After a patient with gastric cancer has been treated, the physician will evaluate the effectiveness of the treatment regimen used based on the efficacy of the treatment to determine whether the patient needs to continue treatment or whether to continue treatment using the same approach. So, how do doctors evaluate the efficacy?
Metrics on patient outcomes
Overall survival (OS)
Overall survival is generally defined as the time from when a patient is diagnosed with gastric cancer or undergoes radical gastric cancer surgery until death from any cause.OS has been considered the most reliable indicator for evaluating patient outcomes in oncology patients. However, OS also has the obvious limitation that it takes time to obtain the final evaluation results from the end of treatment and does not reflect the effect of treatment in a timely manner.
Disease-free survival (DFS)
Disease-free survival is defined as a patient entering observation from a point in time (eg, after a diagnosis of gastric cancer, after radical surgery, after radiotherapy) until tumor recurrence or death from various causes. It is most often used to evaluate the efficacy of treatment with radical surgery or radiotherapy, and can also be used to evaluate the effectiveness of treatment in most chemotherapy patients after they have achieved complete remission. When patients have a long OS, DFS is an important indicator of patient outcome.
Time to progression (time)
Time to progression (TTP), progression-free survival (PFS)
Time to progression is the time from a point in time when a patient enters observation (eg, after being diagnosed with gastric cancer, after radical surgery, after radiotherapy) until tumor progression; death is not counted in the calculation of this metric. Progression-free survival refers to patients entering observation from a certain point in time until tumor progression or death. These two metrics are used to assess the role of therapies in controlling tumors from progressing.
Metrics on tumor response to therapy
Response Evaluation Criteria in Solid Tumors (RECIST) is used to describe how well a tumor responds after treatment.
Physicians evaluate the size of the tumor before treatment by measuring the maximum length of the tumor using CT, magnetic resonance imaging (MRI), etc. The sum of the longest diameters (LD) of all lesions is used as the total diameter at baseline (i.e., before treatment). The sum of the longest diameters (LD) of all lesions was used as the total diameter at baseline (i.e., before treatment).
Tumor response to treatment can be classified into four categories based on the measurement results:
- Complete remission (CR), in which all tumors are found to be gone on clinical and imaging examinations.
- Partial remission (PR), where the sum of the LD of the lesions is reduced by at least 30%, using the total diameter at baseline as a reference.
- Stable disease (SD), where lesion shrinkage does not meet the criteria for PR or lesion enlargement does not meet the criteria for disease progression (PD).
- Disease progression (PD), as defined by the smallest total LD value recorded from the start of treatment, an increase of at least 20% in the sum of the LDs of the measured lesions or the appearance of one or more new lesions. The presence of any new lesion means disease progression. In exceptional cases, definite progression of non-measurable lesions is also accepted as evidence of disease progression.
Physicians use multiple metrics to evaluate the efficacy of gastric cancer treatment, with OS being the “gold standard” but a disadvantage in that it is time-consuming, and DFS, TTP, and PFS have also become the main metrics for evaluating the efficacy of gastric cancer. With the development and exploration of modern technology, some laboratory tests such as tumor markers, circulating tumor cells and circulating nucleic acid have been recognized for the evaluation of early efficacy of treatment. Combining multiple indicators and taking into account the adverse effects of treatment will be a more objective evaluation of treatment. (Coauthored by Songcheng Yin, Department of Gastrointestinal Oncology, The First Hospital of China Medical University)