Receipt of IMRT Is a Predictive Factors for Survival in Oropharyngeal Cancer, Study Shows

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A study of long-term survival among a large cohort of patients with oropharyngeal cancer (OPC) published in Cancer found that outcomes were good amongst those alive at 5 years without recurrence, but compared unfavorably versus those predicted for the general population.

The study revealed that among patients with OPC, those treated with intensity-modulated radiation therapy (IMRT) as well as those with less tobacco exposure experienced better outcomes than others in their cohort.

“Recognizing that the majority of patients with OPC survive at least 5 years (≈80%) and have a low probability of recurrence, we sought to identify factors that influenced long-term survival in a cohort of patients with OPC treated with radiation who survived recurrence-free for at least 5 years after diagnosis,” wrote the study authors, who were led by Kristina R. Dahlstrom, PhD.

In this study, the investigators evaluated newly diagnosed patients with OPC who had been treated with radiation and who were alive without recurrence 5 years after their diagnosis. Overall survival (OS) probabilities past 5 years were predicted and factors associated with OS were also determined.

Of a total of 1699 patients, the additional 2-year, 5-year, and 10-year OS probabilities were found to be 94%, 83%, and 63%, respectively; these rates were lower than those in the general population.

The risk of death among patients with OPC was higher for those who were older, were current or former smokers, had tumors other than those in the tonsil or base of tongue, or had T4 tumors. Conversely, those who had base of tongue tumors and had received IMRT or lower-radiation doses typically had a lower risk of death.

With the exception of patients with HPV-negative status, the standardized mortality ratios (SMRs) for all subgroups were revealed to be significantly larger than 1 as compared with the general population, suggesting a significantly higher mortality rate among patients with OPC. Ultimately, mortality among patients with OPC was 4 times higher when compared with the general population.

Moreover, among current and heavy smokers, standardized mortality ratios (SMRs) were higher; SMRs were lower among those who received IMRT and lower radiation doses.

“Based on this finding, we offer the following interpretations: 1) although patients with OPC who survive at least 5 years after diagnosis have very good long-term outcomes with low recurrence rate, their mortality rate nonetheless remains higher than that of the general population due to their index cancer; 2) unaccounted-for effects of treatment contribute to mortality; or 3) our population of patients was inherently at greater risk for death,” the study authors explained.

Importantly, these study results were not without limitations, including that cause of death was not captured in the data, thus only allowing for speculation on the causes of the observed lower long-term survival rates.

Another limitation identified was the absence of known HPV status for most patients. However, the investigators noted it is unlikely that tumor HPV status directly impacts conditional survival; however, the underlying demographics of those with HPV-related tumors could possibly have some impact on the current findings.

Reference:

Dahlstrom KR, Song J, Thall PF, et al. Conditional survival among patients with oropharyngeal cancer treated with radiation therapy and alive without recurrence 5 years after diagnosis. Cancer. Published December 11, 2020. doi: 10.1002/cncr.33370



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