A. Rijnders

Tumor perfusion rate determined noninvasively by dynamic computed tomography predicts outcome in head-and-neck cancer after radiotherapy

PURPOSE To investigate the value of CT-determined tumor perfusion as a predictive factor of local and regional failure and cause-specific survival in head-and-neck cancer treated by radiotherapy. MATERIALS AND METHODS In 105 patients, the perfusion of a primary head-and-neck squamous cell carcinoma was estimated using dynamic CT. A contrast agent bolus was rapidly injected i.v., while during the first pass a dynamic data acquisition was performed at the level of the largest axial tumor surface. The perfusion in the selected tumor region of interest was calculated by dividing the slope of the tumor-time density curve by the maximal value in arterial density. Primary and nodal tumor volume was calculated from the CT images. All patients were treated by radiotherapy with curative intent; in 15 patients, adjuvant concomitant chemotherapy was administered. Mean follow-up time was 2.2 years. Actuarial (life-table) statistical analysis was done; multivariate analysis was performed using the Cox proportional hazards model. RESULTS When the patients were stratified according to the median perfusion value (83.5 mL/min/100 g), those with the lower perfusion rate had a significantly higher local failure rate (p < 0.05). In the multivariate analysis, perfusion rate (p = 0.01) and T category (p = 0.03) were found to be the independent predictors of local failure. Perfusion rate had predictive value regarding neither regional control nor cause-specific survival. CONCLUSIONS CT-determined tumor perfusion rate was found to be an independent predictor of local outcome in irradiated head-and-neck cancer. The results of this study confirm the hypothesis that less-perfused tumors respond poorly to radiotherapy.

Value of computed tomography as outcome predictor of supraglottic squamous cell carcinoma treated by definitive radiation therapy

PURPOSE To investigate the value of several CT-derived tumor parameters as predictors of local outcome of supraglottic squamous cell carcinoma treated by definitive radiation therapy. METHODS AND MATERIALS The pretreatment CT studies of 103 patients with supraglottic squamous cell carcinoma were reviewed for tumoral involvement of specific laryngeal anatomic subsites and extralaryngeal tumor spread. After redigitizing the films, tumor volume was calculated with the summation-of-areas technique. Mean follow-up time was 3.4 years. Actuarial statistical analysis of local and locoregional outcome was done for each of the covariates; multivariate analysis was performed using Coxs proportional hazards model. RESULTS In the actuarial analysis CT-determined primary tumor volume was significantly correlated with local recurrence rate (p < 0.001). Degree of involvement of the paraglottic space at the level of the true vocal cord (p < 0.05) and subglottic extension (p < 0.001) were also significantly correlated with local recurrence rate. In the multivariate analysis, only degree of involvement of the preepiglottic space (p < 0.01) and subglottic extension (p < 0.01) were found to be independent predictors of local recurrence. Total tumor volume was the strongest independent predictor of locoregional failure (p < 0.01). CONCLUSIONS CT-determined tumor parameters are strong predictors of local and locoregional outcome of supraglottic carcinoma treated by definitive irradiation.

The relation of CT-determined tumor parameters and local and regional outcome of tonsillar cancer after definitive radiation treatment

PURPOSE To investigate the value of CT-derived tumor parameters as predictor of local and regional outcome of tonsillar squamous cell carcinoma treated by definitive radiation therapy. METHODS AND MATERIALS The pretreatment CT studies of 112 patients with tonsillar squamous cell carcinoma were reviewed. After redigitizing the films, primary and nodal tumor volume was calculated with the summation-of-areas technique. The nodal CT aspect was graded using a 3-point scale (homogenous, inhomogeneous, and necrotic). Mean follow-up time was 33 months. Actuarial statistical analysis of local and regional outcome was done for each of the covariates; multivariate analysis was performed using Coxs proportional hazards model. RESULTS In the actuarial analysis, CT-determined primary tumor volume was significantly correlated with local recurrence rate (p < 0.05) when all patients were considered, but primary tumor volume did not predict local control within the T2, T3, and T4 category. CT-determined nodal volume was significantly related to regional outcome (p < 0.01), but nodal density was not. Total tumor volume was not significantly related to locoregional outcome (p = 0.1). In the multivariate analysis, the T and N categories were the independent predictors of local and regional outcomes, respectively. CONCLUSION Compared to other head-and-neck sites, primary and nodal tumor volume have only marginal predictive value regarding local and regional outcome after radiation therapy in tonsillar cancer.

Predicting the local outcome of glottic squamous cell carcinoma after definitive radiation therapy: value of computed tomography-determined tumour parameters

BACKGROUND AND PURPOSE The T-classification has shortcomings in the prediction of local outcome of glottic squamous cell carcinoma (SCC) treated by definitive radiation therapy. In this regard, the value of several CT-derived tumour parameters as predictors of local outcome was investigated. MATERIALS AND METHODS The pretreatment CT studies of 119 patients with glottic SCC (T1, n=61; T2, n=40; T3, n=14; T4, n=4) treated with curative intent by radiation therapy were reviewed for tumoral involvement of specific laryngeal anatomic subsites (including laryngeal cartilages). Tumour volume was calculated with the summation-of-areas technique. Actuarial (life-table) statistical analysis was done for each of the covariates; multivariate analysis was performed using the Cox proportional hazards model. RESULTS In the actuarial analysis tumour volume was significantly correlated with local recurrence rate (P=0.0062). Involvement of the cricoid cartilage (P=0.0052), anterior commissure (P=0.0203), subglottis (P=0.0481) and preepiglottic space (P=0.0134) and degree of involvement of the true vocal cord (P=0.0441) and paraglottic space at the level of the true vocal cord (P=0.0002) were also significantly correlated with local recurrence rate. In the multivariate analysis, only degree of involvement of the paraglottic space (at the level of the true vocal cord) (P=0.0001) and preepiglottic space (P=0.02) were found to be independent predictors of local recurrence. The T-category was significantly correlated with local outcome in the actuarial analysis (P=0.0001), but not in the multivariate analysis (P=0.5915). CONCLUSIONS Several CT-derived parameters are powerful predictors of local outcome in glottic cancer treated with radiation therapy; some of these parameters are stronger linked to the local control rate than the T-classification.

The utility of Spect in determining the relationship between radiation dose and salivary gland dysfunction after radiotherapy

Salivary gland scintigraphy (SGS) is used to depict salivary gland dysfunction after radiotherapy (RT). The aim of this study was to investigate the utility of SGS combined with single photon emission computed tomography (SPECT). Twenty-one patients with a carcinoma of head and neck underwent SGS before and 1 month after RT. After injection of 370 MBq 99Tcm-pertechnetate, a biplanar dynamic acquisition (12×1 min) was started, followed by a SPECT acquisition during 4 min. Carbachol was then injected and a second dynamic study (16×1 min) was performed, again followed by a SPECT acquisition. The salivary excretion fraction (SEF) was calculated both from the geometric mean planar image for each parotid and from the SPECT data for each transverse plane through the parotids. The RT-induced changes in the SEF (dSEF) were correlated with the mean radiation dose calculated using tomography-based dosimetry. The mean radiation dose to the parotids was 44 Gy (range 4.4-68.1 Gy). The mean range of the variation in radiation dose to the transverse slices within the parotids of a patient was 24 Gy (range 6.2-51.9 Gy). Considering all transverse planes through the parotids in all patients, a linear correlation was found between the dSEF calculated using SGS-SPECT and the radiation dose (r = 0.45, P = 0.0001). Thirteen patients had a variation in radiation dose within the parotids of more than 20 Gy. In nine of these a significant intra-individual correlation between radiation dose and the dSEF of the transverse parotid slices was found (r range 0.55-0.97; P value range 0.037-0.0001). In conclusion, SGS-SPECT can be used for monitoring radiation-induced parotid gland dysfunction. It offers the unique possibility for the assessment of intra-individual dose-dysfunction curves in patients with large variations in the radiation dose within the parotids.

Quality control in interstitial brachytherapy of the breast using pulsed dose rate: treatment planning and dose delivery with an Ir-192 afterloading system.

BACKGROUND AND PURPOSE In the Radiotherapy Department of Leuven, about 20% of all breast cancer patients treated with breast conserving surgery and external radiotherapy receive an additional boost with pulsed dose rate (PDR) Ir-192 brachytherapy. An investigation was performed to assess the accuracy of the delivered PDR brachytherapy treatment. Secondly, the feasibility of in vivo measurements during PDR dose delivery was investigated. MATERIALS AND METHODS Two phantoms are manufactured to mimic a breast, one for thermoluminescent dosimetry (TLD) measurements, and one for dosimetry using radiochromic films. The TLD phantom allows measurements at 34 dose points in three planes including the basal dose points. The film phantom is designed in such a way that films can be positioned in a plane parallel and orthogonal to the needles. RESULTS The dose distributions calculated with the TPS are in good agreement with both TLD and radiochromic film measurements (average deviations of point doses <+/-5%). However, close to the interface tissue-air the dose is overestimated by the TPS since it neglects the finite size of a breast and the associated lack of backscatter (average deviations of point doses -14%). CONCLUSION Most deviations between measured and calculated doses, are in the order of magnitude of the uncertainty associated with the source strength specification, except for the point doses measured close to the skin. In vivo dosimetry during PDR brachytherapy treatment was found to be a valuable procedure to detect large errors, e.g. errors caused by an incorrect data transfer.

Breast conserving treatment of Paget's disease

Between 1971 and 1984, 13 patients with histologically proven Pagets disease were treated conservatively with radiotherapy only. The disease was clinically confined to the nipple or surrounding skin, without signs of an underlying tumor. With a mean follow-up of 58.6 months (ranging between 15 and 118 months), and a median follow up of 52 months, no recurrences locally or at distance were seen. Therefore in these selected cases a mastectomy could be avoided. The results with this breast conserving management suggest a place for radiotherapy in the treatment of Pagets disease limited to the nipple.

Practical implications of backscatter from outside the patient on the dose distribution during total body irradiation

Total body irradiation (TBI) sometimes requires the set-up of the patient very close to the wall of the treatment room in order to obtain sufficiently large irradiation fields. Under these conditions, backscattered electrons can become clinically important. In the present study, an attempt was made to quantify the dose contribution to the patient from these electrons. Measurements were performed both in experimental conditions and on patients during their TBI treatment. It is concluded that, with the patient close to the wall, backscattered electrons constitute a significant (up to 20% of the dose obtained under electronic equilibrium at the exit port of the beam) radiation dose which can (under certain conditions) influence measurements of exist dose leading to an overestimation of the midline dose and contribute a superficial irradiation of the patient without therapeutic benefit. This problem can be solved by interposing a 2 cm thick low-Z absorber between wall and patient.