Assessment of lung cancer response after nonoperative therapy: Tumor diameter, bidimensional product, and volume. A serial CT scan-based study

Purpose: Tumor response after nonoperative lung cancer therapy is tradition ally evaluated by bidimensional measurement of maximum tumor diameters. The purpose of this analysis is to investigate whether tumor largest dimension (based on RECIST [Response Evaluation Criteria In Solid Tumors]), bidimens ional tumor product, and volume correlate with each other in evaluating tum ors of patients with locally advanced non-small-cell lung cancer (NSCLC). I n addition, the pace of locally advanced NSCLC volumetric response over tim e, as well as the prognostic value of tumor size, was assessed in this repo rt with software-assisted evaluation of sequential tumor measurement. Methods and Materials: Patients with locally advanced NSCLC treated with th oracic radiotherapy (RT) with or without chemotherapy were included, if the following were available: a pretreatment computed tomography (CT) simulati on and at least two follow-up diagnostic thoracic CT scans taken at our ins titution after 1996 that were available in Dicom format for electronic tran sfer of images from diagnostic radiology to a computer terminal with commer cial statistics software (AcQsim/CMS Focus). Primary lung tumor and grossly involved lymph nodes were contoured manually on pre-RT axial images and on all follow-up CT scans. Tumor/lymph node largest dimensions, bidimensional products (BP), and volumes were measured using the same software. Data wer e presented as percent change in volume or unidimensional and bidimensional measurements, with the CT simulation measurements serving as baseline. Results: A total of 22 patients were evaluated. The median thoracic RT dose was 62.4 Gy (range: 50.0-69.6), and all patients had a Karnofsky performan ce status greater than or equal to 80. Chemotherapy (mostly carboplatin/pac litaxel) was given to 17 patients. Nineteen patients had Stage III NSCLC; I patient was in Stage I, 1 was in Stage IV, and I was recurrent. A total of 107 thoracic CT scans (22 pretreatment and 85 follow-up), averaging 4.9 sc ans per patient, were analyzed. Tumors reached the smallest volume at a med ian of 11.0 months from RT completion in all patients, 8.5 months in patien ts who subsequently failed locally (n = 8), and 11.9 months in those who di d not fail locally. Failure rates were as follows: in-field, 36% (8/22); in trathoracic (lung nodules, effusion, pleura), 55% (12/22); and distant, 50% (11/22). Eleven patients are still alive, 4 free of disease. Overall media n survival time (MST) is 27.3 months. The median initial tumor volume was 8 8.0 cc (range: 3.8-218) for all patients; median BP was 33.0 cm(2) (range: 3.1-112.1), and median tumor largest dimension was 7.6 cm (range: 2.2-13.5) . The MST of patients with initial tumor volume less than or equal to 63.0 cc (n = 9) was >53.0 months and of those with tumor volume >63.0 cc was 17. 3 months. The MST of patients (n = 6) with initial bidimensional tumor prod uct less than or equal to 16 cm(2) was >53.0 months and of those with tumor product >16 cm(2) was 17.3 months. The MST of patients with largest initia l dimension less than or equal to4 cm was >53.1 months and of those with la rgest dimension >4 cm was 25.0 months. At 24 months, 79% of patients with a tumor volume less than or equal to 124.0 cc (n = 18) had locally controlle d tumors, vs. 0% of patients with tumor volumes >124.0 cc. At the same time point, 93% of patients with BP less than or equal to 40 cm(2) were locally controlled, vs. 0% of those with BP >40 cm(2); 100% of patients with tumor dimensions: less than or equal to7.5 cm were locally controlled, vs. 40% o f those with dimensions >7.5 cm. The partial responses in our series (asses sed as the best response obtained during observation period) were as follow s: 4 patients assessed based on either dimension only, product only, or vol ume only; 15 partial responses based on dimension or product; 16 partial re sponses based on volume alone; 3 cases of no tumor response, based on dimen sion or product; and 2 cases based on tumor volume alone. That represents g ood to excellent agreement among all three methods of measurement. Conclusions: (1) The response of locally advanced NSCLC to nonoperative the rapy is a slow process, with tumor volumes reaching their nadir several mon ths after treatment. (2) Smaller initial tumor size, as measured by largest tumor dimension, bidimensional product, or tumor volume, is associated wit h better local control and survival than larger initial measurements. (3) A ny of the three tumor measurements (largest dimension, bidimensional produc t, or volume) can be used as a reliable tool in assessing lung cancer respo nse to nonoperative therapy. This confirms further the validity of RECIST a nd does not suggest that tumor volume is significantly superior for respons e evaluation. (C) 2001 Elsevier Science Inc.