PET Scanning for Accurate Staging of SCLC

Abstract & Commentary

Synopsis: Accurate staging is essential for providing appropriate therapy for small-cell lung cancer because patients with disease confined to one hemi-thorax (limited stage) are treated quite differently that those with more extensive disease at presentation. In the current report from a single institution, the value of pretreatment PET was determined. Of 24 patients considered by conventional imaging studies to have limited disease, two were correctly upstaged on the basis of the PET. Furthermore, 6 patients with limited-stage were shown to have more disease (albeit, still limited-stage) on the basis of the PET. This study, as well as a few other recent reports on the same subject, support the use of this evaluation in the treatment formulation phase of SCLC management.

Source: Bradley JD, et al. J Clin Oncol. 2004;22: 3248-3254.

Treatment of small-cell lung cancer is predicated upon the stage of disease, and therefore an accurate determination of the extent of disease is required to provide optimal therapy. Bradley and colleagues from Washington University report their experience with positron emission tomography with (18F) fluoro-2-deoxy-D-glucose (FDG-PET) in staging patients who were limited-stage SCLC by conventional imaging methods.

For this, 24 patients who were determined to be limited stage (disease encompassed within a reasonable radiotherapy portal, excluding bilateral supraclavicular disease) were prospectively evaluated by PET. Of these, the PET demonstrated findings consistent with extensive-stage SCLC in three. In one of these three, the increased uptake in the contralateral lung was subsequently diagnosed as fungal infection, and in that case the scan was interpreted as a false positive. Thus, the PET correctly upstaged 2 (8.3%) of 24 patients to extensive-stage disease (95% CI, 1.03-27%). The positive predictive value of PET for extensive-stage disease was 66.7% (2 of 3 patients). Of note, PET correctly identified tumor in each SCLC mass (primary or nodal) that was suspected on computed tomorgraphy (CT) imaging, thus giving a lesion-based sensitivity, relative to CT of 100%.

Additionally, PET identified unsuspected regional nodal metastasis in 6 (25%) of the 24 patients, and the radiation therapy plan was significantly altered to include the PET-positive/CT-negative nodes within the high-dose region in each of these patients. Bradley et al concluded that PET has high sensitivity for SCLC and appears to be of value for initial staging and treatment planning of patients with presumed limited-stage disease.

Comment by Willam B. Ershler, MD

In this experience from a single institution, the value of pretreatment PET staging for patients with SCLC was demonstrated. Fluorodeoxyglucose uptake was detected in all of the tumor or suspicious nodal masses detected on CT scan and in a number that were missed by CT. In 2 patients, increased uptake was discovered that had not been appreciated by conventional imaging. In one, this was in a contralateral lymph node, and in the second, increased uptake was detected in bone. In the latter case, a bone scan obtained just one week earlier was negative, but it was not until two months later that a repeat bone scan was positive in that area. In both cases the initial treatment was altered so as to address all disease, either by expanding the portal of radiation, or the use of chemotherapy.

The findings are similar to those presented in two earlier studies,1,2 inasmuch as patients with limited disease were upstaged to extensive disease in each. The Shucmacher study1 examined the role of PET in a series of SCLC patients, of which 14 were considered limited-stage prior to the PET and 7 of these were upstaged on the basis of the PET. In the Kamel report,2 3 (18%) of 17 patients with limited-stage SCLC by conventional staging, were upstaged to extensive disease on the basis of the PET.

Thus, it is apparent that PET has a role in the pretreatment evaluation of patients with SCLC, particularly for those who are considered to have limited-stage disease. By more precisely establishing disease extent we may observe more effective treatment of both limited and extensive disease.

References

1. Schumacher T, et al. Eur J Nucl Med. 2001;28:483-488.

2. Kamel EM, et al. J Nucl Med. 2003;44:1911-1917.

William B. Ershler, MD, INOVA Fairfax Hospital Cancer Center, Fairfax, VA; Director, Institute for Advanced Studies in Aging, Washington, D is Editor of Clinical Oncology Alert.