Top Line: Does a genomic signature of radiation response predict the benefit of adjuvant radiation for breast cancer?
The Study: PORTOS (Post-Operative Radiation Therapy Outcomes Score) is a 24-gene radiation response signature designed to predict the benefit from post-operative prostate fossa RT, and it is derived from the same micro-array platform as the Decipher genomic classifier. In a study of patients from RTOG 0126 and SAKK 09/10, patients with a high PORTOS had better outcomes with dose escalation. In this study, PORTOS was calculated for 765 patients treated in the SweBCG91RT trial, which compared adjuvant RT to observation after breast conservation for early stage breast cancer. PORTOS was significantly associated with the cumulative incidence of recurrence at 10 years. While most patients benefited from adjuvant RT (upper 75% of scores), those with a PORTOS in the lower 25% had no significant benefit. Interestingly, higher PORTOS trended towards association with breast pain (p=.07) suggesting it may also be a predictor of adverse radiation effects. Two other signatures have also been derived from SweBCG91RT (ARTIC and POLAR), however these were designed to capture biological risk of locoregional recurrence. In contrast, PORTOS captures radiation response biology, and it predicted SweBCG91RT outcomes independent of ARTIC and POLAR.
TBL: PORTOS is a 24-gene radiation response signature that was predictive of radiation benefit among breast cancer patients treated with or without adjuvant RT. | Zhao, Clin Cancer Res 2026
The Study: PORTOS (Post-Operative Radiation Therapy Outcomes Score) is a 24-gene radiation response signature designed to predict the benefit from post-operative prostate fossa RT, and it is derived from the same micro-array platform as the Decipher genomic classifier. In a study of patients from RTOG 0126 and SAKK 09/10, patients with a high PORTOS had better outcomes with dose escalation. In this study, PORTOS was calculated for 765 patients treated in the SweBCG91RT trial, which compared adjuvant RT to observation after breast conservation for early stage breast cancer. PORTOS was significantly associated with the cumulative incidence of recurrence at 10 years. While most patients benefited from adjuvant RT (upper 75% of scores), those with a PORTOS in the lower 25% had no significant benefit. Interestingly, higher PORTOS trended towards association with breast pain (p=.07) suggesting it may also be a predictor of adverse radiation effects. Two other signatures have also been derived from SweBCG91RT (ARTIC and POLAR), however these were designed to capture biological risk of locoregional recurrence. In contrast, PORTOS captures radiation response biology, and it predicted SweBCG91RT outcomes independent of ARTIC and POLAR.
TBL: PORTOS is a 24-gene radiation response signature that was predictive of radiation benefit among breast cancer patients treated with or without adjuvant RT. | Zhao, Clin Cancer Res 2026