SAN FRANCISCO – The more metabolically active a woman’s bone metastases of breast cancer are on imaging, the greater her risk of death, researchers reported at a breast cancer symposium sponsored by the American Society of Clinical Oncology.
In a retrospective cohort study of 269 women with newly diagnosed metastatic breast cancer, those whose bone metastases were "hotter" on a PET/CT – as assessed from maximum standardized uptake value (SUV-max) – had poorer overall survival.
Compared with their counterparts with values in the bottom tertile of SUV-max values, women with values in the middle and top tertiles were roughly two to three times more likely to die after other prognostic factors were taken into account.
"To our understanding, this is the first large retrospective series to correlate SUV-max at metastatic breast cancer diagnosis with overall survival," said lead author Dr. Komal Jhaveri of Memorial Sloan-Kettering Cancer Center, New York.
The risk of death also rose with increasing tertile of SUV-max in liver, lung, and lymph node metastases, but those associations were not significant. Their nonsignificance may have been due to the smaller numbers of patients having metastases in those sites, she said.
Session chair Dr. Robert R. Kuske, a radiation oncologist with Arizona Breast Cancer Specialists in Scottsdale, noted that SUV-max is a surrogate for how rapidly the tumor cells are proliferating and, hence, the tumor’s aggressiveness. "So there should be a strong correlation between this SUV on the PET and the Ki-67 [histologic proliferation index]," he said.
"This gives us another tool in our tool chest to evaluate how patients are going to do," he commented. "Now [oncologists] can look at a metastasis on PET, measure the SUV, and get a handle on what the future of that patient is going to be – is it going to be a rapid slide to death, or is it going to be a very slow, indolent progression maybe over 10 or 15 years. And they can tailor the therapy based on the aggressiveness of the disease."
The PET/CT is usually done to determine whether the patient has metastases, so this additional prognostic information "is a little something extra you get from the test."
Will these new findings be practice changing? "I’ll start looking at SUV values in my patients with newly diagnosed metastasis," said Dr. Kuske. "Yes, it will change my practice."
In the study, Dr. Jhaveri and her coinvestigators reviewed records for women with metastatic breast cancer diagnosed between 2001 and 2008 who had a PET/CT scan performed within 60 days of the detection of metastases; had at least one avid metastasis in bone, liver, lung, or lymph node; and had not received chemotherapy in the month before the scan. Prior or current hormonal therapy was permitted.
The investigators determined the SUV-max for individual metastatic sites. They compared values only within a given site because of known variation across sites such as liver and lung, Dr. Jhaveri explained.
The women had a median age of 58 years. The median time elapsed between primary breast cancer diagnosis and PET/CT was 2.3 years. A fifth each had triple-negative disease and HER2-positive disease.
The median duration of follow-up was 40 months. In a multivariate analysis that included other prognostic factors (grade, tumor phenotype, and visceral metastases), overall survival differed across tertiles of SUV-max for bone metastases (P = .006). Women with values in the middle and top tertiles were 1.87 and 2.67 times more likely to die, respectively, than their counterparts with values in the bottom tertile.
"Given the variation in SUV and the differential impact on survival by site, it is possible that SUV-max may not be the most optimal PET variable," Dr. Jhaveri commented. She proposed that an alternate variable, called total lesion glycolysis (TLG), which incorporates tumor lesion size, might perform better and be more informative.
"Ultimately, prospective studies are required to further delineate the role of PET/CT as a prognostic tool in metastatic breast cancer," she concluded.
Dr. Jhaveri and Dr. Kuske reported having no relevant conflicts of interest.