(P104) Esophagus- and Contralateral Lung–Sparing IMRT for Locally Advanced Lung Cancer in the Community Hospital Setting

Johnny Kao, MD, Jeffrey Pettit, MS, Shanata S. Ramsaran, Terry Palatt, MD; Good Samaritan Hospital Medical Center

INTRODUCTION: The optimal technique for performing lung intensity-modulated radiation therapy (IMRT) remains poorly defined. Due to concerns regarding acute and late toxicity, the potential benefit of dose escalation beyond 60 Gy has not been established. We hypothesize that improved dose distributions associated with normal tissue-sparing IMRT can allow for safe dose escalation that will translate into decreased acute and late toxicity.

MATERIALS AND METHODS: We performed a retrospective analysis of 82 consecutive patients with stage II/III or stage IV lung cancer with a single distant metastasis (median age: 69 yr, 53% male, 21% small-cell lung cancer, 83% white, 70% Eastern Cooperative Oncology Group [ECOG] performance status score 0 or 1, 13% stage IV, and 87% receiving concurrent chemotherapy) treated from January 2010 to September 2014. From January 2010 to April 2012 (cohort A), patients were treated with the community standard of predominantly three-dimensional conformal radiotherapy (76%) without specific esophagus or lung constraints. From May 2012 to September 2014 (cohort B), patients were treated with predominantly IMRT (95%) while selectively sparing uninvolved lung and esophagus. The study endpoints were dosimetry, toxicity, and overall survival (OS).

RESULTS: Despite higher mean prescribed radiation doses in cohort B (64.5 Gy ± standard deviation [SD] 5.0 vs 60.8 Gy ± SD 6.2; P = .04), patients in cohort B had significantly lower lung V20, V10, V5, mean lung, maximum esophagus, and mean esophagus doses (P ≤.001). Mean lung V20 was 23.3 Gy ± SD 7.2 in cohort B vs 32.2 Gy ± SD 11.6 for cohort A. Mean esophagus dose was 20.2 Gy ± SD 10.2 in cohort B vs 34.3 Gy ± SD 12.7 for cohort A (P = .001). Patients in cohort B had reduced acute grade ≥ 3 esophagitis (0% vs 11%; P < .001) and late grade ≥ 2 pneumonitis (5% vs 21%; P = .01). The incidence of hospitalization for dehydration and/or pulmonary complaints was 11% for cohort B vs 37% for cohort A (P = .008). Three patients in cohort A who developed grade 5 pneumonitis had lung V20 values of 41%, 48%, and 58% and lung V5 values of 90%, 99%, and 88%, respectively. Median survival in cohort B has not been reached at 24 months vs 13 months for cohort A (P = .13).

CONCLUSION: These data provide proof of principle that suboptimal radiation dose distributions are associated with significant acute and late lung and esophageal toxicity that may result in hospitalization or even premature mortality. We propose a relatively simple four-field IMRT technique with strict attention to commonly accepted lung and esophageal dose-volume constraints as a preferred approach for the majority of locally advanced lung cancers.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org