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Risk of Subsequent Primary Cancers After Carbon Ion Radiotherapy for Localized Prostate Cancer

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Key Points

  • Greater age and smoking were associated with greater risk of subsequent primary cancers in patients treated with carbon ion radiotherapy.
  • In propensity score–weighted analyses, carbon ion radiotherapy was associated with a lower risk of subsequent primary cancers vs photon radiotherapy and vs surgery.

In a Japanese retrospective study reported in The Lancet Oncology, Mohamad et al found that carbon ion radiotherapy was associated with a lower risk of subsequent primary cancers compared with photon radiotherapy in patients with localized prostate cancer.

The study included data on 1,455 patients who received carbon radiotherapy for prostate cancer, 1,983 patients treated with photon radiotherapy, and 5,948 treated with surgery between 1994 and 2012. Propensity score–weighted analyses were performed to compare the incidence of subsequent cancers in patients receiving the different treatments.

Risk of Subsequent Primary Cancers

A total of 234 subsequent primary cancers were diagnosed in the carbon ion radiotherapy cohort. On multivariate analysis, greater age and smoking were associated with greater risk of subsequent primary cancers in patients treated with carbon ion radiotherapy.

After limiting the analysis to a maximum 10-year follow-up, the median follow-up was 7.9 years for patients who received carbon ion radiotherapy, 5.7 years for those who received photon radiotherapy, and 6.0 years for those who received surgery. At least 1 subsequent primary cancer was observed in 13% of patients in the carbon ion radiotherapy cohort, 14% of the photon radiotherapy cohort, and 13% of the surgery cohort. In the propensity score–weighted analyses, carbon ion radiotherapy was associated with a lower risk of subsequent primary cancers vs photon radiotherapy (hazard ratio [HR] = 0.81, P = .038) and vs surgery (HR = 0.80, P = .0088); and photon radiotherapy was associated with a higher risk vs surgery (HR = 1.18, P = .029).

The investigators concluded, “Our analysis suggests that patients with localized prostate cancer treated with carbon ion radiotherapy appear to have a lower risk of subsequent primary cancers than those treated with photon radiotherapy. Although prospective evaluation with longer follow-up is warranted to support these results, our data supports a wider adoption of carbon ion radiotherapy for patients with expected long-term overall survival or those with poor outcomes after receiving conventional treatments.”

Hirokazu Makishima, MD, of the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, is the corresponding author for The Lancet Oncology article.

Disclosure: The study was funded by a Research Project for Heavy Ions at the National Institute of Radiological Sciences (Japan). The study authors’ full disclosures can be found at thelancet.com.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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