SUMMARY: The American Cancer Society estimates that 46,050 new cases of rectal cancer will be diagnosed in the US in 2023. Based on the information from the SEER database, the 5-year relative survival rates for rectal cancer all SEER stages combined is 67%.
Management of invasive locally advanced rectal cancer, defined as Stage II (T3-4, N0) or Stage III (T1-4, N+) disease, mandates a multidisciplinary approach. Neoadjuvant chemoradiation therapy (CRT) followed by Total Mesorectal Excision (TME) and adjuvant chemotherapy is often recommended, whereas standard therapy for early-stage lesions involves surgery with or without adjuvant chemoradiation. The trimodality treatment approach was established as the standard of care for locally advanced rectal cancer based on the findings from the landmark German trial. Preoperative neoadjuvant CRT decreased the local recurrence rate in the pelvis from 25% to less than 10%. However, this treatment modality is associated with short-term and long-term toxicities and can adversely affect quality of life and physical function. With regards to chemotherapy, 4 months of adjuvant systemic chemotherapy following 2 months of Fluoropyrimidine-based chemotherapy with concurrent RT and surgery, is the recommended guideline by the National Comprehensive Cancer Network.
More recently, optimizing the delivery of therapy by intensifying neoadjuvant treatment has gained popularity. Moving chemotherapy from the postoperative (adjuvant) to the preoperative setting allows administration of full doses of systemic treatment with fewer adverse events and better compliance, assessment of the tumor response after neoadjuvant therapy, down staging tumors to increase the likelihood of pathological Complete Response (pCR) and complete resection, as well as opportunities for the selective omission of Radiation Therapy. Further, earlier administration of uninterrupted systemic chemotherapy can potentially eradicate occult micrometastases and help assess chemosensitivity.
FOLFOX chemotherapy regimen has been shown to be associated with high response rates when administered before chemoradiotherapy in patients with locally advanced rectal cancer. In a single institution study, neoadjuvant FOLFOX resulted in favorable outcomes, with few patients requiring radiation therapy and none of the patients developing local recurrence.
The PROSPECT trial is a multicenter, unblinded, noninferiority, randomized Phase III study, conducted to investigate whether neoadjuvant treatment with FOLFOX chemotherapy regimen could allow the elimination of chemoradiotherapy, without increasing the risk of recurrence, in patients with locally advanced rectal cancer that was amenable to sphincter-sparing surgery. This study was designed to test the hypothesis that neoadjuvant FOLFOX (with chemoradiotherapy given only if the primary tumor decreased in size by less than 20% or if FOLFOX was discontinued because of side effects) would be noninferior to neoadjuvant chemoradiotherapy alone, in patients with locally advanced rectal cancer that was amenable to sphincter-sparing surgery.
Eligible patients had pathologically confirmed, locally advanced rectal cancer that had been clinically staged as T2 node-positive, T3 node-negative, or T3 node-positive, and who were candidates for sphincter-sparing surgery. This group accounts for more than half the patients with a diagnosis of locally advanced rectal cancer in the United States. Patients with T4 tumors, four or more pelvic lymph nodes larger than 10 mm, or tumor visible within 3 mm of the radial margin seen on baseline pelvic imaging were ineligible. All patients had a pelvic MRI or contrast-enhanced CT of the chest, abdomen, and pelvis plus endorectal ultrasonography at baseline.
Patients were randomized 1:1 to neoadjuvant FOLFOX (N=585) or chemoradiotherapy (N=543). Patients in the FOLFOX group received 6 cycles of modified FOLFOX6 administered IV every 2 weeks, followed by restaging with pelvic imaging and rectal endoscopy. Patients whose primary tumor had decreased in size by at least 20% underwent surgery. Postoperative chemoradiotherapy was recommended for patients in the FOLFOX group whose resection was not pathologically complete (R0). Patients who were unable to complete at least five cycles of FOLFOX and those whose primary tumor had decreased in size by less than 20% also received chemoradiotherapy. Patients in the chemoradiotherapy group received pelvic radiotherapy with 50.4 Gy delivered in 28 fractions, along with either continuous infusion 5-FU chemotherapy given as a radiosensitizer at a dose of 225 mg/m2 daily or Capecitabine 825 mg/m2 orally twice daily, 5 days per week on days of radiation therapy. The median age was 57 years, a third of the patients were women and approximate 62% had clinically positive lymph nodes. Majority of tumors were in the mid-rectum, with a median distance of 8 cm from the anal verge The Primary end point was Disease Free Survival. Secondary end points included Overall Survival, local recurrence (in a time-to-event analysis), complete pathological resection, Complete Response, and toxicities.
At a median follow up of 58 months, FOLFOX was noninferior to chemoradiotherapy and the study met its Primary endpoint for DFS (HR for disease recurrence or death, 0.92; P=0.005 for noninferiority). Five-year DFS was 80.8% in the FOLFOX group and 78.6% in the chemoradiotherapy group. The Overall Survival was similar in the two treatment groups and the percentage of patients free from local recurrence was also similar in the two groups and exceeded 98% at 5 years. In the FOLFOX group, only 9.1% received preoperative chemoradiotherapy and only 1.4% received postoperative chemoradiotherapy. Over 89% of patients assigned to receive neoadjuvant FOLFOX were ultimately able to avoid receiving chemoradiotherapy.
The authors concluded that in patients with locally advanced rectal cancer who were eligible for sphincter-sparing surgery, preoperative FOLFOX chemotherapy with selective use of chemoradiotherapy was noninferior to preoperative chemoradiotherapy with nearly identical outcomes. These data provide additional treatment options for this patient group without compromising efficacy, and toxicities associated with radiation therapy can be avoided.
Preoperative Treatment of Locally Advanced Rectal Cancer. Schrag D, Shi Q, Weiser MR, et al. June 4, 2023. DOI: 10.1056/NEJMoa2303269
