tl;dr- Yes, it sounds like blue scorpion venom is recognized as a folk treatment for cancer in Cuba, but, no, it's not well-regarded in current medical literature. Below are a few papers that discuss both blue scorpion venom in specific as well as other scorpion venoms. While it sounds like there's an interest in finding possible uses, the scientific opinion of the folk practice seems to be pretty critical.
A recent paper describes a product from blue scorpion venom, Escozul, as a "pseudomedicine", and a paper from 2017-03-21 notes that there wasn't any supportive data from clinical studies in peer-reviewed journals.
Has any definitive research been performed recently?
No, as of 2017, there doesn't appear to be any definitive research.
The scorpion venom is considered a natural source for cancer therapy11. In particular Escozul, (Labiofam) is a commercial product made from the venom of Rhopalurus junceus, a rare blue scorpion found only in Cuba, is considered as a potential novel cancer therapeutic12. [...] There are no data from controlled clinical studies neither for Escozul nor for Vidatox 30-CH in refereed journals. The available information derived from interviews with patients involved or provided within the sites of alternative therapies. Essentially, scientific evidences about the biological activity of Vidatox in cancer cells are missing.
-Venom from Cuban Blue Scorpion has tumor activating effect in hepatocellular carcinoma (2017) (emphasis added)
Several papers have looked at the venom's biological effects while others have studied its effects in limited contexts. The overall opinion appears to be that remedies derived from blue scorpion venom aren't providing a verifiable benefit, with one study suggesting that it can worsen cancerous growth.
The literature seems to show an evolution through time. Back in 2004, it was recognized as a folk treatment with uncertain effects:
Escozul is a folk remedy for cancer, made from the diluted venom of the Caribbean blue scorpion (Rhopalurus junceus). Escozul is gaining popularity in Cuba, its birthplace, and in many other countries as well. Since the early 1990s, even some US citizens have gone to that "forbidden island" for treatment with this unusual substance, which was first developed in 1980 by a Guantanamo province biologist, Misael Bordier. Some years ago, Bordier conceived the idea of trying scorpion venom as a treatment for certain chronic conditions including cancers of various kinds. It seemed to have good effects and word quickly spread. Now many doctors in that area are said to frequently administer diluted doses of the toxin by mouth to patients with malignancies, as well as to those suffering from pelvic inflammation, renal failure, and Parkinson's disease. (Although pure venom is harmful to humans, this product is reputedly non-toxic when diluted and administered orally.) [ILLUSTRATION OMITTED] Some readers have asked me if there is any truth to the glowing reports that are finding their way onto thousands of websites concerning its use as a cancer treatment. My basic answer is that while it shows some promise, it is still a very uncertain remedy. One should not abandon any well-documented therapy in favor of undertaking a treatment about which so little is yet known. Despite the fact that Cuba has a modern public health system, it is also a country with an entrenched belief in folk medicine.
-"A friendly skeptic looks at Escozul" (2004)
Most recent literature sounds pretty skeptical of blue scorpion venom, too.
Complementary and alternative medicine (CAM) is the term used to describe many kinds of products, practices, and systems that are not part of conventional medicine. Cancer patients usually do everything they can to combat the disease, manage its symptoms, and cope with the side effects of treatment. Unfortunately, patients who use CAM underestimate the risk of interaction with cancer therapy or worse they omit conventional therapy thus reducing the possibility of cancer remission. Herein we analyzed the effects of Vidatox 30 CH (venom extracted from the Junceus Rhopalurus scorpion) on hepatocellular carcinoma (HCC), the second leading cause of cancer-related deaths. We found out that Vidatox increases HCC proliferation and invasion whereas it does not seem to interact with sorafenib, the orally active multikinase inhibitor approved for the treatment of advanced hepatocellular carcinoma. Our results suggest that the concentration of Vidatox used in the present study has not anti-neoplastic effects and care must be taken in hiring Vidatox in patients with HCC.
-Venom from Cuban Blue Scorpion has tumor activating effect in hepatocellular carcinoma (2017)
Modern commercial interest
There're a few recent patents for how to prepare blue scorpion venom.
A composition for treating vitiligo and a method of making the same, said composition comprising: a blue scorpion venom; and an alpha lipoic acid. Preferably, the blue scorpion venom is diluted, polarized, and nanosized. Preferably the alpha lipoic acid is polarized and nanosized. The composition may also comprise various vitamins and minerals.
-"Composition for treatment of vitiligo", US Patent 20170100441 A1 (filed 2016)
It's interesting to compare this patent to a variant filed 8 years earlier.
Various embodiments of this invention disclose a polarized dilute blue scorpion venom solution, a method for making a polarized dilute scorpion venom solution, and a method for administering dilute scorpion venom solution. The polarized dilute scorpion venom solution relieves pain, improves immune-system response, treats cancer, prevents cancer, improves quality of sleep, reduces inflammation, and minimizes negative biological response to chemotherapy and radiation treatment.
-"Polarized Scorpion Venom Solution and a Method for Making Polarized Scorpion Venom Solution", US Patent 20090123558 A1 (filed 2008)
While these patents seem to be targeted at different intellectual properties, the description of what blue scorpion venom's uses are seem to have changed despite being from the same author. This may reflect a changing understanding from someone heavily invested in the topic. It's also worth noting that their most recent description doesn't seem to make a particularly solid claim.
Samples of modern research abstracts (post-2010)
This communication describes the first general biochemical, molecular and functional characterization of the venom from the Cuban blue scorpion Rhopalurus junceus, which is often used as a natural product for anti-cancer therapy in Cuba. The soluble venom of this arachnid is not toxic to mice, injected intraperitoneally at doses up to 200 μg/20 g body weight, but it is deadly to insects at doses of 10 μg per animal. The venom causes typical alpha and beta-effects on Na+ channels, when assayed using patch-clamp techniques in neuroblastoma cells in vitro. It also affects K+ currents conducted by ERG (ether-a-go-go related gene) channels. The soluble venom was shown to display phospholipase, hyaluronidase and anti-microbial activities. High performance liquid chromatography of the soluble venom can separate at least 50 components, among which are peptides lethal to crickets. Four such peptides were isolated to homogeneity and their molecular masses and N-terminal amino acid sequence were determined. The major component (RjAa12f) was fully sequenced by Edman degradation. It contains 64 amino acid residues and four disulfide bridges, similar to other known scorpion toxins. A cDNA library prepared from the venomous glands of one scorpion allowed cloning 18 genes that code for peptides of the venom, including RjA12f and eleven other closely related genes. Sequence analyses and phylogenetic reconstruction of the amino acid sequences deduced from the cloned genes showed that this scorpion contains sodium channel like toxin sequences clearly segregated into two monophyletic clusters. Considering the complex set of effects on Na+ currents verified here, this venom certainly warrant further investigation.
-Biochemical and molecular characterization of the venom from the Cuban scorpion Rhopalurus junceus, 2011
Cure for thousands of cases of cancer has emerged from the blue scorpion venom, endemic to Cuba. The blue scorpion venom contains a protein chain that attacks cancer. The "escozul" also acts as "immuno-modulator," raising the defences . A treatment based on scorpion venom loaded with radioactive material is being tested as a way to kill brain tumour. A protein in venom from the yellow Israeli scorpion has been found to bind preferentially to the glioma cells, so scientists have created a synthetic version that does not by itself kill a patient. When the venom protein attaches to the glioma cells, the radiation kills them. Health physicists in a study used a compound called TM-601, a synthetic version of the molecule. The molecule, a protein, was bound to a radioactive substance called I-131 believed to kill glioma cells .
-Animal Venom for Treating Breast Cancer (2014)
Venom of some species of scorpions induces apoptosis and arrests proliferation in cancer cells. This is an important property that can be harnessed and can lead to isolation of compounds of therapeutic importance in cancer research. [...]
These results suggest that venom of O. doriae can be potential source for the isolation of effective anti-proliferative and apoptotic molecules.
-Scorpion venom (Odontobuthus doriae) induces apoptosis by depolarization of mitochondria and reduces S-phase population in human breast cancer cells (MCF-7) (2011)
Scorpion venom possesses protein toxins having numerous biological activities, some of which are potentially anticancerous. Previously we had reported antiproliferative activity of the venom of Indian black scorpion, Heterometrus bengalensis Koch. [...] These results hypothesize that Bengalin might provide a putative molecular mechanism for their anticancer effect on human leukemic cells which might be mediated by mitochondrial death cascade. Inhibition of HSPs might also play a crucial role in induction of apoptosis.
-Apoptosis induction in human leukemic cells by a novel protein Bengalin, isolated from Indian black scorpion venom: Through mitochondrial pathway and inhibition of heat shock proteins (2010)
In Cuba the endemic species of scorpion Rhopalurus junceus has been used in traditional medicine for cancer treatment. However, there is little scientific evidence about its potential in cancer therapy. The effect of a range of scorpion venom concentrations (0.1, 0.25, 0.5, 0.75 and 1mg/ml) against a panel of human tumor cell lines from epithelial (Hela, SiHa, Hep-2, NCI-H292, A549, MDA-MB-231, MDA-MB-468, HT-29), hematopoietic origins (U937, K562, Raji) and normal cells (MRC-5, MDCK, Vero) was determined by the MTT assay. Additionally, the effect of venom on tumor cell death was assayed by Fluorescence microscopy, RT-PCR and western blot. Only the epithelial cancer cells showed significant cell viability reduction, with medium cytotoxic concentration (IC50) ranging from 0.6-1mg/ml, in a concentration-dependent manner. There was no effect on either normal or hematopoietic tumor cells. Scorpion venom demonstrated to induce apoptosis in less sensitive tumor cells (Hela) as evidenced by chromatin condensation, over expression of p53 and bax mRNA, down expression of bcl-2 mRNA and increase of activated caspases 3, 8, 9. In most sensitive tumor cells (A549), scorpion venom induced necrosis evidenced by acridine orange/ethidium bromide fluorescent dyes and down-expression of apoptosis-related genes. We concluded the scorpion venom from R. junceus possessed a selective and differential toxicity against epithelial cancer cells. This is the first report related to biological effect of R. junceus venom against a panel of tumor cells lines. All these results make R. junceus venom as a promise natural product for cancer treatment.
-In vitro anticancer effect of venom from Cuban scorpion Rhopalurus junceus against a panel of human cancer cell lines. (2013)