A new study reports that compared with photon radiotherapy, carbon ion radiotherapy reduces the risk of subsequent primary tumors in patients with localized prostate cancer.
"The risk of subsequent primary cancers in patients with prostate cancer after treatment with photon radiotherapy is small in absolute numbers, but it is higher than that after surgical treatment," explain the authors of the study, which was published in The Lancet Oncology. "Carbon ion radiotherapy has a theoretically lower risk of inducing secondary malignancies than photon radiotherapy, but this risk has not been investigated in practice because of the low number of facilities offering such therapy worldwide and the limited data on long-term follow-up because the therapy has only been available since 1994."
The researchers compared the risk of subsequent primary cancers following carbon ion radiotherapy to that of subsequent cancers after photon radiotherapy or surgery through a review of records of patients diagnosed and treated for prostate cancer between 1994 and 2012 from Japan's National Institute of Radiological Sciences and the Osaka Cancer Registry. In order to be eligible for this retrospective study, patients were required to have histologically confirmed localized prostate cancer with a minimum follow-up of at least three months. Patients with previous or synchronous malignancies, metastasis, node-positive disease, or locally invasive (stage T4) prostate cancer were excluded from the analysis, as were those who had received prior radiotherapy or chemotherapy.
A total of 9,386 patients with localized prostate cancer were included in the analysis. The median follow-up durations were 7.9 years for patients receiving carbon ion radiotherapy, 5.7 years for those receiving photon radiotherapy, and 6.0 years for those receiving surgery.
Photon radiotherapy had a greater risk of subsequent primary cancers than did either carbon ion radiotherapy or surgery.
In the 1,455 patients who received carbon ion radiotherapy for prostate cancer, 234 subsequent primary cancers were diagnosed, with some patients developing multiple tumors. Factors that increased the risk of subsequent primary cancers included older age (71 to 75 years vs under 61 years) and smoking.
"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," the study authors conclude. "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."
For More Information
Mohamad O, Tabuchi T, Nitta Y, et al. Risk of subsequent primary cancers after carbon ion radiotherapy, photon radiotherapy, or surgery for localised prostate cancer: a propensity score-weighted, retrospective, cohort study. Lancet Oncol. [Epub ahead of print] DOI:10.1016/S1470-2045(18)30931-8
Image credit: Otis Brawley. Courtesy of the National Cancer Institute