Prognostic impact of biologically equivalent dose in stereotactic body radiotherapy for renal cancer

Purpose /Objectives Materials/Methods

The National Cancer Database (NCDB) was queried (2004-2017) for patients with RCC who did not have surgical resection but received definitive SBRT. Kaplan-Meier analysis with log-rank test was used to evaluate overall survival (OS). Univariable (UVA) and multivariable (MVA) analysis were conducted using cox proportional hazard models to determine prognostic factors for OS.

Results

A total of 344 patients with median age 77 (IQR 70-85) were included in this study. Median BED₃ was 180 Gy (IQR 126.03-233.97). Median OS was 90 months in the highest quartile compared to 36-52 months in the lower three quartiles (p < 0.01). On UVA, the highest BED₃ quartile was a positive prognostic factor (HR 0.67, p < 0.01 CI 0.51-0.91) while age, tumor size, T-stage, metastasis, renal pelvis location, and transitional cell histology were negative factors. On MVA, the highest BED₃ quartile was remained significant (HR 0.69, p = 0.02; CI 0.49-0.95) as a positive factor, while age, metastasis were negative factors.

Conclusion

Higher BED may be associated with improved OS. Prospective investigation is needed to clearly define optimal BED for SBRT used to treat RCC.

Stereotactic Radiotherapy for Adrenal Metastases: A Multi-Institutional Review of Patient Characteristics and Outcomes - Turkish Society for Radiation Oncology SBRT Group Study (Trod SBRT 10-004)

INTRODUCTION

This study aimed to report the outcomes of stereotactic body radiotherapy (SBRT) for adrenal metastasis in a retrospective multi-institutional cohort.

METHODS

The outcomes of 124 patients with 146 adrenal metastases who underwent SBRT within 11 years (2008-2019) were retrospectively evaluated. Survival outcomes were analyzed by the Kaplan-Meier method. Patient, tumor, and treatment characteristics and their effects on survival, local control (LC), and toxicity outcomes were analyzed by log-rank and multivariate Cox regression methods.

RESULTS

The median age was 60 years. The most frequent primary tumor site was the lung, followed by the gastrointestinal system and breast. The adrenal gland was the only metastatic site in 49 (40%) patients. Median biologically effective dose (BED)10 was 61 Gy. The overall LC rate was 83%, and it was positively correlated with the BED10 and fraction dose. The 1- and 2-year local recurrence-free survival, overall survival (OS), and progression-free survival (PFS) rate was 79% and 69%, 83% and 60%, and 31% and 12%, respectively. OS significantly improved with non-lung cancer and <4-cm lesion and PFS with a fraction dose ≥8 Gy, BED10 >65 Gy, and an isolated adrenal metastasis. Fourteen patients reported an acute toxicity, and late toxicity was observed in 3 patients, including one grade 5.

CONCLUSION

A satisfactory LC rate was achieved for adrenal metastasis via SBRT. A higher BED10 and fraction dose were positive prognostic factors for tumor control. However, the main problem is DM in these patients, and systemic treatment options are needed to be improved.

Evaluation of the urethral α/β ratio and tissue repair half-time for iodine-125 prostate brachytherapy with or without supplemental external beam radiotherapy

PURPOSE

To assess the correlation between postimplant dosimetric quantifiers and the genitourinary (GU) toxicity of low-dose rate brachytherapy for prostate cancer.

METHODS AND MATERIALS

The minimum urethral dose (UD10, 30, and 90) and the percent volume of the urethra receiving the prescription dose (V100, V150) were calculated from the postimplant dose-volume histograms of 182 patients. We then calculated various urethral biologically equivalent doses (uBEDs) using different values of the α/β ratio and tissue repair half-time (t1/2) and examined the correlations with GU toxicity.

RESULTS

Common dosimetric quantifiers, such as UD90 (brachytherapy) + UD50 (external beam radiotherapy), showed no correlation with Grade ≥ 2 GU toxicity. There was a significant correlation between Grade ≥2 GU toxicity and uBED when the α/β value was 0.5 or 1 Gy and t1/2 was 0.5-2.5 h. An uBED (α/β = 1.0, t1/2 = 0.5) had the largest hazard ratio for GU toxicity, and it was also significantly correlated with Grade ≥ 2 GU toxicity according to multivariate analysis.

CONCLUSIONS

We observed a significant correlation of uBED with GU toxicity when α/β was 0.5 or 1.0 Gy and t1/2 was 0.5-2.5 h. As the simple formula we used has not been verified in basic experiments, more data are needed to validate our results.

Palliative Thoracic Radiotherapy for Lung Cancer: What Is the Impact of Total Radiation Dose on Survival?

Background

Effective symptom palliation can be achieved with low-dose palliative thoracic radiotherapy. In several studies, median survival was not improved with higher doses of radiation. More controversy exists regarding the impact of higher doses on 1- and 2-year survival rates. Therefore, a comparison of survival outcomes after radiotherapy with different biologically equivalent doses (equivalent dose in 2-Gy fractions, EQD2) was performed.

Methods

This was a retrospective single-institution study of 232 patients with small or non-small cell lung cancer. Most commonly 2 fractions of 8.5 Gy were prescribed (34%), followed by 10 fractions of 3 Gy or equivalent regimens (30%, EQD2 circa 33 Gy). The highest EQD2 consisted of 45 Gy. Intention-to-treat analyses were performed.

Results

Survival was significantly shorter with regimens of intended EQD2 < 33 Gy, e.g., 2 fractions of 8.5 Gy (median 2.5 months compared to 5.0 and 7.5 months with EQD2 of circa 33 and 45 Gy, respectively). The 2-year survival rates were 0%, 7% and 11%, respectively. In 128 prognostically favorable patients, median survival was comparable for the three different dose levels (6 - 8.3 months). The 2-year survival rates were 0%, 10%, and 13%, respectively (not statistically significant).

Conclusion

Although most of the observed survival differences diminished after exclusion of poor prognosis patients with reduced performance status and/or progressive extrathoracic disease, a slight increase in 2-year survival rates with higher EQD2 cannot be excluded. Because of relatively small improvements, a confirmatory randomized trial in this subgroup would have to include a large number of patients.

Outcomes of patients with unresected stage III and stage IV non-small cell lung cancer: A single institution experience

Introduction:

To report on the demographic profile and survival outcomes of North Indian population affected with stage III and stage IV non-small cell lung cancer (NSCLC).

Materials and Methods:

From November 2008 to January 2012, 138 consecutively diagnosed NSCLC patients were included in this study. The patient, tumor and treatment related factors were analyzed. Median overall survival (OS), Kaplan-Meier survival plots, t-test, Cox proportional hazards models were generated by multivariate analysis [MVA]) and analyzed on SPSS software (version 19.0; SPSS, Inc., Chicago, IL).

Results:

Median OS of stage III patients was 9.26 ± 1.85 months and 2-year survival rate of 13% while stage IV patients had median OS of 5 ± 1.5 months with a 2-year survival rate of 8%. Cox regression modeling for MVA demonstrated higher biologically equivalent dose (BED) (P = 0.01) in stage III while in stage IV non-squamous histology (P = 0.01), administration of chemotherapy (P = 0.02), partial responders to chemotherapy (P = 0.001), higher BED (P = 0.02), and those with skeletal metastasis alone (P = 0.17) showed a better OS.

Conclusion:

Our data showed that a higher BED is associated with favorable outcomes, indicating a role of dose escalated radiation therapy to the primary lesion in both stage III and essentially in stage IV NSCLC. Additionally, optimal use of chemotherapy relates to better survival. The developing, resource restrained nations need to follow an economically feasible multimodality approach.