The Evolving Neoadjuvant Treatment Paradigm for Patients with Locoregional mismatch Repair Proficient Rectal Cancer

Neoadjuvant treatment of colorectal cancer: comprehensive review

BACKGROUND

Neoadjuvant therapy has an established role in the treatment of patients with colorectal cancer. However, its role continues to evolve due to both advances in the available treatment modalities, and refinements in the indications for neoadjuvant treatment and subsequent surgery.

METHODS

A narrative review of the most recent relevant literature was conducted.

RESULTS

Short-course radiotherapy and long-course chemoradiotherapy have an established role in improving local but not systemic disease control in patients with rectal cancer. Total neoadjuvant therapy offers advantages over short-course radiotherapy and long-course chemoradiotherapy, not only in terms of increased local response but also in reducing the risk of systemic relapses. Non-operative management is increasingly preferred to surgery in patients with rectal cancer and clinical complete responses but is still associated with some negative impacts on functional outcomes. Neoadjuvant chemotherapy may be of some benefit in patients with locally advanced colon cancer with proficient mismatch repair, although patient selection is a major challenge. Neoadjuvant immunotherapy in patients with deficient mismatch repair cancers in the colon or rectum is altering the treatment paradigm for these patients.

CONCLUSION

Neoadjuvant treatments for patients with colon or rectal cancers continue to evolve, increasing the complexity of decision-making for patients and clinicians alike. This review describes the current guidance and most recent developments.

Risk-Adapted Neoadjuvant Chemoradiotherapy in Rectal Cancer: Final Report of the OCUM Study

PURPOSE

We investigated whether neoadjuvant chemoradiotherapy (nCRT) in patients with rectal cancer can be restricted to those at high risk of locoregional recurrence (LR) without compromising oncological outcomes.

PATIENTS AND METHODS

In a prospective multicenter interventional study, patients with rectal cancer (cT2-4, any cN, cM0) were classified according to the minimal distance between the tumor, suspicious lymph nodes or tumor deposits, and mesorectal fascia (mrMRF). Patients with a distance >1 mm underwent up-front total mesorectal excision (TME; low-risk group), whereas those with a distance ≤1 mm and/or cT4 and cT3 tumors in the lower rectal third received nCRT followed by TME surgery (high-risk group). The primary end point was 5-year LR rate.

RESULTS

Of the 1,099 patients included, 884 (80.4%) were treated according to the protocol. A total of 530 patients (60%) underwent up-front surgery, and 354 (40%) had nCRT followed by surgery. Kaplan-Meier analyses revealed 5-year LR rates of 4.1% (95% CI, 2.7 to 5.5) for patients treated per protocol, 2.9% (95% CI, 1.3 to 4.5) after up-front surgery, and 5.7% (95% CI, 3.2 to 8.2) after nCRT followed by surgery. The 5-year rate of distant metastases was 15.9% (95% CI, 12.6 to 19.2) and 30.5% (95% CI, 25.4 to 35.6), respectively. In a subgroup analysis of 570 patients with lower and middle rectal third cII and cIII tumors, 257 (45.1%) were at low-risk. The 5-year LR rate in this group was 3.8% (95% CI, 1.4 to 6.2) after up-front surgery. In 271 high-risk patients (involved mrMRF and/or cT4), the 5-year rate of LR was 5.9% (95% CI, 3.0 to 8.8) and of metastases 34.5% (95% CI, 28.6 to 40.4); disease-free survival and overall survival were the worst.

CONCLUSION

The findings support the avoidance of nCRT in low-risk patients and suggest that in high-risk patients, neoadjuvant therapy should be intensified to improve prognosis.

Integrated Intensified Chemoradiation in the Setting of Total Neoadjuvant Therapy (TNT) in Patients with Locally Advanced Rectal Cancer: A Retrospective Single-Arm Study on Feasibility and Efficacy

While surgery is considered the main treatment for early-stage rectal cancer, locally advanced rectal cancer needs to be handled with a multidisciplinary approach. Based on literature data suggesting promising advantages of total neoadjuvant therapy (TNT), we performed a retrospective, single-arm, single-center study on 45 patients affected by histologically and radiologically proven locally advanced rectal cancer, with the aim of analyzing the feasibility and short-term efficacy of an integrated intensified treatment in the setting of TNT. Each analyzed patient performed three cycles of FOLFOX4 or De Gramont induction chemotherapy (iCT), followed by concurrent chemoradiotherapy (CRT) with long course radiotherapy (LCRT) plus concomitant boost and continuous 5-FU infusion, followed by three cycles of FOLFOX4 or De Gramont consolidation chemotherapy (conCT) and then surgery with total mesorectal excision. At a median follow-up of 30 months, this strategy has shown to be feasible and effective in terms of pathological complete response (pCR) and short-term disease-free survival (DFS).

Personalized total neoadjuvant therapy (pTNT) for advanced rectal cancer with tailored treatment sequencing based on clinical stage at presentation

BACKGROUND

This study aimed to assess short-term outcomes of a personalized total neoadjuvant treatment (pTNT) protocol, with treatment sequencing based on clinical stage at presentation.

METHODS

A multidisciplinary pTNT protocol was implemented across two metropolitan hospitals. This consists of two-schema based on clinical stage: patients with distant failure risk were offered induction chemotherapy before chemoradiation (nCRT), and patients with locoregional failure risk received nCRT followed by consolidation chemotherapy. Patients underwent surgical resection unless a complete clinical response (cCR) was achieved, in which case non-operative management (NOM) was offered. A prospective cohort analysis of all patients with rectal cancer who underwent pTNT with curative intent between Jan 2019 and Aug 2022 was performed.

RESULTS

Of 270 patients referred with rectal cancer, 102 received pTNT with curative intent and 79 have completed their treatment thus far. Thirty-three patients (41.8%) received induction chemotherapy and 46 (58.2%) received consolidation chemotherapy per protocol. The percentage of patients with EMVI, resectable M1 disease, cT4 disease, and positive lateral lymph nodes were 54.4%, 36.7%, 27.8% and 15.2%, respectively. Overall, 32 (40.5%) patients had cCR and 4 (5.1%) pCR, and 40 (50.6%) patients had non-operative management. Grade 3 toxicity was reported in 10.1% of patients and only three patients (3.8%) experienced Grade 4 chemotherapy-related toxicity, with no treatment related mortality.

CONCLUSION

Early results with a defined two-schema pTNT protocol are encouraging and suggest that tailoring sequencing to disease risk at presentation may represent the optimal balance between local and distant disease control, as well as treatment toxicity.

Preoperative short-course radiation therapy with PROtons compared to photons in high-risk RECTal cancer (PRORECT): Initial dosimetric experience

Background and purpose

Neoadjuvant short-course radiotherapy (SCRT) followed by full-dose systemic chemotherapy is an established treatment modality in locally advanced rectal cancer (LARC). Until recently, SCRT has been exclusively delivered with photons. Proton beam therapy (PBT) may minimize acute toxicity, which in turn likely impacts favorably on the tolerability to subsequent chemotherapy. The aim of this study is a dosimetric comparison between SCRT with photons and protons in the randomized phase II trial PRORECT (NCT04525989).

Materials and methods

From June 2021 to June 2022, twenty consecutive patients with LARC have been treated according to study protocol. For each patient, both a VMAT and a PBT treatment plans have been generated and compared pairwise.

Results

Dose-volume histogram (DVH) analysis revealed that SCRT with protons significantly reduced radiation dose to pelvic organs at risk including bladder, bones, and bowel in comparison to SCRT with photons. Photon and proton treatment plans had equivalent conformity and homogeneity indexes.

Conclusion

Preoperative SCRT with protons offers a significant reduction of radiation dose to normal tissues compared with current photon-based radiotherapy technique. Demonstrated dosimetric advantages may translate into measurable clinical benefits in patients with LARC. Clinical implications of the dosimetric superiority of SCRT with protons will be presented in the coming reports from the PRORECT trial.