Early surveillance imaging (< 6 months) after stereotactic body radiation therapy for early-stage non–small cell lung cancer (NSCLC) seems to be of limited benefit, resulting in definitive intervention in only 3% of patients, according to the findings of a study in Practical Radiation Oncology. Daly et al concluded that a first surveillance scan at 6 months after treatment of early-stage NSCLC should be adequate for most patients, although larger-scale prospective studies may help to identify those few who might benefit from more aggressive surveillance.
For patients with early-stage inoperable NSCLC, stereotactic body radiation therapy is an effective treatment option, with local tumor control rates of more than 90% at 3-year follow-up. However, regional relapses have been reported in up to 11% of patients and distant relapses, in up to 29% of patients.
The optimal surveillance imaging strategy after therapy in this patient population remains unclear, both in terms of its timing and choice of modality (positron-emission tomography [PET]/computed tomography [CT] or CT alone). Patterns of use tend to vary considerably, from < 4 weeks to > 25 weeks.
To assess the impact of early (within 6 months of stereotactic body radiation therapy) surveillance CT on future therapeutic interventions, the investigators conducted a study in 62 patients treated for early-stage NSCLC at the University of California, Davis, from January 2007 to January 2013.
A histologic glimpse at these patients revealed that 66% of them had adenocarcinoma and 25% had squamous cell carcinoma. The median age of these patients was 76.3 years (range, 48.9–90.5 years). The majority of these tumors (77%) were considered to be medically inoperable by a Board-certified thoracic surgeon. All of these patients received a radiation dose between 48 and 60 Gy, administered in 3 to 8 fractions.
The institution’s surveillance imaging strategy generally included a first CT scan with intravenous contrast and 1- to 1.5-mm slice thickness at 3 months after stereotactic body radiation therapy. However, in this study, patients underwent their first surveillance scans anywhere from 4 weeks to 6 months post-treatment, based on the physician’s preference at the time of therapy.
Treatment Course Altered by Early Imaging in Four Patients
The investigators reported that 92 imaging studies were performed within 6 months of stereotactic body radiation therapy, with a median of 2.1 months post-treatment (range, 0.1–5.9 months). Most of these were CT scans (93%), with the others being PET/CT scans.
Indeterminate new lung nodules were found in seven patients (11%). Metastatic disease was diagnosed in two patients, both of whom were treated subsequently with systemic therapy. Biopsy-proven solitary lung recurrence was diagnosed in two other patients, both of whom were treated successfully with local therapy. The five patients for whom nonspecific new lung nodules were identified were followed with ongoing surveillance CT, and the investigators noted that none of them has progressed radiographically or clinically.
Therefore, early post-treatment imaging altered the subsequent treatment course for four patients (6.5%; 95% confidence interval [CI] = 1.7%–15.2%). Two of these four patients underwent definitive, potentially curative intervention (3.2%; 95% CI = 0.4%–10.8%) for disease detected on surveillance imaging within 6 months of stereotactic body radiation therapy.
In the detection of recurrent or residual disease, imaging within the first 6 months after treatment of early-stage NSCLC appeared to be of limited benefit, according to these study data. However, the investigators admitted that their study has some limitations, including relatively small patient numbers from a single institution, a heterogeneous patient population, and inconsistent timing of early surveillance imaging studies. Larger-scale prospective studies may help to identify those few who might benefit from more aggressive surveillance.
“The development of nuanced surveillance algorithms accounting for both patient- and tumor-specific predictive factors as well as prior imaging findings could ultimately reduce unnecessary imaging while allowing for expedient detection of recurrences,” concluded the investigators.
Megan E. Daly, MD, of the Department of Radiation Oncology, UC Davis Comprehensive Cancer Center, Sacramento, California, is the corresponding author of the article in Practical Radiation Oncology.
This study was supported by a grant from the Biostatistics Shared Resource of the UC Davis Comprehensive Cancer Center. The authors disclosed no potential conflicts of interest.
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