- Stereotactic radiation therapy (SBRT), a single high-dose, small-field, focused irradiation that causes tumor necrosis, like a “radiation knife,” to achieve surgical-like effects;
These are the most common treatments.
SBRT is a good option for patients who are inoperable or unwilling to undergo surgery, while for patients who are operable, the risks of surgery should be fully considered, and if the risks are not high, surgery is recommended as the first option.
What are the advantages of stereotactic radiation therapy?
Stereotactic radiation therapy (SBRT, also known as stereotactic ablative radiotherapy, SABR) is a new radiotherapy technique that uses small field (smaller, more precise), focused (more focused), single high-dose irradiation to necrosis the tumor, like a “radiographic knife,” to achieve surgery-like results.
The term “single high-dose” irradiation is relative to conventional irradiation. The current standard radical radiation therapy dose for lung cancer is 60-66 Gy (Gy is the unit of radiation therapy dose) in 30-33 doses of 2 Gy once a day. However, the biological effects of the radiation are magnified and “more powerful” when higher doses are given in a single session.
For example, if you do stereotactic radiation therapy with a total dose of 60 Gy, you can get 120 Gy of biologic effect, 1.67 times more, if you do 6 sessions of stereotactic radiation therapy with 10 Gy each compared to 30 consecutive sessions of conventional radiation therapy with 2 Gy each.
Therefore, the advantages of stereotactic radiotherapy are:
- More precise localization and less damage to normal tissues;
- Higher biological effect, more lethal to tumors, even comparable to surgery;
- Reduced irradiation frequency and treatment time.
When can SBRT be used instead of surgery?
Stereotactic radiation therapy is mainly used for:
- Early stage lung cancer, “isolated” lung lesions (tumors less than 5 cm, less than 3 cm is better), no metastases elsewhere, and patients who are inoperable or unwilling to operate for various reasons;
- “Oligometastatic” lesions of lung cancer, such as brain metastases (currently accepted as less than 3 lesions, less than 3 cm in diameter), liver metastases, lung metastases, etc.
So, can early-stage lung cancer be treated with SABR instead of surgery? We can understand it from two perspectives.
- If surgery is not tolerated, the answer is yes. From clinical studies, SBRT can provide a long-term survival benefit to these patients that is far better than conventional radiotherapy.
- If surgery is possible, there is no definitive answer to this question. Some previous studies have shown that SBRT is as effective as surgery, but there are problems with these studies, such as the relatively small number of patients covered, the relatively short observation period (most studies were only 3 years), and the relatively poor surgical outcomes in the studies (the “opponents” of SBRT were too weak). Therefore, the results of these studies do not provide a definitive answer to this question.
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At this time, SBRT is recommended for patients with inoperable early-stage lung cancer; for those who are operable, surgery is still preferred and SBRT is not yet the standard of care.
In June 2017, the American Specialty Society released guidelines for stereotactic radiotherapy for early-stage non-small cell lung cancer. The guidelines state that for early-stage patients who are operable, if SBRT is considered, it needs to be evaluated by a thoracic surgeon, preferably with multidisciplinary expertise.
For patients with stage I non-small cell lung cancer,
- If the risk of surgery is at conventional levels, SBRT is not recommended as an alternative to surgery because the short-term efficacy of SBRT is more certain, but the long-term (more than 3 years) outcome is unknown.
- SBRT can be an alternative to surgery if the risk of surgery is high (e.g., if lobectomy is not tolerated but “less than lobectomy” is tolerated, such as segmental resection or wedge resection of the lung).
- If inoperable, SBRT can be used, but physicians should be careful to balance safety and efficacy.