A simple and generally applicable method to estimate the peripheral dose in radiation teletherapy with high energy X-rays or gamma radiation

Many articles have been published on the measurement of the dose to points outside the primary beam, often called the peripheral dose (PD), for instance, to the gonads, for specific treatment machines and/or techniques. We investigated the possibilities for developing a generalized method based on the data from several publications.

: The data from several publications were recalculated for a reference situation, then averaged, and the frequency distributions around the mean were determined. Published data were available for ⁶⁰CO, 4, 6, 8, and 10 MV, and 18 to 25 for a large varity of treatment machines. Furthermore, an analysis of possible corrections for depth dependence, field elongation, irregularly shaped fields, wedges, and shielding blocks was carried out.

: The frequency distributions of all published PD values for square fields for photon energies of 4 MV to 25 MV showed a standard deviation of 33%. The PD values of ⁶⁰Co are significantly different with a standard possibly explain this difference, especially for large distances, where leakage radiation predominates. Taking the uncertainty of the risk factors into consideration, we conclude that the use of average values is justified. Although statistically not significant, the peripheral dose appears to be dependent on photon energy with a minimum around 6 MV.

: It is possible to estimate the peripheral dose for photon energies of 4 MV to 25 MV with an accuracy of ±33%; for ⁶⁰Co, the accuracy is even better. The variation of the PD between different treatment machines is so small that it is justified to use average PD values, irrespective of the treatment machines.     

Dose and interval relationship for the interaction of WR-2721 and nitrogen mustard with normal and malignant cells

The protective effect of WR-2721 on nitrogen mustard (HN2) cytotoxicity against hematopoietic stem cells as well as the potentiation effect previously noted against leukemia cells was further examined for dose and interval dependency for these opposite effects. For AKR leukemia cells, a dose dependent potentiation of HN2 cytotoxicity was noted with WR-2721. The magnitude of the potentiation was about 10-fold with 5 mg/mouse WR-2721 and nearly 100-fold at 10 mg/mouse. Interval studies showed maximum potentiation occurred when WR-2721 was given close in time to HN2 and decreased in magnitude as the interval between the agents increased. However, a pronounced potentiation of cytotoxicity was also found when HN2 followed WR-2721 by 4 to 12 hr. For hematopoietic stem cells, a protective effect of WR-2721 on HN2 cytotoxicity was observed. This effect decreased rapidly with interval between the agents with no protection noted for an interval of 6 hr. These results indicate that agents like WR-2721 may have an important therapeutic role in chemotherapy.     

The sonographic appearance of the irradiated breast

A dedicated supine breast ultrasound scanner was used to perform 48 bilateral breast sonograms on 21 patients who had undergone segmental resection and radiation therapy for breast cancer. Skin thickening was seen in 13 of 21 patients (62%). There was an increased echogenicity of the fat in 13 patients (62%) and poor definition of Cooper's ligaments in nine patients (43%). Fifteen patients (71%) had decreased compressibility and 8 (38%) had decreased penetration of the sound beam into the breast. The radiation changes were seen as early as one month after the completion of radiotherapy and improved by one year in the majority of patients studied with sequential sonograms.     

Bleomycin, cyclophosphamide and radiotherapy in regionally advanced epidermoid carcinoma of the head and neck

We have treated 24 patients with squamous carcinoma of the head and neck and advanced regional (N2-3) disease. The regimen consisted of 3 cycles, each of 28 days. Cyclophosphamide (1 gm/m2 I.V.) was given on day 1, bleomycin (15 u I.M.) on days 2, 4, 9 and 11, and ionizing radiation (60Co, 180 rad/fraction) days 1-5, and 8-12. No therapy was given on days 13-28. After three cycles of therapy, 13 patients had a complete response; following further therapy (surgery, interstitial or external beam radiation), 16 patients were free of disease. However, remissions were not durable and 11/16 patients recurred loco-regionally with a median time to recurrence of 5 months; most (7/11 also developed distant metastases. These patients have biologically aggressive disease and may have a worse prognosis than patients who are Stage IV based on a T4 primary lesion only.     

Carcinoma of the Lung: Evaluation of Histological Grade and Factors Influencing Prognosis

The results in 96 patients with lung cancer who underwent lobectomy or pneumonectomy were analyzed. In reviewing the case histories of these patients, it became apparent that those with poorly differentiated tumor (grade 3) have an increased likelihood of positive lymph node metastases compared with those with well-differentiated (grade 1) or moderately differentiated (grade 2) tumor. Poor differentiation of the tumor, vascular invasion, and lymph node metastases appear to represent poor prognostic indices in patients undergoing operation.Compared with patients with grade 1 and grade 2 tumors, patients with a grade 3 adenocarcinoma had more local recurrences, while those with grade 3 squamous cell carcinoma had more distant metastases. The findings suggest that histological grading is an important adjunct to the clinical evaluation of and planning of treatment for patients with lung cancer.     

Mitigation of radiation nephropathy after internal alpha-particle irradiation of kidneys

PURPOSE: Internal irradiation of kidneys as a consequence of radioimmunotherapy, radiation accidents, or nuclear terrorism can result in radiation nephropathy. We attempted to modify pharmacologically, the functional and morphologic changes in mouse kidneys after injection with the actinium ((225)Ac) nanogenerator, an in vivo generator of alpha- and beta-particle emitting elements. METHODS AND MATERIALS: The animals were injected with 0.35 muCi of the (225)Ac nanogenerator, which delivers a dose of 27.6 Gy to the kidneys. Then, they were randomized to receive captopril (angiotensin-converting enzyme inhibitor), L-158,809 (angiotensin II receptor-1 blocker), spironolactone (aldosterone receptor antagonist), or a placebo. RESULTS: Forty weeks after the (225)Ac injection, the placebo-control mice showed a significant increase in blood urea nitrogen (BUN) (87.6 +/- 6.9 mg/dL), dilated Bowman spaces, and tubulolysis with basement membrane thickening. Captopril treatment accentuated the functional (BUN 119.0 +/- 4.0 mg/dL; p <0.01 vs. placebo controls) and histopathologic damage. In contrast, L-158,809 offered moderate protection (BUN 66.6 +/- 3.9 mg/dL; p = 0.02 vs. placebo controls). Spironolactone treatment, however, significantly prevented the development of histopathologic and functional changes (BUN 31.2 +/- 2.5 mg/dL; p <0.001 vs. placebo controls). CONCLUSIONS: Low-dose spironolactone and, to a lesser extent, angiotensin receptor-1 blockade can offer renal protection in a mouse model of internal alpha-particle irradiation.     

Modeling radiation pneumonitis risk with clinical, dosimetric, and spatial parameters

PURPOSE: To determine the clinical, dosimetric, and spatial parameters that correlate with radiation pneumonitis. METHODS AND MATERIALS: Patients treated with high-dose radiation for non-small-cell lung cancer with three-dimensional treatment planning were reviewed for clinical information and radiation pneumonitis (RP) events. Three-dimensional treatment plans for 219 eligible patients were recovered. Treatment plan information, including parameters defining tumor position and dose-volume parameters, was extracted from non-heterogeneity-corrected dose distributions. Correlation to RP events was assessed by Spearman's rank correlation coefficient (R). Mathematical models were generated that correlate with RP. RESULTS: Of 219 patients, 52 required treatment for RP (median interval, 142 days). Tumor location was the most highly correlated parameter on univariate analysis (R = 0.24). Multiple dose-volume parameters were correlated with RP. Models most frequently selected by bootstrap resampling included tumor position, maximum dose, and D35 (minimum dose to the 35% volume receiving the highest doses) (R = 0.28). The most frequently selected two- or three-parameter models outperformed commonly used metrics, including V20 (fractional volume of normal lung receiving >20 Gy) and mean lung dose (R = 0.18). CONCLUSIONS: Inferior tumor position was highly correlated with pneumonitis events within our population. Models that account for inferior tumor position and dosimetric information, including both high- and low-dose regions (D(35), International Commission on Radiation Units and Measurements maximum dose), risk-stratify patients more accurately than any single dosimetric or clinical parameter.     

Treatment results of chemoradiotherapy for clinical stage I (T1N0M0) esophageal carcinoma

PURPOSE: In 1991, we started a clinical prospective trial for operable esophageal carcinoma, foreseeing organ preservation, to assess the treatment results after definitive chemoradiotherapy (CRT) for clinical Stage I (T1N0M0) esophageal cancer. PATIENTS AND METHODS: Between 1992 and 2003, 63 patients were enrolled in this study. Tumor depth was mucosal cancer (T1a) in 23 and submucosal cancer (T1b) in 40. CRT consisted of 55-66 Gy/50-60 fractions (median, 59.4 Gy); from 1 to 3 cycles (median, 2) of concurrent chemotherapy (Cisplatin and 5-fluorouracil), followed by high-dose-rate intraluminal brachytherapy 10-12 Gy/2-3 fractions. RESULTS: The 5-year overall and cause-specific and disease-free survival rates were 66.4%, 76.3%, and 63.7%, respectively. The 5-year cause-specific survival rates for T1a and T1b cancer patients were 85.2% and 70.0%, respectively (p = 0.06). The 5-year disease-free survival rates for T1a and T1b were 84.4% and 50.5%, respectively (p < 0.01). Esophageal fistula as a late toxicity occurred in 2 patients (G4: 1; G5: 1), and esophageal stricture requiring a liquid diet occurred in 2 patients. Pericardial effusion was observed in 3 patients. CONCLUSION: We confirmed that patients with T1N0M0 esophageal carcinoma had their esophagus preserved in 89.2% of cases after definitive CRT, and the survival rates were equivalent to those of previous reports of surgery.     

Cerebral radiation necrosis: incidence, outcomes, and risk factors with emphasis on radiation parameters and chemotherapy

PURPOSE: To investigate radiation necrosis in patients treated for glioma in terms of incidence, outcomes, predictive and prognostic factors. METHODS AND MATERIALS: Records were reviewed for 426 patients followed up until death or for at least 3 years. Logistic regression analysis was performed to identify predictive and prognostic factors. Multivariate survival analysis was conducted using Cox proportional hazards regression. Separate analyses were performed for the subset of 352 patients who received a biologically effective dose (BED) > or =85.5 Gy2 (> or =45 Gy/25 fractions) who were at highest risk for radionecrosis. RESULTS: Twenty-one patients developed radionecrosis (4.9%). Actuarial incidence plateaued at 13.3% after 3 years. In the high-risk subset, radiation parameters confirmed as risk factors included total dose (p < 0.001), BED (p < 0.005), neuret (p < 0.001), fraction size (p = 0.028), and the product of total dose and fraction size (p = 0.001). No patient receiving a BED <96 Gy2 developed radionecrosis. Subsequent chemotherapy significantly increased the risk of cerebral necrosis (p = 0.001) even when adjusted for BED (odds ratio [OR], 5.8; 95% confidence interval [CI], 1.6-20.3) or length of follow-up (OR, 5.4; 95% CI, 1.5-19.3). Concurrent use of valproate appeared to delay the onset of necrosis (p = 0.013). The development of radionecrosis did not affect survival (p = 0.09). CONCLUSIONS: Cerebral necrosis is unlikely at doses below 50 Gy in 25 fractions. The risk increases significantly with increasing radiation dose, fraction size, and the subsequent administration of chemotherapy.     

High-dose irradiation for prostate cancer via a high-dose-rate brachytherapy boost: results of a phase I to II study

OBJECTIVE: To evaluate outcomes of intermediate- and high-risk prostate cancer patients on a prospective dose-escalation study of pelvic external-beam radiation therapy (EBRT) combined with high-dose-rate (HDR) brachytherapy boost. METHODS: From November 1991 to April 2003, 197 patients were treated for intermediate- and high-risk disease features. All patients had prostate-specific antigen>10 ng/ml, Gleason score>or=7, or clinical stage>or=T2b, and all received pelvic EBRT (46 Gy) while receiving either two or three HDR boost treatments. HDR dose fractionation increased progressively and was divided into two dose levels. The mean prostate biologic equivalency dose was 88.2 Gy for the low-dose group and 116.8 Gy for the high-dose group (alpha/beta=1.2). Clinical failure was either local failure or distant metastasis; clinical event-free survival (cEFS) was defined as patients who lived free of clinical failure. RESULTS: Median follow-up was 4.9 years. The 5-year rates were as follows: biologic failure (BF), 18.6%, clinical failure (CF), 9.8%, cEFS 84.8%, cause-specific survival (CSS), 98.3%, and overall survival (OS), 92.9%. Five-year biochemical failure (68.7% vs. 86%, p<0.001), CF (6.1% vs. 15.6%, p=0.04), cEFS (75.5% vs. 91.7%, p=0.003), CSS (95.4% vs. 100%, p=0.02), and OS (86.2% vs. 97.8%, p=0.002) were significantly better for the high-dose group. Multivariate analysis showed that high-dose group (p=0.01, HR 0.35) and Gleason score (p=0.01, HR 1.84) were significant variables for cEFS. Multivariate analysis showed that high-dose group (p=0.01, HR 0.14) and age (p=0.03, HR 1.09 per year) were significant variables for overall survival. CONCLUSION: There is a strong dose-response relationship for intermediate- to high-risk prostate cancer patients. Improved locoregional control with higher radiation doses alone can significantly decrease biochemical and clinical failures.