Modeling the Impact of Cardiopulmonary Irradiation on Overall Survival in NRG Oncology Trial RTOG 0617

PURPOSE

To quantitatively predict the impact of cardiopulmonary dose on overall survival (OS) after radiotherapy for locally advanced non-small cell lung cancer.

EXPERIMENTAL DESIGN

We used the NRG Oncology/RTOG 0617 dataset. The model building procedure was preregistered on a public website. Patients were split between a training and a set-aside validation subset (N = 306/131). The 191 candidate variables covered disease, patient, treatment, and dose-volume characteristics from multiple cardiopulmonary substructures (atria, lung, pericardium, and ventricles), including the minimum dose to the hottest x% volume (Dx%[Gy]), mean dose of the hottest x% (MOHx%[Gy]), and minimum, mean (Mean[Gy]), and maximum dose. The model building was based on Cox regression and given 191 candidate variables; a Bonferroni-corrected P value threshold of 0.0003 was used to identify predictors. To reduce overreliance on the most highly correlated variables, stepwise multivariable analysis (MVA) was repeated on 1000 bootstrapped replicates. Multivariate sets selected in ≥10% of replicates were fit to the training subset and then averaged to generate a final model. In the validation subset, discrimination was assessed using Harrell c-index, and calibration was tested using risk group stratification.

RESULTS

Four MVA models were identified on bootstrap. The averaged model included atria D45%[Gy], lung Mean[Gy], pericardium MOH55%[Gy], and ventricles MOH5%[Gy]. This model had excellent performance predicting OS in the validation subset (c = 0.89).

CONCLUSIONS

The risk of death due to cardiopulmonary irradiation was accurately modeled, as demonstrated by predictions on the validation subset, and provides guidance on the delivery of safe thoracic radiotherapy.

Multicenter phase Ib/II trial of the radiation enhancer motexafin gadolinium in patients with brain metastases

PURPOSE

Motexafin gadolinium is a magnetic resonance imaging (MRI)--detectable redox active drug that localizes selectively in tumor cells and enhances the effect of radiation therapy. This phase Ib/II trial of motexafin gadolinium, administered concurrently with 30 Gy in 10 fractions whole-brain radiation therapy (WBRT), was conducted to determine maximum-tolerated dose (MTD), dose-limiting toxicity, pharmacokinetics, and biolocalization in patients with brain metastases. Additional endpoints were radiologic response rate and survival.

PATIENTS AND METHODS

Motexafin gadolinium was administered before each radiation treatment in this open-label, multicenter, international trial. In phase Ib, drug dose was escalated until the MTD was exceeded. In phase II, drug was evaluated in a narrow dose range.

RESULTS

In phase Ib, the motexafin gadolinium dose was escalated in 39 patients (0.3 mg/kg to 8.4 mg/kg). In phase II, 22 patients received 5 mg/kg to 6.3 mg/kg motexafin gadolinium. Ten once-daily treatments were well tolerated. The MTD was 6.3 mg/kg, with dose-limiting reversible liver toxicity. Motexafin gadolinium's tumor selectivity was established using MRI. The radiologic response rate was 72% in phase II. Median survival was 4.7 months for all patients, 5.4 months for recursive partitioning analysis (RPA) class 2 patients, and 3.8 months for RPA class 3 patients. One-year actuarial survival for all patients was 25%.

CONCLUSION

Motexafin gadolinium was well tolerated at doses up to 6.3 mg/kg, was selectively accumulated in tumors, and, when combined with WBRT of 30 Gy in 10 fractions, was associated with a high radiologic response rate.

Deciding on radiation therapy for prostate cancer: the physician's perspective

Multiple treatment options are available for the radiation therapy of prostate cancer including whole pelvic radiotherapy (WPRT), prostate-only radiotherapy (PORT), three-dimensional conformal radiotherapy (3DCRT), intensity modulated radiotherapy (IMRT), as well as proton or neutron beam based therapies and brachytherapy. Numerous technical variations hamper objective assessment of these different treatment modalities. These variations are extensive and often subtle (dose to the prostate, the dose per fraction, number and size of fields, the photon energy, patient positioning, prostatic motion, the use of immobilization devices, 2D or 3D planning for treatment, and others) may cause interpretive uncertainty. Despite this confusion, there is some consensus. Prostate-specific antigen (PSA) nadirs, as well as pretreatment PSA levels, significantly alter outcome. Low-risk patients do well no matter which treatment they receive, although the question of dose-escalation therapy to improve results remains unanswered. High-risk patients do poorly regardless of treatment, although the addition of androgen ablation and dose-escalation therapy may improve results. Quality of life (QOL) studies continue to show a problem for radical prostatectomy (RP) patients secondary to impotence and incontinence and a problem for radiotherapy patients due to gastrointestinal (GI) disturbances. Patients can have access to any specific study through technologies such as the Internet. Although this information can be useful, the subtleties of each different article are usually beyond the understanding of most patients. This report examines some of the new radiotherapy modalities as well as corrects some misconceptions regarding radiotherapy results and morbidity. In addition, we discuss some studies comparing surgery and radiotherapy and attempt to objectively compare different radiation therapy strategies for localized prostate cancer.

Treatment planning for prostate implant with loose seeds

A new method of treatment planning for the I-125 and Pd-103 permanent interstitial prostate implant is developed, which does not use the traditional nomograms but automatically generates optimized source configurations. An iterative algorithm is used that places one seed at a step. The volume dose of target is calculated at each step to determine the coldest spot where the next source is to be placed, so that the dose uniformity of target is best improved as source placement proceeds. At each step, the total activity required for the seed configuration as so established is calculated by normalizing the minimal dose to the prescribed dose. An optimized configuration is the one that takes the minimized total activity. Around its minimum the total activity has a very small variation with the number of seeds. Consequently multiple clinically acceptable seed configurations with similar total activity but different individual activities are generated simultaneously. In our computer generated treatment plans most of the seeds are distributed in the periphery of the target, similar to the Paterson-Parker pattern of a volume implant.

Palliation of AIDS-related primary lymphoma of the brain: observations from a multi-institutional database

PURPOSE

To catalogue the presenting symptoms of patients with AIDS who are presumed to have primary central nervous system lymphoma (PCNSL). To document the palliative efficacy of cranial irradiation (RT) relative to the endpoints of complete and overall response for the respective symptoms.

METHODS

An analysis of 163 patients with AIDS-related PCNSL who were evaluated at nine urban hospitals was performed. These patients were treated for PCNSL after the establishment of a tissue diagnosis or on a presumptive basis after failing empiric treatment for toxoplasmosis. All patients were treated between 1983 and 1995 with radiotherapy (median dose-fractionation scheme = 3 Gy x 10) and steroids (>90% dexamethasone). Because multiple fractionation schemes were used, prescriptions were converted to biologically effective doses according to the formula, Gy10 = Total Dose x (1 + fractional dose/alpha-beta); using an alpha-beta value of 10.

RESULTS

The overall palliative response rate for the entire group was 53%. In univariate analysis, trends were present associating complete response rates with higher performance status (KPS > or = 70 vs. KPS < or = 60 = 17% vs. 5%), female gender (women vs. men = 29% vs. 8%), and the delivery of higher biologically effective doses (BED) of RT (Gy10 > 39 vs. < or = 39 = 20% vs. 5%). In multivariate analysis of factors predicting complete response, both higher KPS and higher BED retained independent significance. A separate univariate analysis identified high performance status (KPS > or = 70 vs. KPS < or = 60 = 71% vs. 47%), and young age (< or = 35 vs. > 35 = 61% vs. 40%) as factors significantly correlating with the endpoint of the overall response. In multivariate analysis, high performance status and the delivery of higher biologically effective doses of irradiation correlated significantly with higher overall response rates.

CONCLUSION

Most AIDS patients who develop symptoms from primary lymphoma of the brain can achieve some palliation from a management program that includes cranial irradiation. Young patients with excellent performance status are most likely to respond to treatment. The delivery of higher biologically effective doses of irradiation also may increase the probability of achieving a palliative response.

Performance status and age as independent predictors of survival among AIDS patients with primary CNS lymphoma: a multivariate analysis of a multi-institutional experience

PURPOSE

There is limited information about the outcome of AIDS patients with primary central nervous system lymphoma treated with definitive irradiation. The purpose of this study was to determine factors associated with increased survival in such patients.

METHODS

An analysis was performed of 163 patients with AIDS who were evaluated at nine urban hospitals. These patients were treated for primary central nervous system lymphoma after the establishment of a tissue diagnosis or on a presumptive basis after failing empiric treatment for toxoplasmosis. All patients were treated between 1983 and 1995 with radiotherapy (median dose-fractionation scheme = 3 Gy x 10) and steroids (> 90% dexamethasone). Because multiple fractionation schemes were used, prescriptions were converted to biologically effective dose according to the formula Gy10 = Total Dose x (1 + fractional dose/alpha-beta), using an alpha-beta of 10.

RESULTS

Longer median survival times were associated with high Karnofsky performance status (KPS > or = 70 vs < or = 60: 181 vs 77 days), young age (< 35 vs > 35: 162 vs 61 days), and high total definitive irradiation doses (> 39 Gy10 vs < 39 Gy10: 162 vs 40 days). Tissue diagnosis, gender, race, number of lesions (solitary vs multiple), and the presence of other cancers did not influence outcome. In multivariate analysis, young age, high Karnofsky performance status, and the delivery of higher biologically effective doses of irradiation retained independent significance relative to the endpoint of survival.

CONCLUSIONS

Even at urban tertiary medical centers, few AIDS patients with intracranial lesions undergo biopsies to establish a precise tissue diagnosis. Survival following definitive irradiation is strongly related to two pretreatment factors (young age, high performance status) and one treatment factor (total biologically effective dose of cranial radiotherapy). These variables should be considered in selecting patients for definitive irradiation and in designing future studies.

External beam irradiation versus 125 iodine implant in the definitive treatment of prostate carcinoma

We reviewed the record of all 983 patients seen at the Hahnemann University, Department of Radiation Oncology for evaluation of prostate cancer during the megavoltage era. We compared the results of 276 patients who were treated definitively with either external beam irradiation or Iodine 125 implantation. The groups were similar in most prognostic characteristics. Where appropriate, multivariate statistical techniques were used to compensate for the effects of differences in grade and stage between the two groups. There were striking differences between implant and external beam patients in both local failure rates and disease-free survival, mostly attributable to poor local control in the implant patients. Thirty-eight percent of the Stage A and B implant patients failed locally in the first 5 years whereas only 5% of a comparable group of external beam patients did so. A2 patients, however, exhibited similar disease-free survival in both cohorts. Complication rates were 11% in the implant group and 19% in the external beam group. We conclude that there are serious doubts about the efficacy of Iodine 125 implantation in maintaining local control, and that this translates into worse relapse-free survival. By contrast, local control and relapse-free survival may be satisfactory in the A2 patients, and complication rates may be lower with implant. The above suggests that Iodine 125 interstitial implantation is well suited to only a minority of early stage prostate cancer patients and that most patients with Stage B and C prostatic carcinoma should be treated with either external beam irradiation or with radical prostatectomy.