Radiation Therapy Changed the Second Malignancy Pattern in Rectal Cancer Survivors

Area of Science:

• Oncology
• Radiation Oncology
• Cancer Epidemiology

Background:

• Radiotherapy (RT) is a key treatment for locally advanced rectal cancer, offering survival benefits but potentially increasing second malignancy risk.
• Cancer survivors, especially those treated with RT, face a higher risk of developing new primary cancers.
• The specific impact of RT on the pattern of second malignancies in rectal cancer survivors remains an area of investigation.

Purpose of the Study:

• To investigate and compare the patterns of second primary malignancies in rectal cancer survivors who received radiotherapy versus those who did not.
• To analyze the influence of RT on the incidence of all-site second malignancies and specific cancer types.

Main Methods:

• Utilized the Surveillance, Epidemiology, and End Results (SEER) database, analyzing data from 49,961 rectal cancer patients diagnosed between 2000 and 2012.
• Compared the occurrence of second malignancies in patients who underwent surgery with or without RT.
• Employed standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) to assess cancer risks, using SEER*Stat for calculations.

Main Results:

• A total of 5,582 second malignancies were diagnosed among the 49,961 patients.
• The overall risk of all-site second primary malignancies showed no significant increase in the RT group (SIR=1.00) compared to the no-RT group (SIR=1.14).
• Significantly lower risk of secondary prostate cancer (SIR=0.39) and significantly higher risk of secondary thyroid cancer (SIR=2.80) were observed in the RT group compared to the surgery-only group.

Conclusions:

• Radiotherapy influences the pattern of second malignancies in rectal cancer survivors.
• RT treatment is associated with a decreased risk of secondary prostate cancer.
• A notably increased risk of secondary thyroid cancer is linked to RT in this patient population.