STANFORD, CA – How likely is a second cancer diagnosis after primary cancer treatment with 3-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), or proton beam radiotherapy (PBRT) for lymphoma and other cancers?

Researchers from Stanford University and the Palo Alto, CA, VAMC identified pediatric and adult patients with a first cancer diagnosis between 2004 and 2015 who received 3DCRT, IMRT, or PBRT in the National Cancer Database. The focus was on nine tumor types: head and neck, gastrointestinal, gynecologic, lymphoma, lung, prostate, breast, bone/soft tissue, and brain/central nervous system.

Findings were presented in conjunction with the 2020 American Society of Clinical Oncologists Annual Meeting and also published in the journal Cancer.1

In non-Hodgkin lymphoma, radiation therapy often is used if tumors are discovered in stage I or II, which respond well, and sometimes, for more advanced or aggressive lymphomas, is sometimes used along with chemotherapy.

 A combination of  whole-body radiation might be used with high-dose chemotherapy in conjunction with high-dose chemotherapy for stem cell transplants, according to the American Cancer Society.

Included in the Stanford study were 450,373 patients –3 3.5% received 3DCRT, 65.2% received IMRT, and 1.3% received PBRT —  with median follow-up of 5.1 years after radiation therapy completion and a cumulative follow-up period of 2.54 million person-years.

Results indicated that, 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.

“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,” the authors concluded. “Future work is warranted to determine the cost-effectiveness of PBRT and to identify the population best suited for this treatment.”

  1. Xiang M, Chang DT, Pollom EL. Second cancer risk after primary cancer treatment with three-dimensional conformal, intensity-modulated, or proton beam radiation therapy [published online ahead of print, 2020 May 19]. Cancer. 2020;10.1002/cncr.32938. doi:10.1002/cncr.32938