Ineffectiveness Of Abdominal Compression On Tumor Motion Control In Early-Stage Non-Small Cell Lung Cancer And Oligometastasis To The Lung

Purpose/Objective(s)To study the effect of abdominal compression (AC) on tumor and diaphragm motion in patients with early-stage NSCLC and limited metastases to the lung.Materials/MethodsBetween 2008 and 2011, 248 patients with early-stage NSCLC or oligometastasis to lung < 5cm were treated with stereotactic body radiotherapy (SBRT). 30 patients with assessment of tumor excursion (TE) > 1cm on 4DCT scan or those enrolled on an RTOG protocol routinely receive a second 4DCT with a commercially available AC device affixed to the patient. The AC device was applied to the maximum amount of pressure tolerated by each patient. Four points of interest (POI) (tumor, diaphragm dome, posterior diaphragm, and mid-lung (intersection point of hilum and apex) were located within each scan at points of max inhalation and max exhalation. 3D vectors (3DV) were measured where X = AP, Y = LAT, and Z = SI. Coordinates for 16 POIs (4 POI on 2 breathing phases for 2 separate CT scans, no AC and AC) were compared to define their extent of 3D excursion. POIs were analyzed for association with tumor characteristics, location, and distance from thoracic anatomy.ResultsMedian age was 64 years. Most patients had NSCLC (n = 24, 80%) while the remaining had M1 disease (n = 6, 20%). Mean tumor size was 2.6cm (range: 1.2 - 4.7cm) with a mean GTV of 10.7 cc. Tumors analyzed were primarily located in lower lobes (n = 14, 46%) and quadrants (n = 18, 60%) of the lung. Median distance from the diaphragm and anterior chest wall were 6.3cm and 10.8cm, respectively. AC decreased motion along the X axis and 3DV for the tumor by 0.1cm or 12% of mean tumor path length (p = 0.03). There was a trend towards significant reduction of TE in the SI dimension (mean reduction of Z-axis excursion by 0.25cm), however overall reduction along the Z axis was not statistically reduced by AC (p = 0.09). AC had no significant effect on excursion of the dome of the diaphragm (p = 0.62 and p = 0.19) and did not substantially reduce the ITV (0.8cc reduction with AC or 3% decrease, p = 0.14). For tumors with 3DV >/ = 0.9cm on 4DCT, AC did reduce the ITV; however this reduction was only 2.5cc, yielding an ITV reduction of 11% (p = 0.01). For these more mobile tumors, AC also had an increased impact on TE in the AP direction (32% vs. 12% decrease, p = 0.03) and 3DV length (23% vs. 14% decrease, p = 0.007), yet the absolute decrease in tumor travel was 0.18cm (X axis) and 0.31cm (3DV length). AC appeared to have the least effect on tumors located in the upper lung quadrants with a mean decrease in TE of 0.01cm vs. 0.21cm for tumors closer to diaphragm, however this difference was not significant (p = 0.12).ConclusionsAbdominal compression has minimal effect on reduction of ITV and tumor excursion, even in highly selected tumors with greater than or equal to 0.9cm 3D vector motion on 4DCT. Purpose/Objective(s)To study the effect of abdominal compression (AC) on tumor and diaphragm motion in patients with early-stage NSCLC and limited metastases to the lung. To study the effect of abdominal compression (AC) on tumor and diaphragm motion in patients with early-stage NSCLC and limited metastases to the lung. Materials/MethodsBetween 2008 and 2011, 248 patients with early-stage NSCLC or oligometastasis to lung < 5cm were treated with stereotactic body radiotherapy (SBRT). 30 patients with assessment of tumor excursion (TE) > 1cm on 4DCT scan or those enrolled on an RTOG protocol routinely receive a second 4DCT with a commercially available AC device affixed to the patient. The AC device was applied to the maximum amount of pressure tolerated by each patient. Four points of interest (POI) (tumor, diaphragm dome, posterior diaphragm, and mid-lung (intersection point of hilum and apex) were located within each scan at points of max inhalation and max exhalation. 3D vectors (3DV) were measured where X = AP, Y = LAT, and Z = SI. Coordinates for 16 POIs (4 POI on 2 breathing phases for 2 separate CT scans, no AC and AC) were compared to define their extent of 3D excursion. POIs were analyzed for association with tumor characteristics, location, and distance from thoracic anatomy. Between 2008 and 2011, 248 patients with early-stage NSCLC or oligometastasis to lung < 5cm were treated with stereotactic body radiotherapy (SBRT). 30 patients with assessment of tumor excursion (TE) > 1cm on 4DCT scan or those enrolled on an RTOG protocol routinely receive a second 4DCT with a commercially available AC device affixed to the patient. The AC device was applied to the maximum amount of pressure tolerated by each patient. Four points of interest (POI) (tumor, diaphragm dome, posterior diaphragm, and mid-lung (intersection point of hilum and apex) were located within each scan at points of max inhalation and max exhalation. 3D vectors (3DV) were measured where X = AP, Y = LAT, and Z = SI. Coordinates for 16 POIs (4 POI on 2 breathing phases for 2 separate CT scans, no AC and AC) were compared to define their extent of 3D excursion. POIs were analyzed for association with tumor characteristics, location, and distance from thoracic anatomy. ResultsMedian age was 64 years. Most patients had NSCLC (n = 24, 80%) while the remaining had M1 disease (n = 6, 20%). Mean tumor size was 2.6cm (range: 1.2 - 4.7cm) with a mean GTV of 10.7 cc. Tumors analyzed were primarily located in lower lobes (n = 14, 46%) and quadrants (n = 18, 60%) of the lung. Median distance from the diaphragm and anterior chest wall were 6.3cm and 10.8cm, respectively. AC decreased motion along the X axis and 3DV for the tumor by 0.1cm or 12% of mean tumor path length (p = 0.03). There was a trend towards significant reduction of TE in the SI dimension (mean reduction of Z-axis excursion by 0.25cm), however overall reduction along the Z axis was not statistically reduced by AC (p = 0.09). AC had no significant effect on excursion of the dome of the diaphragm (p = 0.62 and p = 0.19) and did not substantially reduce the ITV (0.8cc reduction with AC or 3% decrease, p = 0.14). For tumors with 3DV >/ = 0.9cm on 4DCT, AC did reduce the ITV; however this reduction was only 2.5cc, yielding an ITV reduction of 11% (p = 0.01). For these more mobile tumors, AC also had an increased impact on TE in the AP direction (32% vs. 12% decrease, p = 0.03) and 3DV length (23% vs. 14% decrease, p = 0.007), yet the absolute decrease in tumor travel was 0.18cm (X axis) and 0.31cm (3DV length). AC appeared to have the least effect on tumors located in the upper lung quadrants with a mean decrease in TE of 0.01cm vs. 0.21cm for tumors closer to diaphragm, however this difference was not significant (p = 0.12). Median age was 64 years. Most patients had NSCLC (n = 24, 80%) while the remaining had M1 disease (n = 6, 20%). Mean tumor size was 2.6cm (range: 1.2 - 4.7cm) with a mean GTV of 10.7 cc. Tumors analyzed were primarily located in lower lobes (n = 14, 46%) and quadrants (n = 18, 60%) of the lung. Median distance from the diaphragm and anterior chest wall were 6.3cm and 10.8cm, respectively. AC decreased motion along the X axis and 3DV for the tumor by 0.1cm or 12% of mean tumor path length (p = 0.03). There was a trend towards significant reduction of TE in the SI dimension (mean reduction of Z-axis excursion by 0.25cm), however overall reduction along the Z axis was not statistically reduced by AC (p = 0.09). AC had no significant effect on excursion of the dome of the diaphragm (p = 0.62 and p = 0.19) and did not substantially reduce the ITV (0.8cc reduction with AC or 3% decrease, p = 0.14). For tumors with 3DV >/ = 0.9cm on 4DCT, AC did reduce the ITV; however this reduction was only 2.5cc, yielding an ITV reduction of 11% (p = 0.01). For these more mobile tumors, AC also had an increased impact on TE in the AP direction (32% vs. 12% decrease, p = 0.03) and 3DV length (23% vs. 14% decrease, p = 0.007), yet the absolute decrease in tumor travel was 0.18cm (X axis) and 0.31cm (3DV length). AC appeared to have the least effect on tumors located in the upper lung quadrants with a mean decrease in TE of 0.01cm vs. 0.21cm for tumors closer to diaphragm, however this difference was not significant (p = 0.12). ConclusionsAbdominal compression has minimal effect on reduction of ITV and tumor excursion, even in highly selected tumors with greater than or equal to 0.9cm 3D vector motion on 4DCT. Abdominal compression has minimal effect on reduction of ITV and tumor excursion, even in highly selected tumors with greater than or equal to 0.9cm 3D vector motion on 4DCT.