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Jayant S Vaidya

Publications and source records attributed to Jayant S Vaidya.

16 recordsLinked to original sources
PubMed2005

Mathematical modelling of radiotherapy strategies for early breast cancer.

Targeted intraoperative radiotherapy (Targit) is a new concept of partial breast irradiation where single fraction radiotherapy is delivered directly to the tumour bed. Apart from logistic advantages, this strategy minimizes the risk of missing the tumour bed and avoids delay between surgery and radiotherapy. It is presently being compared with the standard fractionated external beam radiotherapy (EBRT) in randomized trials. In this paper we present a mathematical model for the growth and invasion of a solid tumour into a domain of tissue (in this case breast tissue), and then a model for surgery and radiation treatment of this tumour. We use the established linear-quadratic (LQ) model to compute the survival probabilities for both tumour cells and irradiated breast tissue and then simulate the effects of conventional EBRT and Targit. True local recurrence of the tumour could arise either from stray tumour cells, or the tumour bed that harbours morphologically normal cells having a predisposition to genetic changes, such as a loss of heterozygosity (LOH) in genes that are crucial for tumourigenesis, e.g. tumour suppressor genes (TSGs). Our mathematical model predicts that the single high dose of radiotherapy delivered by Targit would result in eliminating all these sources of recurrence, whereas the fractionated EBRT would eliminate stray tumour cells, but allow (by virtue of its very schedule) the cells with LOH in TSGs or cell-cycle checkpoint genes to pass on low-dose radiation-induced DNA damage and consequently mutations that may favour the development of a new tumour. The mathematical model presented here is an initial attempt to model a biologically complex phenomenon that has until now received little attention in the literature and provides a 'proof of principle' that it is possible to produce clinically testable hypotheses on the effects of different approaches of radiotherapy for breast cancer.

Brachytherapy↗
PubMed2005

A mathematical model for the effect of a false-negative sentinel node biopsy on breast cancer mortality: a tool for everyday use.

One of the concerns of using sentinel node biopsy (SNB) is the risks of a false-negative result (FNR). We have created a mathematical model to estimate the effects of FNR on mortality because of excess local recurrence and adjuvant therapy inappropriately withheld. With a FNR of 9.7%, the absolute effect on 10-year mortality is estimated to be less than 0.6% for all patients with tumours <2 cm in size. Since the impact of FNR on mortality is small and FNR rates do not improve with training, we suggest that detection rate alone is an adequate criterion for judging competence in SNB.

Breast Neoplasms↗
PubMed2005

TARGeted Intraoperative radiotherapy (TARGIT): an innovative approach to partial-breast irradiation.

A revolution is challenging the dogma that local treatment for all patients with breast cancer treated with breast conservation therapy must include postoperative radiotherapy delivered to the whole breast. Such prolonged postoperative radiotherapy is a burden to patients and hospitals and forces many women to chose mastectomy instead. Furthermore, for patients receiving chemotherapy, the start of conventional radiotherapy may be delayed so long as to increase the risk of local relapse. These problems might be eliminated if effective radiotherapy could be given as a single treatment intraoperatively, immediately after the surgery. Local recurrence after breast-conserving surgery usually occurs in the portion of the breast in the immediate proximity of the tumor, even when radiotherapy is omitted. Therefore, it should usually be possible to restrict radiotherapy to only the area adjacent to the tumor in selected women. Based on this premise, we have devised a new technique of partial breast irradiation, with the intention of completing all local treatment in a single session. In this article, we elaborate on the rationale and on the different methods of delivering intraoperative radiotherapy. If this approach is validated in ongoing randomized trials, it could save time, money, and breasts.

Breast Neoplasms↗
PubMed2004

Functional maps of metastases from breast cancers: proof of the principle that multidimensional scaling can summarize disease progression.

The mathematic technique of multidimensional scaling can create "functional maps" of metastases from breast cancer such that positions of organs in these maps are proportional to the probability of metastases. Areas that are likely to share disease are close together in a functional map, even though they may be physically distant, and vice versa. Two functional maps of breast cancers-one of local metastases to axillary levels I to III and another of distant metastases-are statistically significant and clinically meaningful. The maps accurately reflect the clinical data ( r > 0.97, p < 0.01), and so the progression of disease is revealed in simple visual summaries. As an analogy, the metastatic sites are like buoys on a fluid surface, and cancer spreads from a primary tumor like waves emanating from a point of impact on that surface. Metastases are predicted when the waves swamp the buoys. Because breast cancers do not always spread to the next nearest site, these functional maps do not resemble anatomic maps. The maps are a view of the body as "seen" by the tumor. Several well known clinical features are seen in these maps: most local metastases are to axillary level I; upper-inner primaries spread equally to levels II and III; in-transit metastases in the lymph and blood vessels do not follow the pattern of other distant metastases. Future functional maps can expand these summary diagrams to include biologic parameters (gene-expression profiles or endocrine response) and give valuable insights into patterns of recurrence in different populations.

Adult↗
PubMed2004

Intraoperative radiotherapy for breast cancer.

Postoperative radiotherapy, which forms part of breast-conserving therapy, may not need to encompass the whole breast. Apart from the consumption of huge resources and patients' time, postoperative radiotherapy deters many women from receiving the benefits of breast-conserving surgery, forcing them to choose a mastectomy instead. If radiotherapy could be given in the operating theatre immediately after surgery, many of these disadvantages could be overcome. One striking fact about local recurrence after breast-conserving surgery is that most occurs in the area of breast immediately next to the primary tumour; this is despite the finding that two-thirds of mastectomy samples have microscopic tumours distributed throughout the breast, even when radiotherapy is omitted. Thus, only the area adjacent to the tumour may need treatment with radiotherapy. On the basis of this premise, clinical scientists have used new technology to administer radiotherapy to the area at greatest risk of local recurrence, with the aim of completing the whole local treatment in one sitting. In this review, we have elaborated on the rationale and different methods of delivery of intraoperative radiotherapy. If this approach is validated by the results of current randomised trials, it could save time, money, and breasts.

Breast Neoplasms↗
PubMed2003

Gallstone ileus.

Explore the source record for details and available documents.

Aged↗
PubMed2002

Minimally invasive therapy for the treatment of breast tumours.

Minimally invasive therapy has been explored as a potential means of treating breast tumours with minimal disruption to adjacent soft tissues. The purpose of this is to facilitate improved cosmesis and to offer treatment to women who are unfit for surgery. A number of treatment modalities including thermal therapies (intersitital laser photocoagulation, radiofrequency, focused ultrasound and cryotherapy), percutaneous excision and interstitial radiotherapy are being developed. The experience to date of each of these modalities is described and reviewed. Currently there are too few data to indicate the efficacy of these treatments although the preliminary data are encouraging. The need for large-scale studies examining the role of MIT in relationship to the overall management of breast cancer (including chemotherapy, radiotherapy, and the management of the axilla) and outcome is discussed.

Breast Neoplasms↗
PubMed2002

The novel technique of delivering targeted intraoperative radiotherapy (Targit) for early breast cancer.

AIM: We believe that conservative treatment of early breast cancer may not require radiotherapy that encompasses the whole breast in all patients. We have developed a novel therapeutic approach that allows targeted intraoperative radiotherapy (Targit) to be safely and accurately delivered in a standard operating theatre. We are currently recruiting for a randomized trial testing whether Targit can replace the whole 6 weeks of post-operative radiotherapy after breast conserving surgery. METHODS: This paper describes the operative technique. It employs a miniature electron-beam-driven X-ray source called INTRABEAM (PeC) that emits soft X-rays (50 kV) from within the breast. The X-rays are emitted from the tip of a 10 cm x 3.2 mm diameter probe, that is enclosed in a spherical applicator (available in 2.5-5 cm diameter sizes), which in turn is inserted in the tumour bed and intraoperative radiotherapy is delivered in about 25 min. The prescribed dose is 5 and 20 Gy at 1 cm and 0.2 cm respectively, from the tumour bed. RESULTS: The biologically effective dose is 7-53 Gy for alpha/beta=10 and 20-120 Gy for alpha/beta=1.5. The quick attenuation of the radiation reduces the damage to normal tissues and allows radiotherapy to be delivered in a standard operating theatre. Tungsten impregnated rubber sheets, cut to size, are placed on the chest wall to protect the heart/lungs and over the wound to stop stray radiation. The skin dose is monitored with thermoluminescent detectors (TLDs). After wide local excision of the tumour and good haemostasis, a spherical applicator is inserted in the tumour bed and the target breast tissues are wrapped around it with a purse-string suture. Thus, true conformation of the target around the applicator source is achieved in real time. CONCLUSION: As a tumour bed boost, this technique has the potential to reduce local recurrence by avoiding geographical misses and achieving excellent dosimetry. In patients with low risk of local recurrence, it has the potential to replace the full 6 weeks of post-operative radiotherapy with considerable implications to patients and hospitals.

Breast Neoplasms↗