Gender differences: SUVmax may predict survival in men w/ lung cancer, not women

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Among a cohort of men and women with surgically treated early non-small cell lung cancer, maximum standard uptake value (SUV max) independently predicted overall survival for men, but not for women, according to a study published online Sept. 14 in Journal of Nuclear Medicine.

“Accurate prognostication for patients with non-small cell lung cancer (NSCLC) is both clinically important and elusive,” wrote Zoe Wainer, MD, from the department of surgery at St. Vincent’s Hospital, University of Melbourne in Melbourne, Australia, and colleagues. Previous research has suggested that 18F-FDG uptake may correlate with a more aggressive lung tumor phenotype. However, researchers had not etsablished the role of SUV max in clinical practice.

Wainer and colleagues hypothesized that SUV max could stratify patient survival and aimed to investigate its clinical utility by sex. Thus, the researchers retrospectively analyzed the records of 189 patients (127 men, 62 women) who underwent surgical resection of NSCLC between 2001 and 2009 and a PET/CT exam no more than four weeks prior to surgery.

Among the study population, men were more likely than women to have a smoking history, poorly differentiated tumors and higher pathologic Tumor Node and Metastasis stage. However, researchers found no sex differences with respect to histology type, Eastern Cooperative Oncology Group score, diabetes or ethnicity.

Overall five-year survival was 68.2 percent for women and 54.6 percent for men, and disease-free five-year survival was 57.9 percent for women and 41.6 percent for men, according to the researchers.

SUV max correlated with overall survival in the whole cohort in univariate and multivariate analyses. “In univariate analysis, SUV max correlated significantly with overall survival for men but not for women.”

Researchers determined a receiver-operating characteristic curve SUV max cutoff of 8. When they applied it to a subcohort of 147 patients with lean body mass SUV max data, Wainer and colleagues found the cutoff predicted survival for men in multivariate analysis but not for women. These findings indicate that body composition was not a factor in sex differences.

“After sex disaggregation of our data, the HR [hazard ratio] for men with a high SUV max was 3.42 (P < 0.001), whereas the HR for women was not significant, irrespective of SUV max cutoff calculation method (P= 0.77),” wrote Wainer et al.

The researchers confirmed that lung cancer behaves differently in men and women, and survival differences suggest divergent tumor biology. “Molecular differences between NSCLC in men and women, such as capacity for DNA repair and rates of driver mutations, may contribute to differences in the natural history of NSCLC between the sexes,” wrote the researchers.

Wainer and colleagues called for additional research into possible mechanisms of sex differences in tumor biology and concluded: “Identification of factors resulting in noncorrelation in women may provide insight into a disease phenotype or risk profile in men for which SUV max is not prognostic and may provide novel insight into the biology of NSCLC.”