosfamide-induced nephrotoxicity. I also avoid iodinated contrast for response assessment and substitute with PET scan (if insurance allows) or CT chest w/o contrast + Gadolinium-based MRIs- most trials will accept CT/MRI as effective substitutes for imaging. 

If the treatment is strictly adjuvant, OK to stop the chemotherapy. Might consider radiotherapy if not done pre-op.