Moderate Dose Imrt For Resected Mesothelioma

To determine the pulmonary toxicity and local control associated with moderate dose (≈45 Gy) comprehensive pleural space IMRT after extrapleural pneumonectomy for mesothelioma. 10 patients received IMRT after extrapleural pneumonectomy with curative intent between 7/05 and 12/06 at Duke University. The clinical target volume (CTV) was defined as the entire ipisilateral hemithorax, chest wall incisions including drain sites, and involved nodal stations. The dose prescribed to the clinical target volume (CTV) was 40–50 Gy (mean 45 Gy). Records were reviewed to determine acute and late toxicity, and local control. Toxicity was graded using the RTOG grading scale. Dosimetric parameters from subgroups experiencing pneumonitis and those that did not were compared using a two-tailed T-test. The 10 patients included in the study had Stage I to IV disease; six were left-sided, four were right-sided. Histology was epithelioid in 8 patients; biphasic in 2. Eight received chemotherapy; 2 preoperatively and 6 postoperatively. Median follow up from diagnosis was 12 months, and 6 months from completion of RT. All patients experienced grade 1–2 nausea/vomiting or esophagitis acutely; 4 described grade 1–2 fatigue. Three patients experienced early (within 3 months) grade ≥3 pulmonary toxicity, including one patient who later died ≈6 months after RT, likely due, in part, to lung injury. One patient developed a local recurrence in the chest wall, followed by peritoneal carcinomatosis. One patient developed an ipsilateral brachial plexus injury at 3 months after RT that has persisted. The mean lung dose (MLD) was similar to those with and without symptomatic pneumonitis (8.9 vs 8.1 Gy). There was a trend towards a lower lung V20 (2.3 vs 5.5%) and higher V5 (80 vs 64.2%) in those that developed pneumonitis. Population average dose volume histograms (DVH) constructed from individual patient DVH's confirmed these results. The single pulmonary fatality had a higher MLD than those not experiencing fatality (11.4 vs 8.0 Gy). The lung V20 (6.8 vs 4.3%) and V5 (92 vs 66%) were similarly increased in the case of suspected fatal pneumonitis. Calculation of a p-value is not possible for comparison between a group and a single data point. Serial LFT's monitored in a subset of patients revealed no episodes of enzyme elevation beyond the normal range (mean liver dose 28.6–30.7 Gy) (Table). Moderate dose IMRT provides good local control in mesothelioma, albeit with limited follow-up. Treatment related pulmonary toxicity remains a concern. Our data are consistent with other published data and suggest that the MLD be kept below 8–10 Gy, V20 below ≈4–10%, and V5 below ≈70%.Tabled 1Dosimetric Parameters in Those With and Without FatalityMLD (Gy)V20 (%)V5 (%)Author, InstitutionFatality rateMean RT dose(Median dose/volume with fatality vs not, p-value)Allen, Harvard (1)6/1354 Gy15 vs 13, p = 0.0718 vs 11, p = 0.0899 vs 90, p = 0.20Rice, MDAH (2)6/6345 Gy11 vs 8, p = 0.00311 vs 4, p = <0.00188 vs 72, p = 0.054Larrier, Duke1/1045 Gy11 vs 8, not sig.7 vs 4, not sig.92 vs 66, not sig(1) Allen AM et al, Int J Radiat Oncol Biol Phys 2006;65:640–645.(2) Rice DC et al, ASTRO Proceedings 2006, Abstract #111. Open table in a new tab