Page 64 - Read Online

Enrique et al. J Cancer Metastasis Treat 2019;5:54 I http://dx.doi.org/10.20517/2394-4722.2019.20 Page 9 of 16

Table 4. Most used radiation therapy schemes for WBRT
Dose and fractionation BED (Gy)
30 Gy/2 weeks 60
20 Gy/1 week 46.67
37.5 Gy/3 weeks 68.75
40 Gy/4 weeks 66.67

Abbreviations: BED: Biologically equivalent dose. Gy: Gray

Table 5. Former RTOG dose and fractionation protocols for brain metastases
RTOG brain metastasis protocols
First study Second Study
Scheme # patients Scheme # patients
3000 rad/2 weeks 233 2000 rad/2 weeks 447
3000 rad/3 weeks 217
4000 rad/3 weeks 233 3000 rad/2 weeks 228
4000 rad/4 weeks 227 4000 rad/3 weeks 227

Considerations that can be taken into account as the physician decides on one fractionation scheme over
another are the patient’s performance status, estimated survival, and histology of the primary tumor
because choriocarcinoma, melanoma, and renal cell carcinoma, among other types, present a higher risk of
bleeding [43,48,49] .

The shorter-course fractionation of 20 Gy in 1 week is preferable for most patients with poor performance
status, to avoid unnecessary treatment time, as it has demonstrated similar survival benefits as longer
treatment schemes . However, other fractionation schemes such as 37.5 Gy in 3 weeks is recommended
[50]
in patients who have received a stereotactic radiosurgery boost with one metastatic lesion and should be
considered in patients with one to three lesions .
[51]

WBRT, unlike SRS, is associated with lower intracranial relapse, but when the whole brain is irradiated
with this technique, it may also lead to greater cognitive deterioration (reflected as short-term memory loss),
especially in patients with a longer life expectancy (> 6 months). In Aoyama et al. , global survival did
[52]
not significantly differ between treatment techniques (8.0 vs. 7.5 months) but there was a difference in the
presentation of new metastases (63.7% vs. 41.5%) WBRT as shown Figure 5.

Role of Radiosurgery in the treatment of brain metastases
SRS-based treatment began in 1951, with its implementation by Lars Leksell. It uses multiple rays of radiation,
which converge three-dimensionally on a localized objective, either static or mobile, giving a high dose to a
unique fraction with a high fall-off. This minimizes the damage to the adjacent tissue .
[53]
Luckily, more than half of brain metastasis patients present with three or fewer lesions at diagnosis. It has
been demonstrated that both surgical treatment and SRS lead to longer overall survival in these patients,
especially for lone lesions smaller than 30 mm, where SRS has an overall survival comparable to microsurgery.
However, it is important to take into account that although brain metastases tend not to invade more than
a few millimeters of adjacent tissue, local recurrences are common after resection, meaning that adjuvant
treatment with radiotherapy after surgery is imperative . To reduce cognitive impairment in such patients,
[54]
the use of SRS has grown in use as an alternative to WBRT in the first 6 weeks following surgery, with the
goal being to maintain local control in surgery and preserve neurocognitive functions without lowering
quality of life .
[52]
Clinical presentation with a single metastasis appears in only 10% to 20% of patients, where treatment with
SRS following surgery improves both local recurrence rates and death due to neurological causes [55,56] .