Stereotactic Body Radiation Therapy (SBRT) in treating early-stage non-small cell lung cancers (NSCLC) can be considered a safe and effective alternative treatment to surgical resection especially for patients deemed inoperable according to the study reports presented by American Society for Radiation Oncology (ASTRO). Recent studies indicate that for otherwise healthy patients with operable early stage lung cancer, SBRT may be an acceptable alternative to surgery and may even have a survival advantage.
Traditionally, surgical treatments like lobectomy or pneumonectomy are recommended for early-stage lung cancer resulting in 3-5 year survival rates of 60-80%. Conventionally Fractionated Radiotherapy (CFRT) is also not as effective with respect to 3-year or 5-year survival rates providing a strong rationale for surgical resection.
The use of SBRT in treating early stage-lung cancer has grown rapidly in the last decade as its outcomes are nearly as good as surgical resections in high-risk lung cancer patients. The advanced SBRT radiation demands highly sophisticated treatment planning to deliver precisely higher doses of radiation leaving the surrounding critical tissues and structures unharmed.
Studies reveal a clear dose-response relationship for tumor control with escalated doses in SBRT. This high-precision radiation delivery contributes to treatment effectiveness for patients with lung tumors. It is important that your radiation oncology physician has special expertise in SBRT planning and treatment delivery.
Advantages of SBRT:
SBRT provides a viable alternative to surgery mainly for the following:
- Excellent local control 90% at 3 years)
- Approved level of toxicity.
- Requires five or fewer sessions or fractions.
- Provides a less toxic treatment option for patients with high operative risks. For example, aged patients and those with severe COPD
The American Society for Radiation Oncology (ASTRO) has introduced a new set of evidence-based guidelines in administering SBRT in early stage NSCLC patients. Its main objective is to address lung cancer patients deemed inoperable but require customized SBRT in high-risk clinical scenarios like:
- Salvage therapy after a previous surgery or radiation therapy
- Tumors invading the chest wall
- Very large tumors
Special guidelines are also recommended to treat centrally located tumors which carry high-risk compared to the peripheral ones. These also focus on the appropriateness of SBRT application in operable patients, an area of debate and controversy.
Non-invasive SBRT vs surgery: Comparative evidence-based analyses
[ A ] A past analysis of early stage NSCLC patients deemed unfit for lobectomy revealed no pronounced difference in treatment outcomes between SBRT and wedge resection.
- No differences with respect to local recurrence.
- No distant metastatis or freedom from any failure.
- With SBRT, the risk of local recurrence was less; the overall survival was higher in surgery (87% vs 72%).
- The cause-specific survival remained almost the same (93% with SBRT and 94% with wedge resection). [i]
[ B ] A similar finding was observed in a propensity-matched study with stage 1 patients. 462 of them underwent surgery and 76 were treated with SBRT. Both the groups showed similar rates of local recurrence and disease-specific survival and the 4-year local control was 90%.[ii]
[ C ] A retrospective analysis by Japanese investigators with 87 Stage 1 patients who refused surgery and were treated with SBRT showed following results:
- The 5-year local control rate for T1 and T2 tumors were 92% and 73% respectively.
- The 5-year overall survival rate for Stage 1A and Stage 1B groups were 72% and 62% respectively. Researchers concluded that survival rate with SBRT is almost comparable to surgery.
[ D ] In another propensity-matched analysis by Japan Clinical Oncology Group (JCOG) showed the superiority of SBRT over surgery. 64 patients underwent minimally-invasive surgery and 64 patients were treated with SBRT. 1-year and 3-year loco-regional control rates were found to be superior with SBRT over surgery.
[ E ] In another recent study, SBRT has been found to be effective even in elderly patients (≥80 years of age) resulting in better local control and minimum toxicity.
[ F ] Advanced SBRT with Cyberknife has also shown significant improvement in emotional functioning in a study with patients suffering from Stage I non-small lung cancer. It also showed acceptable survival rate, high local control and low toxicity.
However, several randomized studies comparing the benefits of SBRT and surgery could not be completed because of poor accrual.
Possible improvement in the quality of life and pulmonary function post SBRT:
- Analysis of one Radiation Therapy Oncology Group (RTOG) trial showed no significant effect on overall condition but there were non-significant declines in forced expiratory volume (FEV) and carbon-monoxide diffusing capacity.
- A study from Cleveland Clinic revealed minor declines in diffusing capacity of CO. The quality of life remained same that maintained the same 6-minute walking distance. No increase in dyspnea was reported.
Is SBRT appropriate for all patients with early-stage lung cancer?
Not all patients can be given SBRT but very few can be excluded.
- SBRT is effective in treating small-sized centrally located tumors but the risk of side effects is more with less expectation in local control.
- Emerging evidence shows effectiveness of SBRT in larger tumors (T2) with 4-5 cm diameter but the local control is less than that observed with smaller tumors.
- Patients with poor pulmonary function at the baseline can also be considered for SBRT depending on certain preconditions.
- Patients that are not good candidates for SBRT may be treated with other hypofractionation regimens which may require a few more treatments but also have excellent outcomes with low risk of side effects
Today, a large body of evidence supports the use of SBRT in treating early stage NSCLC but decisions in optimal choice of treatments should be made by a multidisciplinary team after a careful analysis of all possible outcomes.