Quantifying Upstage Rate as a Function of Delay from Diagnostic Imaging for Locally-Advanced Lung Cancer Patients

Abstract

Diagnosis and characterization of non-small cell lung cancer is done with diagnostic F18-FDG PET imaging as it is superior in sensitivity and specificity compared to conventional helical CT scans. Due to the aggressive nature of NSCLC, upstaging of disease is a concern for patients scheduled to undergo radical radiotherapy. We have reviewed our institution’s experience with treatment planning PET-CT scans and quantified the upstage rates. As part of a REB-approved study, PET-CT images acquired for treatment planning purposes. They were compared with PET-CT scans used for initial staging by two independent assessors. Patients’ age at diagnosis, sex, tumor histology, stage & date at diagnostic PET-CT, stage & date at treatment PET-CT and survival/follow-up were collected prospectively. AJCC 7th edition TNM Staging System was applied. Reported stages were compared and differences were reconciled by a third independent party. Descriptive statistics were calculated and the estimates of the upstage rates were obtained using the Kaplan-Meier product-limit method. Between October 2009 and February 2012, 28 patients were accrued to the study. The mean age was 64 years (range: 41-81). Eight were female and 19 were male. The majority of patients had Stage IIIA disease (15), with others having Stage IIIB (11), Stage IIA (1) and Stage IIB (1) disease. Predominant tumor histology was adenocarcinoma (71%). Median time between diagnostic and planning PET-CT scans was 21 days (range: 2-73). Overall upstaging occurred in 25% of patients. The TNM upstage breakdown was as follows: T-stage 7%, N-stage 14% and M-stage 11%. The 3 patients were found to have metastatic disease were switched to treatment with palliative intent. New nodal stations were found in 32% of patients, thereby necessitating a change in the treatment volumes. With the Kaplan-Meier product limit method the rate of overall upstaging increased with delay between staging and treatment planning PET-CT scans: 13% at 20 days (95% CI: 4%-95%), 33% at 40 days (95% CI: 14%-86%), and 56% at 60 days (95% CI: 29%-71%). The use of a treatment planning PET-CT demonstrated upstaging which altered patients’ treatment plans. Lengthened interval period between diagnostic PET and planning PET scans showed an increase in upstaging. Our data is consistent with two published studies which showed similar upstaging rates.