PET/CT and Outcome in Lung Cancer Treated with Stereotactic Body Radiation Therapy

Can stereotactic ablative radiotherapy in early stage lung cancers produce comparable success as surgery?

Early stage non-small cell lung cancer is a potentially curable manifestation of a disease that is typically associated with a grim prognosis. Therapies directed at early stage disease can be challenging to deliver because patients tend to be elderly with multiple comorbidities. Surgery, the standard of care, has been validated with long-term follow-up. However, the risk of perioperative mortality and morbidity can limit the feasibility of an operation for many high-risk patients. Stereotactic ablative radiotherapy uses highly focused, ablative doses of radiation to treat tumors and has emerged as an alternative to surgery.

Radiographic changes after lung stereotactic ablative radiotherapy (SABR)--can we distinguish recurrence from fibrosis? A systematic review of the literature

BACKGROUND

Changes in lung density on computed tomography (CT) are common after stereotactic ablative radiotherapy (SABR) and can confound the early detection of recurrence. We performed a systematic review to describe post-SABR findings on computed tomography (CT) and positron-emission tomography (PET), identify imaging characteristics that predict recurrence and propose a follow-up imaging algorithm.

METHODS

A systematic review was conducted of studies providing detailed radiologic descriptions of anatomic and metabolic lung changes after SABR. Our search returned 824 studies; 26 met our inclusion criteria. Data are presented according to PRISMA guidelines.

RESULTS

Acute changes post-SABR predominantly appear as consolidation or ground glass opacities. Late changes often demonstrate a modified conventional pattern of fibrosis, evolving beyond 2years after treatment. Several CT features, including an enlarging opacity, correlate with recurrence. Although PET SUVmax may rise immediately post-SABR, an SUVmax⩾5 carries a high predictive value of recurrence.

CONCLUSIONS

CT density changes are common post-SABR. The available evidence suggests that recurrent disease should be suspected if high-risk CT changes are seen with SUVmax⩾5 on PET. Further studies are needed to validate the predictive values of such metrics, and for advanced analysis of CT changes to allow early detection of potentially curable local recurrence.

Scalpel or SABR for Treatment of Early-Stage Lung Cancer: Clinical Considerations for the Multidisciplinary Team

Treatment options for early-stage (T1-2 N0) non-small cell lung cancer are often limited by the patient's advanced age, poor performance status, and comorbidities. Despite these challenges, stereotactic ablative radiotherapy (SABR) provides a highly effective and safe therapy for intrathoracic tumors and has become the standard of care for delivering definitive treatment in medically inoperable patients. High-quality treatment, which includes reliable immobilization, accurate tumor targeting, and precise verification of dose delivery, is essential both to achieve successful cure and to avoid debilitating toxicities. Generally, SABR is well tolerated in patients with peripherally located tumors, but even centrally or superiorly located lesions can be treated if there is adequate conformal avoidance of normal structures and/or modified fractionation to meet dose constraints. While several preliminary studies suggest that SABR is as efficacious as surgery in operable patients, results of randomized data will illuminate whether the indications for SABR can be expanded to include patients who are candidates for surgical resection. Herein, we review the rationale for using SABR and its application in treating different patient populations with early-stage lung cancer.