Fractionated stereotactic radiotherapy to the post-operative cavity for radioresistant and radiosensitive brain metastases

Abstract

Following surgical resection for brain metastases, fractionated stereotactic radiotherapy (FSRT) has been used as an alternative to single dose treatment for large cavities and to reduce risks of late toxicity. The purpose of this study was to evaluate the outcomes of patients treated with FSRT to the post-operative bed for both radioresistant and radiosensitive brain metastases. Between December 2009 and May 2013 a total of 65 patients with newly diagnosed brain metastases were treated with resection followed by FSRT. Patients were treated to a total dose of 20-30 Gy in five fractions. Median planning target volume (PTV) was 16.88 cm(3) (range 4.87-128.43 cm(3)). The median follow-up for all patients was 8.5 months (range 1.1-28.6 months) with a median of 12.9 months for living patients. One and two year Kaplan-Meier estimates of local control were 87.0 and 70.0 %, respectively. Local control at 1 year was 85.6 and 88.0% for radioresistant and radiosensitive tumors, respectively (p = 0.44). A PTV ≥17 cm(3), was associated with local failure, HR 8.63 ((1.44-164.78); p = 0.02). One and two year distant control rates were 50.9 and 46.2%, respectively with six patients (9.2%) experiencing leptomeningeal disease. OS rates at 1 and 2 years were 65.2 and 47.5%, respectively. Survival was significantly associated with recursive partitioning analysis class (p = 0.001) and graded prognostic assessment score (p = 0.005). One case of radionecrosis was noted on follow-up imaging. FSRT in five fractions offers excellent local control in both radiosensitive and radioresistant tumors with minimal toxicity.

Postoperative Fractionated Stereotactic Radiosurgery to the Tumor Bed for Surgically Resected Brain Metastases

“…This is in line with several other published series of fSRS which report one-year local control of 79-93%. [2, 4, 6-7]. Our median cavity size was similar to these series at 9.8 cc, and cavities up to 43 cc in size were treated safely.…”

“…Previous single fraction SRS series for intact brain metastases have shown that local control decreases with increasing tumor volume [16-17]. This has been noted in series of brain metastases treated with multimodality therapy, including fSRS [7]. Notably, the incidence of radionecrosis after single-fraction SRS has been shown to increase significantly when the volume receiving 12 Gy is > 8 cm 2  [18].…”

“…Results from multiple series show LC on the order of 75-85% with DBF rates of approximately 40-60% at one year [2-3]. Fractionated stereotactic radiosurgery (fSRS) has been employed in treating surgical cavities of increasing size in an attempt to maintain LC while reducing the risk of treatment toxicity [4-7]. Herein, we report on the postoperative fSRS experience at Vanderbilt University Medical Center.…”

Radionécrose cérébrale après irradiation en conditions stéréotaxiques des berges opératoires : analyse de la littérature à partir de quatre cas

“…Parmi ces 18 % de cas, quatre ont été confirmés histologiquement avec une absence de cellules tumorales permettant d'écarter une récidive locale associée, soit au total 4,2 %. L'incidence de radionécrose en radiothérapie stéréo-taxique postopératoire varie entre 1,5 et 17,5 % selon les études (Tableau 3) [6][7][8][9][10][11]. Cet écart tient notamment à la variabilité des critères retenus dans la définition : critères cliniques et/ou histologiques et/ou radiologiques, auxquels s'ajoute la notion de délai d'apparition.…”

Toxicity of Cranial and Spinal Cord Irradiation

“…There is a wide range of reported data on the rate of actuarial radionecrosis. In recent studies with adequate follow-up, rates vary from as low as 1.5% [26] to as high 34% [19,25,27] The main risk factor of radionecrosis are total dose, maximum tumor diameter and treated volume [25,27,28].…”