Biomedical subjects

Gregory Pond

Publications and source records attributed to Gregory Pond.

7 recordsLinked to original sources

PubMed2006

Computerized tomographic simulation compared with clinical mark-up in palliative radiotherapy: a prospective study.

PURPOSE: To evaluate the impact of computed tomographic (CT) planning in comparison to clinical mark-up (CM) for palliative radiation of chest wall metastases. METHODS AND MATERIALS: In patients treated with CM for chest wall bone metastases (without conventional simulation/fluoroscopy), two consecutive planning CT scans were acquired with and without an external marker to delineate the CM treatment field. The two sets of scans were fused for evaluation of clinical tumor volume (CTV) coverage by the CM technique. Under-coverage was defined as the proportion of CTV not covered by the CM 80% isodose. RESULTS: Twenty-one treatments (ribs 17, sternum 2, and scapula 2) formed the basis of our study. Due to technical reasons, comparable data between CM and CT plans were available for 19 treatments only. CM resulted in a mean CTV under-coverage of 36%. Eleven sites (58%) had an under-coverage of >20%. Mean volume of normal tissues receiving >/=80% of the dose was 5.4% in CM and 9.3% in CT plans (p = 0.017). Based on dose-volume histogram comparisons, CT planning resulted in a change of treatment technique from direct apposition to a tangential pair in 7 of 19 cases. CONCLUSIONS: CT planning demonstrated a 36% under-coverage of CTV with CM of ribs and chest wall metastases.

Bone Neoplasms↗

PubMed2006

Radiation dose to the internal pudendal arteries from permanent-seed prostate brachytherapy as determined by time-of-flight MR angiography.

PURPOSE: To determine the feasibility of time-of-flight magnetic resonance (MR) angiography to visualize the internal pudendal arteries (IPAs) in potent men undergoing permanent-seed prostate brachytherapy and to calculate the radiation dose received by these arteries. METHODS AND MATERIALS: Prostate brachytherapy is performed at the University Health Network/Princess Margaret Hospital by use of transrectal ultrasound (TRUS) preplanning and preloaded needles. All patients received (125)I, with a mean seed activity of 0.32 mCi/seed (0.41 U). Postplan evaluation is performed at 1 month by magnetic resonance-computed tomography fusion. Twenty consecutive potent men had time-of-flight MR angiography as part of their postplan evaluation. RESULTS: The mean V100 was 96.5%, and the mean D90 was171.5 Gy. The IPAs were easily visualized for 18 of the 20 men. The mean peak dose received by the IPA was 17 Gy. The highest peak dose received by any patient was 38.2 Gy, with only 1 other patient receiving a peak dose greater than 30 Gy. Eleven of 18 had a measurable portion of at least 1 IPA that received 10% of the prescribed dose (V10 = 14.5 Gy). Only 2 patients had nonzero values for V25. The distal third of the IPA received the highest dose for 16 of the 18 patients. CONCLUSIONS: The IPAs can be well visualized in the majority of potent men by use of time-of-flight MR angiography 1 month after brachytherapy. The IPAs receive a low but calculable dose from permanent-seed (125)I brachytherapy. Further research is needed to determine if this outcome has any correlation with subsequent potency.

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PubMed2006

Rectal-wall dose dependence on postplan timing after permanent-seed prostate brachytherapy.

PURPOSE: Dose to rectal wall after permanent-seed prostate brachytherapy is dependent on distance between posterior prostatic seeds and anterior rectal wall and is influenced by postimplant periprostatic edema. We analyzed the effect of postplan timing on anterior rectal-wall dose. METHODS AND MATERIALS: Twenty patients received permanent seed 125I brachytherapy as monotherapy (145 Gy). Implants were preplanned by use of transrectal ultrasound (TRUS) and carried out by use of preloaded needles. Postimplant dosimetry was calculated by use of magnetic resonance imaging-computed tomography fusion on Days 1, 8, and 30. The anterior rectal-wall dose is reported as the isodose enclosing 1.0 or 2.0 cc of rectal wall and as the RV100 in cc. RESULTS: The dose to rectal wall increased progressively over time. The median increase in dose to 1.0 cc of rectal wall (RD [1 cc]) from Day 1 to 30 was 39.2 Gy (p < 0.001). RV100 increased from a median of 0.07 cc on Day 1 to 0.67 cc on Day 30. The most significant predictor of rectal-wall dose (RD [1 cc], RD [2 cc], or RV100) was the time of evaluation (p < 0.001). CONCLUSION: Although periprostatic edema cannot be quantified by postimplant imaging, the dose to the anterior rectal wall increases significantly over time as prostatic and periprostatic edema resolve. Critical-organ dose reporting and guidelines for minimizing toxicity must take into account the time of the assessment.

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PubMed2005

Sequential evaluation of prostate edema after permanent seed prostate brachytherapy using CT-MRI fusion.

PURPOSE: To analyze the extent and time course of prostate edema and its effect on dosimetry after permanent seed prostate brachytherapy. METHODS AND MATERIALS: Twenty patients scheduled for permanent seed (125)I prostate brachytherapy agreed to a prospective study on postimplant edema. Implants were preplanned using transrectal ultrasonography. Postimplant dosimetry was calculated using computed tomography-magnetic resonance imaging (CT-MRI) fusion on the day of the implant (Day 1) and Days 8 and 30. The prostate was contoured on MRI, and the seeds were located on CT. Factors investigated for an influence on edema were the number of seeds and needles, preimplant prostate volume, transitional zone index (transition zone volume divided by prostate volume), age, and prostate-specific antigen level. Prostate dosimetry was evaluated by the percentage of the prostate volume receiving 100% of the prescribed dose (V(100)) and percentage of prescribed dose received by 90% of the prostate volume (D(90)). RESULTS: Prostate edema was maximal on Day 1, with the median prostate volume 31% greater than preimplant transrectal ultrasound volume (range, 0.93-1.72; p < 0.001) and decreased with time. It was 21% greater than baseline at Day 8 (p = 0.013) and 5% greater on Day 30 (p < 0.001). Three patients still had a prostate volume greater than baseline by Day 30. The extent of edema depended on the transition zone volume (p = 0.016) and the preplan prostate volume (p = 0.003). The median V(100) on Day 1 was 93.6% (range, 86.0-98.2%) and was 96.3% (range, 85.7-99.5%) on Day 30 (p = 0.079). Patients with a Day 1 V(100) >93% were less affected by edema resolution, showing a median increase in V(100) of 0.67% on Day 30 compared with 2.77% for patients with a V(100) <93 % on Day 1. CONCLUSION: Despite the extreme range of postimplant edema, the effect on dosimetry was less than expected. Dose coverage of the prostate was good for all patients during Days 1-30. Our data indicate that postimplant dosimetry on the day of implant is sufficient for patients with good dose coverage (Day 1 V(100) >93%).

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PubMed2002

Sucralfate mouthwash for prevention and treatment of 5-fluorouracil-induced mucositis: a randomized, placebo-controlled trial.

A randomized, double-blind, placebo-controlled trial was conducted to evaluate the effectiveness of a sucralfate mouthwash in preventing and alleviating oral mucositis induced by 5-fluorouracil (5FU). A total of 81 patients with colorectal cancer were enrolled. Patients were studied during their first cycle of chemotherapy with 5FU and leucovorin (LV) daily for 5 days every 4 weeks (Mayo Clinic schedule). Patients were randomly allocated to receive either a sucralfate suspension or a placebo suspension that was identical in appearance. Patients were instructed to use the suspension as a mouthwash four times daily from the beginning of the chemotherapy cycle. All patients received oral cryotherapy. Patients graded the severity of their own symptoms on a daily basis, and this was the primary outcome measure. There was no difference in the frequency or severity of oral mucositis between the sucralfate- and the placebo-treated group. Some mucositis was reported by 79% of the patient group. Assessment of mucositis by trial staff underestimated the incidence of this problem. Results of this trial do not support the hypothesis that a sucralfate mouthwash can prevent or alleviate oral mucositis induced by 5FU. Patient reporting of mucositis is a more sensitive instrument for assessment of mucositis than review by medical staff.

Administration, Oral↗

PubMed2002

The utility of transition zone index in predicting acute urinary morbidity after 125I prostate brachytherapy.

PURPOSE: Acute urinary morbidity after prostate brachytherapy is common and, although usually self-limited, can be distressing to the patient, especially if acute urinary retention (AUR) develops. We undertook to determine whether prospective measurement of the transition zone index would be predictive of either urinary retention or the severity of urinary symptoms after brachytherapy. METHODS AND MATERIALS: One hundred men undergoing transperineal interstitial permanent prostate brachytherapy (TIPPB) with 125I underwent transrectal ultrasound before the procedure to measure prostate and transition zone (TZ) volumes. TZ index was calculated as TZ volume divided by total prostate volume. TIPPB was performed between July 2000 and January 2002. Patients were observed for 1, 3, or 6 months with an International Prostate Symptom Score (IPSS) at each visit. alpha-Blockers were prescribed prophylactically in all patients. Postimplant dosimetry was performed at 1 month by using CT/MRI fusion for all patients. RESULTS: The mean patient age was 65.1 years (range, 46-77 years). There were 59 T1c tumors and 41 T2a tumors. The Gleason score was 6 in 86% of patients, with 3% being Gleason 4 or 5 and 11% Gleason 7. The mean baseline IPSS was 7.4, with the mean at 1 month being 17.3; at 3 months, 14.4; and at 6 months, 11.3. Baseline IPSS was the only factor predictive of IPSS at 1 and 3 months after TIPPB. Neoadjuvant androgen deprivation was used for 26% of men for 2-6 months to reduce prostate size before the procedure. AUR developed in 17%. In univariate analysis, prior hormone therapy (p = 0.002), duration of hormone therapy (p = 0.005), TZ index (p = 0.014), number of seeds implanted (p = 0.016), T stage (p = 0.035), percentage of the prostate volume receiving at least the full prescribed dose (V100, p = 0.036), percentage of the prostate volume receiving > 200% of the prescribed dose (V200, p = 0.037), and prostate volume (p = 0.038) were all predictive of AUR. When the TZ index was divided into quartiles, the risk of AUR was 4%, 16%, 20%, and 28% (p = 0.032). However, in multivariate analysis, TZ index was no longer predictive of AUR. CONCLUSIONS: Baseline urinary function is the only factor predictive of symptom scores at 1 and 3 months after brachytherapy. TZ index, initial prostate volume, and use of neoadjuvant hormones are interrelated and are all predictive of AUR in univariate analysis, but in multivariate analysis, TZ index is not an independent prognostic factor.

Acute Disease↗

PubMedDate not supplied

Posttreatment complications of early-stage prostate cancer patients: brachytherapy versus three-dimensional conformal radiation therapy.

PURPOSE: The purpose of this study was to compare treatment complications for early-stage prostate cancer managed by either brachytherapy or three-dimensional conformal radiotherapy (3D-CRT). MATERIALS AND METHODS: [corrected] Records were reviewed for 86 men treated with transperineal interstitial permanent prostate brachytherapy and for 76 men treated with dose-escalated (75.6-Gy) six-field 3DCRT between 1998 and 2000. Median ages were 65 and 66 years, respectively; median Gleason scores were 6 and 7; baseline prostate-specific antigen levels were 6.1 and 9.0 ng/mL; and the follow-up period was 42 months. In the urinary domain, patients who underwent brachytherapy recorded an International Prostate Symptom Score prospectively at baseline, as well as 3 months and every 6 months following, whereas patients who underwent 3D-CRT were assigned a Radiation Therapy Oncology Group (RTOG) late toxicity score at similar time intervals. In the bowel domain, RTOG late toxicity score was used for both groups, and physician-dictated notes were used to assess sexual function. All patients who underwent brachytherapy were prescribed tamsulosin (Flomax) to manage urinary symptoms for a minimum of 3 months after treatment. RESULTS: With respect to urinary symptoms, a direct comparison cannot be made between the International Prostate Symptom Score and the RTOG late toxicity score. Nonetheless, it was evident that patients who underwent brachytherapy had more severe urinary sequelae in the months after implantation. Tamsulosin was still being used by 78% of patients at 6 months, decreasing to 55% at 1 year and 27% at 2 years. Intermittent self-catheterization was required at 6 months after treatment by 5% of patients who underwent brachytherapy, and a transurethral resection of the prostate was performed in one of these patients at 12 months. In patients who underwent 3D-CRT, 14% used tamsulosin at some point in the follow-up period and none required catheterization or transurethral resection of the prostate. In the bowel domain, 20% of patients who underwent brachytherapy experienced grade 1 gastrointestinal toxicity, most within the first 12 months of follow-up, compared with 30% grade 1 or 2 gastrointestinal scores in the 3D-CRT group (peaking in the second year after treatment). In the sexual domain, 9% of patients who underwent brachytherapy who were previously potent reported a loss of potency by 18 months, compared with 53% of patients who underwent 3D-CRT. Without the help of sildenafil (Viagra), these figures rose to 24% and 58%. CONCLUSIONS: 3D-CRT is associated with fewer urinary symptoms, whereas brachytherapy has a more favorable toxicity profile for bowel and sexual function. In the absence of a randomized clinical trial, such a comparison can be helpful both in counseling patients as to what to expect from either treatment and in facilitating their treatment decision process.

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