Abstract 90P
Background
Intensity-modulated radiation therapy (IMRT) may reduce radiation-induced toxicity in neoadjuvant radiation therapy (NA-RT) for locally advanced rectal cancer (LARC). The purpose of this study was to compare outcomes and toxicity between three-dimensional conformal radiation therapy (3D-CRT) and IMRT in patients undergoing long-course NA-RT for LARC.
Methods
We retrospectively analyzed a total of 47 consecutive patients who received NA-RT for LARC between January 2011 and September 2022. Seven and 40 patients were diagnosed as clinical stages II and III, respectively. The prescribed dose per fraction was 1.8 Gy for total doses 45 or 50.4 Gy. Seventeen and 30 patients received 3DCRT and IMRT, respectively. NA-RT was delivered with concurrent chemotherapy of oral administration of S-1.
Results
Planned NA-RT was completed without any treatment interruption in 43 patients, except for four patients; two patients experienced treatment interruption and two patients discontinued due to grade ≥3 toxicities. The median follow-up term was 31.4 (range, 7.1-136.6) months. The 2-year local control (LC) rate, progression-free survival (PFS) rate, and overall survival (OS) rate were 90.9% (95% confidence interval [CI], 77.6–96.5), 82.3 (95% CI, 67.6–90.8) and 93.0% (95% CI, 79.7–97.7), respectively. No significant differences were observed between patients receiving 3DCRT and IMRT in LC, PFS, and OS (P = 0.488, 0.259, and 0.636, respectively). Patients receiving IMRT showed significantly fewer non-hematological grade ≥2 acute toxicities than those receiving 3DCRT (P = 0.018), although there were no significant differences in non-hematological grade ≥3 acute toxicities between patients receiving IMRT and 3DCRT (P = 1.000). In addition, patients who received IMRT tended to have less intestinal toxicity of grade ≥2 than those who received 3DCRT (P = 0.057).
Conclusions
Long-course NA-RT combined with oral administration of S-1 showed good clinical outcomes. IMRT significantly reduced the grade ≥2 acute toxicities without compromising oncologic outcome compared to 3DCRT. Therefore, IMRT was considered as a current standard treatment in terms of total neoadjuvant therapy era.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.