The impact of tumour histology and recursive partitioning analysis classification on the prognosis of patients treated with whole-brain hypofractionated radiotherapy for brain metastases: analysis of 382 patients

Volumetric-modulated arc therapy (VMAT) for whole brain radiotherapy: not only for hippocampal sparing, but also for reduction of dose to organs at risk

A prospective clinical trial, Radiation Therapy Oncology Group (RTOG) 0933, has demonstrated that whole brain radiotherapy (WBRT) using conformal radiation delivery technique with hippocampal avoidance is associated with less memory complications. Further sparing of other organs at risk (OARs) including the scalp, ear canals, cochleae, and parotid glands could be associated with reductions in additional toxicities for patients treated with WBRT. We investigated the feasibility of WBRT using volumetric-modulated arc therapy (VMAT) to spare the hippocampi and the aforementioned OARs. Ten patients previously treated with nonconformal WBRT (NC-WBRT) using opposed lateral beams were retrospectively re-planned using VMAT with hippocampal sparing according to the RTOG 0933 protocol. The OARs (scalp, auditory canals, cochleae, and parotid glands) were considered as dose-constrained structures. VMAT plans were generated for a prescription dose of 30 Gy in 10 fractions. Comparison of the dosimetric parameters achieved by VMAT and NC-WBRT plans was performed using paired t-tests using upper bound p-value of < 0.001. Average beam on time and monitor units (MUs) delivered to the patients on VMAT were compared with those obtained with NC-WBRT. All VMAT plans met RTOG 0933 dosimetric criteria including the dose to hippocampi of 100% of the volume (D_100%) of 8.4 ± 0.3 Gy and maximum dose of 15.6 ± 0.4 Gy, respectively. A statistically significant dose reduction (p < 0.001) to all OARs was achieved. The mean and maximum scalp doses were reduced by an average of 9 Gy (32%) and 2 Gy (6%), respectively. The mean and maximum doses to the auditory canals were reduced from 29.5 ± 0.5 Gy and 31.0 ± 0.4 Gy with NC-WBRT, to 21.8 ± 1.6 Gy (26%) and 27.4 ± 1.4 Gy (12%) with VMAT. VMAT also reduced mean and maximum doses to the cochlea by an average of 4 Gy (13%) and 2 Gy (6%), respectively. The parotid glands mean and maximum doses with VMAT were 4.4 ± 1.9 Gy and 15.7 ± 5.0 Gy, compared to 12.8 ± 4.9 Gy and 30.6 ± 0.5 Gy with NC-WBRT, respectively. The average dose reduction of mean and maximum of parotid glands from VMAT were 65% and 50%, respectively. The average beam on time and MUs were 2.3minutes and 719 on VMAT, and 0.7 minutes and 350 on NC-WBRT. This study demonstrated the feasibility of WBRT using VMAT to not only spare the hippocampi, but also significantly reduce dose to OARs. These advantages of VMAT could potentially decrease the toxicities associated with NC-WBRT and improve patients' quality of life, especially for patients with favorable prognosis receiving WBRT or patients receiving prophylactic cranial irradiation (PCI).

Whole brain radiotherapy with adjuvant or concomitant boost in brain metastasis: dosimetric comparison between helical and volumetric IMRT technique

BACKGROUND

To compare and evaluate the possible advantages related to the use of VMAT and helical IMRT and two different modalities of boost delivering, adjuvant stereotactic boost (SRS) or simultaneous integrated boost (SIB), in the treatment of brain metastasis (BM) in RPA classes I-II patients.

METHODS

Ten patients were treated with helical IMRT, 5 of them with SRS after whole brain radiotherapy (WBRT) and 5 with SIB. MRI co-registration with planning CT was mandatory and prescribed doses were 30 Gy in 10 fractions (fr) for WBRT and 15Gy/1fr or 45Gy/10fr in SRS or SIB, respectively. For each patient, 4 "treatment plans" (VMAT SRS and SIB, helical IMRT SRS and SIB) were calculated and accepted if PTV boost was included in 95 % isodose and dose constraints of the main organs at risk were respected without major deviations. Homogeneity Index (HI), Conformal Index (CI) and Conformal Number (CN) were considered to compare the different plans. Moreover, time of treatment delivery was calculated and considered in the analysis.

RESULTS

Volume of brain metastasis ranged between 1.43 and 51.01 cc (mean 12.89 ± 6.37 ml) and 3 patients had double lesions. V95% resulted over 95 % in the average for each kind of technique, but the "target coverage" was inadequate for VMAT planning with two sites. The HI resulted close to the ideal value of zero in all cases; VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS showed mean CI of 2.15, 2.10, 2.44 and 1.66, respectively (optimal range: 1.5-2.0). Helical IMRT-SRS was related to the best and reliable finding of CN (0.66). The mean of treatment time was 210 s, 467 s, 440 s, 1598 s, respectively, for VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS.

CONCLUSIONS

This dosimetric comparison show that helical IMRT obtain better target coverage and respect of CI and CN; VMAT could be acceptable in solitary metastasis. SIB modality can be considered as a good choice for clinical and logistic compliance; literature's preliminary data are confirming also a radiobiological benefit for SIB. Helical IMRT-SRS seems less effective for the long time of treatment compared to other techniques.

Does Graded Prognostic Assessment outperform Recursive Partitioning Analysis in patients with moderate prognosis brain metastases?

AIM

To compare the clinical utility of the Recursive Partitioning Analysis (RPA) and Graded Prognostic Assessment (GPA) in predicting outcomes for moderate prognosis patients with brain metastases.

METHODS & MATERIALS

We reviewed 101 whole brain radiotherapy cases. RPA and GPA were calculated. Overall survival was compared.

RESULTS

Sixty-eight patients had moderate prognosis. RPA patient characteristics for increased death hazard were ≤10 WBRT fractions or no surgery/radiosurgery. GPA patients had increased death risk with no surgery/radiosurgery or lower Karnofsky Performance Status.

CONCLUSION

The indices have similar predicted survival. Patients scored by RPA with longer radiation schedules had longer survival; patients scored by GPA did not. This indicates GPA is more clinically useful, leaving less room for subjective treatment choices.

The treatment of patients with 1-3 brain metastases: is there a place for whole brain radiotherapy alone, yet? A retrospective analysis

AIM

To evaluate the efficacy of whole brain radiotherapy (WBRT) with or without other treatments in patients (pts) with 1-3 brain metastases (BM).

MATERIALS AND METHODS

Toxicities and survival of 134 pts treated between 2009 and 2013 with WBRT alone (58 pts), WBRT plus surgery (SUR-WBRT: 42 pts) or WBRT followed by stereotactic or integrated boost radiotherapy (SRT-WBRT: 34 pts) were analyzed. Differences in toxicity (acute and late) incidence and in overall (OS), disease-free (DFS) and disease-specific survival (DSS) were evaluated (χ(2)-test, uni- and multivariate analysis).

RESULTS

Pts given intensified treatments (SUR- and SBRT-WBRT) had better 3-month local response compared to WBRT alone group (p < 0.045). Better 1-year local control was evident only in SRT-WBRT pts (p < 0.035). Univariate OS analysis confirmed, as favorable prognostic factors, RPA class I (p < 0.001), GPA class III and IV (p < 0.001), single metastasis (p = 0.045), stable primary disease (p = 0.03), intensified treatment (p = 0.000), systemic therapy after radiotherapy (p = 0.04) and response of metastatic lesions (p = 0.002). At multivariate analysis, OS was better in RPA class I pts (p = 0.002), who had more aggressive radiotherapy treatments (p = 0.001), chemotherapy after radiotherapy (p < 0.001) and response to RT (p = 0.003). Response to radiotherapy (p = 0.002) and BM number (p < 0.001) resulted independently prognostic for DFS. About 60 % of patients had mild acute toxicity (G1), especially headache (51 %) and fatigue (34 %); only 2 patients (2 %) had severe (G3) headache and 5 patients (4 %) severe fatigue (G3) reversible with oral steroids. No differences were evident between the different treatment groups. Among 80 pts followed up with MRI, 12 (15 %) had leukoencephalopathy (equally distributed across subgroups) and 5 (6 %) radionecroses, 4/5 asymptomatic, 5/5 in pts given intensified treatments.

CONCLUSIONS

This analysis confirms the known prognostic factors for BM, emphasizing the importance of intensified treatments in a population with favorable features.

Parotid glands in whole-brain radiotherapy: 2D versus 3D technique for no sparing or sparing

PURPOSE

Whole-brain radiotherapy is performed as standard therapy in patients with multiple brain metastases and in patients with more favourable prognosis such as lymphoma and small-cell lung carcinoma in the prophylactic setting. Because of the prognosis and the total prescribed dose, the parotid glands are not usually regarded as an organ at risk in whole-brain radiotherapy. Long-term survival can be expected in some of these patients and late toxicity can be observed, becoming essential to evaluate organs at risk, particularly the parotid glands even in metastatic patients. We compared the 2D with 3D technique to evaluate parotid glands involvement and received dose, and coverage of the clinical target volume.

MATERIALS AND METHODS

Seven patients were considered. The prescribed dose was 30 Gy in ten fractions. On the same day and with the same set-up, all the treatment planning were performed using a 2D and 3D technique. A treatment plan was performed following same technical characteristics as the 2D technique. The parotid glands and whole brain were delineated. Dose-volume statistics were analysed.

RESULTS

Dose-volume histograms of the parotid glands showed that 2/7 patients (28 %) received a mean dose >20 Gy. We found a lack of coverage of the clinical target volume in 6/7 patients.

CONCLUSIONS

Planning whole-brain radiotherapy with only the 2D technique involves a risk of including parotid glands in the field and not covering the clinical target volume. The 3D technique should be systematically performed and the parotid glands should be regarded as an organ at risk in whole-brain radiotherapy.