Tumor volume changes on serial imaging with megavoltage CT for non-small-cell lung cancer during intensity-modulated radiotherapy: How reliable, consistent, and meaningful is the effect?

Conclusions: Although gross tumor regression during treatment may be objectively measured using MVCTs, substantial volumetric decrease occurs only in a minority. The clinical significance of this regression is questionable, because there is no way to document histologic tumor clearance, and therefore field reductions during radiotherapy cannot be recommended.