Second cancer risk after primary cancer treatment with three‐dimensional conformal, intensity‐modulated, or proton beam radiation therapy. Issue 15 (19th May 2020)

• Record Type: Journal Article
• Authors: Xiang, Michael; Chang, Daniel T.; Pollom, Erqi L.
• Is Part Of: Cancer. Volume 126:Issue 15(2020)
• Page Start: 3560
• Page End: 3568
• Publication Date: 2020-05-19
• Subjects: neoplasms -- proton therapy -- radiotherapy, conformal -- radiotherapy, intensity‐modulated -- radiotherapy -- second primary; Cancer -- Periodicals; Cancer -- Cytopathology -- Periodicals; 616.99405
• DOI: 10.1002/cncr.32938
• Languages: English
• ISSNs: 0008-543X

Abstract

Abstract : Background: The comparative risks of a second cancer diagnosis are uncertain after primary cancer treatment with 3‐dimensional conformal radiotherapy (3DCRT), intensity‐modulated radiotherapy (IMRT), or proton beam radiotherapy (PBRT). Methods: Pediatric and adult patients with a first cancer diagnosis between 2004 and 2015 who received 3DCRT, IMRT, or PBRT were identified in the National Cancer Database from 9 tumor types: head and neck, gastrointestinal, gynecologic, lymphoma, lung, prostate, breast, bone/soft tissue, and brain/central nervous system. The diagnosis of second cancer was modeled using multivariable logistic regression adjusting for age, follow‐up duration, radiotherapy (RT) dose, chemotherapy, sociodemographic variables, and other factors. Propensity score matching also was used to balance baseline characteristics. Results: In total, 450, 373 patients were identified (33.5% received 3DCRT, 65.2% received IMRT, and 1.3% received PBRT) with median follow‐up of 5.1 years after RT completion and a cumulative follow‐up period of 2.54 million person‐years. Overall, the incidence of second cancer diagnosis was 1.55 per 100 patient‐years. In a comparison between IMRT versus 3DCRT, there was no overall difference in the risk of second cancer (adjusted odds ratio [OR], 1.00; 95% CI, 0.97‐1.02; P = .75). By comparison, PBRT had an overall lower risk of second cancer versus IMRT (adjusted OR, 0.31; 95% CI, 0.26‐0.36; P < .0001). Results within each tumor type generally were consistent in the pooled analyses and also were maintained in propensity score‐matched analyses. Conclusions: The risk of a second cancer diagnosis was similar after IMRT versus 3DCRT, whereas PBRT was associated with a lower risk of second cancer risk. Future work is warranted to determine the cost‐effectiveness of PBRT and to identify the population best suited for this treatment. Abstract : In this national epidemiological cohort study comprising 9 major tumor types, the risk of a second cancer diagnosis is similar among patients who receive 3‐dimensional conformal or intensity‐modulated radiation and decreases among those who receive proton beam radiation. The results indicate no evidence of increased second cancers after intensity‐modulated radiation, consistent with the hypothesized reduction of second cancers with proton beam radiation, although the absolute benefit observed is low because of the overall rarity of second cancers.