One of the questions that comes up fairly frequently is what to make of a "mixed response" to systemic therapy: after several weeks or months of treatment, a scan shows some areas of known disease shrinking, but others are growing.  Why might this happen? What does it mean? And what should it lead us to do?

Mrs. M was a 46 year-old woman who, despite having never smoked, was diagnosed with metastatic adenocarcinoma of the lung. She had a nice initial response to chemotherapy, and when she eventually progressed, she was treated with Iressa (an EGFR inhibitor similar to Tarceva which is no longer available in the US). To both her and her doctor’s delight, she had near resolution of her lung mass and most of her liver lesions after 2 months on Iressa. Unfortunately, after remaining stable for 10 months, her restaging CT scan showed one lesion in the liver was growing.