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Advances in Radiotherapy
& Nuclear Medicine SRS after WBRT

be potentially brought down through improved systemic at a multi-disciplinary neuro-oncology clinic until the
control using new agents such as immunotherapy. 2,4,6,9,10 3 year, under the assumption that scans are normal. If
12
rd
Patients with intracranial progression after WBRT suspected of having recurrence versus radiation necrosis,
present a therapeutic dilemma. The radiation options asymptomatic patients are started on pentoxifylline
include repeat WBRT or salvage SRS. Several studies (Trental) and vitamin E with repeat scans performed in
reported that repeat WBRT led to a survival time of 8 weeks. If the abnormality persists, patients are indicated
around 4 months. A limited number of studies focusing for dynamic MRI imaging consisting of MRI spectroscopy
2,10
and MRI perfusion to determine whether radiation
on salvage SRS after WBRT failure found SRS a safe and necrosis or disease progression is the cause, and biopsy
effective treatment contributing to a survival time of will be performed if feasible. Cases are often presented in
between 8 and 9 months. 11,12
multi-disciplinary tumor board. Table 1 illustrates patient
While SRS for limited brain metastases after WBRT characteristics of interest.
appears to be a good treatment option, several questions
in this aspect remain unanswered. It is unknown if a short 3. Results
time interval to failure after WBRT would make further A total of 112 patients and 699 treated brain metastases
radiation futile and if there is a cut-off in the number of were evaluated. There were 18 patients who underwent
CNS metastases that can be salvaged with SRS after WBRT SRS multiple times, ranging from two to five times (a total
failure. of 134 SRS sessions). The median time from WBRT to
2. Methods SRS was 266 days (range: 23–1722 days). The majority of
previous WBRT was 30 Gy in 10 fractions. The median
This is an IRB approved by Cooper Medical School of number of CNS metastases treated with salvage SRS was 4
Rowan University (EX1092) for retrospective review (range: 1–29) (Table 1).
of prospective SRS database at a single institution from The median follow-up durations for all patients and
2007 to 2019. We prospectively collected all treatment surviving patients were 116 days and 168 days, respectively,
information for our SRS cases; additional information and the median overall survival was 210 days (7 months).
required for this study was retrospectively collected. Patient The median survival by RPA status was 279, 176, and
charts were reviewed, and multiple variables were recorded. 95 days for RPA 1, 2, and 3, respectively (P < 0.007). Small
Kaplan–Meier with log-rank test was used to compare cell lung cancer (SCLC) and breast cancer were statistically
survival outcomes between variables. Independent t-test
was used to distinguish differences between means of Table 1. Patient characteristics
continuous variables, such as number of central nervous
system (CNS) metastases and Karnofsky performance Characteristics Statistics
(n=112)
scale (KPS) score. Chi-squared test was utilized to test
the significance for categorical variables, such as primary Primary cancer (n, %)
cancer. In addition, recursive partitioning analysis (RPA) Small cell lung cancer 34 (30.3%)
was used as a stratification tool. Survival was calculated Non-small cell lung cancer 34 (30.3%)
from the time SRS was performed. Breast cancer 29 (25.9%)
Radiosurgery was performed with Gamma Knife Melanoma 6 (5.4%)
®
Icon (Elekta, Stockholm Sweden). The majority of patients KPS
™
underwent thin-slice magnetic resonance imaging (MRI) Median 80
scanning on the day of SRS for SRS planning although Range 50–100
patients with high-quality MRI <2 weeks old could use the KPS≥70 94
diagnostic MRI for SRS planning. SRS was usually prescribed Brain metastases treated
to the 50% isodose line although small metastases could be
treated with a higher isodose line to reduce normal brain Median 4
dose. Radiation dose for brain metastases was based on the Range 1–29
size of brain metastases: 0–2 cm treated to 20 Gy, 2–3 cm Percent >5 30.3%
treated to 18 Gy, and 3–4 cm treated to 15 Gy. Interval from previous whole-brain radiation days
Standard follow-up at our institution for patients Median 266
with brain metastases is an MRI scan with contrast every Range 23–1722
3 months for the first 2 years and then every 4 months Abbreviation: KPS: Karnofsky performance scale.

Volume 2 Issue 1 (2024) 2 https://doi.org/10.36922/arnm.2231