Clinical Applications and Integrative Strategies of Stereotactic Radiosurgery in Cancer Treatment
High-precision, high-dose local radiotherapy, combined with immunotherapy and integrated strategies, improves patient survival and quality of life
Free cancer support
Introduction
High-dose Photon Knife, clinically applied as Stereotactic Radiosurgery (SRS) or Stereotactic Body Radiotherapy (SBRT), is a highly precise, high-dose local radiotherapy technique. Its main advantage lies in delivering multiple high-energy photon beams converging on the tumor, inducing irreparable DNA damage in tumor cells while sparing surrounding normal tissues (Guckenberger et al., 2020).
This modality has been widely adopted in brain metastases, lung cancer, liver cancer, pancreatic cancer, and oligometastatic disease. Recently, its potential synergy with immunotherapy has attracted increasing attention (Demaria & Formenti, 2020).
Physical Principles and Treatment Characteristics
Dose Distribution vs. Bragg Peak
Although photon therapy does not have the Bragg peak effect seen in proton therapy, multiple converging photon beams can achieve highly concentrated dose regions, ensuring the tumor receives ablative doses while minimizing exposure to adjacent normal tissues (Brown et al., 2019).
Hypofractionation and High Doses
Traditional radiotherapy typically requires 25–35 sessions at 1.8–2 Gy per fraction. In contrast, SRS/SBRT applies high-dose, low-fraction regimens such as a single 18–24 Gy session or 3–5 fractions, achieving equal or superior tumor control rates (Videtic et al., 2019).
Image-Guided Precision
Through image-guided radiotherapy (IGRT) and respiratory gating techniques, positional uncertainties are minimized, ensuring accurate delivery of high-dose radiation to the tumor (Potters et al., 2017).
Clinical Applications
Brain Tumors and Metastases
Photon Knife was first applied to brain tumors. For brain metastases, vestibular schwannomas, and meningiomas, SRS has become a standard therapy. Local control rates reach 80–90% with a lower toxicity profile compared to whole-brain radiotherapy (WBRT) (Yamamoto et al., 2014).
Lung and Liver Cancers
For patients with early-stage non-small cell lung cancer (NSCLC) who are inoperable, SBRT achieves over 85% 3-year local control, with survival outcomes comparable to surgery (Chang et al., 2015). Similarly, SBRT provides effective local control for hepatocellular carcinoma (HCC) and liver metastases, and can complement ablation or transarterial chemoembolization (TACE) (Bujold et al., 2013).
Oligometastatic Disease (OMD)
In patients with ≤5 metastases, SBRT significantly improves progression-free survival (PFS) and overall survival (OS). The SABR-COMET trial confirmed that OMD patients treated with SBRT achieved a 5-year OS of 42%, markedly better than standard therapy (Palma et al., 2019).
Immunological Effects and Integrative Therapy
| Domain/Strategy | Function & Recommendation | Reference |
|---|---|---|
| Abscopal Effect | High-dose SBRT not only directly kills tumors but also releases tumor-associated antigens, activating dendritic cells and T cells, which may shrink unirradiated tumors as well. | Demaria & Formenti, 2020 |
| Combination with Immune Checkpoint Inhibitors | PD-1/PD-L1 or CTLA-4 inhibitors combined with SBRT have shown synergistic effects in clinical trials for melanoma, lung cancer, and renal cell carcinoma, turning "cold tumors" into "hot tumors" and improving immunotherapy response rates. | Theelen et al., 2019 |
| Integrative Nutrition & Supportive Care | Patients receiving SBRT, combined with immunonutrition (L-arginine, Omega-3 fatty acids, glutamine) and anti-inflammatory diets, may experience reduced gastrointestinal side effects and improved immune recovery. Additionally, exercise and mindfulness-based stress reduction (MBSR) can relieve radiotherapy-related fatigue and anxiety, enhancing adherence and quality of life. | Arends et al., 2021; Greenlee et al., 2017 |
Advantages and Limitations
Advantages:
- High precision with sparing of surrounding tissues
- Fewer sessions, shorter treatment duration
- Suitable for patients unfit for surgery or refusing surgery
- Potential synergy with immunotherapy and targeted therapy
Limitations:
- Best suited for tumors <5 cm
- High cost, limited availability in specialized centers
- Severe toxicity possible if dose delivery errors occur (e.g., cerebral edema, GI ulcers)
Conclusion
High-dose Photon Knife (SRS/SBRT) has become a cornerstone of precision radiotherapy in oncology, offering effective control in brain metastases, early-stage lung cancer, liver cancer, and oligometastatic disease. Its rapid, effective, and minimally toxic profile makes it a critical alternative or adjunct to surgery and conventional radiotherapy.
Most importantly, integration with immunotherapy, nutritional support, and lifestyle interventions enhances survival outcomes and patient quality of life.
Future research priorities include:
- Optimizing timing and sequencing of high-dose radiotherapy with immunotherapy
- Identifying biomarkers predictive of the abscopal effect
- Designing clinical trials that integrate nutritional and mind-body interventions
Contact our professional team now
References
- Arends, J., et al. (2021). ESPEN guidelines on nutrition in cancer patients. Clinical Nutrition, 40(5), 2898–2913.
- Brown, J. M., Carlson, D. J., & Brenner, D. J. (2019). The tumor radiobiology of SRS and SBRT: are more than the 5 R’s involved? International Journal of Radiation Oncology Biology Physics, 110(1), 124–138.
- Bujold, A., et al. (2013). Sequential phase I and II trials of SBRT for hepatocellular carcinoma and liver metastases. Journal of Clinical Oncology, 31(13), 1631–1639.
- Chang, J. Y., et al. (2015). Stereotactic ablative radiotherapy versus lobectomy for operable stage I NSCLC: a pooled analysis of two randomized trials. The Lancet Oncology, 16(6), 630–637.
- Demaria, S., & Formenti, S. C. (2020). Radiation as an immunological adjuvant: current evidence on dose and fractionation. Frontiers in Oncology, 10, 671.
- Guckenberger, M., et al. (2020). Definition and characterization of oligometastatic disease: an ESTRO-ASTRO consensus report. The Lancet Oncology, 21(1), e18–e28.
- Greenlee, H., et al. (2017). Clinical practice guidelines on the use of integrative therapies as supportive care in breast cancer patients. Journal of Clinical Oncology, 35(18), 1962–1981.
- Palma, D. A., et al. (2019). Stereotactic ablative radiotherapy for the comprehensive treatment of oligometastatic cancers (SABR-COMET): long-term results. The Lancet, 393(10185), 2051–2058.
- Potters, L., et al. (2017). American Society for Radiation Oncology (ASTRO) evidence-based guideline for SRS/SBRT. Practical Radiation Oncology, 7(5), 295–301.
- Theelen, W., et al. (2019). Effect of pembrolizumab after stereotactic body radiotherapy vs pembrolizumab alone in advanced NSCLC. JAMA Oncology, 5(9), 1276–1282.
- Videtic, G. M. M., et al. (2019). Stereotactic body radiotherapy for early-stage NSCLC: evidence-based guidelines. Journal of Thoracic Oncology, 14(6), 947–960.
- Yamamoto, M., et al. (2014). SRS alone vs SRS plus WBRT for brain metastases: JLGK0901 trial. The Lancet Oncology, 15(4), 387–395.