JNM: PET/CT predicts head and neck cancer survival

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The use of 18F-FDG PET imaging in oral cavity squamous cell carcinoma (OSCC) staging yields suboptimal results but improves survival risk stratification, suggesting a useful but limited role for the imaging technique in the pre-treatment phases of cancer, a study published in the February issue of The Journal of Nuclear Medicine concluded.

OSCC, the most common neoplasm occurring in head and neck carcinomas, proceeds with a widely variable and thus far imperfectly understood clinical course. Although 18F-FDG PET wields prognostic value in OSCC patients and may be more accurate for lymph node staging than anatomic imaging studies, the modality’s incremental value to staging and patient management is unknown and questionable, according to Chun-Ta Liao, MD, of the department of otorhinolaryngology, head and neck surgery at Chang Gung Memorial Hospital and Chang Gung University in Taoyuan, Taiwan and co-authors. “[L]ittle has been reported about the prognostic significance of PET findings in the neck lymph nodes in patients with OSCC.”

“The objective of this study was two-fold,” Liao and colleagues continued. “The first was to prospectively assess the sensitivity and specificity of 18F-FDG PET/CT for detecting neck lymph node metastases in patients with OSCC, with pathologic results as the reference standard. The second was to investigate whether pretreatment visual scores in the neck lymph nodes may improve risk stratification.”

A total of 473 patients with histologically diagnosed OSCC and previously untreated tumors scheduled for radical surgery underwent 18F-FDG PET/CT within two weeks of surgery. Of these 473 patients, 211 presented pathological diagnoses of positive lymph nodes and the remaining 262 tested negative for neck metastases.

Of these 211 patients with confirmed metastases, 18F-FDG PET correctly diagnosed 164 cases, while accurately identifying 152 of 262 cases as negative for metastases. These findings yielded patient-based sensitivity and specificity values of 77.7 and 58.0 percent, respectively.

When adjusted for age, sex and other prognostic factors, metastatically positive lymph node PET scores were significantly and independently associated with rates of neck control (hazard ratio [HR] 1.36), distant metastasis (HR 1.44), disease-free survival (HR 1.58), disease-specific survival (HR 1.39) and overall survival (HR 1.65).

“When added to conventional prognostic factors, we found that the PET score at the neck lymph node did improve the ability to determine which patients will have a poor outcome for disease-free and overall survival and which will remain disease-free at follow-up,” Liao and colleagues wrote. “These results clearly suggest that PET at the neck lymph node could prove useful in risk stratification or targeting therapies in OSCC patients, even without major diagnostic implications during primary staging.”

Liao and co-authors acknowledged that their sample of Taiwanese-only patients, all of whom lived in a betel quid chewing area (a leaf that is chewed partly for its mild stimulant effects but is a known carcinogen), might limit the generalizability of their results. Additionally, the authors called on future studies to examine the performance of other tracers aside from 18F-FDG for OSCC staging.

“There are two principal findings in this study,” Liao and colleagues concluded. “First, we have shown that PET has suboptimal diagnostic sensitivity and specificity for primary staging of the neck in OSCC patients. However, we found that PET scores at the neck lymph node predicted clinical outcomes in a large group of OSCC patients in an endemic ‘betel quid chewing’ (one of the carcinogens of OSCC) area. Importantly, the PET score improved the accuracy of risk prediction in terms of overall and disease-free survival rates, as assessed by the c-statistics.”