In this study, we showed that there is no major role for PET/CT in defining stage III disease for non-IBC patients. In contrast, it is possible that accurate diagnosis by conventional imaging with PET/CT in IBC patients may affect the long-term prognosis for these patients. To our knowledge, this is the first study to show that imaging techniques can affect RFS and OS in patients with primary breast cancer.
The most important prognostic factor for primary breast cancer is stage of disease at initial diagnosis [14
]. Risk is stratified according to the TNM classification system, because many patients who are diagnosed at an early stage will experience a relapse [14
]. There is currently no definitive evidence supporting the use of combined imaging procedures to carry out baseline staging in breast cancer patients. Indeed, several studies have reported a limited value of breast cancer baseline staging, suggesting that a complete diagnostic workup should be limited to patients with a higher pretest probability of distant metastases [3
]. However, among 144 patients with LABC studied by Al-Husaini et al. [2
], initial staging evaluations identified 15 patients (10.4%) with overt metastatic disease, and additional imaging investigations revealed another four patients with metastatic disease, resulting in a 13.2% prevalence of metastasis. Because accurate staging in LABC patients is crucial, Al-Husaini et al. [2
] recommended that further research be done to define the role and sequence of newer imaging techniques such as MRI and PET [2
]. But our survival data suggest that PET/CT at baseline staging should be limited to IBC patients and not be recommended in all LABC patients.
Our study has some limitations. First, this study is a retrospective evaluation. Retrospective studies are affected by selection bias on the basis of factors such as insurance status and socioeconomic status. Second, this study was done in a single institution. Third, patient and tumor characteristics were not well balanced between the groups imaged without PET/CT and those imaged with PET/CT. For example, the group of patients imaged with PET/CT included higher percentages of patients with N3 lymph node status and with IBC than did the group diagnosed by conventional imaging only. Another limitation was that the number of patients diagnosed using PET/CT was small in our study. Moreover, the median follow-up was short (3.2 years), and the median follow-up for IBC patients was only 2.7 years. Longer follow-up times could potentially lead to a significant statistical difference in OS. Finally, not all patients underwent full conventional imaging (SS, chest CT, and radiography). However, for patients who have no symptoms, the NCCN guidelines recommend only bilateral mammogram, ultrasonography as necessary, and chest imaging.
There has been little evidence, from our study or others, that a long survival duration of patients is closely linked to accurate staging, but the ability to accurately stage patients may still have clinical benefits. First, accurate staging could allow patients to avoid unnecessary surgery. Conversely, the anatomic information contained in a PET/CT scan can help clinicians provide appropriate interventions to prevent complications such as pathologic fracture. Second, clinicians would be better able to advise patients on their prognosis. In the current NCCN guidelines, PET/CT is not used in the primary staging of LABC except in those clinical situations in which other staging studies are equivocal or suggestive of distant metastasis [4
]. Our study showed that conventional imaging plus PET/CT was associated with a longer RFS interval and a trend toward a longer OS time in IBC patients. The reason for these longer survival times may be that IBC patients have a higher rate of systemic relapse than patients with other types of breast cancer. In patients who have a high risk for distant metastases or relapse, such as those with symptoms, abnormal liver function, and abnormal alkaline phosphatase levels, conventional imaging plus PET/CT could definitively detect metastases and improve quality of life.
In summary, among patients with non-IBC stage III disease, the use of PET/CT in staging does not result in a better prognosis. However, in patients with IBC, the addition of PET/CT to the workup to rule out metastases prolongs survival. On the basis of previous studies, as well as our study, we do not recommend conventional imaging plus PET/CT for non-IBC patients, although PET/CT might be able to replace conventional imaging for detecting distant metastases in primary breast cancer staging. Our results indicate a need for a prospective study for screening distant metastases during breast cancer staging in IBC patients.