Breast cancer subtype and intracranial recurrence patterns after brain-directed radiation for brain metastases

PURPOSE

Brain metastases from breast cancer are frequently managed with brain-directed radiation but the impact of subtype on intracranial recurrence patterns after radiation has not been well-described. We investigated intracranial recurrence patterns of brain metastases from breast cancer after brain-directed radiation to facilitate subtype-specific management paradigms.

METHODS

We retrospectively analyzed 349 patients with newly diagnosed brain metastases from breast cancer treated with brain-directed radiation at Brigham and Women's Hospital/Dana-Farber Cancer Institute between 2000 and 2015. Patients were stratified by subtype: hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-), HER2+ positive (HER2+), or triple-negative breast cancer (TNBC). A per-metastasis assessment was conducted. Time-to-event analyses were conducted using multivariable Cox regression.

RESULTS

Of the 349 patients, 116 had HR+/HER2- subtype, 164 had HER2+ subtype, and 69 harbored TNBC. Relative to HR+/HER2- subtype, local recurrence was greater in HER2+ metastases (HR 3.20, 95% CI 1.78-5.75, p < 0.001), while patients with TNBC demonstrated higher rates of new brain metastases after initial treatment (HR 3.16, 95% CI 1.99-5.02, p < 0.001) and shorter time to salvage whole brain radiation (WBRT) (HR 3.79, 95% CI 1.36-10.56, p = 0.01) and salvage stereotactic radiation (HR 1.86, 95% CI 1.11-3.10, p = 0.02).

CONCLUSIONS

We identified a strong association between breast cancer subtype and intracranial recurrence patterns after brain-directed radiation, particularly local progression for HER2+ and distant progression for TNBC patients. If validated, the poorer local control in HER2+ brain metastases may support evaluation of novel local therapy-based approaches, while the increased distant recurrence in TNBC suggests the need for improved systemic therapy and earlier utilization of WBRT.

Local control after brain-directed radiation in patients with cystic versus solid brain metastases

PURPOSE

Brain metastases can be radiographically cystic or solid. Cystic metastases are associated with a greater intracranial disease burden and poorer oncologic outcomes, but the impact of cystic versus solid appearance on local control after radiation remains unknown. We investigated whether cystic versus solid nature is predictive of local control after management with stereotactic or whole brain radiation (WBRT) and whether the radiation modality utilized is an effect modifier.

METHODS

We identified 859 patients with 2211 newly-diagnosed brain metastases managed with upfront stereotactic radiation or WBRT without preceding resection/aspiration at Brigham and Women's Hospital/Dana-Farber Cancer Institute between 2000 and 2015. Multivariable Cox regression with an interaction term and sandwich covariance matrix was used to quantify local failure.

RESULTS

Cystic lesions were more likely to recur than solid ones when managed with stereotactic radiation (HR 2.33, 95% CI 1.32-4.10, p = 0.004) but not WBRT (HR 0.92, 95% CI 0.62-1.36, p = 0.67), p-interaction = 0.007. 1 year local control rates for cystic versus solid metastases treated with stereotactic radiation were 75% versus 88%, respectively; estimates with WBRT were 76% versus 76%, respectively. However, no significant differences were noted between the two cohorts in post-radiation outcomes including all-cause mortality and neurologic death (p > 0.05).

CONCLUSIONS

Among patients with brain metastases, stereotactic radiation yields improved local control and less morbidity than WBRT, and consequently for many patients the cystic versus solid designation does not impact treatment selection. However, our results suggest that in patients with a large number of cystic brain metastases, a lower threshold to consider WBRT, as opposed to stereotactic radiation, should be employed. If our results can be confirmed, further investigation into the underlying mechanism(s) would be warranted.

Neurosurgical Resection and Stereotactic Radiation Versus Stereotactic Radiation Alone in Patients with a Single or Solitary Brain Metastasis

BACKGROUND

Brain metastases commonly manifest in patients with cancer, with ∼20%-50% presenting with 1 intracranial lesion. Among patients with 1, small brain metastasis and controlled or absent extracranial disease, it remains unclear whether aggressive intracranial management using neurosurgical resection plus cavity stereotactic radiosurgery/stereotactic radiotherapy (SRS/SRT) rather than SRS/SRT alone is beneficial. In patients with controlled or absent extracranial disease and 1 brain metastasis ≤2 cm in size, we evaluated the effect of surgery plus SRS/SRT compared with SRS/SRT on oncologic outcomes, including overall survival.

METHODS

We retrospectively identified 86 patients with controlled or absent extracranial disease and 1 brain metastasis ≤2 cm in size who had been treated from 2000 to 2015 at our institution. We examined differences in the rates of local and distant failure, use of salvage treatment, and other oncologic outcomes, including all-cause mortality.

RESULTS

The baseline characteristics were similar between the 2 cohorts. The median follow-up period for the surviving patients was 38 months. On multivariable analysis, surgical resection plus cavity SRS/SRT was associated with a lower risk of all-cause mortality (hazard ratio, 0.44; 95% confidence interval, 0.19-1.00; P = 0.05) compared with SRS/SRT alone. The 1- and 2-year rates of overall survival were 100% and 88% versus 74% and 52% for surgery plus cavity SRS/SRT versus SRS/SRT alone, respectively.

CONCLUSIONS

Aggressive, local therapy, including neurosurgical resection, might benefit patients with 1 brain metastasis in the context of controlled or absent systemic disease, even if the lesion in question is small. Further studies are needed to evaluate these associations.