Radiation Therapy Dose Escalation to Clinically Involved Pelvic Sidewall Lymph Nodes in Locally Advanced Rectal Cancer

Abstract

Purpose Lateral pelvic sidewall lymph nodes (PSW LN) may be involved in up to 24% of locoregionally advanced rectal cancers. PSW LN are not resected in total mesorectal excision (TME), and no standard of care regarding the management of PSW LN exists in the United States. We assessed our institutional experience of preoperative radiation therapy (RT) boost to clinically involved PSW LN that were not planned for resection. Methods and materials Data from all patients with rectal adenocarcinoma treated between 2006 and 2018 were reviewed to identify those who received a cumulative dose of >50.4 Gy to suspicious PSW LN during neoadjuvant chemoradiation therapy (nCRT). Demographic, cancer characteristic, treatment, and toxicity data were derived from the chart. Results Of a total of 261 patients, 12 patients met the inclusion criteria. The median age was 47.5 years, and 83% of patients were men. All patients had T3/4 disease, 17% of patients had N1b disease and the remainder had N2 disease, and 33% had M1 disease (all ≤2 metastases). Seventy-five percent of patients had moderately or poorly differentiated histology. The mean distance from the anal verge was 4.85 cm (range, 2-8.9 cm), and 58% had ≥2 PSW LN with an average short axis diameter of 1.11 cm (range, 0.4-3.2 cm). Boost doses ranged from 53.48 Gy to 60.2 Gy in 27 to 30 fractions (1.8-2.15 Gy/fraction). The median follow-up time was 18 months. One patient who received concurrent capecitabine and irinotecan had grade 3 perineal dermatitis and anemia during nCRT. The median hospitalization time for TME was 6.5 days. Within 90 days of TME, 1 patient required surgical exploration for perineal wound breakdown, and another required a blood transfusion for anemia. At the time of the last follow up, 75% of patients were alive. Local control at 12 months was 90%. Conclusions RT dose escalation to nonresected PSW LN during nCRT was well tolerated with a low risk of acute toxicity and perioperative complications and has a high rate of local control at 12 months. RT boost warrants further study in patients with clinically involved nonresected PSW LN.

Management of Clinically Involved Lateral Lymph Node Metastasis in Locally Advanced Rectal Cancer: A Radiation Dose Escalation Study

“…Here, an attempt at an escalation radiation dose based on the regular dose of 56-58 Gy was prescribed to a subgroup of patients with baseline LLN SA ≥5 mm from 2015. In line with our study, a radiation dose boost for the clinical suspicious LLNs was reported in several studies (19,28,29). In gynecologic cancers, the radiation dose of LLN was boosted to 60 Gy and did not result in higher morbidity rates (28).…”

“…To date, reports on LLN dose escalation in rectal cancer are limited. Only a small-scale study (involving 12 patients) with short-term LR was reported (19). In our study, for patients with LLN metastasis, the LR and LLR rates in the dose escalation subgroup were significantly lower, and size reduction was significantly better than in the nCT and nCRT subgroups.…”

“…However, the findings of studies on the escalation of LLNs in rectal cancer are unclear. There was only one single-center study (12 cases) that tried to boost the LLN doses to 60 Gy, while long-term follow-up was not reported (19).…”

From “East vs West” towards international multidisciplinary collaboration: An appraisal of lateral lymph nodes in rectal cancer

“…Some Western clinicians believe that an irradiation boost may provide the extra enhancement required to treat LLNs without additional LLND surgery. 52 , 53 , 54 Just two studies have evaluated a boost in LLNs, with mixed results. Chen et al 53 studied 12 patients with suspicious LLNs, all of which had received a “boost” as treatment (3 × 5.4 Gy).…”

“…The second study, also with only 12 patients, determined that a boost did not result in an increased risk of toxicity or perioperative complications. 54 However, more research is warranted before a boost should be considered part of a treatment schedule. Furthermore, with the potentiality that according to Ogura et al, 8 only 22% of internal iliac LLNs adequately respond to neoadjuvant treatment, the desired benefit of a boost may be limited.…”