Don't know for sure if this applies to melanoma, but can't see why it wouldn't.
Cancer Persister Cells
Similar to the obstacle in treatment of patients that develop resistance to antimicrobials, acquisition of resistance to anticancer drugs is a major problem in cancer therapy. Most treatments, even ones that work, fail over time because tumor cells become resistant. Different mechanisms of resistance have been described for cancer cells such as modification of drug target and active extrusion of drugs by efflux pumps and, therefore, it was largely assumed that random gene changes confer resistance to drugs [19]. However, this does not explain an increasingly observed phenomenon in cancer chemotherapy; “retreatment response” [20], [21]. In this model, it is proposed that once a small number of cells that survive exposure to drugs that killed the majority of the cells are given a “drug holiday,” they eventually regain their sensitivity to the drug [22]. These observations indicate that acquired resistance to cancer drugs may not necessarily result from stable genetic mutations but may also involve a reversible “drug-tolerant” state [22], [23].
from this article:
http://tiny.cc/meep7w
(Mostly about anti-microbials, but the above paragraph on cancer seemed very intriguing)
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