The Impact of Intensity Modulated Radiation Therapy on Hospitalization Outcomes in the SEER-Medicare Population With Anal Squamous Cell Carcinoma

Abstract

Purpose: We examined the impact of intensity modulated radiation therapy (IMRT) on hospitalization rates in the Surveillance, Epidemiology, and End Results (SEER) —Medicare population with anal squamous cell carcinoma (SCC). Methods and Materials: We performed a retrospective cohort study using the SEER-Medicare database. We identified patients with nonmetastatic anal SCC diagnosed between 2001 and 2011 and treated with chemoradiation therapy. We assessed the relation between IMRT and first hospitalization by use of a multivariate competing-risk model, as well as instrumental variable analysis, using provider IMRT affinity as our instrument. Results: Of the 1165 patients included in our study, 458 (39%) received IMRT. IMRT use increased over time and was associated more with regional and provider characteristics than with patient characteristics. The 3- and 6-month cumulative incidences of first hospitalization were 41.9% (95% confidence interval [CI], 37.3%−46.4%) and 47.6% (95% CI, 43.0%−52.2%), respectively, for the IMRT cohort and 46.7% (95% CI, 43.0%−50.4%) and 52.1% (95% CI, 48.4%−55.7%), respectively, for the non-IMRT cohort. IMRT was associated with a decreased hazard of first hospitalization compared with 3-dimensional radiation techniques (hazard ratio, 0.70; 95% CI, 0.58–0.84; PZ.0002). Instrumental variable analysis suggested an even greater reduction in hospitalizations with IMRT after controlling for unmeasured confounders. There was a trend toward improved overall survival with IMRT, with an adjusted hazard ratio of 0.77 (95% CI, 0.59–1.00; PZ.05). Conclusions: The use of IMRT is associated with reduced hospitalizations in elderly patients with anal SCC. Further work is warranted to understand the long-term health and cost impact of IMRT, particularly for patient subgroups most at risk of toxicity and hospitalization.

Intensity Modulated Radiation Therapy Versus Conventional Radiation for Anal Cancer in the Veterans Affairs System

“…We found a lower risk of tumor-related ostomy placement among IMRT patients, which might be attributable in part to higher chemotherapy completion rates, given randomized data showing an improvement in colostomy-free survival with concurrent chemotherapy (27). Finally, we found no difference in survival outcomes after multivariable adjustment, consistent with prior data that have not demonstrated a large survival improvement for IMRT (6,7,25).…”

“…As a retrospective analysis, our conclusions are likely subject to selection bias and confounding by indication; although we attempted to address this limitation by including a wide range of measured covariates and using analytic techniques, such as the frailty model and instrumental variable analysis to account for unmeasured covariates, the potential for residual confounding remains. We were unable to review IMRT plans to assess quality, although our study included more granular and extensive radiation data than other comparable retrospective analyses (7). As IMRT use increased over the study period, our analyses may be subject to confounding by changing practice patterns or standards of care over time, although we controlled for year of diagnosis in the analysis.…”

“…In anal cancer, adoption of IMRT has been encouraged by the substantial hematologic, gastrointestinal, and dermatologic toxicities of combined chemotherapy and radiation treatment. Retrospective studies comparing IMRT and conventional conformal radiation therapy (RT) have suggested decreased hospitalization and toxicity benefits (1,(3)(4)(5)(6)(7). A phase 2 trial (Radiation Therapy Oncology Group [RTOG] 0529) comparing dose-painted IMRT with a historical conventional radiation arm did not reach its primary endpoint of lower combined gastrointestinal and genitourinary toxicity, although the investigators did find improvements in grade 2þ hematologic toxicity and grade 3þ dermatologic or gastrointestinal toxicity (2).…”

Impact of Intensity-Modulated Radiotherapy on Health Care Costs of Patients With Anal Squamous Cell Carcinoma

“…Additional details of the cohort selection process were previously described in an earlier publication. 10 The Institutional Review Board of Stanford University (Stanford, CA) deemed this study exempt from review.…”

“…10 Chemotherapy administration and type were identified though Medicare claims. 17 Radiotherapy was determined to have been delivered at a freestanding facility if radiotherapy claims were present only in the NCH file.…”