Expert Discussion: Hypofractionated Radiation Therapy - Standard for All Indications?

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Hypofractionated Radiation Induced the Immunogenic Death of Bladder Cancer Cells Leading to the Immune Sensitization of Dendritic Cells

Purpose Radiotherapy is a commonly used method in the treatment of bladder cancer (BC). Radiation induced immunogenic death (ID) and antitumor immune response are related to the prognosis of radiotherapy. As the most powerful antigen-presenting cell in the body, the role of dendritic cells (DCs) is not very clear. Methods Apoptosis level, cell cycle analysis and expression levels of high mobility group protein 1 (HMGB1), calreticulin (CRT) and heat shock protein 70 (HSP70) were performed for bladder cancer cells after hypofractionated radiotherapy. The effects of the conditioned media on DCs for antitumor immune response activation were studied as well. Results The significantly increased apoptosis level, G2/M phase cell cycle arrest and significantly increased HMGB1, CRT and HSP70 expressions, and increased secretion of CCL5 and CCL21 in the supernatant of bladder cancer cells after hypofractionated radiotherapy. The expression of CD80, CD86, CCR5 and CCR7 on DCs was upregulated in the conditioned media of bladder cancer cells after hypofractionated radiotherapy. Conclusion Hypofractionated radiation blocked the cell cycle of BC cells in the G2/M phase and induced ID occurrence, resulting in DCs immune sensitization, which is of great clinical significance in understanding the radiotherapy of BC and the immunoregulation function of DCs.

CTNI-37. ISOEFFECTIVE HYPOFRACTIONATION FOR ELDERLY OR FRAIL PATIENTS WITH A NEWLY DIAGNOSED GLIOBLASTOMA: A POOLED INTERNATIONAL STUDY

PURPOSE The standard of care (SOC) for elderly or frail glioblastoma (GBM) patients is 40 Gy in 15 fraction radiotherapy. However, this regimen has a lower BED compared to the Stupp regimen, 60 Gy in 30 fractions. We hypothesize that isoeffective hypofractionated radiation of 52.5 Gy in 15 fractions (BED equivalent to Stupp) will have superior survival compared to standard of care. METHODS Elderly GBM patients treated with 52.5 Gy in 15 fractions were pooled from 2 phase II studies, 1 phase 1 and a prospective observation study. Overall survival (OS) and progression free survival (PFS) were defined as the time elapsed between surgery/biopsy and death from any cause or progression. Univariate and multivariate analyses were performed. RESULTS 62 newly-diagnosed patients were eligible for this analysis. Median follow-up was 10 months. The median OS and PFS was 10.3 and 6.9 mos, respectively. Patients with KPS ≥ 70 and < 70 had a median OS of 15.3 and 9.5 mos. No survival difference was seen between unmethylated and methylated patients with a median OS of 10.2 and 10.3 months, respectively. Multivariable analysis demonstrated that concurrent chemotherapy was an independent prognostic factor for improved PFS and OS. Grade 3 neurologic toxicity was seen in 2 patients (3.2%). CONCLUSION This is the first pooled, prospective analysis of elderly/frail GBM patients treated with dose-escalated hypofractionated radiation. Treatment was well tolerated and demonstrated excellent OS and PFS, exceeding that from prior elderly trials (Roa; 6.5 mo [poor KPS]/Perry; 9.3mo [good KPS]). This treatment regimen gives the elderly population an alternative to Stupp that is not de-escalating therapy. Future prospective trials are needed to validate these results.