AUA 2021: Risk of Secondary Malignancies After Pelvic Radiation: A Population-Based Analysis

( In this analysis by Andrew Salib and colleagues, the authors explore on a larger scale the risk of developing secondary malignancies after pelvic radiation therapy for a primary pelvic malignancy (rectal/anal, bladder, prostate, uterine, cervical). While confirming that radiation treatment for pelvic malignancies increases the risk of developing secondary malignancies over the patient’s lifetime, the risk is different depending on the primary tumor histology.

First, the authors note that radiation therapy (RT) is an integral component of the multimodal therapy of pelvic malignancies, either as primary treatment or in combination with surgical resection. But, in addition to local treatment effects on nearby pelvic organs, RT has been established as a risk factor for delayed secondary malignancies. In this study, they examine the rate of developing any secondary malignancies following RT for primary pelvic malignancies, with a specific emphasis on secondary pelvic malignancies. While prior studies have focused on individual histologies, none have approached this topic from a broader overview all pelvic malignancies. 

They used the SEER (Surveillance, Epidemiology, and Ends Results) database, and retrospectively examined 2,102,192 patients with primary pelvic malignancies (prostate, bladder, uterine, rectal, cervical). For each disease site, they compared the rate of developing any/all secondary malignancies in radiated patients against patient who did not receive any radiation therapy. Secondary malignancies were then stratified as pelvic and non-pelvic malignancies, in order to determine the local effect of RT on malignancy risk.

A total of 2,102,192 patients were examined (1,189,108 prostate, 315,026 bladder, 88,809 cervical, 249,535 uterine, 259,714 rectal). A total of 113,322 patients developed secondary malignancies after RT (Table 1). The overall relative risk (RR) of RT on developing a secondary malignancy was 1.79 (1.77-1.80 CI, P<0.0001), particularly in patients with prostate (RR 2.57), uterine (RR 1.24) and cervical cancer (1.09).


In contrast, 26,299 patients developed a secondary pelvic malignancies after RT (18,411 prostate, 1,026 bladder, 1,410 cervical, 2,179 uterine, 3,273 rectal) (Table 2). The overall RR of RT on developing a secondary pelvic malignancy was 2.09 (2.06-2.13 CI, P<0.0001), particularly in patients with bladder (RR 6.90), prostate (RR 2.74), and uterine cancer (RR 1.21).


Based on this, the authors conclude that radiation treatment for pelvic malignancies increases the risk of developing secondary malignancies, and specifically secondary pelvic malignancies, over the patient’s lifetime. However, further work needs to be done to identify at-risk populations and the relationship to patients subsets’ competing risks of survival.


Presented by: Andrew Salib, MD, Resident, Thomas Jefferson University


Written by: Thenappan (Thenu) Chandrasekar, MD – Urologic Oncologist, Assistant Professor of Urology, Sidney Kimmel Cancer Center, Thomas Jefferson University, @tchandra_uromd on Twitter during the 2021 American Urological Association, (AUA) Annual Meeting, Fri, Sep 10, 2021 – Mon, Sep 13, 2021.