External Beam Radiotherapy For Prostate Cancer Research Articles

Implementation and validation of a 3-dimensional deformable registration algorithm for targeted prostate cancer radiotherapy

The daily position and shape changes of the prostate pose an obstacle to reducing the safety margin and decreasing radiation to the surrounding normal tissues during prostate cancer external beam radiotherapy. The daily prostate deformation also complicates accurate dose tracking. The uncertainty in dosimetry is further accentuated when intraprostatic targets based on molecular imaging need to be treated to a desired dose. Against this background, we have implemented and validated a 3-dimensional deformable registration algorithm to aid targeted prostate radiotherapy.

Risk of bladder cancer following external beam radiation for prostate cancer

Abstract Introduction: Increased rates of secondary malignancies of the bladder have been reported after external beam radiation therapy (EBRT) for gynecologic malignancies with relative risks varying from 3–57. This study will determine if there is increased risk of subsequent bladder cancer for men treated with EBRT for prostate cancer from 1970–1999. Methods: We retrospectively reviewed the Mayo Clinic Cancer Registry for patients who received EBRT for prostate cancer, and isolated a cohort of patients with 10,000 man-years of follow-up after radiation. Medical histories of patients who developed subsequent bladder cancer were reviewed. Comparative cancer incidence rates were obtained from the SEER database (2000). Results: Of 3700 patients treated with EBRT for prostate cancer from 1970–1999, 806 patients (with 10,002 follow-up years) were randomly selected. 26 developed a subsequent bladder cancer. 20 sporadic cases of TCC were expected in a similarly aged population without radiation (from SEER data). Our data demonstrates the relative risk of developing a subsequent bladder cancer is 1.3 (CI 0.85–1.91) which is elevated but not statistically significant. Conclusions: This retrospective review shows the risk of bladder cancer in men who received radiation for prostate cancer is slightly higher than expected in a non-irradiated population. It is, however, lower than the risk reported in the gynecologic literature. Both radiation cystitis and bladder tumors can present with hematuria and irritative voiding. Urologists should be vigilant in evaluation of this subset of patients at increased risk for vesical neoplasms.

Bcl-2 is significantly overexpressed in localized radio-recurrent prostate carcinoma, compared with localized radio-naive prostate carcinoma

Purpose We set out to determine whether patients who underwent prostatectomy for recurrence after external-beam radiotherapy for prostate cancer had a higher incidence of alterations in the apoptotic pathway than did patients who underwent surgery as initial treatment. Methods and materials Twenty patients who underwent unsuccessful full-dose external-beam radiotherapy for prostate cancer and subsequently underwent salvage radical surgery (radio-recurrent group), and 20 patients matched for various clinical parameters who underwent only radical prostatectomy for localized or locally advanced prostate cancer (radio-naive group), were studied. Tissue samples were examined for immunoreactivity for p53, p21, Bcl-2, and Ki-67 proteins. Statistically, the two groups were compared using exact logistic regression. Results Fifty-five percent of the tumors from patients initially treated with radiotherapy were noted to overexpress Bcl-2; whereas, in the radio-naive group, no patient had Bcl-2 overexpression ( p = 0.0004). More patients who underwent salvage radical surgery were found to have a higher mean proliferative index (Ki-67 staining) (39.6%), compared with patients undergoing prostatectomy alone (22.1%), p = 0.0800. No significant difference was noted in immunohistochemical expression of p53 and p21 between the two groups. Conclusion Patients undergoing radical prostatectomy after radiotherapy had a significantly higher rate of Bcl-2 overexpression than did patients who underwent surgery as the initial treatment. Alterations in the apoptotic pathway may be important in the development of local recurrence after radiation therapy.

Dosimetric consequence of three setup correction schemes for external-beam radiotherapy of prostate cancer

Purpose/Objective: Conventionally, electronic portal imaging (or port film) is performed weekly on prostate cancer patients to remove setup errors based on pelvic bone registration. With the advent of image-guided therapy, more aggressive offline and online correction strategies have been proposed. This study aims to investigate whether these correction strategies significantly outperform weekly portal imaging and to what extent.

Health outcomes after external-beam radiation therapy for clinically localized prostate cancer: results from the Prostate Cancer Outcomes Study.

Studies reporting effects of radiotherapy for prostate cancer on sexual, bowel, and urinary function have been conducted primarily in referral centers or academic institutions. Effects of external-beam radiotherapy for prostate cancer among a population-based cohort were assessed. The study population included 497 white, Hispanic, and African-American men with localized prostate cancer from six US cancer registries who were diagnosed between October 1, 1994, and October 31, 1995, and treated initially with external-beam radiotherapy. They were interviewed at regular intervals, and medical records were reviewed. Distributions of responses for bowel-, urinary-, and sexual-related functions at 6, 12, and 24 months after diagnosis and adjusted mean composite change scores for each domain were analyzed. Declines of 28.9% in the sexual function score and 5.4% in the bowel function score occurred by 24 months, whereas at this time, the urinary function score was relatively unchanged. A total of 43% of those who were potent before diagnosis became impotent after 24 months. More than two thirds of the men were satisfied with their treatment and would make the same decision again. Sexual function was the most adversely affected quality-of-life domain, with problems continuing to increase between 12 and 24 months. Bowel function problems increased at 6 months, with partial resolution observed by 24 months. Despite the side effects, satisfaction with therapy was high. These results are representative of men in community practice settings and may be of assistance to men and to clinicians when making treatment decisions.

Diabetes mellitus: a predictor for late radiation morbidity

Purpose: Given the high frequency of diabetes, as well as prostate cancer in the elderly population, we sought to determine whether diabetic patients treated with three-dimensional conformal external-beam radiotherapy (3DCRT) had an increased risk of late gastrointestinal (GI) or genitourinary (GU) complications. Methods and Materials: Nine-hundred forty-four prostate cancer patients were treated between April 1989 and October 1996 using 3DCRT. Median patient age was 69 years (range 48–89), median center of prostate dose was 7211 cGy (range 6211–8074) and median follow-up was 36 months (range 2–99). Patients were evaluated every 6 months with digital rectal examinations, serum PSAs and symptom questionnaires. Radiation morbidity was quantified using Radiation Therapy Oncology Group (RTOG) and modified Late Effects Normal Tissue Task Force (LENT) scales. Patients with a preexisting history of either Type I or Type II diabetes mellitus were coded as diabetics. Results: One hundred twenty-one patients had diabetes (13% of total). Rates of acute morbidity did not differ between diabetics and nondiabetics; however, diabetics experienced significantly more late grade 2 GI toxicity (28% vs. 17%, p = 0.011) and late grade 2 GU toxicity (14% vs. 6%, p = 0.001). There was a trend toward increased late grade 3 and 4 GI complications in diabetics, but not for late grade 3 and 4 GU complications; however, the total number of recorded events for these categories was small. Examining the onset of late toxicity, diabetics developed GU complications earlier than nondiabetics (median: 10 months vs. 24 months, p = 0.02). Considering age, dose, rectal blocking, field size, and history of diabetes in a stepwise multivariate regression model for late grade 2 GI toxicity, dose ( p = 0.0001), diabetes ( p = 0.0110), and rectal blocking ( p = 0.0163) emerged independently predictive for complications. For late grade 2 GU toxicity, only the presence of diabetes remained independently significant ( p = 0.0014). Conclusion: Diabetes mellitus is common in the elderly prostate cancer population. Diabetics are at a significant risk for the development of late grade 2 GI and GU complications after external-beam radiotherapy for prostate cancer. While diabetes, radiation dose, and rectal blocking predict for late GI complications, only the presence of diabetes influences late GU morbidity. Physicians may consider treatment modifications for diabetic patients, particularly those patients wishing to enter dose-escalation studies. Further study of the relationship between diabetes and late radiation complications is needed.