A Prospective Study of Conventionally Fractionated Dose Constraints for Reirradiation of Primary Brain Tumors in Adults

Third Course of Radical Intent Conformal Radiation in Patients with Primary Brain Tumors

AIMS

Reirradiation is increasingly considered in patients with recurrent primary brain tumours. However, second course of radical reirradiation (RT2) or third course of radiation (RT3) delivering higher doses is uncommon. The current study was undertaken to report the clinical outcomes after the third course of radical radiation.

MATERIALS AND METHODS

The patients undergoing three courses of cranial radiation were obtained from the radiation oncology database. The clinical and treatment details were obtained by reviewing electronic medical records and radiation charts and plans when available. Treatment outcomes, including disease status and radionecrosis, were assessed by reviewing imaging. Analysis was done using descriptive statistics and survival outcomes using Kaplan-Meier survival plots.

RESULTS

Eight patients were identified between 2015 and 2023 treated with a third course of radiotherapy (second reirradiation). Histopathology included ependymoma in seven and glioblastoma in one patient. The median age during first radiation was 13.5 years (range: 4-31 years) with interquartile range (IQR) of 7-26 years, and during RT3 was 22 years (range: 9-43 years, IQR: 14-32 years). The median doses at RT1, RT2, and RT3 were 59.4 Gy (IQR: 54.80-60 Gy), 54 Gy (IQR: 51.3-54.0 Gy), and 50.4 Gy (IQR: 50.0-50.4 Gy), respectively. The median interval between RT1 and RT2 was 37 months (IQR: 29-63 months), RT2 and RT3 was 39 months (IQR: 25-67 months). The median cumulative EQD2 from three courses was 153Gy2 (IQR: 148.7-159.1 Gy2). After 3rd course, the median follow-up was 25 months (IQR: 15-37 months) with a 2-year overall survival of 85%. One patient had developed symptomatic radionecrosis 14 months after RT3 and was treated with bevacizumab.

CONCLUSION

The third course of radical dose of radiation can be considered a reasonable approach for tumours with local recurrence after a reasonable interval of at least two years between each course, allowing for tissue recovery.

Practice Patterns of Reirradiation for Brain and Spinal Tumors-An International Survey From the Reirradiation Collaborative Group (ReCOG)

PURPOSE

An international workshop was convened by the Reirradiation Collaborative Group. We conducted a survey among the invited attendants to assess practice patterns of reirradiation for central nervous system tumors.

METHODS AND MATERIALS

A web-based survey regarding central nervous system reirradiation was distributed to an international group of radiation oncologists and medical physicists via email.

RESULTS

Sixty-six respondents from 20 countries completed at least one section of the survey. The most important clinical considerations were treatment goal, degree of overlap, and cumulative dose. Among technical challenges, uncertainties in tolerance of organs at risk (OARs), tissue recovery factors (TRFs) and dose accumulation ranked the highest. Most respondents (68%) used a planning OAR volume with 0 to 3 mm margin. Highly conformal radiation techniques were preferred, including stereotactic body radiation therapy for spine (85%), intensity modulated radiation therapy for adult primary brain tumors (93%), and intensity modulated radiation therapy (100%) and proton therapy (83%) for pediatric cases. Most performed dose accumulation (65%) and evaluated cumulative biological (ie, equieffective) dose (88%). Sixty-one percent preferred rigid registration, whereas 35% used deformable registration, most commonly in pediatric cases (67%). The most frequently used α/β value for OARs was 2 Gy (76%). There was no clear consensus on OAR tolerance for any disease site. Different dose metrics were used for evaluation, including Dmax (48%) and D0.1cc (48%). Most (79%) considered time intervals between radiation courses. For adult primary brain tumors and brain metastasis, 50% and 46% recommended against reirradiation within a short interval (3-6 months). Most respondents (52%) used time dependent TRFs.

CONCLUSIONS

Among respondents, there are substantial variations in approaches to reirradiation (eg, addition of systemic therapy) and uncertainties in technical implementation (eg, OAR tolerance, TRF, and dose accumulation). Future collaborative registry-based and prospective studies should help address these uncertainties.

FCB-CHOPS: An Evolution of a Commonly Used Acronym for Evaluating Radiation Treatment Plans

Checklists have been used across many fields as a systematic framework to reduce human error and improve safety. In radiation oncology, the CB-CHOP acronym was previously developed as a tool to aid physicians in assessing the quality of radiation treatment plans for approval. This manuscript updates the acronym for the modern era with the addition of F and S to create FCB-CHOPS: fusion, contours, beams, coverage, heterogeneity, organs at risk, prescription, and dose summation. These 2 additions reflect the evolution and importance of image fusion to aid in the delineation of targets and organs at risk and dose summation to reflect the increased incidence of reirradiation and the need to consider prior treatment courses in the final plan evaluation. Utilization of this and similar checklists is critical in maintaining high-quality and safe radiation oncology treatments.