IMRT versus conventional 3DCRT on prostate and normal tissue dosimetry using an endorectal balloon for prostate immobilization.

This study was undertaken to compare prostate and normal tissue dosimetry in prostate cancer patients treated with intensity-modulated radiation therapy (IMRT) and conventional 3-dimensional conformal radiotherapy (3DCRT) using an endorectal balloon for prostate immobilization. Ten prostate cancer patients were studied using both IMRT and conventional 3DCRT at Houston Veterans Affairs Medical Center. For IMRT, the prescription was 70 Gy at 2 Gy/fraction at the 83.4% isodose line, allowing no more than 15% of the rectum and 33% of the bladder to receive above 68 and 65 Gy, respectively. For conventional 3DCRT, a 6-field arrangement with lateral and oblique fields was used to deliver 76 Gy at 2Gy/fraction, ensuring complete tumor coverage by the 72-Gy isodose line. Mean doses for prostate and seminal vesicles were 75.10 and 75.11 Gy, respectively, for IMRT and 75.40 and 75.02 Gy, respectively, for 3DCRT (p > 0.218). 3DCRT delivered significantly higher doses to 33%, 50%, and 66% volumes of rectum by 3.55, 6.64, and 10.18 Gy, respectively (p < 0.002), and upper rectum by 7.26, 9.86, and 9.16 Gy, respectively (p < 0.007). 3DCRT also delivered higher doses to femur volumes of 33% and 50% by 9.38 and 10.19 Gy, respectively, (p < 0.001). Insignificant differences in tumor control probability (TCP) values between IMRT and 3DCRT were calculated for prostate (p = 0.320) and seminal vesicles (p = 0.289). Compared to 3DCRT, IMRT resulted in significantly reduced normal tissue complication probability (NTCP) only for upper rectum (p = 0.025) and femurs (p = 0.021). This study demonstrates that IMRT achieves superior normal tissue avoidance, especially for rectum and femurs compared to 3DCRT, with comparable target dose escalation.

Impact of setup uncertainty in the dosimetry of prostate and surrounding tissues in prostate cancer patients treated with Peacock/IMRT.

The purpose of this paper was to assess the effect of setup uncertainty on dosimetry of prostate, seminal vesicles, bladder, rectum, and colon in prostate cancer patients treated with Peacock intensity-modulated radiation therapy (IMRT). Ten patients underwent computed tomography (CT) scans using the "prostate box" for external, and an "endorectal balloon" for target immobilization devices, and treatment plans were generated (T1). A maximum of +/-5-mm setup error was chosen to model dosimetric effects. Isodose lines from the T1 treatment plan were then superimposed on each patient's CT anatomy shifted by 5 mm toward the cephalad and caudal direction, generating 2 more dosimetric plans (H1 and H2, respectively). Average mean doses ranged from 74.5 to 74.92 Gy for prostate and 73.65 to 74.94 Gy for seminal vesicles. Average percent target volume below 70 Gy increased significantly for seminal vesicles, from 0.53% to 6.26%, but minimally for prostate, from 2.08% to 4.4%. Dose statistics adhered to prescription limits for normal tissues. Setup uncertainty had minimum impact on target dose escalation and normal tissue dosing. The impact of target dose inhomogeneity is currently evaluated in clinical studies.

Dosimetric predictors of xerostomia for head-and-neck cancer patients treated with the smart (simultaneous modulated accelerated radiation therapy) boost technique.

PURPOSE: To evaluate the predictors of xerostomia in the treatment of head-and-neck cancers treated with intensity-modulated radiation therapy (IMRT), using the simultaneous modulated accelerated radiation therapy (SMART) boost technique. Dosimetric parameters of the parotid glands are correlated to subjective salivary gland function. MATERIALS AND METHODS: Between January 1996 and June 2000, 30 patients with at least 6 months follow-up were evaluated for subjective xerostomia after being treated definitively for head-and-neck cancer with the SMART boost technique. Threshold limits for the ipsilateral and contralateral parotid glands were 35 Gy and 25 Gy, respectively. Dosimetric parameters to the parotid glands were evaluated. The median follow-up time was 38.5 months (mean 39.9 months). The results of the dosimetric parameters and questionnaire were statistically correlated. RESULTS: Xerostomia was assessed with a 10-question subjective salivary gland function questionnaire. The salivary gland function questionnaire (questions 1, 2, 3, 4, 6, and 9) correlated significantly with the dosimetric parameters (mean and maximum doses and volume and percent above tolerance) of the parotid glands. These questions related to overall comfort, eating, and abnormal taste. Questions related to thirst, difficulty with speech or sleep, and the need to carry water daily did not correlate statistically with the dosimetric parameters of the parotid glands. CONCLUSIONS: Questions regarding overall comfort, eating, and abnormal taste correlated significantly with the dosimetric parameters of the parotid glands. Questions related to thirst, difficulty with speech or sleep, and the need to carry water daily did not correlate statistically with the dosimetric parameters of the parotid glands. Dosimetric sparing of the parotid glands improved subjective xerostomia. IMRT in the treatment of head-and-neck cancer can be exploited to preserve the parotid glands and decrease xerostomia. This is feasible even with an accelerated treatment regimen like the SMART boost. More patients need to be evaluated using IMRT to identify relevant dosimetric parameters.

Evaluation of patients after extraperitoneal lymph node dissection and subsequent radiotherapy for cervical cancer.

OBJECTIVE: The presence of nodal metastases is the most important prognostic factor in cervical cancer. To adjust our therapy based on the true extent of the patient's disease, we performed an extraperitoneal lymph node dissection (EPLND) in all patients with cervical cancer prior to radiotherapy (RT) or radical hysterectomy. METHODS: Thirty-three patients with carcinoma of the cervix underwent EPLND. The value of this procedure as a diagnostic tool for monitoring the extension of the disease was determined. Additionally, EPLND/RT-associated treatment complications were monitored. RESULTS: The combined treatment approach of EPLND with RT or chemotherapy/RT was without major complications. Nineteen patients showed a temperature elevation, but only one patient had a fever of greater than 39.0 degrees C. Fourteen (48.3%) of 29 patients experienced some degree of proctitis or diarrhea and 3 (10.3%) experienced cystitis during the course of RT. No grade 3 or 4 acute or late genitourinary or gastrointestinal toxicities were noted. EPLND changed the clinical management for 6 patients from a radical hysterectomy to RT and for 7 patients from standard-field RT to extended-field RT. Without EPLND these 7 patients would have received RT with standard pelvic fields that would not have treated involved lymph node areas at high risk for subsequent failure. CONCLUSION: Thirteen (44.8%) of 29 patients received a different treatment than would otherwise have been administered with standard treatment planning. Therefore, we suggest that EPLND should be performed in all patients with cervical cancer prior to radical surgery or RT.

Using technology to decrease xerostomia for head and neck cancer patients treated with radiation therapy.

The treatment of head and neck cancer has evolved from conventional fields encompassing large volumes of normal tissue to focused treatment aimed at conforming the dose around the target while avoiding normal tissue. Intensity modulated radiation therapy has changed the way radiation oncologists think about head and neck cancer. Using the concepts of conformal treatment and avoidance, the therapeutic ratio can be improved and technology exploited to the patients' advantage. This is particularly evident with head and neck irradiation, where a common side effect is xerostomia. By decreasing xerostomia through conformal avoidance of the parotid glands, we can improve patient satisfaction and quality of life. In this study, xerostomia is assessed through a subjective salivary gland function questionnaire. This article examines the use of intensity modulated radiation therapy in the treatment of head and neck cancer to decrease xerostomia. The purpose of this article is to evaluate the significance of parotid gland dosimetry in relation to subjective salivary gland function.