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Vascular invasion, tumor deposits more prognostic than TNM for rectal cancer

Annals of Surgery
Reuters Health - 30/09/2020 - In patients with rectal cancer, MRI assessment of non-nodal tumor nodules (tumor deposits; mrTDs) and extramural venous invasion (EMVI) are more accurate prognosticators than tumor size and lymph node metastases (mrLNMs), researchers say.

"If an MRI scan shows enlarged lymph nodes, the standard course of treatment for rectal cancer currently is radiotherapy," Dr. Gina Brown of Royal Marsden NHS Foundation Trust in London, UK told Reuters Health by email. However, "other factors, such as the spread of the tumor into the veins and their related deposits should be used instead."

"Non-nodal tumor nodules have a distinct MRI appearance compared to lymph node metastases and have a serious effect on prognosis that can be reversed by the use of chemoradiotherapy," Dr. Brown said.

The study could be "practice changing," she added, "and patients who were previously thought of as being 'high risk' could possibly not be and vice versa."

As reported in Annals of Surgery, Dr. Brown and colleagues analyzed data from 233 rectal cancer patients (median age,66; 62% men) who underwent surgery between 2007-2015; 52% had neoadjuvant therapy, and of these, most had long-course chemoradiotherapy.

With respect to surgery, 74% underwent an anterior resection; 20%, an abdominoperineal excision of rectum; 4%, a Hartmann's Procedure; and 2% had a proctocolectomy. Fifty-four percent went on to have adjuvant chemotherapy.

Median followup was 61 months. For the whole cohort, five-year overall survival was 76% and disease-free survival, 61%. The local recurrence rate was 12% and distant recurrence, 25%.

On multivariable analysis, baseline mrTD/mrEMVI (extramural venous invasion) status was the only significant MRI factor for adverse survival (HR, 2.36), for overall survival (HR, 2.37) and for disease-free survival, superseding T and N categories.

By contrast, mrLNMs were associated with good overall survival (HR 0.50) and disease-free survival (HR, 0.60).

Further, on multivariable analysis, mrTDs/mrEMVI were strongly associated with distant recurrence (HR, 6.53), but T and N category was not.

A subgroup analysis of post-treatment MRIs in post-chemoradiotherapy (CRT) patients also showed that mrTD/mrEMVI status was the only significant prognostic factor; in addition, those who showed a good treatment response had a prognosis similar to patients who were mrTD/mrEMVI-negative at baseline.

The authors conclude, "Current MRI staging predicting T and N status does not adequately predict prognosis. Positive mrTD/mrEMVI status has greater prognostic accuracy and would be superior in determining treatment and follow-up protocols. CRT may be a highly effective treatment strategy in mrTD/mrEMVI positive patients."

Dr. Brown added, "The results suggest we need specialist radiologists...who are trained to look at these other factors, so we're not just measuring lymph nodes but looking at vascular invasion and tumor deposits, too. This will help us avoid overtreating patients who don't need radiotherapy at that time."

Dr. Andreas Kaiser, a colorectal surgeon at City of Hope in Duarte, California, commented in an email to Reuters Health, "Most cancers are currently staged based on the TNM classification, which has allowed us to make substantial standardization and comparability of different patient groups. The depth of invasion and the presence/absence of metastatic lymph nodes have been the core parameters to define the stage."

"However," he noted, "it has become clear that TNM classification is not 100% straightforward in predicting the chances of cure."

"It is always important not to throw out existing classification systems and replace them from (moment) to moment," he said. "But it is certainly important to add additional prognostic parameters to sub-define groups of patients who might benefit from more intense or a different sequence of treatment modalities."

"Unquestionably, the future in rectal cancer management will be to tailor treatment as specifically as possible to the individual patient," he added. "The more precisely we can predict the risk of spread or local recurrence in a patient, the more precisely we can use or hold back on certain treatments."

By Marilynn Larkin

SOURCE: https://bit.ly/36hjDgV Annals of Surgery, online September 15, 2020.

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