The following article features coverage from the Connective Tissue Oncology Society (CTOS) 2018 meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

Findings from a long-term follow-up study presented at the Connective Tissue Oncology Society (CTOS) 2018 Annual Meeting in Rome, Italy, confirmed the conclusions of a 2014 paper published in the Journal of Clinical Oncology: treatment with intensity-modulated radiation therapy (IMRT) significantly reduced local recurrence of primary soft tissue sarcoma of the extremity following limb-sparing surgery and adjuvant radiotherapy compared with treatment with conventional/conformal 3D external-beam radiation therapy (which can be abbreviated as CRT, 3D-CRT, or EBRT).1,2

Furthermore, after adjusting for tumor size and patient age, IMRT was determined to be a significant predictor of reduced local recurrence (HR 0.46; 95% confidence interval [CI], 0.24-0.89; P = .02). This was still the finding despite the fact that patients in the IMRT group were associated with higher risk features for recurrence.

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For the retrospective review, the IMRT cohort was expanded. Patients undergoing treatment with either CRT or IMRT were evaluated from 1996 to 2015, which allowed for a follow-up of at least 3 years. A total of 475 patients were included in the review. The researchers controlled for various factors, including chemotherapy type administered across groups.

Presenter Michael Folkert, MD, radiation oncologist, Memorial Sloan Kettering Cancer Center in New York, New York, emphasized that everyone in the study was treated with the same margins — so why, questioned a CTOS audience member, was IMRT linked to better local control?

Dr Folkert theorized that IMRT was more effective at staving off local recurrence because of the “improved conformational coverage of homogeneity of the dose” — he reasoned that the beamlets that are characteristic of IMRT allowed more even coverage of the target compared with CRT, which uses beams with uniform intensity.

Median follow-up for patients treated with CRT was 6 years compared with 4.3 years with IMRT. Median time to local recurrence was 19.3 months (range of 1.2 months to 109.2 months). Across both cohorts, the 5-year cumulative incidence of local recurrence was 9.1%.

While these findings appear to favor IMRT over CRT, it is notable that there was no difference in disease-free survival (DFS), distant metastatic disease-free survival (DMFS), or overall survival (OS) between the 2 treatment subtypes at 5 years following the conclusion of the study.

A second CTOS audience member posited that surgical quality could be a potential confounding variable of the study, and mentioned that surgeons are likely cutting less margin than they have in the past. The attendee also asked Dr Folkert: Could improvements in surgical education during the study period have influenced the study outcomes or conclusions? Dr Folkert answered: “We weren’t able to get that granular.”

Read more of Cancer Therapy Advisor‘s coverage of the CTOS 2018 meeting by visiting the conference page.

References

  1. Yang JC, Folkert M, Crago AM, Yoon SS, Singer S, Alektiar K. Long-term comparison of local recurrence after conventional and intensity-modulated radiation therapy for primary soft tissue sarcomas of the extremity. Presented at: CTOS 2018 Annual Meeting; Rome, Italy: November 14-17. Paper 048.
  2. Folkert MR, Singer S, Brennan MF, et al. Comparison of local recurrence with conventional and intensity-modulated radiation therapy for primary soft-tissue sarcomas of the extremity. J Clin Oncol. 2014;32(29):3236-3241.