Consideration is given to the concern that future improvements in radiation therapy which achieve increases of local control probabilities will fail to yield gains in survival, in that the new local control patients will ultimately fail because of the development of distant metastasis. The concept is that the local failure merely represents a marker of the exceptionally malignant nature of the tumor; hence, elimination of the local tumor will not affect the ultimate outcome, viz distant failure. This would mean that all tumors which fail locally after the current best radiation therapy will have established distant metastasis (subclinical) at the time of treatment of the primary tumor in stage M0 patients. Thus, a more effective local treatment would not impact on the ultimate fate of the patient. Several lines of evidence are discussed which document that tumor free survival is greater after treatment which yields higher local control probabilities than those achieved by conventional external beam radiation therapy. That is, not all of the new local control patients develop distant metastasis.(ABSTRACT TRUNCATED AT 400 WORDS)