Tumor volume as a prognostic factor for local control and overall survival in advanced larynx cancer.

OBJECTIVES/HYPOTHESIS: Tumor volume has been postulated to be an important prognostic factor for oncological outcome after radiotherapy or chemoradiotherapy. This postulate was retrospectively investigated in a consecutively treated cohort of T3-T4 larynx cancer patients. STUDY DESIGN: Retrospective cohort study. METHODS: For 166 patients with T3-T4 larynx cancer (1999-2008), pretreatment computed tomography and magnetic resonance imaging scans were available for tumor volume delineation. Patients were treated with radiotherapy, chemoradiotherapy, or total laryngectomy with postoperative radiotherapy. Both a dedicated head and neck radiologist and the first author determined all tumor volumes. Statistical analysis was by Kaplan-Meier plots and Cox proportional hazard models. RESULTS: Patients with T3 larynx cancer had significantly smaller tumor volumes than patients with T4 larynx cancer (median = 8.1 cm(3) and 15.8 cm(3), respectively; P < .0001). In the group treated with total laryngectomy and postoperative radiotherapy, no association was found between tumor volume and local or locoregional control or overall survival. In the group treated with radiotherapy, a nonsignificant trend was observed between local control and tumor volume. In the chemoradiotherapy group, however, a significant impact of tumor volume was found on local control (hazard ratio = 1.07; 95% confidence interval = 1.01-1.13; P = .028). CONCLUSIONS: Tumor volume was not significantly associated with local control, locoregional control, or overall survival in the surgically treated group. In the group treated with radiotherapy, there was no statistically significant association, but a trend was observed between local control and tumor volume. Only in patients treated with concurrent chemoradiotherapy was a significant impact of tumor volume on local control found. LEVEL OF EVIDENCE: 4.

Tumor volume as prognostic factor in chemoradiation for advanced head and neck cancer.

BACKGROUND: Tumor volume is an important predictor of outcome in radiotherapy alone. Its significance in concomitant chemoradiation (CCRT) is much less clear. We analyzed the prognostic value of primary tumor volume for advanced head and neck squamous cell carcinoma (HNSCC) treated with CCRT. METHODS: Three hundred sixty patients treated with definitive CCRT for advanced HNSCC were selected. The pretreatment MRI or CT scan was used to calculate the primary tumor volume. Median follow-up was 19.8 months. RESULTS: The average primary tumor volume was 37.0 cm³ (range, 2.1-182.7 cm³; median, 28.7 cm³). Multivariate analysis showed a significant effect of tumor volume on local control. The hazard ratio for a local recurrence increased by 14% per 10 cm³ volume increase (95% CI, 8% to 21%). There was no significant independent effect of T and N status on local control. CONCLUSION: For advanced HNSCC, tumor volume is more powerful for predicting outcome after CCRT than TNM status.

Quantification of shape variation of prostate and seminal vesicles during external beam radiotherapy.

PURPOSE: The prostate is known to translate and rotate under influence of rectal filling changes and many studies have addressed the magnitude of these motions. However, prostate shape variations also have been reported. For image-guided radiotherapy, it is essential to know the relative magnitude of translations, rotations, and shape variation so that the most appropriate correction strategy can be chosen. However, no quantitative analysis of shape variation has been performed. It is, therefore, the purpose of this article to develop a method to determine shape variation of complex organs and apply it to determine shape variation during external beam radiotherapy of a GTV (gross tumor volume) consisting of prostate and seminal vesicles. METHODS AND MATERIALS: For this study, the data of 19 patients with prostate cancer were used. Each patient received a planning computed tomography (CT) scan and 8-12 (11 on average) repeat CT scans that were made during the course of conformal radiotherapy. One observer delineated the GTV in all scans, and volume variations were measured. After matching the GTVs for each patient for translation and rotation, a coverage probability matrix was constructed and the 50% isosurface was taken to determine the average GTV surface. Perpendicular distances between the average GTV and the individual GTVs were calculated for each point of the average GTV, and their variation was expressed in terms of local standard deviation (SD). The local SDs of the shape variation of all 19 patients were mapped onto a reference case by matching and morphing of the individual average GTVs. Repeated delineation of the GTV was done for 6 patients to determine intraobserver variation. Finally, the measured shape variation was corrected for intraobserver variation to estimate the "real" shape variation. RESULTS: No significant variations in GTV volume were observed. The measured shape variation (including delineation variation) was largest at the tip of the vesicles (SD = 2.0 mm), smallest at the left and right side of the prostate (SD = 1.0 mm), and average elsewhere (SD = 1.5 mm). At the left, right, and cranial sides of the prostate, the intraobserver variation was of the same order of magnitude as the measured shape variation; elsewhere it was smaller. However, the accuracy of the estimated SD for intraobserver variation was about half of the accuracy of the estimated SD for the measured shape variation, giving an overall uncertainty of maximum 0.6 mm SD in the estimate of the "real" shape variation. The "real" shape variation was small at the left, right, and cranial side of the prostate (SD <0.5 mm) and between 0.5 mm and 1.6 mm elsewhere. CONCLUSIONS: We developed a method to quantify shape variation of organs with a complex shape and applied it to a GTV consisting of prostate and seminal vesicles. Deformation of prostate and seminal vesicles during the course of radiotherapy is small (relative to organ motion). Therefore, it is a valid approximation in image-guided radiotherapy of prostate cancer, in first order, to correct only for setup errors and organ motion. Prostate and seminal vesicles deformation can be considered as a second-order effect.

Pretreatment probability model for predicting outcome after intraarterial chemoradiation for advanced head and neck carcinoma.

BACKGROUND: Concurrent chemoradiation is being used increasingly to treat patients with advanced-stage head and neck carcinoma. In the current study, a clinical nomogram was developed to predict local control and overall survival rates for individual patients who will undergo chemoradiation. METHODS: Ninety-two consecutive patients with UICC TNM Stage III/IV squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx, and supraglottic larynx were treated with selective-targeted chemoradiation (acronym: RADPLAT). All living patients had a minimum follow-up of 2 years. In addition to general factors, the following parameters were analyzed in a multivariable analysis: primary tumor volume, lymph node tumor volume, total tumor volume, lowest involved neck level, comorbidity, pretreatment hemoglobin level, pretreatment weight loss, and unilateral/bilateral intraarterial infusion. Relevant factors for local control and survival were analyzed using the Cox proportional hazards model. RESULTS: At 5 years, the local control and overall survival rates for the whole group were 60% and 38%, respectively. Primary tumor volume (hazard ratio [HR], 1.03; P = 0.01) and unilateral infusion (HR, 5.05; P = 0.004) were found to influence local control significantly. Using tumor volume as a continuous variable, an adjusted risk ratio of 1.026 was found, indicating that each 1-cm(3) increase in volume was associated with a 2.6% decrease in probability of local control. Primary tumor volume (HR, 1.01; P = 0.003), comorbidity (American Society of Anesthesiologists [ASA] physical status 1 vs. > 1; HR, 2.47; P = 0.01), lowest involved neck level (HR, 3.45; P = 0.007), and pretreatment weight loss > 10% (HR, 2.04; P = 0.02) were found to be significant predictors of worse overall survival. Variables from the multivariable analysis were used to develop a nomogram capable of predicting local control and overall survival. CONCLUSIONS: Tumor volume was found to play a significant role in predicting local control and overall survival in patients with advanced-stage head and neck carcinoma who were treated with targeted chemoradiation. The nomograms may be useful for pretreatment selection of patients with advanced-stage head and neck carcinoma.

A model to predict bladder shapes from changes in bladder and rectal filling.

The purpose of this study is to develop a model that quantifies in three dimensions changes in bladder shape due to changes in bladder and/or rectal volume. The new technique enables us to predict changes in bladder shape over a short period of time, based on known urinary inflow. Shortly prior to the treatment, the patient will be scanned using a cone beam CT scanner (x-ray volume imager) that is integrated with the linear accelerator. After (automated) delineation of the bladder, the model will be used to predict the short-term shape changes of the bladder for the time interval between image acquisition and dose delivery. The model was developed using multiple daily CT scans of the pelvic area of 19 patients. For each patient, the rigid bony structure in follow-up scans was matched to that of the planning CT scan, and the outer bladder and rectal wall were delineated. Each bladder wall was subdivided in 2500 domains. A fixed reference point inside the bladder was used to calculate for each bladder structure a "Mercator-like" 2D scalar map (similar to a height map of the globe), containing the distances from this reference point to each domain on the bladder wall. Subsequently, for all bladder shapes of a patient and for all domains on the wall individually, the distance to the reference point was fitted by a linear function of both bladder and rectal volume. The model uses an existing bladder structure to create a new structure via expansion (or contraction), until the expressed volume is reached. To evaluate the predictive power of the model, the jack-knife method was used. The errors in the fitting procedure depended on the part of the bladder and range from 0 to 0.5 cm (0.2 cm on average). It was found that a volume increase of 150 cc can lead to a displacement up to about 2.5 cm of the cranial part of the bladder. With the model, the uncertainty in the position of the bladder wall can be reduced down to a maximum value of about 0.5 cm in case the bladder volume increase is known. Furthermore, it was found that a change in rectal filling causes a shift of the bladder, while its shape is hardly influenced. In conclusion, we developed a model that describes the bladder shape and position as a function of the bladder volume and the rectal filling. The model accurately describes the complex shape of the bladder as it works on each domain of the bladder separately.

Application of video imaging for improvement of patient set-up.

BACKGROUND AND PURPOSE: For radiotherapy of prostate cancer, the patient is usually positioned in the left-right (LR) direction by aligning a single marker on the skin with the projection of a room laser. The aim of this study is to investigate the feasibility of a room-mounted video camera in combination with previously acquired CT data to improve patient set-up along the LR axis. MATERIAL AND METHODS: The camera was mounted in the treatment room at the caudal side of the patient. For 22 patients with prostate cancer 127 video and portal images were acquired. The set-up error determined by video imaging was found by matching video images with rendered CT images using various techniques. This set-up error was retrospectively compared with the set-up error derived from portal images. It was investigated whether the number of corrections based on portal imaging would decrease if the information obtained from the video images had been used prior to irradiation. Movement of the skin with respect to bone was quantified using an analysis of variance method. RESULTS: The measurement of the set-up error was most accurate for a technique where outlines and groins on the left and right side of the patient were delineated and aligned individually to the corresponding features extracted from the rendered CT image. The standard deviations (SD) of the systematic and random components of the set-up errors derived from the portal images in the LR direction were 1.5 and 2.1 mm, respectively. When the set-up of the patients was retrospectively adjusted based on the video images, the SD of the systematic and random errors decreased to 1.1 and 1.3 mm, respectively. From retrospective analysis, a reduction of the number of set-up corrections (from nine to six corrections) is expected when the set-up would have been adjusted using the video images. The SD of the magnitude of motion of the skin of the patient with respect to the bony anatomy was estimated to be 1.1 mm. CONCLUSION: Video imaging is an accurate technique for measuring the set-up of prostate cancer patients in the LR direction. The outline of the patient is a more accurate estimate of the set-up of the bony anatomy than the marker on the patient's abdomen.