Significance and therapeutic implications of tumor regression following radiotherapy in patients treated for squamous cell carcinoma of the oropharynx and pharyngolarynx

The prognostic significance of tumor regression following radiotherapy was evaluated in 1,897 patients with oro- and pharyngolaryngeal cancer. Complete tumor regression occurred in 62% and 80% at the end of treatment and 2 months later, respectively. Complete regression was significantly higher for early tumors than for advanced stages and for exophytic lesions compared to deeply infiltrative cancers. Depending on tumor location, 75% to 90% of T1, T2 stages and 50% to 80% of more advanced tumors were locally controlled in patients who experienced complete tumor regression at 2 months. The local failure rate was at least 80% for those who did not have complete regression. The local failure rate for the incomplete responder was the same for early and advanced tumors. Complete tumor clearance following radiotherapy is a reliable indicator of permanent local control. Tumor regression after a dose of 5,000 to 5,500 cGy should be used as a guide to select patients who could be treated by either radical irradiation or surgery.