2622 - Postoperative Treatment for Metastatic Brain Metastases from Non-Small Cell Lung Cancer after Intracranial Tumor Resection: A Multi-Institutional Retrospective Study

M. Uto¹, D. Torizuka¹, Y. Mineharu^2,3, Y. Ueno⁴, N. Fukui⁵, Y. Kurosaki⁶, M. Chin⁶, T. Nakakuki⁷, H. Toda⁸, N. Takebe⁸, S. Horiguchi⁹, K. Fujimoto¹⁰, M. Hojo¹¹, S. Torikoshi¹², M. Nishimura¹², H. Chihara¹³, R. Narukami^1,14, Y. Makino¹⁵, T. Mizowaki¹, and Y. Arakawa²; ¹Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, Kyoto, Japan, ²Department of Neurosurgery, Kyoto University Graduate School of Medicine, Kyoto, Japan, ³Department of Artificial Intelligence in Healthcare and Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan, ⁴Department of Neurosurgery, Shinko Hospital, Kobe, Japan, ⁵Department of Neurosurgery, Kobe City Medical Center General Hospital, Kobe, Japan, ⁶Department of Neurosurgery, Kurashiki Central Hospital, Kurashiki, Okayama, Japan, ⁷Department of Neurosurgery, Kyoto Katsura Hospital, Kyoto, Japan, ⁸Department of Neurosurgery, Medical Research Institute Kitano Hospital, PIIF Tazuke-kofukai, Osaka, Japan, ⁹Department of Neurosurgery, Nagahama City Hospital, Nagahama, Shiga, Japan, ¹⁰Department of Neurosurgery, Kishiwada City Hospital, Kishiwada, Osaka, Japan, ¹¹Department of Neurosurgery, Shiga General Hospital, Moriyama, Shiga, Japan, ¹²Department of Neurosurgery, Japanese Red Cross Fukui Hospital, Fukui, Japan, ¹³Department of Neurosurgery, Hikone Municipal Hospital, Hikone, Shiga, Japan, ¹⁴Department of Radiology, Hikone Municipal Hospital, Hikone, Shiga, Japan, ¹⁵Department of Neurosurgery, NHO Kyoto Medical Center, Kyoto, Japan

Purpose/Objective(s): Whole brain radiotherapy (WBRT) has traditionally been used postoperative treatment for brain metastases, but based on the results of NCCTG N107/CEC-3, SRS for the resected cavity has also been performed. In addition, JCOG0504, a phase III non-inferiority trial comparing WBRT and salvage SRS (salvage SRS for residual lesions and follow-up if no residual lesions after total resection), demonstrated the non-inferiority of the salvage SRS group. Therefore, WBRT, SRS for the resected cavity, and salvage SRS are performed on a case-by-case, institution-by-institution in Japan. We analyzed the status of post-treatment after resection of metastatic brain tumors in Japan to optimize the treatment strategy. Materials/

Methods: This study included patients who were diagnosed as non-small cell lung cancer histopathologically and underwent resection for metastatic brain tumors between May 2016 and April 2020. Twelve centers associated with Kyoto University participated in the study and 117 patients were enrolled. Eighty-eight patients had adenocarcinoma and 12 had EGFR mutations. The median age at surgery was 69 years and 29 patients had extracranial lesions that required treatment at the same time as metastatic brain tumor lesions. The en bloc/piece meal method was used in 53/64 cases, respectively. Survival and intracranial progression-free survival were analyzed in 3 groups: no postoperative radiotherapy (NR)/WBRT/local irradiation (LR) including 3D-CRT and SRS.
Results: In 93 total and 24 non-total resected cases, NR/WBRT/LR was performed in 42/26/25 and 4/12/8 cases, respectively. The median follow-up was 17.3 months (range, 0.3-73.8). The median overall survival was 28.5 months, and the survival rate at 12, 18, and 24 months was 75.0 %, 64.1 %, 52.3 %, respectively. The median intracranial progression-free survival (IPFS) was 15.0 months, and the 12-, 18-, and 24-month IPFS rates were 52.3%, 47.9%, and 41.6%, respectively. The cumulative intracranial recurrence rate at 12, 18, 24 months, considering competing risks, was 27.7 %, 29.9 %, 32.2 %, respectively. There were no significant differences in survival or IPFS between the two groups in terms of removal method (en bloc vs. piece meal) or degree of removal (total vs. non-total removal), but overall survival was significantly better in the NR group compared with the WBRT group (p=0.005).
Conclusion: The median survival of 28.5 months was longer compared to previous reports, possibly reflecting the improved prognosis due to the advance of systemic therapy. Although we cannot deny the possibility that this retrospective analysis reflects the current situation in which WBRT is performed to patients with multiple brain metastases or poor prognosis, LR and NR based on close follow-up may be a promising strategy for postoperative treatment of metastatic brain tumors.