Poster ViewingEffect of Tumor Volume Doubling Time on Prognosis for Stage I Non–small Cell Lung Cancers

Computed tomography (CT)-based screening has been found to improve overall survival (OS) by detecting earlier stage non-small cell lung cancers (NSCLC); however, some tumors may exhibit indolent growth and additional prognostic indicators are needed for treatment management decisions. The literature suggests that lung cancers with volume doubling times (VDTs) ≥400 days might be over-diagnosed. We hypothesized better outcomes would be associated with longer VDTs. A retrospective review identified 172 consecutive patients from XXXX with Stage I NSCLC diagnosed between January 2010 - December 2012, of whom 37 met the following additional criteria for this study: ≥1 year follow-up and ≥3 month interval between ≥2 CT scans prior to treatment. Collected data included patient demographics, stage, operability status, histology, Karnofsky Performance Score, Charlson-Deyo Comorbidity Index (CDCI) grades, smoking status, and tumor size changes. VDTs were calculated using a modified Schwartz equation for exponential growth from CT-derived tumor measurements. Estimates of recurrence-free survival (RFS) and OS were calculated from the date of biopsy using the Kaplan–Meier method. Univariate Cox proportional hazards models for RFS and OS were evaluated, with significance defined as p<0.05. Median follow-up for all patients was 60.4 months, and the median time between analyzed scans was 10.2 months. The median age was 71 years (range, 46 - 86), with a median KPS of 70 and all patients having a CDCI ≥1. Fifty-nine percent (n=22) of the patients were female and 54% (n=20) exhibited VDTs ≥400 days. Seventy eight percent (n=29) were diagnosed with adenocarcinoma, 14% squamous cell, and 8% were not specified. Regarding treatment, 59% (n=22) underwent surgery, 24% received radiation, 11% received radiofrequency ablation, and 5% were observed. Improved RFS was significantly associated with a VDT ≥400 days (p=0.003), with a 5-year RFS of 100% vs. 57%. Fourteen percent (n=5) recurred locally and 1 patient had distant failure, all with VDTs <400 days. No other investigated factor was significantly associated with either OS or RFS, but 5-year OS was 74% vs. 62% (p=0.34) for patients with VDTs ≥400 and <400, respectively. Longer VDT (≥400 days) was associated with significantly improved RFS. Results suggest patients with longer VDTs have a better prognosis and perhaps less aggressive management may be taken, such as an active surveillance approach. Prospective studies with an emphasis on cause-specific survival are warranted to investigate whether it is safe to delay or avoid biopsy and treatment of indolent lesions.