Effect of radiation dose on the prevalence of apical periodontitis--a dosimetric analysis.

OBJECTIVES: The objective of this study is to analyse the effect of the radiation dose of oral radiotherapy for cancer on the presence of apical periodontitis in patients without dental pre-screening or specific preventive measures. MATERIALS AND METHODS: All selected patients had been diagnosed with cancer in the head and neck region and presented in the dental clinic post radiotherapy with side effects (mainly radiation caries). The panoramic radiographs of these patients were examined for several parameters, including tooth decay and apical periodontitis. The total radiation dose per tooth was determined. RESULTS: A total of 36 patient files were included, which accounted for 628 teeth to be scored. Tooth decay was present in 88.2% of teeth. Radiographic signs of apical periodontitis were found in 9.1% of the teeth. Teeth with apical periodontitis had significantly more caries present. The radiation dose was significantly higher for teeth with apical periodontitis (37.2 vs. 24.9 Gy). Binary logistic regression found the radiation dose to be the only explanatory variable in the presence of apical periodontitis. CONCLUSIONS: This study found that in zones with higher radiation dose, inflammation of the jawbone due to bacterial infection of the root canal is more likely to develop. This is probably due to bone changes post radiotherapy. CLINICAL RELEVANCE: An increase of this prevalance of apical periodontitis in irradiated bone found in this study needs to be taken into account in the dental evaluation before the start of radiotherapy.

Intensity-modulated radiation therapy for prostate cancer: late morbidity and results on biochemical control.

PURPOSE: To report on late morbidity and biochemical relapse-free survival (bRFS) after intensity-modulated radiation therapy (IMRT) for prostate cancer. METHODS: Between 1998 and 2005 133 patients were treated with IMRT for T(1-4) N0 M0 prostate cancer. The median follow-up time was 36 months. In a first cohort, patients received a median planning target volume (PTV) dose of 74 Gy with a hard constraint on maximum rectum dose of 72 Gy (74R72, n=51). Later, median PTV and maximum rectum dose were increased to 76 and 74 Gy, respectively (76R74; n=82). We defined low-risk (n=20), intermediate-risk (n=70) and high-risk (n=43) groups. Androgen deprivation was given to patients in the intermediate- and high-risk group. Late gastro-intestinal (GI) and genito-urinary (GU) morbidity and biochemical relapse, in accordance with the ASTRO consensus, were recorded. RESULTS: We observed grade 2 GI (17%) and GU (19%), grade 3 GI (1%) and GU (3%) late toxicities. Except for hematuria, the median duration of side-effects was 6 months. Biochemical relapse-free survival (bRFS) at 3 and 5 years was 88% and 83%, respectively, with a significantly better 3-year bRSF for the 76R74 than for the 74R72 group (p=0.01). Five-year bRFS for patients in the low-risk, intermediate-risk and high-risk group was 100%, 94% and 74%, respectively (p<0.01). CONCLUSION: IMRT for localized or locally advanced prostate cancer combines low morbidity with excellent biochemical control.

Magnetic resonance imaging anatomy of the prostate and periprostatic area: a guide for radiotherapists.

Magnetic resonance imaging (MRI) offers superb soft tissue contrast on T2-weighted images and allows direct multiplanar image acquisition. It can show the internal prostatic anatomy, prostatic margins, and the extent of prostatic tumors in much more detail than computed tomography (CT) images. The present article reviews some key prostatic and periprostatic radiologic landmarks that can be helpful for the radiotherapist using T2-weighted MRI as an adjunct to CT in treatment planning for prostate cancer.

Interobserver delineation variation using CT versus combined CT + MRI in intensity-modulated radiotherapy for prostate cancer.

PURPOSE: To quantify interobserver variation of prostate and seminal vesicle delineations using CT only versus CT + MRI in consensus reading with a radiologist. MATERIAL AND METHODS: The prostate and seminal vesicles of 13 patients treated with intensity-modulated radiotherapy for prostatic adenocarcinoma were retrospectively delineated by three radiation oncologists on CT only and on CT + MRI in consensus reading with a radiologist. The volumes and margin positions were calculated and intermodality and interobserver variations were assessed for the clinical target volume (CTV), seminal vesicles, prostate and three prostatic subdivisions (apical, middle and basal third). RESULTS: Using CT + MRI as compared to CT alone, the mean CTV, prostate and seminal vesicle volumes significantly decreased by 6.54%, 5.21% and 10.47%, respectively. More importantly, their standard deviations significantly decreased by 63.06%, 62.65% and 44.83%, respectively. The highest level of variation was found at the prostatic apex, followed by the prostatic base and seminal vesicles. CONCLUSION: Addition of MRI to CT in consensus reading with a radiologist results in a moderate decrease of the CTV, but an important decrease of the interobserver delineation variation, especially at the prostatic apex.

Magnetic resonance assessment of prostate localization variability in intensity-modulated radiotherapy for prostate cancer.

PURPOSE: To measure prostate motion with magnetic resonance imaging (MRI) during a course of intensity-modulated radiotherapy. METHODS AND MATERIALS: Seven patients with prostate carcinoma were scanned supine on a 1.5-Tesla MRI system with weekly pretreatment and on-treatment HASTE T2-weighted images in 3 orthogonal planes. The bladder and rectal volumes and position of the prostatic midpoint (PMP) and margins relative to the bony pelvis were measured. RESULTS: All pretreatment positions were at the mean position as computed from the on-treatment scans in each patient. The PMP variability (given as 1 SD) in the anterior-posterior (AP), superior-inferior (SI), and right-left (RL) directions was 2.6, 2.4, and 1.0 mm, respectively. The largest variabilities occurred at the posterior (3.2 mm), superior (2.6 mm), and inferior (2.6 mm) margins. A strong correlation was found between large rectal volume (>95th percentile) and anterior PMP displacement. A weak correlation was found between bladder volume and superior PMP displacement. CONCLUSIONS: All pretreatment positions were representative of the subsequent on-treatment positions. A clinical target volume (CTV) expansion of 5.3 mm in any direction was sufficient to ascertain a 95% coverage of the CTV within the planning target volume (PTV), provided that a rectal suppository is administered to avoid rectal overdistension and that the patient has a comfortably filled bladder (<300 mL).

The incidence of inclusion of the sigmoid colon and small bowel in the planning target volume in radiotherapy for prostate cancer.

BACKGROUND AND PURPOSE: In radiotherapy for prostate cancer, the rectum is considered the dose-limiting organ. The incidence of overlap between the sigmoid colon and/or small bowel and the planning target volume (PTV) as well as the dose to sigmoid colon and small bowel were investigated. PATIENTS AND METHODS: The CT data of 75 prostate cancer patients were analyzed. The clinical target volume (CTV) consisted of prostate and seminal vesicles. The PTV was defined as a three-dimensional expansion of the CTV with a 10-mm margin in craniocaudal and a 7-mm margin in the other directions. All patients were planned to a mean CTV dose of at least 76 Gy. Minimum CTV dose was set at 70 Gy. Dose inhomogeneity within the CTV was kept between 12% and 17%. Sigmoid colon was defined upward from the level where the rectum turned in a transverse plane. Contrast-filled small bowel was contoured on all slices where it was visible. The presence of sigmoid colon and/or small bowel in close vicinity to or overlapping with the PTV was recorded. For each case, the dose to the sigmoid colon and small bowel was calculated. RESULTS: The PTV was found to overlap with the sigmoid colon in 60% and with the small bowel in 19% of the cases. In these patients, mean maximum dose to the sigmoid colon was 76.2 Gy (5th-95th percentile: 70.0-80.7 Gy). Mean maximum dose to the small bowel was 74.9 Gy (5th-95th percentile: 68.0-80.0 Gy). CONCLUSION: When systematically investigating the anatomic position of sigmoid colon and small bowel in patients accepted for prostate irradiation, parts of both organs were often observed in close vicinity to the PTV. Apart from the rectum, these organs may be dose-limiting in prostate radiotherapy.