Proton therapy offers new treatment for recurrent lung cancer
In the largest analysis to date of reirradiation using intensity-modulated proton therapy (IMPT) for lung and other thoracic tumors, more than three-fourths of patients were free from local recurrence at one year following retreatment, and fewer than one in ten patients experienced severe side effects.
Lung cancer causes more deaths in the United States than any other type of cancer, due in part to its aggressive nature and likelihood of recurrence.
Historically, recurrences have been challenging to treat, because many of these patients are not candidates for surgery.
Moreover, concerns about cumulative radiation doses to essential organs near thoracic tumors (e.g., heart, lungs, esophagus) may limit the use of curative radiation therapy (RT) for patients who received thoracic RT in the past.
Accordingly, patients whose lung cancer recurs are generally offered only palliative options to manage pain and other symptoms.
Proton therapy, an advanced type of RT, allows radiation oncologists to spare critical normal tissues while delivering escalated, curative doses of radiation to nearby tumors.
In particular, IMPT is able to exactly target a tumor, even if the tumor wraps around a critical normal tissue structure, such as a lung.
Researchers retrospectively examined the records of 27 patients who received reirradiation for thoracic tumors using the IMPT technique through prospective clinical trials at a single institution between 2011 and 2016.
Twenty-two patients (81%) had non-small cell lung cancer (NSCLC). All patients had previously received curative thoracic RT.
Time to reirradiation ranged from 0.1 months to 212 months, with a median of 29.5 months. The median radiation dose was 66 Gray (Gy), with a range of 43.2 to 84 Gy, and it was delivered in 2 Gy fractions. The median follow-up for all patients in the study was 11.2 months.
The median overall survival (OS) for patients in this study was 18 months following IMPT reirradiation. At one year following retreatment, the majority of patients were free from local and regional relapse.
Just over half of the patients were free from disease progression and the one-year OS rate was 54 percent. Four of the patients (15%) experienced a local recurrence within one year of retreatment.
Patients who were prescribed a higher dose of IMPT reirradiation were even less likely to experience recurrence or progression.
At one-year follow-up, patients who received IMPT reirradiation doses at or above the population median were twice as likely to be free from local failure and nearly four times as likely to be free from local-regional failure.
Reirradiation with IMPT was well-tolerated among the patients. Only two patients (7%) experienced moderate to severe long-term lung toxicity (i.e., grade 3 or higher side effects).
There were no severe long-term esophageal side effects nor any life-threatening toxicities among these patients. ■
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