Maximum standardized uptake value (SUVmax) of lymph nodes on a pretreatment PET/CT exam may be an independent prognostic factor for breast cancer recurrence among women with invasive ductal carcinoma, according to a study published in the September issue of Journal of Nuclear Medicine.

Although approximately one-third of women diagnosed with breast cancer eventually die from the disease, it is a remarkably heterogeneous disease, according to Bong-Il Song, MD, from the department of nuclear medicine at Kyungpook National University Hospital in Daegu, South Korea, and colleagues. “Therefore, precise prediction of prognosis and selection of optimal treatment are important.”

Lymph node involvement is recognized as a prognostic factor, but is difficult to assess with precision. The researchers hypothesized that FDG uptake in lymph nodes measured by SUVmax might provide prognostic value and designed a study to investigate the relationship between nodal SUVmax and known prognostic factors. A secondary aim of the study was to determine the prognostic value of nodal SUVmax for disease-free survival.

The study population included 65 women (mean age 49.4 years) diagnosed with invasive ductal carcinoma who underwent 18F-FDG PET/CT from June 2006 to March 2009. Patients underwent treatment and were followed for a range of 21 to 57 months. Two nuclear medicine physicians interpreted the exams and reached consensus for all patients.

Among the patients, 53 were disease-free and 12 had disease recurrence during the follow-up period.

While both the primary-tumor and nodal SUVmax were higher in patients with recurrence, the nodal SUVmax was significantly higher.

The mean nodal SUVmax of the 65 patients was 2.5. “The mean nodal SUVmax of the disease-free group was 1.9, and that of the recurrence group was 5.2,” wrote Song and colleagues. The mean primary tumor SUVmax of the disease-free group was 5.5. In the recurrence group, the mean primary tumor SUVmax was 8.9.

Receiver operating characteristic curve analysis demonstrated that a nodal SUVmax of 2.8 and primary tumor SUVmax of 6.9 provided the optimal cutoffs for predicting disease-free survival.

Song and colleagues noted the advantages of PET for obtaining information about lymph node involvement. It is noninvasive and can be obtained prior to surgery, and also indicates the degree of tumor glucose metabolism, which may be a useful adjunct to conventional preoperative clinical assessment.  

The researchers offered several possible reasons to explain why SUVmax might predict outcomes. Previous research has linked increased FDG uptake with the density of viable cancer cells, microvessel density and proliferative activity; and lymph node involvement is a key prognostic factor in breast cancer.

“One of the important roles of molecular imaging in cancer research is to noninvasively predict precise prognosis. Our results showed significant improvement in the accuracy of risk prediction for disease-free survival rates when nodal SUVmax was added to well-known established risk factors,” study author Sang-Woo Lee, MD, PhD, said in a release. “Our study suggests that F-18-FDG PET/CT could yield useful information for risk stratification and treatment strategies in invasive ductal carcinoma patients with axillary lymph node involvement.”

However, the findings are hampered by three limitations, according to Song et al. The study included only node-positive patients, SUV of small metastatic lymph nodes may be underestimated and the short follow-up precluded survival analysis and prognostic significance after relapse.

“Thus, further prospective multinstitutional studies are required for nodal SUVmax to be accepted as a decisive prognostic factor for disease recurrence in invasive ductal carcinoma patients with axillary lymph node involvement,” wrote Song and colleagues.