Radiotherapy for a second primary lung cancer arising post-pneumonectomy: planning considerations and clinical outcomes.

Background: Second primary non-small cell lung cancer (SPLC) is a significant cause of death amongst lung cancer survivors. As subsequent surgery is seldom feasible post-pneumonectomy, we studied the long-term clinical outcomes achieved with curative radiotherapy using modern delivery techniques.

Methods: Retrospective review of an institutional database between 2003-2011 identified 27 patients who had received curative radiotherapy for SPLC arising post-pneumonectomy. Treatments included; stereotactic ablative radiotherapy (SABR, n=20, dose 54-60 Gy in 3-8 fractions), hypofractionated radiotherapy (HFR, n=6, dose 39-60 Gy in 12-23 fractions) and conventional radiotherapy (RT, n=1, 60 Gy in 30 fractions). Clinical follow-up with a CT scan at 3, 6 and 12 months, then yearly was performed. Toxicities were scored using the common toxicity criteria for adverse events (version 4.0).

Results: The median overall survival was 39 months (95% CI, 33-44 months). After a median follow-up of 52 months (95% CI, 37-67 months), any recurrence was observed in four (15%) patients. Actuarial 3-year rates of local, regional and distant recurrences were 8% (95% CI, 0-21 months), 10% (95% CI, 0-23%) and 9% (95% CI, 0-20%), respectively. Patients receiving HFR or RT all had centrally located tumors. Of the patients treated with HFR delivered 12 fractions, 75% (3/4) developed grade 3 or higher radiation pneumonitis (RP), including one probable grade 5 toxicity. Of those receiving RT or HFR in 13 or more fractions no (0/3) grade 3 or worse RP was observed, despite such treatment being used for larger tumors and resulting in worse lung dose-volume histogram metrics. All the patients who developed RP had radiotherapy plans, which prioritized the sparing of central structures over lung sparing. No non-RP grade 3 or higher toxicities were observed.

Conclusions: Curative radiotherapy is an effective treatment for SPLC arising post-pneumonectomy. For larger central tumors, our data suggests that plans should prioritize reducing lung doses above the sparing of central structures.