Imaging may be misleading when determining the success of cancer treatment
A new analysis calls into question the use of imaging alone to determine the efficacy of ablative radiation therapy treatments.
Stereotactic ablative radiotherapy (SABR) is a common option for non-small cell lung cancer (NSCLC), prostate adenocarcinoma, hepatocellular carcinoma (HCC), renal cell carcinoma and for patients with cancer that has spread to other parts of the body. PET imaging is routinely used following SABR to ascertain if the treatment effectively removed all cancerous tissue. But the authors of a new editorial in Oncotarget propose that relying solely on imaging to guide cancer management may leave many patients vulnerable to recurrence.
“SABR is considered ablative due to excellent radiographic local control rates,” Muzamil Arshad, MD, PhD, an assistant professor of radiation and cellular oncology at University of Chicago Medicine, and colleagues noted. “Pathological analysis, however, shows SABR is potentially not ablative.”
The group points out that numerous studies have highlighted fluctuations in cancer control when imaging was used to determine whether patients had any residual cancer after SABR treatment. Histologically, residual cancer is identified in 40% of NSCLC, 57%–69% of RCC, 7.7%–47.6% of prostate and 0%–86.7% of hepatocellular carcinomas.
Residual disease that may not be obvious on imaging after SABR poses significant risks to patients and can lead to poorer outcomes. This is why it is critical for providers to assess treatment success using multiple factors.
The authors suggested these judgements extend beyond just clinical complete response (cCR)—defined as no visible disease on radiographic or physical examination—to always include measures of pathological complete response (pCR), which includes histological evidence, or lack thereof, of cancer.
To back their suggestion, the group highlighted evidence from Memorial Sloan Kettering Cancer Center, which details the effects of using imaging alone versus histological analysis to gauge the effectiveness of each in identifying residual disease.
“The Memorial Sloan Kettering Cancer Center watch-and-wait experience in nonoperative management of rectal cancer confirms the negative prognostic value of residual disease. Among patients with pCR after neoadjuvant therapy and surgery, 5-year overall survival/disease-free survival is 94/92% versus 73/75% for those with a cCR,” the authors explained.
The group acknowledged that SABR is an effective treatment but offered suggestions on how to improve its ablative potential. They recommended including radiation dose-escalation and novel immune modulating systemic therapies in addition to SABR. They also suggested routinely measuring treatment responses using both cCR and pCR.
The full opinion piece can be viewed here.
In addition to her background in journalism, Hannah also has patient-facing experience in clinical settings, having spent more than 12 years working as a registered rad tech. She began covering the medical imaging industry for Innovate Healthcare in 2021.