Outcome in disappearing colorectal cancer liver metastases during oxaliplatin-based chemotherapy.

Some colorectal cancer liver metastases (CLMs) disappear on serial imaging during chemotherapy and the optimal treatment strategy for such lesions remains undetermined. The purpose of this study was to investigate the outcome in disappearing CLMs, as few studies have focused on this topic, with conflicting results. Among 125 patients with CLMs treated with modified FOLFOX6 with or without bevacizumab, those in whom all CLMs disappeared on computed tomography were identified. Recurrence of such disappearing lesions in situ was examined on a tumor-by-tumor basis. Five (4%) patients with a total of 44 CLMs met the evaluation criteria. The median number of CLMs prior to chemotherapy was 8 (range, 2-16). The median maximal diameter of the CLMs was 1.8 cm (range, 1.0-2.4). The median time-to-disappearance of all eligible lesions was 6.5 months (range, 4.5-7.5). Histological examination of scar lesions on the liver surface revealed no viable cancer cells. Two lesions were surgically resected. During clinical follow-up of the remaining 42 lesions, in situ recurrence was observed in 8. The cumulative 1-, 2- and 3-year rates of relapse in situ were 9.1, 9.1 and 31.1%, respectively. Given the low risk of recurrence in situ, the results suggest that the sites of disappearing CLMs may be left unresected but should be carefully monitored during follow-up, with resection an option if the lesion should recur. However, to validate such a treatment strategy, further investigation with a larger series of patients is warranted.