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Negative PET-CT imaging after chemoradiation for head and neck cancer predicts response to therapy and identifies patients who don't need surgery, data from a small clinical series showed.

For assessment of tumor response at the primary site, PET-CT had a negative predictive value of 92%. However, false-positive results were common, reflected in a specificity of 54%. For neck disease, PET-CT had a specificity and negative predictive value in excess of 90%, regardless of pretreatment nodal status.

" PET-CT performed six to eight weeks after the completion of intra-arterial chemoradiation therapy for advanced squamous-cell cancer of the head and neck is a valuable tool for measuring treatment response and facilitating clinical decision making," James P. Malone, MD, of Southern Illinois University in Springfield, and colleagues reported in the November issue of Archives of Otolaryngology -- Head and Neck Surgery.

"Our data support the recent paradigm shift toward observation of patients with negative PET-CT findings after the completion of chemoradiation therapy for advanced disease," they added.

Studies of PET and PET-CT after chemoradiation therapy yielded inconsistent results, the authors continued. Moreover, the time of imaging studies remained controversial. A meta-analysis showed that PET alone less than 10 weeks after completion of chemoradiation had a loss of sensitivity but that specificity was unaffected by timing.

Few studies had examined the timing of PET-CT imaging after completion of chemoradiation, leading Malone and co-authors to perform a retrospective analysis of outcomes from a clinical series of 31 patients.

The patients underwent PET-CT imaging six to eight weeks after chemoradiation. Patients with clinical findings on physical examination, CT, or PET-CT suggestive of residual disease had surgery for pathologic assessment. Patients who had a complete clinical response were followed by routine physical examination, and no evidence of disease at six months was considered confirmation of complete clinical response.

The patients had a median follow-up of 24 months. Using presence or absence of residual or recurrent disease at follow-up, the authors calculated the sensitivity, specificity, and positive and negative predictive values PET-CT for the primary tumor site and neck.

For assessment of tumor response at the primary site, PET-CT had a sensitivity of 83%, specificity of 54%, positive predictive value of 31%, and negative predictive value of 92%. In patients with pretreatment N1 to N3 disease, post-treatment PET-CT had a sensitivity of 75%, specificity greater than 94%, positive predictive value greater than 75%, and negative predictive value of 94%.

Specificity and negative predictive value for patients with pretreatment N0 disease were 92% and greater than 92%, respectively.

The low specificity (54%) and positive predictive value (31%) for assessment of the primary tumor site reflected a high false-positive rate and resulted in an overall accuracy of 60% for PET-CT assessment of the primary site.

"A better understanding of the ability of PET-CT to accurately predict disease response at the primary tumor site and cervical lymph nodes after chemoradiation therapy may prevent unnecessary surgical interventions designed to determine the completeness of nonoperative treatment," the authors concluded.

Source: Medpage Today

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