Cannabis has demonstrated positive impacts on cancer treatment and on assisting traditional cancer-treatment methodologies like chemotherapy and radiation, and the side effects of those treatments.  While the research is promising, there have not been enough clinical trials. This is specifically difficult in the United States due to cannabis still being federally illegal and classified as a schedule I drug.
Much research still needs to be done, but the research so far states, “Phytocannabinoids are known to have potential anti-cancer activity. Previously, it was shown that phytocannabinoids can prevent proliferation, metastasis, and angiogenesis, as well as induce apoptosis in a variety of cancer cell types including breast, lung, prostate, skin, intestine and glioma.” 
Cannabis works differently inside every person because every person has a different endocannabinoid system (ECS). Therefore, it is vital to understand how cannabinoids interact with the cannabinoid receptors in the body. The other key is understanding how the ECS reacts during cancer and traditional cancer treatments.
A 2021 study showed that tetrahydrocannabinol (THC) or cannabidiol (CBD) when used with cannabichromene (CBC) “led to cell cycle arrest and cell apoptosis [… and] inhibited cell migration and affected F-actin integrity.”  F-actin is a filamentous protein involved in many cellular processes, including determining cell shape and enabling cell motility. It has been shown to be involved in tumor cell invasion and metastasis.
While these researchers were specifically studying “bladder urothelial carcinoma (UC), the most common urinary system cancer,” these findings might be applicable to other cancers.
The study authors stated, “In multiple studies, CBD and THC were previously suggested to possess anticancer activity for a variety of malignancies, whereas CBC was mostly associated with anticancer activity on prostate carcinomas.”
It is important to note that the entourage/ensemble effect may provide more benefits medically than attempting to use the cannabinoids in isolated form. The authors reported synergy between CBC and THC. “The synergistic interaction between these two cannabis compounds was dependent on specific ratios and might be related to the entourage effect.” 
Cannabinoids were found to impact cell migration differently. “Interestingly, CBC + THC treatment inhibits horizontal migration more than MMC [mytomicin-C], but MMC treatment has a greater inhibition of vertical cell movement. This suggests that each treatment has a greater effect on one cell-movement mode than the other does.” (Mytomicin-C is a chemotherapy drug that stops cancer cell proliferation.)
The treatments reduced cell migration, affected cell cytoskeleton, and induced apoptosis which suggests that it could “reduce cancer cell invasion or the onset of metastasis.” 
Research showing the benefits of cannabis as a method of treating cancer or supporting existing methods of treatment is ongoing. It is likely that the research will continue to show the benefits of this plant and its phytochemicals to the medical community.
References Kovalchuk O, Kovalchuk I. Cannabinoids as anticancer therapeutic agents. Cell Cycle. 2020;19(9):961-989. [journal impact factor=3.304; times cited=19].
 Anis O, Vinayaka AC, Shalev N, et al. Cannabis-derived compounds cannabichromene and Δ9-tetrahydrocannabinol interact and exhibit cytotoxic activity against urothelial cell carcinoma correlated with inhibition of cell migration and cytoskeleton organization. Molecules. 2021;26(2):465. [journal impact factor=4.411; times cited=6]