Prevalence Of Secondary Cancers Highlights Need For Trial Inclusion
등록일 2019년 01월 07일 금요일
수정일 2017년 11월 24일 금요일

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In the US alone, the number of cancer survivors is on the rise.This has mainly been driven by the aging population, expanding cancer screening efforts, and improvements in cancer treatment.Statistics show that over the past 30 years the cancer survivor population increased by up to four times to hit 15.5 million in 2016 and is expected to reach 26.1 million by 2040.Additionally about half of all survivors have lived 10 years after their initial diagnosis and a meager two-thirds has survived beyond 5 years.

This can be attributed to the demanding health needs that the cancer survivors need such as surveillance for recurrence, monitoring treatment-related toxic effects, and managing emerging diagnoses such as chronic conditions or even new primary cancers.This is particularly worrying because cancer survivors tend to be barred from undergoing cancer clinical trials.In fact, more than 80 percent of National Cancer Institute affiliated lung cancer trials exclude as many as 25 percent of patients newly diagnosed with cancer from participating trials.

Big strides have been made in understanding the risks of a future primary cancer among specific groups of cancer survivors.However, the studies have not addressed how many patients diagnosed with incident cancer have survived prior cancer.Understanding how common a subsequent cancer is among patients with a history of cancer is crucial for understanding ongoing or new cancer risk in survivors.

In a study conducted by Caitlin C.Murphy, Ph.D., M.P.H, of the University of Texas Southwestern Medical Centre, 740,990 patients diagnosed with cancer from 2009 to 2013 were allowed to participate.The study aimed to examine the prevalence of prior cancer among individuals newly diagnosed with cancer.The results showed that of 765,843 incident cancers diagnosed, 141,021 cases (18.4 percent) represented a second order or higher primary cancer.

The study showed that the prevalence of previous cancer cases was dependent on the age of the patient.It was 11 percent among patients aged 20 to 64 years and 25.2 percent among ages 65 years or older.Prevalence also differed by the incident cancer type, with myeloid and monocytic leukemia being the most prevalent at 24.8 percent.Cancer of the anus, anal canal and rectum stood at 18.2 percent, cancer of the cervix and other female genital organs, e.g., vagina, vulva stands at 15 percent, and lung and other respiratory cancers stand at 14.6 percent.

Previous cancers among the younger age group occurred at a different cancer site although some like second order breast cancer, cervical cancer, and other female genital, male genital and testicular cancers occurred more often in the same site.Among patients 65 years and older, incident cancers with the highest prevalence of prior cancer were melanoma at 36.9 percent, myeloid and monocytic leukemia at 36.9 percent, bones and joints at 34 percent, and urinary bladder and other urinary organs at 32.5 percent.Most prior cancers among this age group occurred in a different site with the exception of breast cancer melanoma.

The implications of prior cancer cannot be underestimated when it comes to cancer care delivery.The cancer patients may have priorities which are conflicting concerning their treatment decisions, e.g., a new diagnosis can interrupt management, adhering to treatment or even outcomes related to prior cancer.The differences in the prevalence of prior cancer by incident cancer type also highlight the shared risk factors that may be amenable to targeted surveillance. 

With this information the many cancer clinical trials that bar patients with prior cancer may find that they are excluding a good number of otherwise eligible patients.This practice probably arose from a belief that has been over the years that a prior cancer diagnosis may interfere with the study conduct and/or even the outcome.However, this criterion is restrictive, and it limits the generalization and trial generated knowledge to patients with first or only primary cancers.

Patients with prior cancer also tend to be excluded from observational research which includes treatment and outcome studies from various research data in a number of organizations.This study could help clear the path for observational studies that normally provide real-world data to complement clinical trials.In addition, this could be important in advancing evidence-based practice.

Sandi L.Pruitt, Ph.D., MPH, assistant professor of epidemiology in the department of clinical sciences at the University of Texas and a co-author of the study, said, "We feel that this study presents a key first step in understanding this large, important and often overlooked patient population.As evidenced by our results prior cancer diagnoses can be quite common among individuals with cancer.To know whether these patients should be included routinely in clinical trials, further work is needed."

Pruitt later added, "If it is shown that prior cancer diagnoses do not adversely impact clinical outcomes for the cancer types in the present study  – as we previously demonstrated for individuals with lung cancer – then it seems reasonable and appropriate to open up clinical trials to these patients."

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