Original StudyOutcomes of Modestly Hypofractionated Radiation for Lung Tumors: Pre- and Mid-Treatment Positron Emission Tomography-Computed Tomography Metrics as Prognostic Factors
Introduction
Modestly hypofractionated radiation therapy (HypoRT) allows for treatment completion within a shorter period and could be advantageous for patients with locally advanced lung tumors and a poor performance status or an inability to tolerate concurrent chemotherapy. HypoRT results in fewer daily treatments and a reduced cost compared with conventionally fractionated RT (CFRT) or combined chemotherapy and RT (chemoRT). Although small tumors can be treated effectively and safely with stereotactic ablative radiotherapy (SABR), a more fractionated approach is generally considered necessary for safe treatment of more advanced disease. Studies have shown effective treatment is attained with HypoRT for both early-stage non–small-cell lung cancer (NSCLC) and late-stage NSCLC and, with more accelerated courses, for oligometastatic lung cancer.1, 2, 3, 4, 5, 6, 7, 8, 9, 10 One concern is the potential for increased toxicity from HypoRT. However, the reported toxicities have generally been found to be acceptable compared with CFRT with appropriate patient selection and conformal radiation techniques. Although HypoRT can be effective, currently, limited prognostic factors are available to guide treatment and predict the outcomes.
Fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) combined with computed tomography (PET-CT) is an important tool for staging primary lung cancer and could potentially be used as a prognostic indicator of disease control and patient survival. Determining the metrics for tumor response could be used to tailor and potentially adjust treatment. Previous studies have demonstrated the usefulness of the CT-determined gross tumor volume (GTV) and metabolic tumor volume (MTV) for predicting the outcomes for NSCLC after both CFRT and SABR.11, 12, 13, 14, 15, 16 Additionally, analysis of the mid-RT PET-CT findings of different radiation fractionations and doses for lung tumors has shown that a decrease in FDG uptake is associated with improved outcomes.17, 18, 19, 20 To our knowledge, no other studies have been conducted that examined the benefit of mid-RT PET-CT with regard to MTV or as a prognosticator for patients undergoing HypoRT.
We sought to demonstrate the prognostic usefulness of pre- and mid-RT PET-CT metrics and to share our institutional experience of patients with lung cancer treated with a modestly hypofractionated course (60-66 Gy in 3-Gy fractions) of RT.
Section snippets
Patient Population
After approval by our institutional review board, we reviewed the medical records of all patients with an intrathoracic tumor treated with a modestly hypofractionated course of RT (60-66 Gy in 3-Gy fractions) using either 3-dimensional conformal (3D-CRT) or intensity-modulated RT (IMRT) at the Stanford Cancer Institute from January 2006 to January 2012. Intrathoracic tumors were those located in the lung cavity or thoracic lymph nodes. The patients included those with both primary or metastatic
Patient and Treatment Outcomes
Our review identified 29 patients who met the inclusion criteria. One patient died before the 3-month follow-up examination, and the rest were evaluated during the follow-up period. The patient characteristics are summarized in Table 1.
The median follow-up period for all patients was 15 months (range, 4-50 months) and for the surviving patients was 10 months (range, 4-50 months). Of the 29 patients, 12 (41%) developed local progression after RT, with a median interval of 10 months (range, 5-32
Discussion
We sought to share our institutional experience of patients with lung tumors treated with HypoRT and to demonstrate the prognostic usefulness of pre- and mid-RT PET-CT. The pre-RT PET-CT metrics and the change in SUV measured from the mid-RT PET scan have been shown to be useful tools for predicting the outcomes after RT for patients with lung cancer.11, 12, 13, 14, 15, 16, 17, 18, 19, 20 We focused our study on a cohort of patients with primary and metastatic lung tumors who had undergone
Conclusion
We have shared our institutional experience that HypoRT is a safe and effective method for treating primary and metastatic lung tumors in selected patients. We also performed a hypothesis-generating study that demonstrated the usefulness of pre- and mid-RT PET-CT. The PET metrics (MTVEdge, MTV50%, and SUVMax) predicted OS and PFS better than did the CT metrics (pre- and mid-RT GTV). If validated in future randomized studies, these imaging techniques could help risk stratify patients and modify
Disclosure
B.W.L., M.D., P.G.M., and E.E.G. have received research support from Varian Medical Systems. B.W.L. and P.G.M. have received research support from RaySearch Laboratories and speaking honoraria from Varian Medical Systems.
Acknowledgments
J.P.H. and C.N.C. were supported by the Stanford Medical Scholars Fellowship Program.
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Cited by (0)
J.P.H. and C.C.-H. contributed equally to this work as first authors.