Evaluation of Treatment Response After Nonoperative Therapy for Early-Stage Non-Small Cell Lung Carcinoma

Abstract

Nonsurgical management of early primary lung cancer has grown tremendously in recent years, and today, available options extend far beyond that of conventional radiation therapy (CRT) to include minimally invasive image-guided delivery of thermal energies, specifically radiofrequency ablation, microwave ablation, and cryoablation, and more conformal stereotactic body radiation therapy. Because the tumor is never resected with these nonoperative interventions, histopathological evaluation of tumor margins for the presence of residual tumor is impossible, and as such, tumor response after each of these therapies is largely based on imaging. To date, computerized tomography and computerized tomography-positron emission tomography remain the most readily available modalities for assessment of therapeutic efficacy, and to this end as detailed within this article, strict imaging survey and familiarity with the expected imaging characteristics of the treated tumor will aid in recognition of unexpected findings, specifically those of incomplete therapy and/or tumor recurrence.

Integrated imaging of non-small cell lung cancer recurrence: CT and PET-CT findings, possible pitfalls and risk of recurrence criteria

“…Distinguishing recurrence in these patients can therefore be challenging and requires experienced readers, also considering the fact that radiation-induced fibrosis can appear more than 1 year after the end of therapy [38]. Detection of recurrence may be difficult within 9 months of the delivery of SBRT because of secondary radiation pneumonitis [39]. Matsuo et al [40] reported that, among other factors, only growth of consolidation after 12 months on CT was a statistically relevant predictor of recurrence.…”

“…Matsuo et al [40] reported that, among other factors, only growth of consolidation after 12 months on CT was a statistically relevant predictor of recurrence. Otherwise, other findings already described as signs of recurrence after conventional radiotherapy can be used to suspect recurrence after SBRT; these include the filling of radiation-induced ectatic bronchi [41], development of bulging at margins of radiation-induced consolidation, and [39]. PET-CT is also a helpful technique for early detection of recurrence after SBRT, even though it needs to be applied in conjunction with other techniques [42].…”

Assessment of Response to Therapy

“…However, Eradat et al in their comprehensive review have stated that 1 week after ablation is too soon to detect treatment response by 18F-FDG PET (Eradat et al 2011). In fact, post-ablation inflammation may obscure subcentimeter residual tissue, and so it is usually delayed until 2 months (Okuma et al 2006).…”

“…In fact, post-ablation inflammation may obscure subcentimeter residual tissue, and so it is usually delayed until 2 months (Okuma et al 2006). However, during the intermediate phase (1 week to 2 months), a reduction of less than 60 % of uptake relative to pretreatment value is an indicator of persistent disease (Eradat et al 2011).…”

“…The critical role of PET in these settings is emphasized by the fact that almost 170,000 people are diagnosed with lung cancer just in the United States each year (Erdi et al 2000). The tremendous growth in non-surgical management of early primary lung cancer in recent years, and the availability of different therapeutic options far beyond conventional radiation therapy, emphasize the need for effective tools to assess the response to treatment early after or even during the course of such therapies (Eradat et al 2011). A recent comprehensive review reported by Langer confirms that due to improved care and less exposure to futile treatments, personalized medicine using PET may be cost-effective, the strongest evidence for which is still in the staging of NSCLC (Langer 2010).…”