GI Lower
2026-06-21
ARS Appropriate Use Criteria: Locoregionally Recurrent Rectal Cancer
TL;DRMargin-negative (R0) resection drives survival and local control; preop RT or systemic therapy downsizes tumor to improve R0 likelihood.
The RT lever here is downsizing for resectability: preop RT, or reirradiation in previously-treated pts, is endorsed to raise the odds of a margin-negative resection, the one determinant of survival and local control. Moves the decision to offer neoadjuvant (re)irradiation before attempted salvage resection.
8 details 5 trials watching
- 💊 Preop systemic therapy, RT, or both facilitate downsizing → improve likelihood of margin-negative resection
- 🔍 RT and reirradiation endorsed mainly to downsize for resectability, not as standalone definitive therapy
- 🔍 Five PICO questions addressed
- Role of surgery
- Role of preop/periop therapy
- Role of nonoperative management (NOM)
- Role of RT/reirradiation
- Role of systemic therapy (chemo/IO)
- 🔍 Evidence base: 116 peer-reviewed trials (Jan 2013–Jul 2025)
- 10 well-designed (phase 2 randomized + phase 3)
- 29 moderately designed (matched cohort + phase 2)
- 76 retrospective (design limitations)
- 1 meta-analysis
- 🔍 Update to 2012 ACR recurrent-rectal-cancer AUC; multispecialty modified-Delphi (RAND/UCLA) consensus, 2 voting rounds
- 📊 R0 (margin-negative) resection is the ultimate determinant of survival and local control
- ⚠️ Evidence base mostly retrospective: 76 of 116 references, only 10 well-designed RCTs
- Bottom line: no major change to current practice, reaffirms combined-modality therapy
- Optimal reirradiation dose and technique in previously irradiated LRRC recruiting Pencil Beam Proton Therapy for Pelvic Recurrences in Rectal Cancer Patients Previously Treated With Radiotherapy Phase 2n=65 · primary completion 2025-10 · dose-escalated proton reRT for rectal recurrencen=31 · primary completion 2025-12 · carbon ion reRT 74Gy/20fx for unresectable LRRCrecruiting Hypofractionated Radiotherapy Plus Immunotherapy Versus Conventional Radiotherapy in Locally Recurrent Rectal Cancer Phase 2n=221 · primary completion 2030-03 · hypofrac vs conventional reRT, randomized
- Role of total neoadjuvant therapy vs preop chemoRT in LRRC n=88 · primary completion 2026-06 · TNT + reRT for previously irradiated LRRC
- Role of nonoperative management in unresectable LRRC n=31 · primary completion 2026-11 · definitive SBRT + PD-1 for unresectable LRRC
📚 Sources · 📄 1 paper
Abstract
2026-06-02 ASCO Annual Meeting 2026
mRCAT-III NCT06507371
ForpMMR/MSS LARC, cT3-4N0/+, tumor ≤10cm from anal verge
TL;DRpCR 61.0% vs 28.6% (P<0.0001) for node-sparing SCRT + CAPOX + tislelizumab vs conventional SCRT + CAPOX in pMMR LARC.
The RT read is target volume: the experimental arm both spared elective nodal RT (tumor bed only) and added tislelizumab, so the pCR doubling can't isolate node-sparing's contribution. pCR is also blind to nodal failure, the very risk nodal omission creates, so EFS (pending), not pCR, gates whether to drop elective nodal coverage with IO.
- Control pCR 28.6% matches SCRT + consolidation-chemo TNT benchmarks (e.g. RAPIDO); increment reflects added IO plus node-sparing
| Endpoint | Experimental (n=77) | Control (n=77) | P |
|---|---|---|---|
| pCR (ITT) | 61.0% (47/77) | 28.6% (22/77) | <0.0001 |
| MPR (TRG0+TRG1) | 77.9% (60/77) | 50.6% (39/77) | <0.0001 |
+1 more figure
7 details 5 trials watching
- 🔍 Phase 3 open-label RCT, N=154 (77/arm), 17 China sites; primary pCR by blinded independent central review
- 🔍 RT: short-course 5Gy×5d (25Gy/5fx) both arms; experimental spared elective nodal RT (tumor bed only, no draining nodes)
- 💊 Experimental added tislelizumab 200mg IV to the CAPOX backbone; control got CAPOX alone
- 🔍 MSS/pMMR rectal is typically IO-refractory; a pCR doubling with PD-1 here is the provocative signal, pending confirmation
CONSORT flow
- ⚠️ Confounded: experimental arm both spared nodal RT AND added tislelizumab, so pCR gain can't be attributed to node-sparing alone
- ⚠️ pCR can't detect nodal failure, the risk omitting elective nodal RT creates; locoregional control and EFS unreported
- ⚠️ Fewer severe GI AEs reported in experimental arm; no effect size reported in source
- Is the pCR gain from node-sparing RT or added tislelizumab? recruiting Neoadjuvant Chemoradiotherapy Plus Tislelizumab With or Without Probio-M9 in pMMR/MSS Locally Advanced Rectal Cancer Phase 2n=50 · primary completion 2027-05 · tislelizumab+CRT vs CRT-only isolates PD-1 effectrecruiting Node-Sparing Short-Course Radiotherapy Sequential Chemotherapy and PD-1 Inhibitor for Mid/Low pMMR/MSS Rectal Cancer (MODIFI-RC-II) Phase 2/3n=430 · primary completion 2030-12 · node-sparing vs conventional RT, PD-1 held constant
- Does omitting elective nodal RT compromise locoregional control? recruiting Node-Sparing Short-Course Radiotherapy Sequential Chemotherapy and PD-1 Inhibitor for Mid/Low pMMR/MSS Rectal Cancer (MODIFI-RC-II) Phase 2/3n=430 · primary completion 2030-12 · node-sparing vs conventional RT, head-to-head RCT
- Will the pCR benefit translate to organ preservation, EFS, OS? recruiting Nodes-sparing Short-course Radiation Combined With CAPOX and Tislelizumab for MSS Middle and Low Rectal Cancer Phase 2n=32 · primary completion 2024-08 · same regimen; tracks organ-preservation raterecruiting MR-guided Adaptive Radiotherapy Combined With PD-1 Antibody and CAPOX for Locally Advanced Rectal Cancer Phase 2n=46 · primary completion 2026-08 · reports 3y DFS/OS after PD-1+CAPOX neoadjuvant
📚 Sources · 🐦 1 tweet
One of most interesting rectal ca studies at #ASCO26
— Dr. Nina Niu Sanford (@NiuSanford) June 2, 2026
P3 RCT in pMMR LARC: Node-sparing short-course RT + CAPOX + tislelizumab doubled pCR v conventional SCRT + CAPOX (61 v 29%)
Hypothesis = sparing elective node RT preserves antitumor immunity & improves PD1 response @OncoAlert pic.twitter.com/6xvA6ne0mg
2026-06-01 ASCO Annual Meeting 2026
ctDNA in nonoperative management of stage II-III rectal cancer
ForMSS stage II-III rectal adeno, cCR/nCR after NAT, on watch-and-wait
TL;DRctDNA sensitivity only 41% for local regrowth (94% specificity) in NOM rectal ca; misses most salvageable regrowth, can't replace endoscopic surveillance.
The organ-preservation read: ctDNA can't replace endoscopic/MRI surveillance. At 41% sensitivity (12/29) it misses most local regrowths, the salvageable event RT-based watch-and-wait depends on. Its real value is flagging distant failure (74% sensitivity) and risk stratification, so keep imaging-led surveillance during NOM.
| Endpoint | Sensitivity | Specificity | Accuracy |
|---|---|---|---|
| Local regrowth | 41% (12/29) | 94% (480/509) | 91% (492/538) |
| Distant mets | 74% (31/42) | 97% (611/627) | 96% (642/669) |
9 details 2 trials watching
- 🔍 INTERCEPT program (MD Anderson), retrospective, n=110 MSS rectal adeno with cCR/nCR after NAT on NOM, 2020-2024
- 🔍 tumor-informed ctDNA (Signatera Exome); 669 serial draws analyzed per-sample; median f/u 25mo (IQR 18-37)
- 🔍 NAT was TNT in 104/110 (CRT 5, chemo 1); initial response cCR 69 / nCR 41
- 📊 events on NOM: local regrowth 23 (21%), distant mets 12 (11%)
- 📊 ever-positive longitudinal ctDNA → worse 2yr local-regrowth-free and metastasis-free survival (log-rank p=0.0002)
- 📊 first post-NAT ctDNA positive → lower regrowth-free/mets-free survival, but only n=12 evaluable (log-rank p=0.0006)
- ⚠️ negative ctDNA misses most local regrowths (sensitivity 41%); the salvageable event, so it can't replace endoscopic/MRI surveillance
- ⚠️ ctDNA+ at regrowth → more advanced salvage path: ypT3-4 75% (6/8) vs 21% (3/14), p=0.01
- ⚠️ per-sample (n=669) denominator inflates n vs 110 pts; only 29 windows had regrowth, 12 pts evaluable for first-ctDNA
- Prospective validation of ctDNA-guided NOM surveillance n=200 · primary completion 2027-11 · phase 2 Signatera-guided rectal mgmt vs SOC
- Can ctDNA sensitivity for local regrowth be improved?
- Optimal integration of ctDNA with MRI/endoscopic surveillance n=68 · primary completion 2030-09 · ctDNA substudy within phase 3 watch-and-wait
📚 Sources · 🐦 1 tweet
Important study re: ctDNA for non-op surveillance in rectal ca.
— Dr. Nina Niu Sanford (@NiuSanford) June 1, 2026
Pos ctDNA associated w regrowth (60%) & distant mets (60%), but neg ctDNA doesn't exclude local regrowth (sensitivity only 41%)
ctDNA good for risk stratification but not surveillance replacement #ASCO26 @OncoAlert pic.twitter.com/UQQub5QfNB
2026-05-31
MIRACLE-2
For1L MSS unresectable metastatic rectal ca, synchronous liver/lung mets
TL;DRORR 68%, mOS 23.2mo, 18% reached NED with upfront RT then systemic + PD1 in 1L unresectable MSS met rectal ca.
The RT read is upfront priming: HFRT to primary plus HFRT/SBRT to mets precedes systemic + PD1, and 18% (9/50) of unresectable pts reached NED, an unusual signal in immune-cold MSS. RT dose/fractionation isn't in source and no omission arm isolates its effect, so adding RT to a systemic backbone stays hypothesis-only.
- MSS ~95% of mCRC and intrinsically IO-resistant; single-agent PD1 inactive in MSS
10 details 4 trials watching
- 🔍 Prospective single-arm phase I, N=50, 1L MSS unresectable met rectal ca, primary ≤10cm from anal verge
- 🔍 RT given upfront: HFRT to primary, HFRT or SBRT to mets. Dose/fractionation not reported in source
- 💊 Then FOLFOX-bev-tislelizumab (RAS/BRAF-mut) or FOLFIRI-cetux-tislelizumab (WT); RAS/BRAF mut in 56.0%
- 📊 Efficacy outcomes (single-arm, N=50)
Endpoint Value 95% CI ETS rate (1°) 76.0% 62.4-86.8% ORR 68.0% 53.6-80.0% DCR 88.0% 76.0-95.2% Median PFS 9.3 mo 7.1-11.5 Median OS 23.2 mo 15.1-31.3 Median DOR 8.0 mo 5.2-10.8 - 📊 18% (9/50) reached NED; 1-yr OS 93.3%, 1-yr PFS 33.4%, 1-yr DOR 20%
- ⚠️ Grade 3/4 TRAEs, heme-dominant
- Lymphopenia 36.7%
- Neutropenia 26.5%
- Leukopenia 20.4%
- ⚠️ RT-associated lymphopenia a plausible driver of the 36.7% G3/4 lymphopenia
- ⚠️ RT contribution unmeasurable: no RT-omission arm, effect confounded with systemic + PD1
- ⚠️ 1° EP is ETS (≥20% shrinkage at 8wk), an early surrogate not OS/PFS; mFU only 19.9mo (16.4-23.4)
- ⚠️ Durability thin: 1-yr DOR 20%, mDOR 8.0mo despite high 1-yr OS
- Does RT add benefit over systemic + PD1 alone (no control arm)? recruiting A Phase II Study of Pirfenidone Plus PD-1 Inhibitor With or Without Hypofractionated Radiotherapy for Refractory pMMR/MSS Colorectal Cancer Phase 2n=48 · primary completion 2027-01 · PD-1 backbone ± hypofractionated RT in MSS CRCrecruiting Node-Sparing Short-Course Radiotherapy Plus Chemotherapy, Bevacizumab and PD-1 Inhibitor in Metastatic pMMR/MSS Colorectal Cancer (MODIFI-CRC) Phase 2/3n=286 · primary completion 2030-12 · randomizes RT + 1L vs 1L alone in met MSS CRC
- Biomarkers selecting MSS responders to trimodal therapy n=200 · primary completion 2024-02 · mines predictive biomarkers in MSS CRC IOn=60 · primary completion 2032-07 · single-cell profiling of IO response in MSS CRC
- Durability beyond short follow-up (1-yr DOR only 20%)
📚 Sources · 🐦 1 tweet
MIRACLE-2: RT to primary/mets -> chemo + tislelizumab in MSS unresectable met rectal ca (N=50): 68% ORR & median OS 23 mo.
— Dr. Nina Niu Sanford (@NiuSanford) May 31, 2026
Early, single-arm data, but ~1 in 5 pts reached NED.
Suggests RT + systemic + PD1 blockade could overcome immune resistance in MSS mCRC. #ASCO26 @OncoAlert pic.twitter.com/sjnUW8x7f3
2026-05-18
OPERA Trial (5-year rectal preservation)
ForRectal cancer s/p neoadjuvant therapy, organ-preservation candidates
TL;DRW14 clinical exam (DRE+rectoscopy±MRI) reliably flags complete response; 5-yr organ preservation similar for cCR vs nCR (81% vs 77%).
The RT read: near-complete response carries nearly the same 5-yr organ-preservation rate as complete response (77% vs 81%), so radiation-induced nCR shouldn't trigger salvage TME. W14 clinical exam (DRE+rectoscopy, 98% MRI-concordant) lets you commit to watch-and-wait a month after NAT rather than waiting to W24.
8 details 3 trials watching
- 🔍 Post-hoc analysis of OPERA (phase 3 rectal organ-preservation RCT), N=141; tests W14 decision vs the trial's prespecified W24 assessment.
- 🔍 Arms not labeled in source slides; per published OPERA, Arm B = contact X-ray brachytherapy boost, Arm A = EBRT boost.
- 📊 W14 clinical tumor response eval feasible in 122/141 (87%): 76% good response (cCR+nCR), 24% PR.
- 📊 W14 good response and 5-yr organ preservation by arm
Endpoint Arm A Arm B p W14 good response 65% 88% 0.004 5-yr organ preservation 75% 83% 0.24 - 📊 MRI concordance high: TRG1-2 in 98% (80/82) of clinical-CR pts.
- 📊 5-yr OP similar for cCR vs nCR (81% vs 77%): near-complete response not prognostically inferior.
- ⚠️ nCR reflects radiation side effects, not residual tumor (authors); should not justify radical surgery.
- ⚠️ W14-vs-W24 timing not a randomized comparison; who proceeds to OP is selected, so the timing read is confounded.
- Prospective validation of W14 versus W24 response-assessment timing n=40 · primary completion 2026-01 · prospective longitudinal multimodal response assessment
- Durability of watch-and-wait organ preservation beyond 5 years active Short RT Versus RCT,Followed by Chemo.and Organ Preservation for Interm and High-risk Rectal Cancer Patients Phase 3n=702 · primary completion 2023-09 · randomized W&W arm for cCR after TNTn=394 · primary completion 2030-03 · phase 3 W&W arm, long-term oncologic outcomes
📚 Sources · 🐦 1 tweet
Day FOUR of #ESTRO26 Coverage by OncoAlert 🚨
— OncoAlert (@OncoAlert) May 18, 2026
Five-year Results of the OPERA Trial: When and How to Assess Tumor Response to Guide Rectal Preservation Presented by Syrine Ben Dhia 🇫🇷 #RadOnc ☢️
This post-hoc analysis of the OPERA trial evaluated early tumor response… pic.twitter.com/KUanFTxeFh